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Photographic Chemicals

and Solutions By J.

I.

CRABTREE

and G.

Kodak Research

E.

MATTHEWS

Laboratories

Rochester, A". T.

AMERICAN PHOTOGRAPHIC PUBLISHING BOSTON, MASS. 1938

CO.


Copyright 1938

By

J.

I.

Made and

Crabtree and G. E. Matthews

Printed in the United States of America

by the Plimpton Press

•

Norwood

Massachusetts


PREFACE This book represents some of the knowledge acquired during the past twenty-five years in

compounding photographic

their application to

photography

in the

solutions

and studying

Research Laboratories of the

Eastman Kodak Company.

ERRATA Page 337

— Formula DK-20R — Replenisher Solution should read:

Kodalk Potassium Sulpliocyanate (Thiocyanate)

2 ounces, 290

grains

20.0

grams

290

grains

5.0

grams

Pages 341, 343, 345 Firm name should be spelled as follows: Lalance

&

Grosjean Corp.,

Woodhaven, N. Y. Page 359

— Index

Reference should read as follows: Fine-grain development 295, 337.

ui

November

1938.

i-K.

i»i rt 1 1

n n. WO"


Made and

Printed in the United Stales of America

by the Plimpton Press

•

Norwood

Massachusetts


PREFACE This book represents some of the knowledge acquired during the past twenty-five years in compounding photographic solutions and studying their application to

photography

Research Laboratories of the

in the

Eastman Kodak Company. The nucleus of this work was contained pare Photographic Solutions " (Brit.

quently

many

scientific

by the authors and in these

J.

How

Phot. 66: 365, 1919).

to Pre-

Subse-

papers cognate to this subject were published

their co-workers

and the material of practical value

papers has been extracted and combined

for reference purposes.

''

in the article

To

this compilation

in this single

volume

has been added consider-

able hitherto unpublished information.

The requirements

of the small as well as the large user of photographic

chemicals have been kept in mind throughout and

book

will therefore

be of value to

all

it

is

hoped that the

types of photographers including

amateurs, professionals, scientific investigators, x-ray, photofinishing,

photo-mechanical, and motion-picture workers.

Acknowledgment

who generously

is

due

to the various

manufacturers of equipment

supplied data and photographs, to Mr. C. E. Ives, to

Mrs. R. F. Quirk, and to our other numerous colleagues

in the

Kodak

organization for their suggestions and helpful criticism. J. I.

G. E.

November

1938.

Crabtree

Matthews


Digitized by the Internet Archive in

2010

http://www.archive'.org/details/photographicchemOOcrab


CONTENTS

Preface

.......... .........

PAGE iii

Introduction CHAPTER I.

II.

III.

...... ......

Terminology and Arrangement of Photographic Formulas Photographic Arithmetic and Conversion of For MULAS Apparatus and Methods of Use

IV. Materials for

....

Construction of Photographic Proc

ESSiNG Apparatus V.

Temperature Measurement and Control

...... ...... ......

VI.

Effect of the Water Supply on Photographic Solu

VII.

Technique of Mixing and Using Photographic Solu

tions

tions VIII.

6 15

Handling Solutions at High Temperatures

51

79

100

114 178

IX. Storage and Transportation of Chemicals and Solu

tions

X. Substitution of Chemicals XI. Stains on Negatives and Prints XII. Cleaning Photographic

191

214 230

Processing Apparatus and

Removal of Stains from the Hands and Clothing

262

.....

270

XIII. General Suggestions and Precautions

Photographic Chemicals XIV. Appendix

on Handling

....... ....... ....... .... ...... .........

A.

Formulary

B.

Table of Solubilities of Photographic Chemicals

C. List of

279

338

Manufacturers of Apparatus and Sup-

plies

341

D. Conversion Table of Fahrenheit, Centigrade,

AND Reaumur Degrees

347

Index of Formulas by Purpose

348

Subject Index

358


INTRODUCTION Chemicals chemicals, or

for 2.

photographic work are supplied either as

i.

individual

as mixtures of dry powders or solutions requiring only

the addition of water to prepare

them

for use.

The majority

photographers prefer to purchase their chemicals

in the

of

amateur

prepared form.

Within recent years an increasing number of advanced amateurs, pro-

and photofinishers have

fessional photographers,

age chemicals more extensively, but

also

begun

many workers and

to use pack-

the majority of

motion picture laboratories prepare their photographic solutions from the

component chemicals. It should be understood clearly, however, knowledge of the fundamental principles of solution preparation

that a

and use

is

important w^hether prepared powders or component chemicals

are preferred.

It is the

purpose of

this

book

to

supply such information.

In order to be able to prepare correctly any and every solution used in

photography, a knowledge of the properties of the chemicals used and

of the chemical reactions involved during the mixing

is

essential,

though

by adhering strictly to printed directions it is usually possible for an unskilled worker to prepare the developing and fixing solutions as generally used. However, instructions for the use of various materials differ; for example, in the case of some developing formulas it is recommended to dissolve the developing agent

should be dissolved tized

method

of mixing

first,

while according to others the sulphite

Both methods may be

first.

is

right,

followed, and especially

if

but

if

a systema-

the photographer

has a knowledge of the reactions involved, he can then proceed to mix

any photographic solution with confidence and, what is more, he will be able to locate the trouble if for any reason the solution does not work correctly after mixing.

In recent years automatic developing with processing machines has for motion picture and photofinishing work, and these machines necessitate the use of large volumes of solution which require special equipment for their preparation and handling. In each chapter, therefore, an attempt has been made to deal with specific meth-

been introduced, notably

ods for the handling of both small and large quantities of chemicals.


CHAPTER

I

TERMINOLOGY AND ARRANGEMENT OF PHOTOGRAPHIC FORMULAS A

solution of

any kind

is

obtained by uniformly mixing with and dis-

tributing a solid or a liquid through another liquid (or solid).

may

of gases in liquids

37% tion

is

a

solution of the gas, formaldehyde, in water; but this type of solu-

The substance being

rarely used in photography.

is

and the liquid The extent to which the

which

called the solute

in

solvent.

solute

its

Solutions

which

also be prepared, such as formalin,

and when the solvent

solubility

will

it

is

dissolved

dissolved

soluble in the solvent

is

is

called the

is

is

called

hold no more of the solute

it is

said to be saturated.

The degree

of solubility of

any chemical depends on the nature and

temperature of the solvent. a saturated solution

If

is

cooled

down

to a lower temperature, crystals

usually form which settle out until the saturation point

reached at that

is

particular temperature, though in the case of a substance like hypo, all

dust

is

called supersaturated solution of to

hypo grow

is

if

excluded, crystals do not separate out on cooling and a so-

added

is

until the saturation point

is

a small crystal

if

immediately form and continue

reached.

paring a saturated solution, therefore, water, cool to

However,

obtained.

to the solution, crystals

is

The

method

best

of pre-

to dissolve the chemical in hot

room temperature with shaking, allow

to stand,

and

filter.

For photographic work, saturated solutions are not recommended, because even though the solution care

any

taken to note

is

crystals

its

may

which

may have

been prepared correctly, unless

condition each time

it is

used, and to dissolve

have formed, serious errors

These errors can be avoided by

may

be introduced.

always using solutions of a definite per-

centage strength as will be explained

later.

Diluting to Volume. When a chemical is dissolved in water the volume of the solution is usually greater than that of the water used, because the particles or molecules of the chemical occupy a certain space

when liquid

in solution. is

In case two liquids are mixed, the final volume of the

not necessarily equal to the

before mixing,

it

may

be greater or

it

sum

may

of the volumes of the liquids

be

less.

Thus

fifty

volumes of

volumes of water at 7o°F. (2i°C.) produce ninety-seven volumes of the mixture and not one hundred. Moreover, equal weights of different chemicals do not occupy the same volume. alcohol

when added

to fifty


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

2

In photography

we

are concerned only with the weight or

volume

of

each chemical in a fixed volume of the solution, so that when mixing, the chemical should be dissolved in a volume of water appreciably less than

volume

that called for in the formula and then water added up to the stated.

Systems o£ Measurement.

— In photographic

practice, solids are

weighed and liquids are measured either by the metric or the avoirdupois system.

Although a large majority of photographers use the avoirdupois system of weights and measures, this system is inconvenient and complicated as compared with the metric system. The metric unit of length is the meter (m) (which means measure).

The meter

is

divided into one hundred parts called centimeters, abbre-

viated as cm.

The is

unit of

mass or weight

is

a platinum-iridium cylinder,

at the International

Bureau

of

the kilogram (kg) the original of which

which

is

in a special

thousandth part of the kilogram equals written g though preferably entiate

it

gram.

i

A

good rule

is

words of

to spell out all

in formulas.

unit of

volume

is

the

liter (1)

which

is

the

kilogram of pure water at the temperature of

namely 4°C. (39.2 °F.) and subjected Therefore,

The The gram may be

should be spelled out completely to differ-

from the term, grain.

one syllable

The

it

underground vault

Weights and Measures near Paris.

i

liter

of water weighs

one-thousandth part of the

The thousandth

part of a

liter

liter is

i

to

volume occupied by its

maximum

i

density,

normal atmospheric pressure.

kilogram or 1000 grams and

or the milliliter (ml) weighs

i

i

gram.

usually designated also as a cubic cen-

timeter (cc) although 1000 milliliters or

liter

i

equals 1000.028 cubic

centimeters {Report on Metric Units oj Volume, Brit. Standards Institu-

London, 1933). The difference between the two units is 28 parts which is so small as to be of no significance except in very precise scientific work. The term " cubic centimeter " has become so universally used that it is commonly accepted as the thousandth part tion,

in a million,

of a liter and will, therefore, be used in this

book with

this connotation.

For compounding metric photographic formulas, only grams, liters

in the case of the

U.

S.

currency which

is

a metric currency.

ginner should therefore think of grams and parts of a

were dollars and cents. 535 -iii grams.

100

and

cc,

are used, and fractions are always expressed as a decimal just as

gram

The as

if

be-

they

Thus, 5.35 grams corresponds to $5.35 or


TERMINOLOGY AND ARRANGEMENT In photography the following table

is

used:

Weight

drams (or drachms)

8

ounces

16

Volume

=

437"i grains

i

ounce

=1

ounce

=

pound

i

==

60 minims

drams (or drachms) 480 minims * 128 ounces

— Much confusion

Uniformity of Formulas. formulas could be avoided

Mees/

if

i

8 fluid

* 16 ounces

cation.

3

(or

=1

= = =

dram

fluid

drachm)

fluid

ounce

i

fluid

ounce

i

pint

i

gallon

in the conversion of

authors would adopt a standard for publi-

Ausserwinkler,- and others have suggested standards for

writing formulas but for practical use in publication, these have certain objections.

The

simplest standard, perhaps,

is

the liter (32 ounces) or

quarter fraction thereof, 250 cc, 500 cc, and 750 cc (8 ounces, 16 ounces,

and 24 ounces respectively) I

for tray dilutions,

and 4

liters

gallon) or quarter fraction thereof for tank dilutions.

always be published total

in

both metric and avoirdupois equivalents with the

volumes on the above

The

(128 ounces or

Formulas should

basis.

variation of the British measure from the American

is

sometimes

a source of confusion, because in the former, the British imperial gallon

(160 ounces) equals 4.546 3.785 liters (see page 6). tion of the British

liters

whereas the U.

It is

Chambers

of

S.

gallon (128 ounces)

is

encouraging to note that the Associa-

Commerce have by resolution suggested The Metric Committee of

the adoption of the liter as the standard.^

American Chemical Society have

the

equivalents should be published for

also

recommended

A very

recommended above.

that metric

photographic formulas

This world resolution

tion to avoirdupois values.*

the standard

all

is

in

in addi-

agreement with

clear article on the use of the

metric system in photography has been published by Chappell.''

Order of Chemicals

in a

Formula.

— When mixing photographic

solutions, the importance of following manufacturers' instructions can-

not be overestimated.

The

quantities

been established by extensive

tests

and the order of ingredients have to change them is very apt to

and

affect the useful properties of the solution. *

page

These are U.

S. units.

For

1

Brit. J. Phot. 64, 535 (ipi/)-

2

Phot. Rimd. 62, 130 (1925). Ind. Eng. Chcm. News Ed.

3

&

2, 2

(Oct. 10, 1924).

Amcr. Chcm. Soc. 81 (1925). Camera (Phila., Pa.) 47. i45-i55 (Sept. 1933)-

* Proc. 5

a discussion of the British imperial measure, see

6.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

4

The

order in which the ingredients are arranged in the formula

In some cases water

importance.

is

placed

first,

is

of

but

in other cases last,

as a general rule it should appear last and be written " water to make." With two- and three-solution developers, an exception to the rule maybe made if only one or two chemicals, such as sodium carbonate, are to be dissolved, when the total volume of water should be given first. It is also useful with most developer formulas (pyro and amidol excepted) to

include the expression, " water (about i25'-"F.) (52°C.) " at the top of

the formulas in a volume sufficient to dissolve readily It

is

all

the chemicals.

unnecessary, except in the case of difficultly soluble chemicals like

alum, borax, (52°C.).

to use

etc.,

Also,

water at a temperature higher than i2 5°F.

too hot water

if

is

used

much time may be wasted

in

cooling the solution to a temperature suitable for use.

When it is

mixing very large volumes of solution, as

sometimes simpler and more practical

will

be discussed

later,

to avoid the necessity of heat-

ing water higher than 65° to 7o°F. (18° to 2i°C.).

For simplicity, the volume given at the top of the formula should be

Then total volume of the solution. given as " cold water to make," the developer

an even quarter fraction of the the final dilution

more apt

to

is

be nearer the temperature for use than

if

if is

no instructions

were given.

Whenever a solution must be diluted for use, the expression " Stock Solution " should precede the formula. An example embodying these suggestions

is

as follows:

A

Stock Solution

Avoirdupois

Water (about

125° F.){52°C.)

Elon

Sodium

ounces

16

grains

60

Sulphite, desiccated

Cold water to

ounce ounce ounces

Vi Y^

Hydroquinone

make

32

Metric 500.0 cc 4. 1

15.0 15.0

grams grams grams

l.o liter

Stock Solution B Water

32

Sodium Carbonate, desiccated Potassium Bromide

30

The chemicals should be given dissolved, servative,

which i.e.,

in the case of a

V^

ounces ounce grains

in the order in

developer

sulphite, bisulphite,

is

1.0 liter

15.0 2.1

grams grams

which they are

usually as follows:

or metabisulphite;

2.

to i.

be

pre-

developing

agent; 3. accelerator or alkali such as carbonate; 4. restrainer or bro-

mide; If

5.

" water to

make."

a strong alkali, such as sodium hydroxide (caustic soda)

the water should always be written

first

and expressed as

is

given,

" cold

wa-


TERMINOLOGY AND ARRANGEMENT because on mixing, considerable heat

ter/'

is

5

evolved and the solution

is

apt to boil with explosive violence. If the formula contains sulphuric acid, the acid should appear at the end of the formula so that the concentrated acid will be added to the water. If this procedure is reversed, that is, the water added to the acid,

serious burns

may

be produced by a spattering of the acid caused by the

excessive heat generated on mixing.

Names and

Abbreviations,

— Although

it

common

is

designate particular chemicals by several different names,

practice to

it is

suggested

that the standard chemical terminology found in any good textbook of

Such archaic terms as carbonate of sodium, bichro-

chemistry be used.

mate etc.,

of potash, soda crystals, sulphuret of hydrogen, potassa carbonate,

In the same class

should be discarded.

carb., pot. bromide, ammonio-chloride, etc.

names

is

Sodium thiosulphate, used

commonly used

chemical

is

"'

name sodium

has been used for so

that practically everyone understands

it

is

commonly

is

This

not a fixing agent,

many years by photographers mean sodium thiosulphate.

in a formula,

preferably as a io9f solution to be added as so

than a dram

is

hyposulphite.

— When quantities

Small Quantities of Chemicals. i gram or 15 grains are included

under

to

It

in photographic practice.

quite a different substance and

but the term " hypo

be used.

of preferred chemical

as a photographic fixing agent,

called " hypo," an abbreviation of the

less

abbreviations like soda

list

given in the table of solubilities in the Appendix, page 338.

includes most of the chemicals

latter

fall

A

of chemicals

they are expressed

many

cc or drams.

If

required, an even quarter fraction thereof ought to

This plan avoids using " drops " as a unit of measure which

is

method of measuring the volume of a liquid. There is wide variation in the number of drops to a dram with liquids of different specific gravity. Even drops of the same liquid vary in size according to the shape of the mouth of the discharging vessel. Other a very uncertain

factors influencing the size of the drop are the rate of delivery of the liquid to

from the

vessel, the surface tension of the liquid,

which the mouth of the vessel

is

A

moistened.

and the extent

note published in the

some idea of the variation in shown is from 45 drops The average drop from with ammonia to 138 with ethyl alcohol (95 /c ) the usual dropping bottle or burette used in technical research work Photographic Journal of America

^

gives

volume which may occur. The range

in the table .

measures about

i

minim

or approximately one-twentieth of a cc.

Directions are given later for mixing percentage solutions. 8

Phot.

J.

Amcr.

S9,

412 (1922).


CHAPTER

II

PHOTOGRAPHIC ARITHMETIC AND CONVERSION OF FORMULAS In photographic practice, solids are weighed and Hquids are measured

by the avoirdupois

either

The

or the metric system.

following tables of weights and measures give

all

the equivalent

values required for converting photographic formulas expressed either in

metric or U.

S. liquid

measure.

Weights and Measures

— Conversion Tables

Avoirdupois to Metric Weight Pounds


:

..

ARITHMETIC AND CONVERSION OF FORMULAS Measure

British Imperial Liquid to Metric Quarts

Gallons

Drams

Fluid

(J'^x^s

CenUmeters

''»»*^^'»

1.0

4.0

160.0

1280.0

4546.0

4.546

0.25

1.0

40.0

.UO.O

1136.0

1.0

8.0

1.136 .02841

0.003125 0.2200

0.125 0.03520 35.20

0.8800

28.41

1.0 (60

min.)

3.551

0.2816 281.6

.003.551

.001

1.0

1000.0

1.0

Solid Conversion Values Grains

tirains

1

.,

l

<>

niiart

per British imperial quart multiplied by 0.833 = ounces f,, «,;! ,' .rlT.- ..^ (40 fluid ounces) pounds ^^^ ""''' """•^'^s) Grains per British imperial quart multiplied by 0.05696 = )>rams per liter = ftrams per liter Ounces per British imperial quart multiplied by 24.92 = grams per liter Pounds per British imperial quart multiplied by 398.7 = grains per British imperial quart Grams per liter multiplied by 17.54 = ounces per British imperial quart Grams per liter multiplied by 0.0401 Grams per liter multiplied by 0.002506 = pounds per British imperial quart

Ounces Pounds

]

Ounces

(fluid)

per British imperial quart multiplied by

Ounces

(fluid)

per British imperial quart multiplied by 25.00 = cubic centimeters

j

Liquid Conversion Values 0.8

= ounces

(fluid)

per U. S.

quart per

liter

Cubic centimeters per

liter

= ounces

multiplied by 0.03999

(fluid)

per Brit-

ish imperial quart

British texts sometimes refer to the Winchester

which equals

2

im-

perial quarts.

Example

of a

— When

Formula Conversion. it may

pressed in grains, ounces, anci pounds,

a formula

is

ex-

be converted into a metric

formula by using the above conversion values which take into account the difference between 32 ounces and

After a conversion has

liter.

i

been made, the values obtained should be rounded

off to

working quantities.

Tiie-errorintroduced in rounding

not be greater than

3%

and the

ratio

give convenient

off

a value should

between chemicals such as Elon

and hydroquinone or carbonate and sulphite should not be changed. Thus a developer formula for a 3^ gallon tank would be converted as follows

T^ Formula ,

Water (about

125° F.) (52° C.)

1

149

Elon

Sodium Sulphite (desiccated) Sodium Bisulphite Hydroquinone Sodium Carbonate (desiccated) Potassium Bromide Cold water to

Water (about

125° F.) (52°

....

.

Hydroquinone Sodium Carbonate (desiccated) Potassium Bromide

make

1 ounce 139 grains 83 grains 3hi gallons

Direct ounces 32 423^ grains

C).

Sodium Sulphite (desiccated) Sodium Bisulphite

ounces 240 grains grains grains

Gallon (Avoirdupois)

1

Elon

Cold water to

96 288

make

Conversion to

gallon grains

10

3

27'^ 82J4 165 23?^ 1

ounces 4 grains grains grains grains grains gallon

Rounded

Off 32 ounces 43 grains 3

ounces

28 grains 82 grains 165 grains 24 grains 1 gallon


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

8

Conversion to 4 Liters (Metric) Rounded

Direct

Water (about

125° F.) (52° C.)

10

..

Sodium Sulphite (desiccated) Sodium Bisulphite Hydroquinone Sodium Carbonate (desiccated) Potassium Bromide

make

Cold water to

liter

Off

1.0 liter 2.9 ftrams

2.94 grams 90.3 grams 1.88 grams 5.64 grams 11.28 grams 1.62 grams 4.0 liters

Elon

90.3

grams

1.9 grams 5.6 grams 11.3 grams 1.6 grams 4.0 liters

a formula called for 453^ grains and this quantity were cut to an

If

even 450, the difference would not be detectable by photographic means, though if a quantity of 6^ grains were cut to 5 grains, the error (23%) would be serious. In rounding

when

3.82

rounded off to

the quantity, for example, of Elon, in a formula, an

off

4.7% may

error of

grams

off in the

25.0 grams, a

separately

is

be introduced in bringing

made

is

opposite direction, that

7%

error

is

is,

if

if

to a certain value, as

the hydroquinone

26.8 grams

between the Elon and hydroquinone

do not change the

ratio

is

12%

is

which

is

in

rounding

between the constituents of a formula.

i

liter

the basic

liter

Liter

or :

pound

some value

practice of con-

in the avoirdupois

later time, reconverting the 8 gallon

liters is

fundamentally unsound.

i

quart formula.

120 Gallon Conversion.

a metric formula (grams per

I

The common

quart.

The 96

formula should be obtained by a direct conversion from

because each gram to

best

derived, whenever possible, from one

liter or i

96 ounces or to 3

ounce or 3 i

The

usually permissible in photographic work.

system such as 8 gallons and, at a

I

values

off,

verting a liter formula, for example, to

The

off

below 3%. is to keep the error, in rounding introduced would error that could then be be less than

basic formula, such as

to

in

changed.

watch that errors

Working formulas should be

formula

made

introduced and the

rule to accomplish this

The maximum

is

rounded

Neither of these errors taken

introduced.

It is important, therefore, to

6%

is

very serious in photography but since they were

opposite directions, a total error of nearly ratio

up

it

Then

4.0 grams.

in the

in the

i

liter) to liter

— A very rapid conversion

a 120 gallon

of

formula can be made

formula can be changed directly over

120 gallon formula with an error of

less

than 0.2%.

a simple matter to express fractions of a pound in ounces (avoir.) or to break the ounces into quarter fractions of an ounce. This scheme It is

is

of value, obviously, for large scale work.

In photography two kinds Percentage Solutions. are commonly used as follows:

of solutions


ARITHMETIC AND CONVERSION OF FORMULAS A A

A. B.

9

solid in a liquid.

liquid in a liquid.

The misunderstandings which have method

ing the correct

arisen from time to time regard-

of preparing solutions of a definite percentage

strength are due to the fact that there are three ways of doing

make a

example, we can

For

it.

s7( solution of potassium bromide as follows:

Dissolve 5 grams in loo cc of water. Dissolve 5 grams in 95 grams of water making 100 grams of solu-

1.

2.

tion.

Dissolve 5 grams in a

3.

In case

A

i.

little

we might have 102

chemist would use method

mass

water and add water to make 100

2.

because he

and not

of the solids in solution

and

cc of solution

is

in the

photographic work to

fill

cc. cc.

interested chiefly in the

volume, but method

used when preparing photographic solutions because tice in

about 97

in case 2.

common

it is

and

vessels to a definite level

3. is

prac-

it is

con-

venient to measure stock solutions or small quantities by taking a definite

volume of the

Method

solution.

i

not used for the reason that equal

is

weights of different chemicals do not occupy the same volume.

The percentage strength of a photographic solution, how much of the chemical is dissolved in 100

indicates

Table of Solubilities

(see

To

7%

prepare a

grams

cc.

ured

7

If

Appendix, page 338).

in

solution of potassium bromide, therefore, take 7

of the salt, dissolve

100

in a little water,

it

we now measure out 100

grams of the

I

10%

solution of a solid

ounce and making up to 10 ounces with water.

figures into solution.

to make we have meas-

and add water

cc of the solution

solid.

In the avoirdupois system a ing

therefore, merely

cc of the solution

grams and cc we have, roughly, 30 grams

Strictly speaking, this

is

in

not correct since

= 29.57

is

made by

tak-

Converting these

i

300

cc, or

ounce (U.

a

10%

S.)

ounce

=

28.35 grams and

i

10 fluid ounces

equivalent to 28.35 grams in 295.7 cc or 9.6 grams in

is

fluid

ounce (U.

S.)

cc so that

i

in

100. If a

photographic solution

or 3, the error involved

is

is

less

made by any

than

3%

of the above methods, 1,2,

and therefore

negligible for ordi-

nary photographic purposes, though since the correct method est, it

is

the easi-

should be followed.

Although somewhat of an anomaly, solution of a substance like

occupy a space of 100 cc)

A 10%

it is

possible to prepare a

100%

hypo by dissolving 100 grams (which do not

in sufficient

water to make 100 cc of solution.

solution of a liquid in water

is

made by

taking 10 cc of the


10

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

liquid

and adding water

to

make loo

cc.

The concentrated form of mean

certain liquids used in photographic practice does not necessarily

that the solution contains

ioo%

of the liquid or gas in question.

Sul-

phuric acid, pure concentrated, for example, represents a 95/^ solution; nitric acid, pure concentrated, 65%; hydrochloric acid, pure concentrated,

28%

35%;

37%

formalin,

ammonia

of

gas.

and ammonia,

of the gas, formaldehyde;

When

preparing a dilute solution of any of these

concentrated liquids for photographic use, however, their strength

100%.

usually taken as

prepared by taking

adding water

to

i

make

A 10%

solution of

ammonia,

When

diluting

most concentrated

the acid should always be added slowly to about sired

volume of water.

The

90% is

danger of the acid

articles,

much

the authors would clearly define the

if

Finally, water

the solution to volume.

In the publication of photographic

avoided

acids,

of the total de-

spattering on the hands and causing serious burns.

make up

is

solution should be stirred while adding the

acid to insure thorough mixing, otherwise there

should be added to

is

(28%) ammonia and

part of the concentrated 10 parts.

for instance,

whenever the term " percentage solution

" is

confusion would be method used by them

introduced.

Inconsisten-

and mistakes introduced by a lack of understanding of percentage solutions have been pointed out by Dobson ^ and Lockett.- Although cies

made is slight when small quantities are measured, it becomes when the percentage of the substance dissolved is 25%, 30%,

the error serious

or greater.

â&#x20AC;&#x201D;

Usefulness of Per Cent Solutions. The great advantage of any solution in parts per hundred is that a definite mental picture is at once created of its relative strength, and by means of a number of stock solutions it is possible to compound certain formulas by simply measuring out a definite volume of each solution thus dispensing with a balance. Thus supposing we have a 10% solution of potassium ferricyanide and of potassium bromide already at hand and it is

stating the strength of

make up

desired to

the following solution:

Potassium Ferricyanide Potassium Bromide Water to

then

it is

grams

2.3 grams 1.0 liter

only necessary to measure out 60 cc of the ferricyanide solu-

tion, 23 cc of the

solution

6.0

is

bromide solution, and add water up

made.

1

Camera Craft

2

Brit. J. Pilot. 70, 95 (1924).

2j, 2gi (1920).

to

1000 cc and the


ARITHMETIC AND CONVERSION OF FORMULAS In the case of very concentrated solutions

it is

11

not always possible to

use this method, though in view of the time saved and the accuracy of the

method

should be applied whenever possible.

it

Suppose a formula

gram.

calls for o.i

impossible to weigh this

It is

quantity accurately on the usual photographic scale, but by measuring out is

I

cc of a

less

10%

An

solved.

and adding

solution,

than lo cc

by means

is

end

mark and then allowed

until the liquid

The to

liquid

is

problem

a calibrated

is

sucked up into the tube

run out by placing the finger over the

even with the mark.

is

raising the finger slightly

which

of the chemical pipette,

tube with an orifice at one end. past the

this to the mixture, the

accurate and convenient method of measuring volumes of

It is

then discharged by

from the end.

â&#x20AC;&#x201D;

Photographic Arithmetic. much greater than

tity of solution

It is

often required to mix up a quan-

by the formula,

that given

in

which

case the photographer must perform a very simple exercise in arithmetic in

order to secure the desired result.

cate the

A.

method

Mix

The two

following examples indi-

of solution of such simple problems.

6 ounces of solution according to the following formula: Potassium Ferricyanide

4.0

Water

grams

10.0 grams 100.0 cc

Hypo to

(In order to simplify the arithmetic,

will

it

be assumed that

equals 30 cc instead of the more exact value, 29.57 cc.)

ounces

= 6 X 30 =

180

little

error introduced

is

X

^

ounce

X4=

6

7-2

18 grams of hypo.

Dis-

water and make up to 180 cc or 6 ounces.

The

grams of ferricyanide and 180/100 solve these in a

we need 180/100

Therefore,

cc.

i

Now,

1.7'

r

which

is

10

usually permissible in photographic

work. B.

How would

you mix

i

pint of a

7%

solution of sodium sulphite?

To make 100 ounces of a 7'^r solution we need 7 ounces of sulphite. i-i2 ounces Therefore, to make i pint (16 ounces) we need 0.16 X 7 i ounce dissolve therefore, or I ounce 53 grains. To prepare the solution, pint). ounces 53 grains of sulphite in water and make up to 16

= ( i

The Meaning

of " Parts."

â&#x20AC;&#x201D;

It is ofte^i

say, 10 parts of a solid in 100 parts of water. ingless because a solid chemical

though

if

the metric system

then grams and cc

may

is

is

recommended

weighed while a liquid

used, since

i

to dissolve,

Such a statement is

is

mean-

measured,

cc of water weighs

i

gram,

be considered synonymous with parts.

In the case of liquids, parts should be taken as meaning units of volume, and in the case of solids as units of weight. A " part " may there-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

12

fore

mean

either a gram, a ton, a cc, or a gallon so long as the other

same

quantities are reckoned in the

A

three partsl

B

one part

mav may mpan mean

V .

units of weight or volume.

(A ^oo

J

If the

and

avoirdupois system

liquids,

if

is

cc

^ IBioocc

A

1=;

^

ounces

1^5

ounces

f

nr or

J <

Thus:

J .

used and the formula contains both solids

ounces (liquid) and ounces (solid) are substituted for

" parts," the error involved falls within permissible limits.

Problem:

Mix

I

gallon of solution according to the following formula.

Sodium Sulphite

10 parts

Pyro

1

Water

Now,

I

part

100 parts

to

gallon equals 128 ounces.

Therefore, dissolve 12.8 ounces

of sulphite in water, add 1.3 ounces of pyro, and

make up

to

gallon.

i

For the sake of simplicity and clearness, however, exact quantities should always be given rather than " parts."

If this

is

done and a stand-

ard volume adopted for the total volume of the solution, directions for

mixing

will

be

much

easier to follow.

The Hydrometer

Test.

— Many photographers are accustomed

to

making up their stock solutions of hypo, carbonate, sulphite, etc., by means of the hydrometer. This method has the advantage that in case the hypo, for example, has become moist and contains an unknown quantity of water, a definite reading on the hydrometer will give a solution of the

When

same strength as

a stock solution

is

perfectly dry chemicals

if

had been used.

made from moist chemicals by

weighing, the

by the presence of water may be as high as 25% or 509^ The hydrometer method has the serious disadvantage that the ad-

error caused

justment of a solution to the required strength takes considerable time, the hydrometer reading does not convey

any idea

as to the percentage

strength of the solution, and the reading varies with the temperature.

For instance, say, 45 ister all

if

Baume

a stock solution

made with hot water and

this registers,

when

may

It is therefore absolutely necessary either to

48 or 50 Be.

readings

is

(Be.) on the hydrometer, on cooling, the liquid

the solutions have cooled to

room temperature,

reg-

make or to

prepare a table giving the variation of density of each solution with temperature.

For example, the

specific gravity of acetic acid at 59 °F.

(i5°C.) with increasing concentration of acid increases to a value of 1.07 at

A

hydrometer

80% is

and then decreases

to 1.058 at

99%

maximum

acid.

useful, however, in checking the strength of certain

liquid chemicals such as alcohol, acetic acid

and sulphuric

acid.

If

a


ARITHMETIC AND CONVERSION OF FORMULAS solution

known

is

13

pure ethyl alcohol and water, for ex-

to contain only

ample, then from the hydrometer reading at a definite temperature, the percentage strength can be determined with accuracy.

Mixing stock solutions by hydrometer cause

it is

much

simpler to

compound

hydrometer reading, however,

sometimes a rough check that the solu-

been mixed correctly.

tion has

A

is

recommended beby weighing. A subsequent

test is not

these

hydrometer

The only way

test of a

mixed developer has no meaning whatever.

to test a developer

tographic material for which

Hydrometer readings no relation

to the

it is

is

to

develop actually therein the pho-

intended.''

of acid hardening fixing baths also bear little or

time required for the film to clear and therefore repre-

method

sent an unreliable

of checking the condition of a fixing bath

(see further details on page 162).

as

Hydrometers are graduated according to many different scales such Baume, Twaddell, etc. Others read directly in specific gravity which

volume of the liquid to the weight same volume of water at a standard temperature. Dilution of Liquids. It is often required to reduce the percentage strength of a solution. For example: How would you mix two gallons gives the ratio of the weight of a given

of the

â&#x20AC;&#x201D;

of 289^ acetic acid, from a supply of glacial acetic acid?

To make 100 cc of 28% acid we need 28 cc of glacial acid. To make i cc of 28% acid we need 28/100 cc of glacial acid. To make 2 gallons 7570 cc of 28'/^ acid we need 28 X 75-7 ^2120 cc (71^ ounces) of glacial acid.

Therefore take 71? ounces 2120 cc of glacial acid and add water to

make

To

2

gallons 7570 cc.

dilute a solution three times

we do not add

three times the

of water but approximately twice the

volume and so on.

One volume

volumes of water

of solution plus about

solution which

is

2

volume

For example:

=

3

volumes of

one-third as strong or three times as dilute as the

original.

Stock Solutions.

â&#x20AC;&#x201D; A stock

solution

is

a concentrated solution to

which water is added before use. In the case of simple solutions containing only one salt such as potassium bromide, sodium carbonate, etc., a 10% solution is most convenient because by dividing the volume of the solution in cc by 10 we get the number of grams present in the solution.

Thus 3

"

75 cc of

10%

potassium bromide contains

Photographic Methods of Testing Developers Amcr. Ann. Phot. 36, 184 (1922).

^9> 153 (1922)

;

"

by

7.5

J. I.

grams. Crahtree.

Brit. J. Phot.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

14

The

limiting strength of solution

which

it is

possible to

make

particular case depends on the solubility of the chemical,

in

any

and as the

solubility diminishes with temperature a solution should not

be made

stronger than a saturated solution at 40째F. (4.4째C.), otherwise in cold

weather the substance would crystallize out (see table of

solubilities

given in the Appendix, page 338).

A sible

stock solution of sodium sulphite should be

(20%

tion oxidizes very slowly

solution

it

made

as strong as pos-

of the desiccated salt) because at such a strength the solu-

and

will therefore keep,

combines with the oxygen

in the air

whereas in weaker

very readily and

is

then

useless as a preservative.

In making up any stock solution,

its

strength should be such that

can be diluted easily to give a solution of working strength. ample, hypo

often mixed as a

is

volume of water a triple, or

2 5

%

solution

50% is

solution

it

For ex-

and then by doubling the

This plan of mixing double,

obtained.

quadruple strength stock solutions

is

often a valuable

means

of

saving both space and time.

The term is

"

Stock Solution " should precede a published formula that

to be diluted for use, as otherwise there

a formula

may

is

always the possibility that

be mistaken for a working solution.


CHAPTER

III

APPARATUS AND METHODS OF USE

Types of Weighing Devices. Apparatus for weighing chemimay be classified conveniently into several sizes according to the maximum volume of solution to be prepared as follows: Four Liters (i Gallon). A small double pan scale weighing to cals

100 or 200 grams {y\ to studio use.

Fig. ia

Two common

— Small studio

One Hundred of

ounces)

7

is

satisfactory for amateur or small

types are shown

in

Figures

i.A

or lal)oiator>- scale, capacity 100 prams

—A

Liters (25 Gallons).

for the

moderate

size studio,

ounces).

(3'.

scale having a capacity

5000 grams (about 10 pounds) should be provided.

ample

and iB.

It

should be

photofinishing plant, and x-ray

laboratory (see Fig. iC).

Four Hundred Liters (100 Gallons).

— For

large commercial es-

tablishments, photofinishing plants, and small motion picture laboratories a scale

weighing from 8 to 10 kilos

(

18 to 22 pounds)

is

required.

shown in Figure iD is very satisfactory. Oscillations of the pointer are damped by an oil dash pot. The capacThis model may ity of the model shown is 12.5 kilos (27-^ pounds). also be used for small scale weighing by removing the large scoop and its For. rapid weighing, the type

tare weight.

Two Thousand Liters weighing

in either

(500 Gallons) or More.

— Platform

scales

kilograms or pounds (and ounces) should be pro-


A

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

16

Two

vided for work requiring very large volumes of solutions. are

shown

These are satisfactory

in Figure 2.

for large

types

motion picture

laboratories or very large commercial plants. It

may

be desirable to have two or more types of scales in the larger

establishments to facilitate rapid mixing of small as well as large vol-

umes

of solution, such as the type

shown

in

Figure

iD and

Figure

2

and 2B.

Fig.

Small laboratory scale, capacity 500 grams (i pound). Torsion Balance Co., New York, N. Y.

IB

Weighing Very Small Quantities sionally required to

mix very

of Chemicals.

gram

is

needed which

will

For such work, a sensitive

weigh accurately

(or fractions of a grain).

Figure

3.

Type A with

general use.

Two

is

0.02

in

hundredth parts of a

types of balances are illustrated in

the hinged glass cover

Its sensitiveness

It is occa-

dilute solutions of chemicals, particularly

of dyes for toning or desensitizing baths.

balance

â&#x20AC;&#x201D;

Courtesy

gram

(

is

a practical balance for

1/32 grain) and

its

capacity,

120 grams (4 ounces).

Type B

represents a

more accurate balance commonly used

in

ana-


APPARATUS AND METHODS OF USE lytical

work.

rider as

It is

equipped with a calibrated chain instead of a movable

One end

on type A.

arm, the other to a vernier weight of the chain

The chain

is

17

is

added

moved by

of the chain

is

attached to the balance

As the vernier scale is lowered, more the balance arm and less as it is raised.

scale.

to

rotating a crank extending through the side of

the balance case.

Fig. ic

â&#x20AC;&#x201D; Double

pan

scale,

Courtesy Torsion

capacity 5 kilos (10 pounds).

Balance Co.,

New

York, N. Y.

Balance pans should preferably be made of a non-corroding metal, such as nickel, 18-8 stainless steel,* or nickel-plated brass, although porcelain pans are also satisfactory.

Containers for Mixing. glass flasks

*

known

â&#x20AC;&#x201D; For small volumes

as Erlenmeyer

flasks are the

There are several manufacturers of the type of

(18% chromium-8%

The

of solution, conical

most suitable mixing

stainless steel

known

as

18-8

i8-8 stainless steel to photographic solutions varies somewhat, however, depending on the content of carbon, molybdenum, titanium, zirconium, selenium, etc. and the heat treatment which the steel has received at the mill. A method of testing 18-8 stainless steels for their resistance to corrosive attack by photographic solutions is described on pages 53-57-

Two

nickel).

corrosion resistance of

recognized text books on stainless steel are the following

:

" Stainless Iron

and

Steel," by J. H. G. Monypenny, Chapman & Hall, London, 1926, and "The Book of Stainless Steel," Amer. Soc. of Steel Treating, 7016 Euclid Ave., Cleveland, Ohio.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

18

vessels.

(see Fig.

For larger volumes use enameled pails or hard rubber buckets 32D, page 66) For still larger volumes, tanks, drums, or crocks .

of a suitable material such as

ware, or an 18-8 stainless

Fig. id

wood, Alberene stone, hard glazed stone-

steel,

â&#x20AC;&#x201D; Single pan and scoop

such as Allegheny metal (Fig. 4)

scale.

may

Courtesy Fairbanks, Morse & Co., Chicago, 111.

be used.

For large scale work the solution should be pumped or emptied

by gravity

into a larger storage tank

mechanical

stirrers

and allowed

where

to clear

by

it is

thoroughly mixed with

settling before

emptying into

the circulating tank (see Fig. 19, page 39).

Weighing and Measuring.

â&#x20AC;&#x201D; Chemicals

should

preferably

be

room which is separated from the developing room and care should be taken when handling such

weighed out and the solutions prepared

in a

substances as hydroquinone, resublimed pyro, potassium ferricyanide, etc.,

not to shake the finer particles into the

air,

otherwise they

may

enter

the ventilating system and settle out on benches or shelves where negatives

and prints are stored.

Such chemical dust almost invariably pro-


APPARATUS AND METHODS OF USE

19

duces spots and stains (Fig. 5) particularly if the sensitive materials are wet when contaminated by the dust particles. It is good practice to

mix developers and

fixing baths in separate rooms, in order to avoid

possible contamination of developers

â&#x20AC;&#x201D; Platform

Fig. 2\-

with beam.

scale

Fairbanks, Morse

&

Fig. 2B

and

mixing vessel do not shake the paper but drop water to flow over

it

â&#x20AC;&#x201D;

dial.

111.

pieces of paper

any

bath chemicals.

fixing

Platform scale with Courtesy Toledo Scale Co., Toledo, Ohio.

Courtesy

Co., Chicago,

Weigh out chemicals on

by the

after transferring to the

it

into the sink

so as to dissolve the dust.

and allow

Larger quantities are

most conveniently weighed out in buckets. Shallow wooden trays about 16 by 20 inches and lined with rubberized cloth are useful containers for weighing out large quantities of chemicals previous to dissolving (Fig. 6).

A

different tray preferably should be used for each chemical

by marking the or

tray.

Metal scoops made of aluminum,

and

labelled

stainless steel,

Monel may be used effectively for weighing large quantities of chemiThey should be washed out carefully after weighing each different

cals.

chemical to avoid contamination.

The

zero points on

quent intervals tant

all scales

and balances should be checked at

to insure accurate weighing.

when using

This

is

fre-

especially impor-

sensitive balances for weighing small quantities.

For small volumes

of liquids a glass graduate

marked

off in cc or


V

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

20

For larger volumes use a bucket previously

ounces should be used. graduated, or

mark

off the inside of the

tank or crock used for mixing

(see discussion on paddles on pages 24-2 7 )

When

.

measuring a liquid

a glass graduate place the eye on a level with the graduation

Fig. 3A

â&#x20AC;&#x201D; Chemical and dyestuffs balance with sion Balance Co.,

New

in the liquid until the lowest part of the

with

this level.

it

warm

is

drawn up the

sides so that

made

as

shown

liquid contracts

Dissolving.

in Figure 7

and

at

its

solubility

and degree

temperature of the solvent, and the rate of

effect

is

side-

All readings

room temperature because

on cooling.

â&#x20AC;&#x201D; The rapidity with which a substance

solvent depends on

stirring

on viewing

appears as though the liquid has two surfaces.

should be a

curved surface coincides

to capillary attraction the liquid in contact with

the walls of the graduate

ways

Courtesy Tor-

calibrated rider.

York, N. Y.

pour

Owing

in

mark and

dissolves in

any

of fineness, the nature

and

stirring.

The method

of

very important and the shape of the paddle has considerable

on the rate of dissolution (see paragraph discussing paddles on

pages 24-27).

Most

solutions are rendered completely

homogeneous


APPARATUS AND METHODS OF USE

21

only with difficulty. caustic soda, will

if

For example, when mixing solutions containing they are not thoroughly agitated the heavier caustic liquid

remain at the bottom and when used the solution

form composition.

them thoroughly

Fig. 3B

It is

warm is

water with

usually

The

way

is

is

usually

more

stirring.

warm enough

Water

to dissolve

is

be of uni-

solutions to stir

Courtesy Christian Becker,

soluble in

of mixing a solution

will not

all

complcttYl and before use.

balance using calibrated chain. Inc., New York, X. Y.

Since a chemical the quickest

after the mixini:

:it:;)in

— Chemical

important, therefore, with

to

warm

water than

in cold

powder and dissolve

at a temperature of

it

in

i25°F. (52°C.)

most photographic chemicals

readily.

use of water at higher temperatures, especially boiling water,

is

not

recommended because there may be danger of decomposing the chemical and if the solution is to be used immediately, it will require considerable time to cool the solution to the required temperature. Since most solutions are intended for use at ordinary temperatures (65° to 7o°F.) (18° to 2i°C.), the solution

must be cooled

off

if

very hot water

again

if it is

is

used for dissolving,

required for immediate use,


:

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

22

though usually the time taken to do

would be taken up

this is less

than the extra time which

in dissolving the chemicals in cold water.

When

mixing, therefore, as a general rule, dissolve each chemical in as small

a volume as possible of water at about i25°F. (52°C.), cool, and dilute

Fk;. 4

— Stainless

stt'cl

(iS-S) mixinti tank and

The gallons or 75 liters capacity). hard rubber faucet and pipe is inserted through a stirrer

(20

and held

soft rubber stopper

in place

with a metal

plate.

with cold water.

oughly

if

After diluting with water, shake the solution, thor-

in a bottle,* or stir

if

in a tank, otherwise the

water added will

tend to float on top of the heavier solution.

When

mixing a solution

in

a tank,

it is

possible to proceed in one of

two ways A. Dissolve the chemicals separately in buckets or small vessels, add

each solution to the tank

ume B.

Add

filled half

*

in the

necessary order, and then dilute to vol-

with cool water. the solid chemicals directly to the large mixing tank which or three-quarters full with water at 65° to 75°F.

To permit thorough mixing,

the capacity of the bottle should be

than the volume of the solution to be mixed.

is

(18° to

somewhat larger


APPARATUS AND METHODS OF USE 24°C.).

23

After diluting to volume with cool water, the temperature of

the solution will be about right for immediate use.

It

is

very important,

however, when mixing very large volumes of solution, such as looo gallons (4000 liters) or more, to avoid the necessity of cooling the final solu-

FiG. 5

— Spots produced

on film by chemical

dust.

Hypo

(left)

and potassium

ferricyanide (right).

Fig. 6

— Trays lor weighing chemicals.

tion, as this operation takes considerable time,

which

may

be shortened

only by the use of an expensive refrigeration installation.

For large scale mixing, method B.

is

usually to be preferred.

practice to dissolve the chemicals directly in the tank w^hich

developing and

facilities

is

It

is

should be provided for filtering the solution at

some point between the mixing and developing tanks. When dissolving finely powdered Caking of Chemicals.

cated

salts,

there

is

bad

used for

a tendency for the salt to form a hard cake

quantities of the chemical are

dumped

if

desic-

large

into the water without stirring,


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

24 or

if

the water

is

added

This

to the chemical.

is

due

to the

tendency of

the desiccated salt to combine with water to form a crystalline compound.

This cake dissolves very slowly and

by pouring the

salt slowly into the

formation should be avoided

its

water while agitating the solution

vigorously.

30

UQ ^ \0

*v_y Fig.

7

â&#x20AC;&#x201D; Position

of eye

when judging

level

Another way of decreasing the caking

is

of liquid in a column.

to use chemicals

not too finely powdered, since the smaller the particle

size,

which are the greater

the caking tendency, especially with chemicals such as sulphite and car-

bonate.

now

So called granulated samples of

many

desiccated chemicals are

more quickly, have less tendency to float on the surface of the water, and are practically dustless when handled. The monohydrated variety of sodium carbonate, howavailable which pour easily, dissolve

ever, does not appear to

have any

less

tendency

to

cake than the desic-

cated variety.

As a general working rule, however, for all desiccated salts, the chemialways be added slowly to the water with stirring and not water to the chemical, or some caking trouble may be encountered. Equipment for stirring chemiMethods of Stirring Solutions. cal should

â&#x20AC;&#x201D;

cals

when mixing

as the mixing

solution

up

is

solutions

done:

to 100 or

i.

may

be classified into two types according

by hand

or 2.

by machinery.

200 gallons, hand mixing

is

For volumes of

usually employed, but


APPARATUS AND METHODS OF USE for larger volumes,

mechanical

more

stirrers are

efficient.

chanical stirrers also offer advantages for mixing volumes of

25

Small me2 5

gallons

or more.

The

simplest type of stirring device

either as a solid rod or as

Fig. 8

â&#x20AC;&#x201D; T> pes of hand A

sealed at both ends (see Fig. 8).

which

fits

is

a rod, preferably

heavy walled tubing (about

made

of glass,

| inch diameter)

stirring devices.

rubber hose or jacket (i inch long)

snugly around the end will usually prevent breakage of either

the rod or the vessel in which

used.

it is

A

stirring rod is only satisfac-

tory for use with very small volumes of solution, usually not greater

than

2

gallons.

If a glass

tube

is

chosen, a cork

may

be forced tightly

into the glass tube before sealing the ends in such a position that the

bottom of the cork

will serve as a

measure of volume when the rod is Additional volume calibra-

held upright in a particular mixing crock. tions

may

be made

in several

by choosing the length 2. by marking by putting more than one cork in the

ways as follows

:

i

.

of the cork so that both ends represent definite volumes,

the side of the cork with ink, or

3.


26

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

tube.

Too many

confusing.

A

calibrations should not be

made

become should be wedged

or they will

small card explaining the calibrations

into the tube.

For mixing volumes of solution from 8 in size, a useful

Fig. 9

to

40

liters (2 to

10 gallons)

mixing device consists of a metal rod (Monel, nickel,

â&#x20AC;&#x201D; Motion of paddle

for efficient agitation of deep nar-

row width

tank.

or Allegheny metal) with a metal disk fastened to one end (Fig. 8).

This

stirrer is

used

much

like the old-fashioned

hand churn by moving

up and down inside the mixing vessel. A wooden stick or paddle made of hard wood such as maple or cypress is a convenient form of stirrer for volumes up to 100 or 200 gallons (400 or 800 liters), but a separate paddle, marked with the name of the soluthe handle

tion,

should be used for each solution, to eliminate the possibility of con-

tamination.

Wooden

paddles should not be wax impregnated to resist

the action of the solution, because this treatment decreases their

resili-

ency and with hot solutions some of the wax is apt to melt and get into the solution. When the solution becomes cool, the wax particles, unless filtered out,

may

settle

on the surface of the

film.

The paddle shown second from the right in Figure 8 deep tanks by pushing it vertically down along one or crock,

is

used

in

narrow

side of the tank

moving it across the bottom by using the top edge of the vessel and drawing it upwards along the opposite side of the

as a fulcrum, vessel.

The paddle on

type which

is

the extreme right in Figure 8

used most effectively by thrusting

it

is

the conventional

vertically inside a


APPARATUS AND METHODS OF USE

27

tank along one wall and moving the blade through an arc by using the top edge of the tank as a fulcrum as shown in Figure 9. Considerable agitation may be secured with this type of paddle, providing the diameter of the tank

is

enough

large

to permit the

movement

of the paddle

through a fairly wide arc.

Fig. 10

â&#x20AC;&#x201D;-Portable

stirrer installed in a large

mixing tank.

Courtesy

M-G-M

Laboratories, Hollywood, Calif.

Notches cut

in the side of a

wooden paddle may

measuring a definite volume of solution

serve as a

in a particular

means

of

tank or crock by

holding the paddle vertically and adding water to the mark.

Mechanical Stirrers. types, namely, portable in

â&#x20AC;&#x201D; Mechanical

and stationary.

stirrers

two general is

supplied

a variety of sizes with telescoping metal shafts which, for photographic

solutions, should be stirrers

may

made

of nickel,

Monel, or 18-8

stainless steel.

The

be clamped onto the edge of the vessel or tank, as shown in

Figure 10, which represents an actual illustration

a large motion picture laboratory. is

are of

The former type

attached to the

stirrer.

in

a mixing room of

The motor

( 1/20 to 10 horse power) The blades are arranged to create an upward

current which insures thorough mixing, as shown in Figure iiA.

The two most common

types of stationary mechanical stirrers are the

mixing

tank

(Fig.

11 A)

and

1.

those

2.

those installed horizontally, through the side and near the base of the

installed

vertically

in


28

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

tank (Fig. iiB).

A

suitable stuffing

box

is

fitted at the point

where

the drive shaft enters the tank to prevent leakage.

In general, an electric motor should never be placed directly over a solution unless

it is

enclosed tightly, owing to the danger of contamina-

tion with oil from the

motor

shaft.

— Agitation

Fig. iia^

able vertical stirrer.

currents formed by port-

Courtesy Mixing Equipment

Co., Rochester, N. Y.

Theory

of Stirring/''

— Most

photographic chemicals are fairly

soluble in water at normal temperature and the majority are readily solu-

The method of stirring is not so imwhen mixing small volumes of solution, but it is of importance

ble in water at 125° F. (52°C.).

portant,

from the standpoint

of time saved, cost of labor,

when large volumes are The movement of the paddle

solution

to

and

clarity of the final

be mixed.

or stirring device

may

be considered

from several standpoints according to the nature and effectiveness of the motion produced. These different movements are as follows: * The authors are indebted for many Equipment Co., Rochester, N. Y.

of

tlie

ideas in this section to the

Mixing


APPARATUS AND METHODS OF USE I.

Free Rotational.

stirring

movements.

— This ^

It is

one of the most

is

tical shafts

supported

sets of horizontal paddles as

Fig.

I

common

types of

usually effected with stirrers which have ver-

one or more

of stirrer tends to set

29

in the center of the

mixing tank and which have

shown

in

Figure 12.

This type

up one or more horizontally moving layers

IB

— Agitation

in the

currents set up by hori-

Courtesy Mixing Equipment Co.,

zontal stirrer.

Rochester, N. Y.

mixing vessel (according to the number of paddles) and rate of solution.

slow

If the solution contains an alkali of heavier density

than water, the solution

probably tend to be denser at the bottom

will

than at the top. 2.

effects a

Impeded Rotational.

— This movement

is

similar to the free ro-

around the side of the tank created by the uniform motion

tational except that there are baffles installed

which tend

to

break up the stratification

of horizontally

moving paddles.

cals results with a

tendency 3.

mixer of

More

this type,

rapid dissolution of the chemi-

but there

is still

a fairly strong

for separate layer formation.

Vortex Movement.

— When a propeller type

of stirrer

is

placed

near or in the center of a liquid column, the rotation tends to create a

downward time.

swirling motion which assumes a vortex shape in a very short

This stirring motion

is

useful

when

dissolving a light fluffy solid

on the surface, but a considerable quantity of air This latter feature is is introduced into the solution at the same time. photographic somany because objectionable in photographic practice

which tends

to float


2

PHOTOGRAPHIC CHE^HCALS AND SOLUTIONS lutions are oxidizable

by

Furthermore, the entrapped

air.

air

bubbles

tend to cling to film surfaces and produce airbell markings. 4.

â&#x20AC;&#x201D; Most

Controlled Directional Flow.

liquid or liquid-liquid solutions

is

effective

mixing of

solid-

secured by stirring devices which in-

sure a controlled directional flow of the liquid within the mixing vessel.

Fig.

Motor driven

1

Paddle

vertical

shaft.

stirrer.

This flowing motion should be largely vertical and of drive

the top. ler,

heaw

any

solid or liquid portion

Such motion

is

best secured with the aid of a rotating propel-

the blades of which thrust

tion.

The

entire

mix

in a vertical plane.

same shaft

if

in a

is

sufficient force to

from the bottom of the vessel to

downward

in

an angular off-center posi-

thereby turned over and over from bottom to top

Two

or

more propellers ma}' be employed on the

deep tank (4 to 8

feet)

but their action should not be

opposed or their efficiency will be reduced. are used, the bottom blade

is

unable to

lift

\Mien opposed propellers

materials of different densities


APPARATUS AND METHODS OF USE

31

from the tank bottom, because of the retarding downward current of the upper blade. Propellers of the type described are

shown

tached to a portable stirring device and

motor

Figure

fitted to a shaft entering the side of the tank.

preferred for almost

all

Fig. 15

The

1

1,

A and

if

B, at-

a gear drive

Type A

is

to

be

photographic mixing operations on a large scale.

â&#x20AC;&#x201D; Glass funnel

fitted

with

filter cloth.

position of the propeller in relation to the tank design

Xow,

tant.

in

this, in turn, to

the tank

best results are secured

is

is

impor-

considered to be di\ided into four quadrants,

when

the stirrer

is

attached to the wall and in-

own quadrant.

In very

clined so that the shaft will rotate within

its

large tanks of

installation should be used.

The

3000 gallon capacity, a side

shaft should enter the tank on a line parallel with but off the center

line to insure a controlled directional flow.

These types of

stirrers represent

more rapid mixing with which have

less

free rotational or

is

to

dust in

is

possible with mixers

impeded rotational motion.

â&#x20AC;&#x201D;

The purpose of filtering and clarifyremove suspended matter such as dirt caused by the presence of the chemicals used and also any residue or undissolved particles

Filtering and Clarifying. ing

compact mechanisms which insure

power outlay than

which might

settle

on the sensitive photographic material during de-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

32

Furthermore, while some solu-

velopment, and produce spots or stains.

and

tions are being exhausted, for example, certain developers

fixing

and and scum which should be removed

baths, they tend to accumulate a sludge consisting of by-products

foreign matter, such as gelatin, dirt,

from the solution several times during

its

in order to prevent the

life,

sediment from adhering to the emulsion surface and causing spots and stains.

Filtration

may

be defined as the act of separation of a solid from a

by passing

liquid brought about

through the

filter is

known

to clear

allowing the particles

them by

The

etc.

liquid

which passes

as the filtrate, whereas the solid remaining

Clarification

in the filter is called the residue or filter cake.

term meaning

medium

the liquid through a filtering

such as cloth, paper, charcoal, sawdust,

a broader

is

up a suspension or cloudiness in a solution by to settle out by sedimentation, or by removing

In photographic work, the purpose of filtering

filtration.

is

usually to remove a small quantity of solid from a large volume of liquid.

The

filtration of

water to be used for mixing photographic solutions

represents a specialized application of filtration and

is

discussed in

Chapter VI, page 107.

The removal

of particles

remaining

in a solution after

may

mixing

be

accomplished by any of the following methods: A. Allow the solution to stand and draw pernatant liquid.

pended matter

is

This method so fine that

it

is

off or

decant the clear su-

particularly useful

will pass

when

through a coarse

the sus-

filter.

Since coarse particles settle quickly, the rate of settling of a semicolloidal sludge

can usually be hastened by mixing the solution

in

hot

water, because the heat tends to coagulate the suspension and causes the particles to cluster together.

Thus

crystals of

if

sodium sulphide

which are brown from the presence of iron are dissolved

in

hot water

the colloidal iron sulphide coagulates and settles out rapidly leaving a perfectly colorless solution.

B. Filter the solution through fabric or (Fig. 13).

Filtering through paper

is

filter

continual dropping of the solution exposes oxidation.

It

is

usually sufficient to

paper held

in a funnel

usually a slow process and the

filter

it

to the air, thus causing

through very

fine cloth or

muslin suspended from the edge of a glass funnel or an enameled

New

pail.

washed thoroughly, otherwise the sizing matter in the fabric will be washed into the solution and settle out as a sludge. C. As a modification of method B, when mixing a quantity of solution in a tank, stretch a filter bag made of strong toweling cloth (28 mesh) cloth should be


APPARATUS AND METHODS OF USE

33

over the tank, place the chemicals in the bag (about 6 inches deep) and allow hot water to flow into

and the solution

it.

filtered at the

In this

same

way

used for each solution so as to eliminate

Fig. 14A

Fig. 14B

The method is

fitted

â&#x20AC;&#x201D; Frame support

over a wooden frame and

less steel

bag is

A

all risk

for filter bap:

â&#x20AC;&#x201D; Method of supporting

of supporting the

the chemicals are dissolved

time.

filter

is

separate bag should be of contamination.

on deep tank.

bag over top of deep tank.

shown

in

Figure 14A.

held in place by

means

The bag

of four stain-

bars passing through loops along the edges of the bag.

In the case of deep tanks, the wooden frame can be dispensed with


:

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

34

by adopting the arrangement shown in Figure 14B. The cloth bag 5 inches deep is supported by means of bars passing through seams along opposite edges of the bag, and in turn the bars are held in place either by means of two pieces of wood passing over the ends of the bars as shown, or by metal stirrups fitted to the sides of the tank. It is important, when filtering chemicals through a bag, to add only comparatively small quantities of the chemical to the bag at one time. about

Warm water bag

(about i25째F.) (52째C.) from a hose should be run into the

slow stream, and as the chemicals are dissolved, more of the

in a

solid should be added.

If too

much

solid

and

for caking with desiccated salts

is

added, there

this interferes

is

a tendency

with the rapid dis-

solving of the chemical.

Some substances

are so finely divided that they will pass through a

bag unless one

filter

of very fine

mesh

is

used.

This

is

true of most de-

veloping agents, which therefore should be dissolved separately in as small a volume as possible of water at i25째F. (52 째C.) and then the solution poured into the filter bag.

The

sulphite

and carbonate compo-

nents of a developer may, however, be mixed and filtered by the bag

method.

In preparing large volumes of stock solutions of single chemi-

cals such as

hypo

or carbonate the filter

bag plan

offers

a rapid and

thorough method. It

is

important that the bag used should be wide and not too deep,

otherwise

will dip into the solution

it

and the chemicals

will dissolve

very slowly.

D.

A

A and C

combination of methods

is

the best and most desirable

as follows

For quantities of solution up

to 5 gallons, filter

through a cloth into

a bottle or crock fitted with a side tube of hard rubber inserted through a soft

rubber stopper (see Fig. 79, page 196). In this way the fine parout but the drainage tube is sufficiently high so as not to

ticles settle

disturb the sediment.

Charles

^

has described a number of useful methods of dissolving

chemicals which involve the suspension principle.

As one scheme, he

suggests adding the solid chemicals to a perforated earthenware pot

(such as

is

sold for electroplaters' use)

entirely below the surface of the water. inside the pot so that the solution

is

and suspending

A

filter

filtered as

this

pot almost

cloth could be placed

soon as the chemicals are

dissolved.

For small scale plants, the solutions should be mixed 1

Brit. J. Phot. 71, 519 (1924).

in

separate


APPARATUS AND METHODS OF USE

35

wooden vats or stoneware crocks in the chemical room, where they can by settling before transferring the clear liquid to the darkroom.

clarify

A

simple device for developer clarification consists essentially of a

water pump, a trap, and a vacuum nozzle as shown

FiG.

â&#x20AC;&#x201D; Suction

15-

device

and de-

in Fig. 15

removal of developer tank

for

sludge.

scribed

by

Ives, Miller,

and Crabtree.-

to stand overnight or until clarified

moved by

inserting the

tice,

the bulk of

much

solution should be allowed

bottom

in the

re-

nozzle in the solution and moving

it

up the sludge. With practhe sludge may be withdrawn rapidly without removing

carefully along the

very

vacuum

The

and the sediment

bottom so as not

to stir

of the liquid developer.

In a recirculating system as used on automatic developing machines for

motion picture work (see Fig. 90, page 211),

the sludge

by

on the return or suction

inserting a filter line

filters

it is

from the machine

to the circulating tank.

as used in other chemical processes

rapid filtration (Figs.

In addition to the

possible to

remove

at some point in the system, for example,

may

Pressure

be necessary for

16A and 16B).

filtering

media described, several others are

avail-

ble as follows: 1.

Sawdust contained

in a perforated

bulky and inconvenient 2.

-

to

Several types of charcoal. J.

box or

vessel.

This

handle when replacing the

Soc. Mot. Pict. Eng. 17, 26 (July 1931).

is

rather

filter.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

36

form of powder or cakes.

3.

Silicious materials in the

4.

Fine wire and glass-cloth screens.

5.

Paper pulp,

Fig.

To

i6a-

etc.

Small plate pressure filter showing construction. Engineering Co., New York, N. Y.

date, few of these materials

Courtesy Alsop

have been used by the photographic

industry but some of them will undoubtedly find extensive use in the future.

In the filtration of a gelatinous precipitate, such as a silver chloride sludge, a simple working

filter

can be constructed economically by lining

wooden box with canvas (Fig. 17). The box should be about 8 inches wide, 2 feet deep, and 4 feet long, or, if smaller, of about the same proportions. Since the perforations weaken the strength of the sides, these should be held together preferably at each end by a perforated

several metal bolts of 18-8 stainless steel. filtration to

add some

silicious

powder

It is

necessary for efficient

to the solution to

be

filtered to

prevent the gelatinous sludge from plugging up the pores of the canvas.

Such filters

filter

(see

aids are obtainable from several companies manufacturing

Appendix, page 342).


APPARATUS AND METHODS OF USE When quired. large so

filtering a silver sulphide sludge,

37

a different type of box

The box should be a shallow one, about 6 inches deep and that the sludge, when settled, will represent a thin cake.

A

box should be perforated and lined with canvas.

filter

aid

is

is

re-

fairly

The

necessary

to prevent stoppage of the pores in the canvas.*

Fig. i6b

â&#x20AC;&#x201D; Detail

of plate pressure

filter

Alsop Engineering Co.,

One

useful type of mixing

and

showing construction. York, N. Y.

filtering

apparatus consists of an enamel

lined mixing tank fitted with a portable stirrer.

through a small gear is

pump

to a

connected to the storage tank.

pressure

forated metal screen cylinders separated

paper or

filter

cloth

(Fig. i8).

is

filter

is

placed.

forced through the sides

*

The authors are indebted embodied

in this section.

to

Mr. R.

is

connected

which, in turn,

consists of

by a wrapping

a pressure of about 25 pounds per square inch.

tions

filter

These three units

cylinder on which a tightly fitting cover

the base of the column and

This tank

compact pressure

The

Courtesy

New

fit

two per-

of either

filter

inside a metal

The

liquid enters

by the pump under

The pump may

also

S. Scott for several of the filtering sugges-


.

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

38

be operated independently of the in the

filter

(see list of filter manufacturers

Appendix, page 342 )

^ 00000 o o o * * 00*-* O o

*

*

» -

-i

»

A Fig. 17

Fig. 18

— Canvas lined

— Cylindrical pressure neering Co.,

wooden

filter

box.

Courtesy Alsop EngiYork, N. Y.

filter.

New

Apparatus Arrangement for Large Scale Mixing.

— For mo-

work or large photofinishing establishments, the chemical room should be situated on the floor above the developing room when-

tion picture

ever possible so that there

is

no chance of contamination of the develop-

ing and drying rooms with chemical dust, while the solutions

may

be


APPARATUS AND IMETHODS OF USE piped to the various rooms without the use of pumps. cal solutions directly

avoided because this settles as

it is

in

fixing

Mixing of chemitanks should be

the dirt

when mixing, and

the developing and

impossible to

filter

out

all

39

a sludge at the bottom of the tank (see Chapter

IX

further details on conveying solutions; also Chapter IV' on suitable terials for the construction of

for

ma-

apparatus).

GRAVITV rCElO

Fig. 19

â&#x20AC;&#x201D; Mixing

tanks using (A) gravity feed, and (B)

pump

feed to storage tank.

When the mixing room is located above the developing room, the may be fed by gravity from the mixing tanks through a cloth

tions

A

solufilter

Hgure 19. Most efficient filtering with a cloth filter is accomplished by using a cloth of sufficient size to permit of occasional movement of the cloth across the into the feed or circulating tank as

shown

in

of


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

40

top of the

system

is

box

filter

so as to expose a fresh filtering surface.

pump would need

a recirculating one, a

If the

to be used to return

In some laboratories, it is inconvenient room on the floor above the processing room and it on the same floor or the floor below (B in Fig. 19).

the solution to the feed tank. locate the mixing

placed either

Fig. 20

Removing Scum. scum usually

skimming

off

If solutions are not filtered

This scum consists of

with a towel or a skimmer

is

device.

after mixing, a

has been allowed to

rises to the surface after the solution

stand a few hours.

be skimmed

— Solution

to

fibers, dust, etc.,

made

and

it

should

of several thicknesses of

cheesecloth stretched on a wire frame (Fig. 20).

When

a fixing bath has been used for some time and

is

allowed to

stand undisturbed for a few days, any hydrogen sulphide gas which

may

be present in the atmosphere forms a metallic looking scum of silver sulphide at the surface of the liquid and on immersing the film, this attaches

itself to

the gelatin and remains even after washing

Before the solution

is

used, any such

(

scum should be removed

scum

Fig. 21).

carefully

with a sheet of blotting paper or by using a cheesecloth skimmer as described above.

Layout o£ Chemical Mixing Room. will

vary

— The chemical mixing room

in size according to the extent of the

requirements of the user.

For the commercial photographer with a small business, necessary to build a small cupboard such as is

of sufficient size

and capacity

is

to hold the

shown

done.

The scale

rests

is

The door

lowered when there

on a wooden base which

it

may

only be

Figure 22, which

dry and liquid chemicals,

the scales, bottles, and a few other accessories. section holding the small scale

in

slides

is

of the center

weighing to be

on two guides.


APPARATUS AND METHODS OF USE

41

In large laboratories, the chemical mixing and storage room

occupy considerable

floor

may

Dry chemicals

space (see Fig. 82, page 200).

are received in barrels, drums, and cans and liciuid chemicals in cans,

and carboys.

barrels,

room

These should usually be stored

a separate

in

closely adjoining the mixing room.

-^"J^^^V

Fig. 21

â&#x20AC;&#x201D; Spot on film caused by

silver sulphide

scum.

(200 x)

Waterproof Floors for Chemical Mixing Rooms and DarkThe floors of rooms where photographic chemicals and solu-

rooms/''

â&#x20AC;&#x201D;

tions are to be handled should be constructed of waterproof materials to

prevent chemical attack and to permit easy washing.

Existing floors

wood and concrete. Xo attempt should be made to lay a waterproof floor over another floor, however, unless the latter is in good condition. All boards of wooden

are usually of two types:

floors

should be solid and fastened securely

move, they

If the

in place.

break up the waterproofing.

will

boards can

Concrete floors must be

smooth and should show no signs of disintegration. There are four general types of waterproofing materials as A. hard rubber

tile

blocks;

B.

mastic

(applied

hot);

*

The authors

are indebted to the Engineering Dept. at the

many

follows:

asphalt-

The rubber

concrete (applied cold); and D. reinforced concrete.

Rochester, N. Y., for

C.

tile

Kodak Park Works,

suggestions incorporated in this section.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

42

to

wood only, the mastic and asphalt-concrete on wood or and the reinforced concrete on concrete. All laboratory floors should be equipped with a side curb and drain permit easy washing with a hose (see drain construction in Fig. 23).

A

false floor

is

usually laid on

concrete,

made

of cypress should be built over the

main

floor at

such

height as to facilitate easy access to deep tanks.

Fig. 22

The Use

of a Fabric

â&#x20AC;&#x201D; Chemical

Membrane.

cupboard.

â&#x20AC;&#x201D;

It is general practice

when

constructing any of the waterproof floors listed above to lay a fabric

membrane in pitch before the waterproof floor is laid. A pitch-saturated open mesh cotton fabric is recommended. Paper membranes crack easily

The

and are not as satisfactory clean dry surface should

point) with waterproofing pitch.

with strips of fabric, allowing a

mopped with hot

as cloth.

be mopped (beginning at the lowest The hot pitch should then be covered 2 -inch overlap. The edges should be

first

pitch before the seams are overlapped.

layers of fabric should be applied over the first layer

should separate each layer.

Each ply

Two

additional

and a layer

of pitch

of fabric should be staggered


APPARATUS AND METHODS OF USE

43

about 24 inches from the hip of the previous hiyer. Fabric should not touch fabric at any point and no wrinkles should exist.

When

the third ply has been laid, the entire top should be

with hot pitch before

it is

covered with the specified

mopped

floor finish.

-3fc Wi°^' "•JT

"

SLOPE BOTH SUnrACCS TOWARD DRAIN V3 PLV WATER PROOriNQ MEMBRANE

^/ATtR PROOrcD

MEMBRANE SECURELY CLAMPED BETWEEN CLAMPINGi RINCa AND DRAIN. CLAMPINCi RIN& HAS SLOTS AT THE BOTTOM TO ALLOVrf WATER TO DRAIN OTF TOP OF MEMBRANE

NOTE: -^ TOP COURSE l» PLACED MONOLITHIC WITH XI' BASE

-5

\

COURSE Fig. 23

— Detail

of waterproof concrete floor construction showing arrangement of tank support and drain.

The membrane should be

carried

up 4 inches on

walls above the top of the finished floor.

the floor (see

D below)

A

all

pipe sleeves and

cove built monolithic with

should protect the membrane on the walls.

When

the fabric and cove are constructed against an existing plastered wall, the plaster is first removed to a point 3 inches above the top of the cove and then replaced to rest on the cove. Details on the various methods of waterproofing are as follows: Hard rubber tile may be A. Hard Rubber Tile Over Wood. laid down with waterproof cement on the waterproof fabric membrane.

If

much weight

tiles

is

to be placed

should be fairly thick,

-^-

to

on the i

floors,

at the corners.

B. Mastic Over

Wood

from trucks or tanks, the

inch, because the thin tiles will break

or Cement.

— !Mastic

sand, pea stone and fluxed asphalt mixture and

is

consists of a silica

obtainable from con-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

44

tractor supply houses.

It is

applied hot and,

when cool, varies in hardThe most waterproof

ness according to the ratio of sand to asphalt. floor

secured with a small proportion of sand.

is

not be used, however,

warm

weather.

if it is

Mastic

much

to receive

floors

which

will

traffic

Such a

should

floor

because

it

softens in

be walked on considerably

The surface will crack, The mastic should preferably be laid over a

should have more sand in proportion to asphalt.

however,

if it is

too hard.

waterproof fabric as described previously. All tanks should be supported on concrete blocks or curbing covered

over with a piece of sheet lead. sides until

it

The

laps over the mastic.

lead should be bent

No

down over

the

supports should rest directly on

the mastic floor or they will gradually sink through the mastic and cause leaks.

Wood

Asphalt-Concrete Flooring Over

C.

or Concrete.

â&#x20AC;&#x201D;

This consists of a mixture of cement, sand, emulsified asphalt, and pea stone.

It is laid

^ to

i

inch thick on top of the three-ply asphalt satu-

wood

rated waterproofing fabric placed over the

or concrete

and provides

a somewhat harder surface than the hot mastic type.

D. Waterproof Concrete Floor Finish for Concrete Floors.

â&#x20AC;&#x201D; Where new

waterproof conditions are desired for large laboratories or

buildings, a reinforced concrete finish, 23 inches thick, should be laid

on the waterproofed fabric membrane (see previous description, page 42).

Special brass floor drains with clamping rings should be used,

which

in addition to draining

off

water from the

any water which reaches the top

The

concrete finish that

soft.

The lower

and

is

layer

mixed as

is

is

constructed in

layers laid

the upper layer should be poured while the

lithic,

is,

floor finish will also drain

membrane. the form of two

of the

layer containing a welded steel fabric i

layer

first

is i

monois still

j inches thick

part cement and 3 parts standard concrete.

This

divided into sections of about 10 feet square, or smaller, and

the sections are separated from each other

by the use

of strips of elastite,*

or similar asphalt impregnated material, \ inch thick.

The

top layer

is

laid f inch thick

and

is

composed

of

i

part cement

sand (uniformly graded), with 3.5 gallons of water per bag of cement. This top layer is spread, tamped, screeded, and to 3.1 parts silica

leveled,

and then treated with a heavy power

float.

The

joints in the top

layer are ^ inch wide and are constructed directly over those in the

lower layer by the use of an edging tool for this purpose. *

Manufactured by Phillip-Carey

mason supply

dealers.

Co.,

Cincinnati,

Ohio,

After the

and obtainable from


APPARATUS AND METHODS OF USE completed

finish

has been cured for ten days, the ^-inch joints are care-

compound.

fully filled with a plastic

Where extremely heavy would prevent the

tomary

them

to

45

finish

loads on the lloor are encountered, which

from assuming

its

proper shrinkage,

extend these foundations through the floor

finish

directly on the waterproofing cloth (see drawing).

it is

cus-

and

rest

Lighter loads

or smaller tank foundations are placed directly on top of the finished floor.

Useful suggestions on waterproofing of floors are contained phlet

No.

92, published

writers, 85

John

Fig. ^4

St.,

Nov.

New

15,

in

Pam-

1937 by the National Board of Under-

York, N. Y.

â&#x20AC;&#x201D; Alberene stone

sink

and

ledge.

Note rubber mat

on ledge and trough at back.

Finish of Walls, Benches and Sinks. mixing or processing room should be painted

â&#x20AC;&#x201D; The walls light

of a chemical

gray or green, or white

with a semi-gloss enamel paint which can be washed easily. tory wall paint walls since

it

is

Kodak Panchromatic Green,

especially for

reflects chiefly the light transmitted

by a

A

satisfac-

darkroom

series 3

Wratten

temporary walls of composition board are used for a developing room, they should be protected behind the tanks by strips of safelight.

If


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

46

asphalt roofing paper.

Several sheets

solutions will run to the floor

may

and not drip

be overlapped so that the

off

on the wall.

Permanent Koda-

walls should be painted with a chemically resistant paint such as

coat paint.

25

â&#x20AC;&#x201D;

Vitrolite ledge

Sinks should be

The

water.

sink

on Alberene stone

sink.

An

of

ample proportions and piped with hot and cold be of wood covered with lead sheeting (burned

hard glazed stoneware (Fig.

excellent covering for all stone surfaces, particularly

vessels are to be used, strip of this should

any stone ledges

right.

may

joints) or preferably of Alberene stone or

24).

Drying cabinet shown on

is

if

glass

ordinary black corrugated rubber matting.

be cut to

or tables

fit

A

the bottom of the sink and the tops of

where solutions are

to

be mixed or handled.

This scheme minimizes greatly the possibility of breakage and provides a surface that rosion.

A

may

be washed quickly, and which

is

not subject to cor-

trough leading into the sink and placed next to the wall at

the back of the working ledge as

shown

in

Figure 24 represents a useful

adjunct to the sink.

Bench tops where of

wood such

or left bare.

dry chemicals are

as hard maple,

and covered

to

be used are best constructed

either with battleship linoleum

In either case they should be treated with several coats of

a hard floor wax, rubbed

down

well,

and polished.

Although hard rubber

sheets have been utilized only to a limited extent to date for coverings


APPARATUS AND METHODS OF USE

47

chemical bench tops, they appear to possess satisfactory character-

for

istics for

such purposes.

The

sheets should be cut to

and cemented with a waterproof cement surface.

If

in close

fit

the bench top

contact with the table

chemical solutions are apt to be spilled on the bench, Alber-

ene stone, plate glass, or lead covered wood are satisfactory construction materials.

An

opal plate glass

known

as Vitrolite has been used to a

KEV A -MO AC C

-CUPBOARD

on- DRAWER SS-SNAP SWITCH

FO-TLOOR C3RAIN W-^VATER OW-Ot5Tli,UED WATER

MW-HOT WATER OMW-OISTILLEO HOT WATER IG- ILI-UMPNATING GAS

CA- COMPRESSED *IR SD-STORAGE DRAWER rOR DRY CHEMtCAl_S SO-STOCK DEVELOPER 0WH-01STIl_l_ED l_-

Fig. 26

â&#x20AC;&#x201D; Diagram

of a chemical mixing

SOV.

WATER HEATE

LIGHT

room.

and drain boards. It is easy to clean and ismost photographic solutions. A darktype of construction is shown in Figure 25.

limited extent for sink ledges

resistant to chemical attack of

room equipped with

this

Storage space should be provided for etc., its

and each

vessel or piece of

all

buckets, crocks, stirring rods,

equipment should be cleaned and put

in

place after using.

A

diagram of a chemical mixing room

weighing bench

and

sink.

is

is

shown

in

Figure 26.

The

located centrally and conveniently to the mixing bench

Storage drawers for bulk chemicals, such as sulphite and car-

bonate, are arranged under the weighing bench and bottles of developing agents, bromide, and alum, are placed on a shelf over the bench. solutions of developers

and

fixing baths are kept in

Stock

stoneware crocks

This mixing room would be the room. and portrait photographer or for a moderate size photofinishing plant. Acids should be placed on a shelf behind the sink. See also Figure 83, page 201 for a design of a chemical storage

and tanks on the

left side of

satisfactory for a commercial

,

and mixing room

A

in a

typical mixing

weekly

is

shown

in

moderate

size

room capable

photographic plant.

of handling several

hundred gallons

Note wooden

trays for holding

Figure 80, page 197.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

48

weighed chemicals and types of stoneware and wooden tanks

A

solutions.

mixing room

in a photofinishing plant is

for storing

shown

in

Figure

8i,page 199.

Wooden

barrels are used for mixing vessels, arranged in two rows,

The upper row

one row being on a level above the other. mixing and each unit

for

is

equipped with a mechanical

lower row represents storage tanks.

provided

is

The

stirrer.

Behind the upper row of barrels

is

a platform equipped with a large sink, weighing table, and storage bins Solutions are fed from the storage tanks to the defor dry chemicals. veloping machines and printing rooms on the floor below.

laboratory

is

A

large mixing

Chapter IX, Figure 82, page 200. Note the the mixing and storage tanks, each of which

illustrated in

sink located centrally to

feeds to the developing machines on the floor below.

Portable mechani-

cal stirrers are used.

Every chemical mixing room and darkroom should be well

A

1

ventilated.

0-inch propellor fan will handle about 300 cubic feet of air per

minute, and

is

large

enough

taining 4,000 cubic feet of

and greater

to give air.

adequate ventilation

Proper

in a

room concomfort

air circulation insures

efficiency of the occupants of a

darkroom.

General Hints on Cleanliness and Handling of Solutions. â&#x20AC;&#x201D; Whenever possible, all chemicals should be stored and solutions mixed in a separate room from the developing, printing, or drying rooms. Chemicals keep best when stored in a cool, dry place and all containers should be closed when not in use. â&#x20AC;˘

Chemical dust

may

arise

cans, barrels, kegs, etc.,

and ing.

3.

spilling of

2.

from the following sources: spilling of

i.

leakage from

dry chemicals during handling,

wet chemicals which subsequently crystallize on dry-

Such dust frequently gets into the ventilating system when

it

in-

variably produces spots on films and prints (see Fig. 5).

The

floor of the

mixing room should have a drain so that

flooded occasionally to

may

wash away any

have accumulated (Fig. 23).

kept scrupulously clean.

it

may

particles of chemical dust

be

which

Scales and mixing vessels should be

^Mixing vessels, measuring dishes, and stirring

paddles should be washed thoroughly at once after use. In the developing and printing rooms

handle the solutions with care.

A

fixing

it

is

even more important to

bath splashed on the

floor will

dry up and the hypo crystals formed, after being pulverized by persons walking 23). prints.

in the

room,

will get into the air

Particles of dust

and cause spots (Fig.

5,

page

on the negatives produce white spots on the

If prints are dried

on cheesecloth stretchers, the cloth should


APPARATUS AND :\IETHODS OF USE

49

be removed and washed regularly to avoid trouble from stains.

De-

velopers and fixing baths should be

skimmed each morning before use (see paragraph on page 40). The developing and printing room floors should be washed at least once a week by flooding with a hose if a drain is present or, if not, by mopping frequently. Deep tanks of wood or stoneware should be sterilized at intervals to kill

fungus growths as explained on page 265.

All bottles, crocks, jars, etc.,

which are used as storage containers

solutions should be labelled carefully. label

A

which

is

It

is

good practice

to lacquer

for

any

intended as a permanent legend of the vessel's contents.

satisfactory lacquer can be prepared

by dissolving

amyl

film scrap in

Zl

MAPLE TOP BENCH

STONEWARE. SINK

THICK

Ij^"

KEY A — 110 AC SS^-SNTAP SWITCH

SL-SArC U\GMT DR- DRAWER

A

C-CUPBOARO

a

|m

(t)l.

I

FS-FOOT SWITCH

4'!-

OH

W — WATER

I

I

HW— HOT WATER OR

Q-

DC-DRYING CUPBOARD I- ILLUMINATOR

FS

r^rt LINOLEUM toVEREDJ BENCH

1

R-RE.5ISTANCE: U-LlGiHT

SiL ^

Fig. 27

— Plan

of a small darkroom.

acetate until the solution has the consistency of molasses. solution should be covered

Layout of Darkroom.

when not

— A plan

This lacquer

in use.

darkroom suitable for is shown in Figure This design was adopted by the Photographic Chemistry Departof a typical

a professional photographer or an advanced amateur 27,

ment of

the

Kodak Research

Laboratories after

many

years of experience

and solutions are handled on one side of the room and printing on the other side. Figure 25 shows the view of one side of a room built according to the plan. The Vitrolite ledge represents an alternative material to the wood construction shown in the plan. with various plans.

Note the

All chemicals

The

location of safelights and the illuminator.

turned on with a foot switch.

which blows

air

The drying

downward through a

cabinet

cloth

heating by means of electric coils are possible.

is

filter.

A

latter

be

Several degrees of

vertical

movable

plate has been installed inside in order that the size of the drying

may

may

equipped with a fan

be varied, thereby controlling the velocity of the

baffle

chamber

air current.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

50

Figure 28 shows a view of the bench and cabinets on the opposite side

An exposure box is located at the end of the bench. This equipped with several diaphragms and a rheostat for controlling the

of the room. is

light.

It is

exposures

very convenient, and often important, to be able to duplicate

when

For

printing.

this purpose, the rheostat is included in

Darkroom exposure box, with the

lamp

circuit,

and a voltmeter

is

rheostat and voltmeter.

attached across the lamp terminals.

Fluctuations in line voltage result in serious changes in exposure

from

no

Voltages for printing should be a

The

;

a drop

100 volts will almost cut the intensity of the lamp in half.

to

little

below normal, say, 105 volts. darkroom is an important

installation of suitable safelights in a

Overhead safelights may be either of the direct or indirect style. Bench or sink safelights may be fastened permanently to the wall or arranged to be moved. The degree of safety of a safelight to a specified sensitive material may be determined by exposing the material for vari-

matter.

ous times at a

by covering a

known

distance from the safelight.

strip of film

This

is

accomplished

with a piece of cardboard and moving the card

along an inch or so after each exposure until the material has received several exposures.

The

material should then be developed for a standard

time and temperature, whereupon a record will be obtained from which the time of exposure that

is

safe

may

be determined.

Every darkroom should be well ventilated Refrigerating units of small size are cost,

and

it

now

(see details on

page 48).

available at a reasonable

should be possible to utilize such units for controlling the

temperature of the

air in

darkrooms.


:

CHAPTER

IV

MATERIALS FOR CONSTRUCTION OF PHOTOGRAPHIC PROCESSING APPARATUS* When

selecting a material for the construction of

any particular piece

of photographic processing apparatus, several factors should be con-

namely:

sidered, 1.

The

which

it

resistivity of the material to the

come

will

fairly satisfactory for

most corrosive liquid with

For example, a galvanized tank, while

in contact.

washing purposes,

is

very rapidly corroded and

therefore unsuitable for use with fixing baths. 2.

The

solution.

on the photographic properties of the

effect of the material

For instance, a developer solution

visibly unchanged, but on testing,

it

may

in

a brass tank

may

appear

fog emulsions badly, due to

the copper salts dissolved from the brass. 3.

The time during which

material.

If a

developer

ultimately soften and peel 4. 5.

for

The The

the solution will be in contact with the

stored in a japanned tank, the japan will

off.

cost of the material.

adaptability of the material for construction purposes.

example,

and the

is

is

entirely unsuitable for large tanks because of

difficulty of

Glass,

its fragility,

annealing such tanks.

There are three general classes of materials suitable

for the construc-

tion of photographic apparatus intended for use as containers for or to

be immersed

in

photographic solutions, namely:

coated metals, and non-metallic materials.

These

metallic materials,

may

be subclassified

as follows

A. Metallic materials: Unplated and plated metals; alloys. B. Coated metals:

Enameled

steel,

asphalt-coated metals and lac-

quered metals. C. Non-metallic

materials:

Glass,

impregnated fibrous materials,

wood, paraffined wood, porcelain and glazed earthenware, rubber, rubber composition, nitro-cellulose materials, slate and Alberene stone.

Metallic Materials. will resist corrosion *

â&#x20AC;&#x201D; No metal or

completely in

The experimental work reported

thors in conjunction with H. A. Hartt,

J.

in

all

alloy has yet been found which

photographic solutions, and

this chapter

it

was carried out by the au-

F. Ross, and L. E. Muehler.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

52

is

therefore necessary to restrict their use to specific purposes.

]Metanic

materials possess certain desirable properties, however, such as duc-

and general workability, that render them parthe manufacture of several types of photographic apparatus such as small tanks, racks, film hangers, clips and non-fragility

tility,

suitable

ticularly

for

reels.

In considering the suitability of a particular metal for construction purposes,

it is

very important to

know whether

a single metal or of two or more metals.

the article will be built of

In the former case only the

corrosive effect of the solution itself need be considered, whereas in

the latter case an electrical current flows between the two different metals, and

effect

its

must be considered

in

addition to the chemical

action.

In testing the resistivity of various metallic materials to chemical action,

it

2.

necessary to observe the effects obtained under two sets of

is

conditions:

i.

those in which only a single metal or alloy

those in which two or

more metals or

is

involved and

alloys are in contact with each

other and also with the photographic solutions.

The

Resistivity oÂŁ Single Metals in Photographic Solutions.

â&#x20AC;&#x201D; An extended

has been carried out to determine the

series of tests

tivity of a large

number

of metals

The experimental

solutions.

details of the

materials given in the following

to

are recorded in a paper

list,

resis-

common photographic tests made on most of the

and alloys

by the

authors.^

Metals: Aluminum, iron, lead nickel,

tin, zinc.

Plated Metals: Galvanized iron, tinned iron, lead-coated iron, chro-

mium,

and cadmium-plated brass. Xo. 136 (aluminum-magnesium-copper), Corronil

silver

Alloys: (nickel

Aterite

alloy).

G

Illium

Duralumin

(aluminum-magnesium-copper), Duriron,

(chromium-iron-nickel),

Monel, Niaco

(nickel alloy),

Inconel

(chromium-iron-nickel),

Xichrome (nickel-chromium),

(copper-zinc-nickel-iron), Nicolene

nickel silver

(nickel-copper), phosphor bronze

(copper-tin-phosphorus), solder (both high and low tin content), Rezistal

1

J. I.

steel

" Tlie

(chromium

steel),

Resistivity of Various Materials

Crabtree and G. E. Matthews.

Eng. Chcm.

stainless

steel*

(iS^c

chromium-S^c

Toward Photographic

Solutions " by

Brit. J. Phot. 70, 366, 3S5 (1923)

;

also Iiid.

&

666 (1923). * Stainless steels of 18â&#x20AC;&#x201D;8 composition and containing small percentages of otlier metals are supplied by several manufacturers in the United State under various trade names, such as Allegheny metal, Carpalloy 8, Enduro KA-2, Rezistal KA-2, USS 1

8-8, etc.

15,


MATERIALS FOR CONSTRUCTION

with varying carbon titanium, zirconium, selenium content),

nickel

type metal (lead-tin-antimony),

USS 18-8 Mo

molybdenum) and various stainless steels. Method of Testing Metal Samples. is contemplated, tests should be made of the

quantity is

53

is

A

fabricated.

essentially the

(chromium-nickel-iron-

a large scale installation

If

metallic material before

simple but effective test

same as used by the authors

any

the following which

is

studying the materials

in

listed above.

The

strip of the

mouth

a wide

page 286) fixing

A

.

bath

metal or alloy to be tested should be half immersed

bottle containing the developer

sample should also be placed

tests

should be

made both

F-5, Appendix, page 310) and in the

The

latter test is desirable to

to plate out

from a used

fixing bath.

with a clean, new, cork stopper. the severity of the test it

in the acid fixing bath.

in fresh acid fixing

same bath when

determine

there

if

The

in

(Formula D-19 Appendix,

bottle

is

bath

(

The

Formula

partially exhausted.

a tendency for silver

mouth should be

closed

Although a closed container increases

somewhat because

it

gives a stronger vapor phase,

has been found an effective method of measuring the resistivity of two

more materials (such as different samples of 18-8 stainless steel) which very nearly the same resistance to vapor attack. Duplicate tests should be made at room temperatures, 65° to yo'F. (18- to 2i°C.) and at no F. (43°C.) and should be continued for at least i month and or

offer

3 days respectively.

The

results at high temperatures should not be

regarded as conclusive but merely as an indication of the resistivity of the material.

Observations should be made frequently of the appearance of the

samples and the developer should be tested

for its fogging propensity

The

condition

of the metal samples should be noted both above and below the

air line of

by

developing therein a strip of film for a

the solution.

The

normal time.

results of these tests give a fairly reliable indication

of the effective resistivity of the metal or alloy.

The Resistivity of Two or More Metals in When two Towards Photographic Solutions.

placed in contact and immersed in a solution, an

formed which causes more or metals. metals,

This electrical action

when some

less

may

Metallic Contact different metals are

electrolytic battery

is

rapid disintegration of one of the

occur

in several

ways; with plated

of the plating wears off; with soldered metals, be-

tween the solder and the metal; and with of the various metals which

compose the

alloys,

between the tiny crystals

alloy.

In making metal containers for photographic solutions,

it

is

often


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

54

necessary to use a second metal or alloy in the form of solder, to render the joints or seams free from leaks. lines for transporting solutions,

or fittings of the

trouble which

same material

may

it is

Also, in the construction of pipe

frequently not possible to use faucets

as the pipe line.

A specific example of

from the metallic contact

arise

in a solution

is

the

as

follows:

Fig. 29

â&#x20AC;&#x201D; Spotted

type of corrosion of copper-nickel

alloy after prolonged

immersion

in acid fixing bath.

In the course of a series of tests on metal tanks of a copper-nickel alloy, soldered if

on the inside with a lead-tin solder,

it

was observed that

a developing solution remained in the tank for a short time the de-

veloper gave very bad fog.

The

solder with which the seams of the tank

were soldered appeared to be etched slightly and the original luster of the metal

The

had disappeared and was replaced by a dark, grainy deposit. was unaffected as far as could be detected from its

alloy itself

physical appearance.

A

series of tests definitely

proved that

this ex-

was a result of the tin constituent of the solder passing into solution, due to the flow of an electric current through the solder, the When the joints were soldered on the outsolution and the alloy. side, no developer fog was produced and corrosion was considerably

cessive fog

less.


-

FOR CONSTRUCTION

:\IATERIALS

55

Corrosion was also observed due to the same cause when a tank

from

and soldered on the

this alloy

inside

was used as a container

made an

for

acid fixing bath, except that the alloy was corroded instead of the solder

The most

(Fig. 29).

above the air-liquid

shown

rapid corrosion of any metal tank usually occurs

An advanced

line.

in Figure 30.^,

case of air-line corrosion

is

which represents a portion of a rack made from

nickel-copper alloy which had been suspended in acid fixing bath for several months. .An extended study of this aspect of corrosion has been results are given completely in

made and

the

two papers.

Value of Various Metallic Materials.

â&#x20AC;&#x201D; Only

the practical ap-

plication of the results of tests on the various metals will be considered in this article; the original

papers should be consulted for more detailed

information.

Metals.

â&#x20AC;&#x201D; Lead

and nickel were the only metals tested which ap-

peared to be of any especial importance for use with photographic solualthough iron

tions,

of value for particular purposes.

is

and wrought iron tanks or piping can be used developing solutions although lead veloper.

Iron

is

attacked more or

form oxides and hydroxides filter

is

most

attacked by strongly alkaline de-

less

by most developers and tends

in the solution so that

Tanks

out such particles before use.

Lead, nickel

satisfactorily for

it

is

to

important to

lined with lead or nickel can

be used for fixing solutions but they are slowly attacked, become coated with silver and must eventually be replaced.

Plated Metals.

â&#x20AC;&#x201D; Galvanized

facture of washing tanks although of apparatus.

Vessels

made

iron has long been used for the it is

manu-

not entirely suitable for this type

of this material

must not be used, however,

mixing developers which contain sodium bisulphite, because the bisulphite attacks the zinc coating, forming sodium hydrosulphite which for

causes fog.^

Xickel-plated brass

is

are used intermittently.

satisfactory for small developing tanks which

Metals plated with

from an exhausted fixing bath or by

by deposition more resistant to

silver, either

electroplating, are

~ " The Effect of Electrolysis on the Rate of Corrosion of Metals in Photographic Eng. Chcm. Solutions " by J. I. Crabtree, H. .\. Hartt, and G. E. Matthews. Ind.

&

16, 13 (1924)

and

" Corrosion of

Crabtree and G. E. Matthews.

Monel Metal in Photographic Solutions" by Ind. & Chcm. i6, 671 (1924).

J.

1.

Contact with 3 " The Fogging Properties of Developing Solutions Stored in Various Metals and Alloys " by J. F. Ross and J. I. Crabtree. Aiucr. Phot. 23. 254 (1929).


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

56

developing solutions according to the homogeneity of the silver coating,

but their resistance towards fixing baths that of the unplated metals.

do not satisfactorily

resist

is

only slightly greater than

Aluminum- and cadmium-coated metals

photographic solutions.

metals would probably be satisfactory

if

Chromium-plated

were possible

it

to secure a

continuous nonporous coating over the base metal, but no such coatings are available to date.

washing tanks

if

Lead-coated iron can be used for developing and

the iron base-metal

is

not exposed, but

is

not very

satisfactory.

Plated metals and alloys are always open to the objection that as soon as

some

of the plating wears

electrolytic corrosion sets in,

Alloys.

â&#x20AC;&#x201D; Of

off,

exposing the other metal underneath,

and disintegration takes place rapidly.

numerous known alloys, Monel metal and 18-8 which have been adopted to any great photographic use. ]Monel metal is attacked and coated with the

stainless steel are the only ones

extent for silver

when used

for

storing exhausted fixing solutions.

Inconel, a

nickel-chromium alloy, appears somewhat more promising than Monel because tures.

does not plate out silver except very slowly at high tempera-

it

A

chromium-iron-nickel alloy

known

as Illium

B

also appears

promising.

Most samples

of 18-8 stainless steels are quite resistant to both de-

veloping and fixing solutions but some show a tendency to form corrosion pits above the air-solution line with acid fixing baths (Fig. 30B).

A

stabilized

form of 18-8

of titanium represents

stainless steel containing a small percentage

an improvement over the older 18-8

pecially for tank construction

provement

of the

18-8

where welds are required.

is

4%)

of

steels, es-

further im-

steels relative to their corrosion resistance to

acid fixing baths has been realized (2 to

A

molybdenum.

somewhat higher (25

to

The

by adding

to

them a small percentage

relative cost of such steels, however,

50%)

than regular 18-8 stainless

steel.

Another form that has high corrosion resistance contains a greater chro-

mium and

nickel content

advantage that

The

it

â&#x20AC;&#x201D;

12% nickel) and has the more than the regular 18-8 steel.

(24% chromium

costs only slightly

selection of a stainless steel for a construction material in connection

with photographic equipment depends, therefore, upon the type of use the equipment will receive and the fabrication requirements necessary

when forming the equipment. The welding of stainless rosion

may

chapter.

steels

must be done carefully or

occur at the welded joints.

cor-

See discussion at end of this


MATERIALS FOR CONSTRUCTION

57

An idea of the variation in composition of stainless steels of the 18-8 may be gained from an examination of the following table compiled

type

by

Smith.''

TABLE

I

Percentage Composition Ranges of Various Types of

Enduro Stainless Steel Type


PHOTOGRAPHIC CHEAHCALS AND SOLUTIONS

58

^

r

Fig. 30A line

Corrosion above air on section of metal developer

v/.

\^^'

v.*^

M

l-ii:.

iS-S

,,oi;

corro-idii

Pittfii

stainless

steel

above

ot

air-

liquid level after several weeks' ex-

rack.

posure to the vapors of an acid bath at 90°F. (32 °C.).

fixing

Coated Metals.

— The

resistivity

of

metals which readily cor-

rode can be greatly increased by coating them with a more resistant

metal or non-metallic substance.

The

properties and applications of a

few such coated metals are described below.

Enameled trays

Steel. Enameled steel is extensively used for small and tanks, and has proven fairly satisfactory. When the under-

coating of steel

is

vitreous enamel,

laid bare

it

by the chipping away

of the relatively brittle

corrodes very rapidly, and the vessel

is

rendered use-

Smooth, hard enamel coatings are resistant to weak acids used in photographic practice, but with developers and alkaline solutions the surface becomes etched, making it difficult to clean. Dye solutions

less.

permanently discolor such roughened surfaces of enamel. Glass Enameled Steel. Equipment having very satisfactory

re-


MATERIALS FOR CONSTRUCTION sistance to

velopers)

is

most photographic solutions (except strongly alkaline deavailable in the form of mixing tanks and agitators (5-gallon

upwards) suitable

made by

59

for

motion picture laboratory

use.

Such equipment

is

fusing resistive silicate enamels onto substantial steel shells at a

temperature of 980 ""C. (i8oo°F.).

Advantages claimed are less weight and bulk and greater heat conductivity than with cast metals or earthenware.

The

glass

enamel on the

than ordinary enamel since

steel

is

much more

resistant to breakage

Repairs

actually fused onto the metal.

it is

the event of breakage, however, are difficult to

make without

in

returning

the entire unit to the factory.

Lacquered and Painted Metals.

â&#x20AC;&#x201D;A

satisfactory photographic

lacquer consists of asphalt paint or a mixture of asphalt paint with rub-

ber cement, the latter serving to overcome the slight brittleness of the

Baked japan

asphalt coating.

is

very satisfactory, but none of these

materials will resist developing solutions containing a high percentage of alkali.

Freshly applied asphalt paint will often produce a scum on the

developer.

Kodacoat paint represents a satisfactory material metallic surface from corrosion

when subjected

graphic solutions or their vapors.

A

secure

maximum

tained

by using oxygenated

protection.

for protecting

a

intermittently to photo-

Several coats should be applied to

thicker protective coating

asphalt.

may

be ob-

This material requires melting

and must be applied hot for best results. Halogenated rubber paints such as Tornesit

*

and some other rubber

paints such as Pliolite f are also fairly resistant to the action of developers and fixing baths. Some types of bakelite lacquers, such as Larcoloid, t are quite resistant to the action of corrosive vapors.

As a general

rule,

it is

best to use paints

and lacquers on surfaces that

only receive intermittent exposure to solutions or their vapors because it is

it

very

difficult to treat

a surface with a paint or lacquer so as to render

completely impervious to the penetration of a liquid. It is

important to protect the exterior as well as the interior surfaces of

tanks to prevent corrosion of the base metal.

Consideration should be

given to the possibility of abrasion and pressure to which the exterior

may

A

heavy tank resting on a beam, for example, would soon press through any protective coating and allow surface

*

May

be subjected.

large

Products Co., Newark, N. Y.

Staten Island, N. Y.

& Lambert

t

Pratt

:

Larkin

Co., Buffalo,

Co., Buffalo,

N. Y.

N. Y.

Also Perry-Austen Manufacturing Co.,


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

60

corrosion of the base metal to occur.

All surfaces

which are

likely to

be abraded or worn away should be recoated at frequent intervals.

Laminated Metals. als

— About 1931, several types ^

of laminated met-

were introduced, which consisted of thin sheets of a corrosion-resistant

metal on a thicker metal base such as iron. steel, for

terials

Lead, nickel, and stainless

example, have been laminated onto

may

find

some uses

for

Such ma-

steel or iron.

photographic work but are open to the

objection that once the thin upper coating

is

broken through, the base

metal would probably corrode rapidly.

Non-Metallic Materials. in

— Several

satisfactory materials for use

handling photographic solutions on a large scale are to be found

in

the non-metallic group.

Glass.

— Glass

apparatus well annealed, free from

the corners of small trays and tanks rounded is

one of the most resistant materials available.

An

however, glass

is

opal plate glass,

and with

Owing

to its

not suitable for large trays and tanks.

known

as Vitrolite, represents a satisfactory

material for bench or table tops where chemicals are to be used. fairly resistant to it

may

most photographic solutions except strong

be kept clean easily.

Like other glasses,

and, therefore, care must be used that

it is

possibility of breakage of glassware

if

It is

alkalis

this material

and

brittle

is

not struck with a metal object.

A disadvantage common with stoneware or Alberene is the ever may

and

For the storage of

strong alkalis, special, resistant glass should be used. fragility,

ribs,

quite satisfactory

off, is

present

dropped on such surfaces.

This

be avoided by using a sheet of rubber matting on the surface where

glassware

is

to

be placed.

Impregnated Fibrous Materials.

— Trays or tanks prepared from

paper or other fibrous materials impregnated with varnish or lacquer develop cracks with use, thus permitting access of the solutions to the

under layers.

Such trays and tanks are entirely unsatisfactory

for use

with solutions containing strong alkalis, or with fixing baths, because these solutions disintegrate the fibrous materials through crystallization, as explained later under " Porcelain fiber trays carefully

tory for intermittent use

Containers

and Glazed Earthenware."

Small

impregnated with a high melting wax are satisfacif

carefully handled.

made from most laminated

phenolic condensation products

can be used with photographic solutions, with the exception of strong

Some samples of these materials have been found to and warp out of shape when used with strongly alkaline solutions.

oxidizing solutions. swell


INIATERIALS

Wood.

â&#x20AC;&#x201D; Wood

ing purposes,

and

FOR CONSTRUCTION

61

and wash-

fairly satisfactory for developing, fixing

is

cheaper than any other available material.

is

It

has

the disadvantage that, unless strongly braced, the tanks have a tendency

warp out

This tendency is at a minimum with round tanks, which should be well braced with iron rings that are tightened up as to

of shape.

I

Fig. 31

â&#x20AC;&#x201D; Splintering

of

wood

in a

hypo storage tank caused by wood.

crystallization

of the salt in the pores of the

much

as possible after the tank has been soaked thoroughly

with water and allowing If

it

by

filling

stand for several days.

used as containers for fixing baths, the tanks should preferably be

constructed of paraffined crystallize

on the

the tank

filled

many

as

wood

as described below.

sides, will penetrate the

splinter or crack as

In

to

shown

much

localities

in

Figure 31.

wood

in

Hypo,

if

allowed to

time and cause

it

to

This can be avoided by keeping

as possible.

fungus growths accumulate on the outside of the

washing tanks which must be removed frequently, while the inside of wash tanks often become coated with a layer of slime which necessitates frequent cleaning (see Chapter XII, page 265).

Wooden

containers

become permanently discolored if they are used for dye solutions. The most satisfactory varieties of wood for the construction of tanks are cypress, spruce, redwood, maple and teak. also


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

62

Paraffined

Wood.

— Although

woods such

certain

as cypress

and

teak are frequently used for the construction of containers for photo-

graphic solutions, paraffin-impregnated It also possesses the additional

wood

is

much more

advantage that

it

cumulate slimy layers as rapidly as unwaxed wood. advantage of paraffined wood

is

that

it is

satisfactory.

does not tend to ac-

The

chief dis-

too heavy for the construction

equipment which is to be handled manually. It is also quite and breaks easily if dropped. Methods of impregnating wood with paraffin have been investigated by Eberlin and Burgess, who found that the best results were obtained with cypress and spruce by soaking in of large

brittle

•"*

water for twelve hours, and then immersing

two hours at around

The soaking water

2

serves to swell the

in the pores

is

molten paraffin wax

in

for

50°F. (i20°C.).

wood and

in the

hot paraffin bath the

The wood should be wiped

replaced by paraffin.

thoroughly with a cloth on removing from the paraffin bath so as to

remove the excess wax.

made by grooving joint,

Watertight joints with paraffined wood are best

the pieces of

wood

to

be joined together, as for a T-

and inserting tightly a small piece

groove.

When

of unparaffined

caulks the seam.

Porcelain and Glazed Earthenware. ware, and

tile

wood

in the

placed in water the untreated strip swells and completely

— Porcelain, glazed

biscuit

material are usually unsatisfactory because the glaze in-

variably cracks, causing minute fissures into which the solution penetrates

and

The

crystallizes.

crystals then

grow and cause the biscuit Tanks of

ware to disintegrate, incidentally causing the glaze to chip.

high grade, dark brown earthenware, glazed on both sides, are especially

recommended

for storing ordinary developing

and hypo

solutions, but

should not be used with strong alkalis.

During 1933 a new form of hard glazed stoneware was introduced which was claimed to be free of all internal fissures, lighter and thinner than the older types of stoneware, but equally as strong and as chemically resistant.®

Rubber, Rubber Composition, Nitrocellulose and Asphaltum Materials.

— Pure hard

rubber will withstand practically

graphic solutions at normal temperatures.

5

"

Impregnating

Wood

with Paraffin " by L.

W.

all

photo-

Hard rubber thermoplastics Eberlin and A. M. Burgess,

Iiid.

& Eng. 6

40,

Chcm. 19, 87 (1927), Revised 1928. Ind. & Eng. Chcm. 25, Adv. Sec. 35 (Sept. 1933)

270 (May 1933)-

;

also

Chcm.

&

Met. Eng.


MATERIALS FOR CONSTRUCTION

63

(said to be sulphur free) were introduced in 1933/ These appear promising for the construction of small trays and tanks for photographic use.

For certain types of factory because

FiG. 32A

â&#x20AC;&#x201D; Hard

it is

hard rubber piping is very satisand may be threaded easily. Its chief disad-

installations,

light

rubber-lined steel tank showing; seam con-ti uction.

American Hard Rubber Co.,

vantage

is

its

brittleness.

New

Courtesv

York. N. Y.

Iron pipe lined with hard rubber, which

is

firmly cemented in the pipe, represents a very satisfactory type of piping

photographic solutions.

for

hard rubber pipe that

it

It possesses the

advantages over ordinary

does not require support every few feet and

is

not subject to breakage by impact.

Some

so-called hard rubber tanks are

made from a mixture

or rubber composition with an excess of mineral

somewhat

brittle,

warp under

filler.

of asphalt

Such tanks are

and when used as containers for same manner as porous earthenware.

heat,

salt solutions disintegrate in the

Smooth surfaces reduce the tendency

to etching since less strain

is

ex-

erted on the walls during the crystallization process.

Black hard rubber sheet or fabric-backed rubber sheet

may

be used

bench tops or sink ledges where photographic chemicals are to be handled. The sheets should be cemented to a wood table top with for

waterproof cement such as Plastikon cement, supplied by the B. F.

Goodrich Co., Akron, Ohio.

Rubber cements are now "

lud.

&

Eug. Chcm.

26,

available which produce a highly tenacious

123-129 (Feb. 1934)-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

64

bond between hard rubber and metal, wood, porcelain, and other surfaces, and which have fairly high resistance to corrosive attack of acids and

alkalis.

According to Fritz and Hoover

pounded

solutions of salts

Fig. 32B

immersion

to resist actual

and

Above 150'F. (65°C.) the

alkalis.

and

effects of

â&#x20AC;&#x201D; Hard rubber-lined

steel tank showing corner and edge construction. Courtesy American Hard Rubber Co., New York, X. Y.

oxidation, diffusion,

is

vulcanized rubber can be com-

for long periods in organic acids

and absorption become aggravated.

construction of soft and hard rubber it

-

is

described

by

A

three-ply

these authors which

claimed represents an improved type of material for coating the

surface of metal tanks.

The

and corner construction of two hard rubber-lined steel tanks 32A and Fig. 32B. Note method of filling corner with a triangular piece of rubber in Fig. 32 B, to produce a surface, which may is

joint

shown

in Fig.

be cleaned more easily.

These tanks are lined with a two-ply rubber

coating consisting of hard rubber bonded to soft rubber which, in turn, is

bonded

to the steel.

If the

made with overlapped seams

tanks are large enough,

as

all joints

can be

shown in Figure 3 2 A. With deep narmethod of assembly is used. They are

row tanks, however, a different usually formed as two shells with right angle bends at the edges where the joint is to be made. A soft rubber gasket is then set between the faces of the two shell edges as shown in Figure 32C and, when these faces 8

"

The Chemical Resistance

Fritz and J. R. Hoover. terials,

March

9,

of RulDljer as an Engineering Material " by H. E.

Reprint of Symposium on Rubber, Amer. Soc. Testing

1932, p. 79.

Ma-


MATERIALS FOR COXSTRUCTIOX are

drawn together with

occurs on the steel,

no

it is

bolts, the

tank

is

formed.

65

Whenever a corner

important that the weld be smoothed out so that

air pocket is formed when it is covered with rubber. Tanks may be constructed economically from steel

a thin

(^ inch) soft black rubber sheet

rubber

is

is

sheets on which

cemented intimately.

The

permitted to extend over the edges of the steel and " squeezed

joints " are

made

to

form the bottom and walls of the tank by bolting

Z

^^

^///////

t.

STEEL PLATE "^,

d \

SOFT RUBBER CASKET Fig. 32c

â&#x20AC;&#x201D;

Construction detail of joint in a rubber lined steel tank. Courtesy American Hard Rubber Co., New York, N. Y.

two opposite sides together and allowing the rubber sheets at the joint.

When

the bolts are

to protrude

drawn up, the two rubber

sheets are

pressed together and form solution-tight joints.

Rubber sheeting and rubberized cloth are often used for coating the wooden trays and troughs, and are very satisfactory provided

inside of

the surface

is

not subjected to

Cheap rubber sheeting

much

abrasion during use.

or tubing often contains an excess of free sul-

phur which reacts with photographic developers and causes chemical fog.^ Pure gum rubber materials are quite satisfactory. For handling long lengths of wide film (Cirkut film), a rubberized tray

is

e.xcellent.

Since solutions used in a tray or trough are usually in contact with the

rubber for only a relatively short time, more corrosive solutions can be used than 9

"

in the case of a rubber-lined tank.

Chemical Fog

"

by

J. I.

Crabtree.

Amcr. Ann. Phot.

33, 20 (1919)-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

66

A

flocculent precipitate

is

produced when some grades of soft rubber

are placed in a developer solution for several days. will

This precipitate

The use

tend to settle on film and produce scum markings.

of rub-

ber sheeting giving such precipitates should be avoided.

Rubber buckets such as the type made from Flexite) represent useful

FiG. 32D

dling of solutions

32D (which

is

containers for the intermittent han-

â&#x20AC;&#x201D; Rubber

bucket. Courtesy Goodrich Co., Akron, Ohio.

and are

tographic solutions.

illustrated in Figure

most pho-

resistant to the corrosive attack of

The handle should

preferably be

made

of stainless

steel.

Kodacoat paint

as mentioned on page 59 represents a satisfactory

material for coating wood, stone, and metal to protect them against the intermittent attack of acid or alkaline solutions.

A

may be applied with maximum protection.

It

a brush and several coats should be used to give

tarry material called oxygenated asphalt supplied

by the Stand-

ard Oil Co., has been found to be a satisfactory protective coating for use with

all

kinds of photographic solutions.

This material

while hot, as a thick coating over the metal or surface

is

is

if

is

applied,

a smooth

desired the coating can be smoothed out by the use of a blow

torch (Fig. 33).

weather

wood and

will

This coating

adhere to metal

is

normally somewhat tacky and

articles.

Therefore,

if

in

hot

a photofinishing tank

coated with this material, the upper edges of the tank should be pro-

vided with wooden supports for the metal rods carrying the hangers.


MATERIALS FOR CONSTRUCTION

67

Nitrocellulose lacquer (E. K. Lacquer

wooden

articles

No. 5119) is useful for coating such as racks for handling motion picture film, although

several coatings are usually necessary. nitrocellulose sheeting

A

aqueous solution."*

Fig. 33

â&#x20AC;&#x201D; Showing use

such material terial is

is

blow torch

to

Figure 34.

in

smooth out asphalt coating

Wooden

have also proved satisfactory.

that

it is

made from

small film developing reel and tank

of

shown

Small apparatus constructed of

satisfactory for use with almost every type of

is

very inflammable.

Slate and Alberene Stone.

A

in a tank.

tanks lined with this ma-

disadvantage of such sheeting

â&#x20AC;&#x201D; These materials are very

suitable for

For

constructing large tanks for containing developing solutions.

fix-

ing solutions, Alberene stone (a gray, finely crystalline variety of soapstone) splits

is

quite satisfactory, but slate

is

not recommended as

it

along planes of cleavage as a result of crystallization.

varieties of soapstone are not resistant to fixing baths,^^

disintegrate where the

sodium thiosulphate

often

Some

and tend

to

crystallizes out.

Develop-

above the

air-line of

ers also attack these varieties of soapstone chiefly

the solution and produce disintegration as indicated in Figure 35. 10 " Plastic Cellulose in Scientific

man,

Research " by K. Hickman and D. E. Hynd-

Frank. Inst. 207, 231 (1929). 11 " The Action of Hypo Solution on Stone Tanks " by D. Research, Xat. Bur. Standards 16, 161-164 (Feb. 1936). /.

'

'

W.

Kessler.

/.

of


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

68

A

satisfactory

cement

for joining large pieces of soapstone, as in con-

structing a tank, can be prepared from

i

part whiting,

2

parts litharge,

thoroughly mixed and made into a putty with boiled linseed ture of litharge and glycerine

is

recommended

for

oil.

A

mix-

cementing small

fit-

tings into the tanks.

Fig. 34

in

— Small

reel

and tank made from sheet

film base.

Oxygenated asphalt can sometimes be used effectively to repair cracks a soapstone sink. It has the advantage that it expands and contracts

slightly with changes in temperature.

Practical Suggestions Materials suitable for constructing various types of photographic apparatus are as follows:

Small Apparatus. (18-8)

is

(Clips,

film

hangers, etc.)

Stainless

one of the most satisfactory materials known, but

ommended

for use in toning solutions.

enced with film hangers made of

this

No

trouble

is

steel

not rec-

usually experi-

metal and having welded

cause such hangers receive only intermittent use.

is

joints, be-

Note: Stainless

steels

(18-8) containing small percentages of molybdenum (2-4%) are more resistant to corrosion than ordinary 18-8 stainless steel. Inconel and, to a less extent, nickel and Monel, have properties somewhat similar to those of 18-8 stainless steel.

Trays, Dishes and Small Tanks.

— Since

these containers are

generally used for a variety of purposes, they should be resistant to most

photographic solutions.

Suitable materials are glass, enameled steel,

hard rubber, teak wood or spruce impregnated with paraffin wax, wood, or metal coated with sheet rubber or rubberized cloth,

wood coated with


â&#x20AC;&#x201D;

MATERIALS FOR CONSTRUCTION

69

oxygenated asphalt, and well-glazed porcelain or stoneware. Plioform,* a rubber product that does not contain sulphur, represents a promising material for the manufacture of small trays and tanks. It is much more resilient than most types of hard rubber. Small amateur trays made of heavy cardboard impregnated with a high melting wax are fairly satis-

Disintegration of soapstonc tank above air-solution

FiG. 35

factory provided they do not receive rough treatment.

Monel, 18-8 stainless

steel (see note,

washing or developing, and

for

line.

Small tanks of

above), or Inconel are satisfactory

for fixing purposes

when

the tanks are

to be used intermittently.

Deep Tanks. finishing.)

â&#x20AC;&#x201D; (For

motion picture work and commercial photo-

Alberene stone, well-glazed stoneware and wood (cypress)

are suitable for developing and fixing baths.

Lead-lined wooden tanks

are fairly satisfactory for developing solutions provided the joints are

lead burned and not soldered.

Glass enameled steel tanks also are sat-

isfactory for use with developing solutions.

Iron tanks lined with hard rubber sheeting or, preferably, with soft rubber sheeting (sulphur-free) represent a useful type of container that *

Goodyear Tire & Rubber

Co.,

Akron, Ohio.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

70

is

resistant to corrosive attack (see Fig.

may

pansion joints

202) and

.

Overlapping ex-

be used with the hard rubber (see Fig. 84, page with soft rubber. The latter are produced

" squeeze joints "

by squeezing together

the rubber that protrudes over the edge of the

steel at the corner of the

An

32A and 32B)

tank by bolting opposite sides together.

economical method of constructing a tank consists in assembling

a rough form with slabs of slate or soapstone, treating these while

warm

with asphalt, and lining the form with sheets of double thickness window

warmed)

glass (also

It

.

is

important to cover the slate surfaces liberally

with asphalt.^-

wooden tanks are usually satisfactory but they tend to accumuStorage and circulating tanks made of cypress wood are used extensively in laboratories in Hollywood and New York (see Fig. 10, page 27). Tanks of paraffined wood can be used if the wood is properly joined together with strips of untreated wood as explained on page 62. Tanks of Portland cement have been found satisfactory for developers of low alkali content. Metal or wooden tanks coated with oxyPlain

late slime.

genated asphalt are excellent provided the base material

from chipping

Deep tanks

of the asphalt.

not exposed

is

of 18-8 stainless steel with

welded

joints have also proved satisfactory as containers for developers and wash water. Tanks for fixing baths should preferably be fabricated from 18-8 stainless steel containing 2-4% molybdenum, to prevent

from the acid vapors above the solution

pitting

page 205).

Covers for Tanks. namely: 2. dirt,

i.

grease,

made

in

for tanks serve several useful purposes,

they prevent too rapid oxidation of the solution by the air;

and other foreign matter are prevented from dropping

into the solution;

be

â&#x20AC;&#x201D; Covers

(see Fig. 85C,

level

and

3.

the rate of evaporation

two ways either

the solution.

;

to

fit

In the latter case, the solution

tection against oxidation.

is

may

Covers

reduced.

over the top of the tank, or to float on is

given the

maximum promay be

For small tanks, satisfactory covers

constructed of hard rubber or cypress

wood

or sheet celluloid.

It is

usually unnecessary to use floating covers for very small tanks since the

by adding

A piece of nitro-

volume can be maintained

easily

cellulose sheeting, in the

form of a shallow tray or boat,

floated

of 100 gallons or larger capacity, covers

wood about

joints (Fig. 36). 12

is

sometimes

on the solution.

For tanks pine

replenisher.

Tech.

News

6 inches wide

One

by | inch

may

be built of

thick and grooved with "

layer should be fitted together tightly

Bull. No. 246, Nat. Bur. Stand.,

T

"

and an-

Washington, D. C, 105 (Oct. 1937).


MATERIALS FOR CONSTRUCTION other cut to

fit

on the

first

layer at right angles.

71

The boards should be

screwed firmly together from one side with Monel or 18-8 stainless screws, counter-sunk below the surface.

The cover should then be

steel

given

No. 5119 is satisfactory), dry thoroughly before the next is ap-

several coats of a nitrocellulose lacquer (E. K.

and each application allowed If desired, the

plied.

cover

together by a shoulder joint.

Fig. 36

â&#x20AC;&#x201D; Large

to

may

be made in two parts which are fitted Most covers built of wood become badly

tank cover showing laminated con^-uucLiuii.

months of use but the degree of warping of the one described will be a minimum. For circulating systems, floating covers may be made of molded sheet celluloid or 18-8 stainless steel with the edges turned up slightly and the seams welded to form a shallow tray or

warped

boat.

may

after a few

A

be

fairly satisfactory cover for

made

tanks of 50 to 100 gallons capacity

of hard surfaced asbestos sheeting or Transite board.

Such

covers should be painted with an acid proof paint such as Kodacoat,

Probus, Tornesit, or Pliolite and the edges protected from chipping by

them with rubber edging as used around automobile windshields. may be held together by attaching a small strip of rubber at the points where the side strips meet. The most satisfactory cover for storage tanks of acid fixing bath and developers is one made from 18-8 fitting

Corners

Mo

stainless steel.

Floating covers

have been used

They

made

of sheet iron

for developer

and coated with oxygenated asphalt

supply tanks for large automatic machines.

are fairly satisfactory for such purposes but should not be used

with fixing baths or other solutions.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

72

Tubes, Sprockets and Idlers for Motion Picture Developing Machines. Hard rubber, lead, 18-8 and 18-8 Mo stainless steel, and Pyrex glass have been found satisfactory for developing tubes. Lead

gathers a deposit of silver from the fixing bath, and in time this tends to obstruct the tube, but this deposit can be removed by scraping.

Brass

or copper tubing should not be used since both materials affect devel-

The body

opers and are corroded by fixing baths. sprockets should preferably be

made

structed of Monel, Inconel, or 18-8

part of idlers and

of hard rubber with teeth con-

Mo

stainless steel.

should not be soldered with solders containing

tin.

Metal tubing

Seamless tubing

is

be preferred.

to

Bakelite impregnated fabric represents a useful material for sprock-

and

ets

idlers,

which are exposed

to the action of developers

baths.

Troughs

for Reel Development.

and

fixing

— Glazed stoneware and wooden

troughs lined with sheet rubber or rubberized cloth are satisfactory for practically all ordinary processing solutions.

Mo

stainless

steel,

Leads, nickel, and 18-8

Monel, and Inconel metals are satisfactory

for

use with developing solutions, and although they are slowly attacked

they

may

For acid oxidizing solutions or

be used with fixing solutions.

strong alkalis, hard glazed stoneware troughs are

emergency

if

recommended but the

Metal troughs may be used

troughs should be emptied after use.

the interior of the trough

is

lined with pure

gum

in

an

rubber

This latter lining is applied by coating the heavy canvas cloth and sticking it to the The cloth is then brushed metal with cumar resin (medium hard grade) over with molten hard paraffin wax and the surface finally smoothed off with a hot iron. The wax should be renewed at frequent intervals. Metal troughs may also be coated with oxygenated asphalt but great care should be taken to insure that the metal is covered completely and that the coating is free from bubbles. Japanned metal ware is only satsheeting or paraffined cloth.

interior of the trough with

.

isfactory for intermittent use.

Piping, Pumps, Faucets, Etc. lutions,

hard rubber, iron, Duriron, Inconel, and 18-8

piping and

pumps

steel faucets is

Hard rubber

should be used, especially

necessary.

Mo

For transporting

if

or 18-8

Mo

stainless

continual exposure to the solu-

fixing solutions,

hard rubber piping,

pumps are recommended (see also Chapter IX, page Gear pumps of hard rubber represent a simple and economical

valves and

so-

stainless steel

are satisfactory and should be used in connection

with faucets of similar materials.

tions

— For transporting developing

203). installa-


MATERIALS FOR CONSTRUCTION

73

when a flow not greater than 5 to 6 gallons per minute is required. Such gear pumps require priming and must be kept wet while running.

tion

For a more rapid flow, a centrifugal

pump

Tinned

should be installed.

or tin-lined, copper, or brass faucets or piping should be avoided for

use with developers or

fi,\ing solutions.

however, pipe lines and

fittings of

Pure aluminum piping

are satisfactory.

water

tilled

For conveying

lines.

tin solder

also satisfactory for dis-

is

has the advantage over

It

distilled water,

block tin soldered with pure

tin

and rubber that long

spans do not need supporting.

Lead piping dered.

joints should be "

apparatus

If silver-plated

wiped is

" or

lead-burned, and not sol-

used, the plating should be free

from pinholes or scratches.

A

suitable packing for

the aid of a

pumps consists of asbestos rope twisted with Hard rubber faucets, piping, etc., must

hard grease.

little

be protected from impacts or excessive pressure.

The

and 75 summarizes the above recommendations.

table on pages 74

Precautions to be Taken terials.

â&#x20AC;&#x201D;

I.

come

als to

Do

not permit

in contact

developers, because

When

tin,

Selecting Construction Ma-

copper, or alloys containing these met-

with developing solutions, especially concentrated

more or

less of the tin or

copper

will dissolve

and

cause either serious chemical fog or rapid oxidation of the developer.

Do

not use galvanized iron vessels to mix developing solutions contain-

ing sodium bisulphite because

sodium hydrosulphite

which

Likewise, the zinc in the inner coating

a bad fogging agent.

is

will

be formed,

of galvanized piping will cause developer fog.

Contact of two or more different metals or alloys exposed

to

a devel-

oper will hasten the rate of corrosion of the metal and thus increase the

amount

of fog obtained.

with developers, but

one

free

from

of solder 2.

is

tin

if

Soldered joints are particularly to be avoided

such joints are unavoidable, a low-tin solder or

should be used, and the joints so

made

that a

minimum

exposed to the solution.

^Maximum

corrosion resistance to developers and acid fixing baths

with stainless steel will be secured by using an 18-8 type containing

4%

2

to

or

when

molybdenum.

special fabrication

should be chosen

problem.

in

When maximum is

resistance

is

not required

needed, other types of 18-8 stainless steel

accordance with the individual conditions of the

Stainless steels with low carbon content (below 0.2 ^f)

containing small quantities of

molybdenum should be chosen

and

for con-

struction of tanks, trays, hangers, etc., that will be exposed to acid fixing


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

74

TABLE 3 CONSTRUCTION MATERIALS Solution

Developer

Storage Tanks

Wood

Pipe Lines Iron (ungalvanized)

(cypress)

Stainless steel *

Iron (ungalvanized)

Hard rubber Hard rubber-

Asphalt-coated wood Lead-lined

wood

Hard-glazed stoneGlass-enameled

Rubber-coated con-

Wood

Inconel

Nickel

ware

Hypo not

coated steel Stainless steel *

steel steel

Hard rubber

(cypress)

taining

Lead

Soft rubber

silver

Asphalt-coated wood

Lead

Hard-glazed stone-

Rubber-coated

ware

steel

Rubber-coated

steel

Glass-enameled

Stainless steel *

steel

Stainless steel *

Acid hypo

Wood

(cypress)

Hard rubber

containing

Asphalt-coated wood

Soft rubber

silver

Hard-glazed stoneware

Rubber-coated

Rubber-coated Glass-enameled

18-8

Mo

steel

steel steel

stainless

1

8-8

Mo stainless

steel *

steel *

Water

Same

as under

Developer

Distilled

*

Note

Block

Soft and hard rubber Stainless steel *

Block

tin

Aluminum

water

Galvanized iron

(pure)

tin

Aluminum

(pure)

These materials corrode under certain conditions of use with acid fixing Mo stainless steel is considered to be the most resistant. Refer to the discussion of stainless steels and other alloys on page 56. :

baths but 18-8


MATERIALS FOR CONSTRUCTION

75


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

76

Joints should be welded and heat treated,

baths.

if

necessary, accord-

Occlusions should be ground

ing to the manufacturer's instructions.

away from the back of the weld. The use of steels containing colombium and molybdenum is claimed to decrease corrosion by preventing segregation of carbon near the weld. 3.

For

fixing, toning,

ever possible. cloth 4.

and acid oxidizing solutions, avoid metals when-

Trays lined with pure

may be used for this purpose. When choosing metals for the

gum

rubber sheeting or paraffined

construction of apparatus, a single

metal should be used whenever possible, and

welded or soldered from the outside

Seams

in containers

made

to

it

should be either electro-

avoid electrolytic corrosion.

of sheet lead should be joined together

by

lead burning. 5.

Apparatus constructed

of

aluminum,

zinc, or galvanized iron should

not be used with either developers or fixing baths, since these metals react with such solutions with the formation of precipitates which leave

a deposit on the film and often stain the gelatin. zinc

wash tank

will usually

salts carried over

by the

A

galvanized iron or

corrode rapidly from the action of the silver

film or prints

from the acid

fixing bath.

Plated metals should be avoided whenever possible for use with

6.

photographic solutions and only single metals or alloys used

in prefer-

ence, since electrolytic corrosion sets in as soon as a little of the plating

wears 7.

off.

For fixing baths or strong saline solutions, avoid porous materials

such as incompletely glazed earthenware, impregnated fibrous materials, or rubber compositions, because crystallization of the salts within the

pores of the materials causes disintegration. 8.

Trays or tanks coated with lacquer or baked japan are not

re-

sistant to strongly alkaline developers or fixing baths of high acid con-

centration. 9.

Avoid the use of cheap rubber tubing or other materials contain-

ing free sulphur or metallic sulphides in connection with developing solutions,

because the alkali

in the

developer attacks these, forming alkaline

sulphides which cause chemical fog. 10.

Corrosion of stainless steels and other alloys will be minimized

greatly provided the surface of the alloy

is

cleaned at regular intervals.

â&#x20AC;&#x201D;

In constructing Notes on Welding Stainless Steel Tanks/'' tanks of the 18-8 molybdenum stainless steel, it is important that the * The authors are indebted to Eastman Kodak Co., Rochester, N.

tlie

Engineering and Maintenance Shops of the

Y., for the data supplied in this section.


.

MATERIALS FOR CONSTRUCTION material be furnished with a low carbon content. the carbon content be 0.08'

It

77

is

essential that

or less in order to inhibit the intergranular

,

corrosion which occurs at the joints of welded seams due to deposition of excess carbides

when

the welding heat

is

applied.

It

has been found

that with a carbon content of o.oSS' or under, this characteristic will be

controlled and there will be practically no excess carbides deposited

along the grain boundaries.

For tanks which are large enough to hold 50 to 100 gallons, stainless gauge thickness should be used. Where pos-

steel sheets of at least 16 sible,

corner welds should be avoided, particularly

inside of the tank are to be polished.

formed that the joints

sides should be so

the sheets on the

if

In other words, the bottoms and

come

will

inch or

i

.so

from

the corners so that the seams will be easier to grind and a straight butt

type of seam fully

a

may

be welded.

and where the tanks are

No. 2-B

Stainless steel sheets should be annealed to

be cleaned easily, should have at least

finish.

There are four commonly accepted methods of welding in

stainless steel

These are as follows:

commercial use today. O.xyacetylene method

1

3.

Carbon arc (electric method) Atomic hydrogen arc

4.

Metallic arc

2.

The

first

Use uncoated electrodes

]

Use coated electrodes

two methods are not recommended since there

carbon pick-up

For

this reason,

where the

ance value of the 18-8 molybdenum stainless

method

recommended. The use

is

of distortion and,

corrosion resist-

full

steel is to

arc with uncoated electrode will result in a very

mum

danger of

welded seam by the use of either the oxyacetylene

in the

or carbon arc method.

third or fourth

is

of the flat

on the whole, with very good

be realized, the

atomic hydrogen

seam with a miniresults.

It will

be

found, however, that there are comparatively few skilled operators for the atomic hydrogen arc welding method.

ably not be available

The tric

metallic arc

many

themselves.

That

will is

It

For

this reason,

it

will

prob-

locations.

method makes use

arc welding machines.

welding wire which

The

in

is

of the ordinary

commercial

elec-

well to specify the use of electrodes or

have the same approximate analysis as the sheets

to say, iS^r

chrome,

S'/r

nickel,

3%

electrodes should be coated so that full advantage

the protective gas which

is

released

by the use

molybdenum.

may

be taken of

of this type of electrode,


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

78

resulting in a

more

ductile weld

due

to the protection

oxidization of the deposited weld metal.

used with

work

all

types of metallic arc welding of stainless steel, that

or tank sheet should be the negative terminal

positive one.

mately

50%

from the rapid

Reversed polarity should be

The

co-efficient of

expansion of 18-8 alloys

greater than mild steel.

For

job for welding due allowance should be

is

for

the

approxi-

this reason, in setting

made

is,

and the electrode the

up the

expansion and contrac-

That is, greater care should be taken to use proper welding fixand clamps to prevent localized strains and distortion of the tank. After the weld has been made, it will be noticed that there is a discoloration along the sides of the weld seam. This is due to the scale which is formed at the high temperature of the welding arc. This scale and excess weld metal should be removed by grinding. tion.

tures


CHAPTER V

TEMPERATURE MEASUREMENT AND CONTROL The importance graphic solutions

of temperature in the preparation

by an increase

actions are accelerated tion

is

not always desirable since

A

reactions.

it

and use

of photo-

Most chemical

too frequently underestimated.

is

re-

temperature but such accelera-

in

may

result in undesirable

secondary

developer, for example, will require less time to produce

a certain density at 8o°F. (27°C.) than at 65°F. (i8°C.) but the solu-

much more

tion will also oxidize

a resulting increase in to

produce

with

Also,

fog.

film will swell

if

the temperature

and soften

The

difficulty.

rapidly at this higher temperature with

propensity to stain the gelatin of the film and

its

is

sufficiently high, the gelatin

such an extent that

to

it

can be handled only

use of suitable equipment for the control of tem-

perature represents an effective means for minimizing photographic troubles,

and devices

measurement and recording of

for the accurate

temperature constitute indispensable assets in the modern photographic plant.

Two thermometer Systems of Temperature Measurement. common use for measuring temperature, namely Centigrade

scales are in

and Fahrenheit.

On

the Centigrade scale (also called the Celsius) water

freezes at zero degrees

and

boils at ioo°,

and on the Fahrenheit

scale,

the corresponding readings are 32° and 212°.

Degrees Centigrade are

" °F."

Conversion of one scale

marked

" °C."

and degrees Fahrenheit

to the other should

be made as follows:

Since ioo°C.

= 2i2°F. — 32°F. or i8o°F.

i°C.=

and

°C. °F.

9/s°F.

X 9/5 + 32 = °F. -32°X 5/9 =°C.

In photographic practice, the Fahrenheit scale

employed, whereas

in research

work

in

is

almost universally

American and British univer-

and industries the Centigrade scale is used almost exclusively. For thermometers having unit scale divisions of equal width, the precision in reading a Fahrenheit scale is usually greater, since an error

sities

of 1° in reading the Centigrade scale

means an

error of nearly

2''

on

the Fahrenheit scale.

On

the continent of Europe, the

though most

thermometers are calibrated

in

Reaumur

scale

is

used extensively

al-

employ the Centigrade scale. Many both scales. The values on the Reaumur

scientific laboratories


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

80

scale differ

from the Centigrade values

scales

is

included in Chapter

50 °r

XIV, page

table

and Reaumur

347.

10°F

HVPROQumoNe Fig. 37

A

proportion 4:5.

in the

of comparative readings for the Fahrenheit, Centigrade,

— Comparative

ELON

rates of

development

of

Elon and hydroquinone de-

velopers at 50° and 7o°F.

Temperature

Effects

on

Photographic

Solutions.

chemical reactions proceed more rapidly as the temperature

and

than when cold.

w^ill

act

— Most

increased,

photography, so that

this is true of all the reactions involved in

developers and fixing baths

is

much more

rapidly

when warm

Different reactions are stimulated to different extents

by rise of temperature, and the effect of temperature can be measured numerically, the result obtained being termed the " temperature coefficient " of the reaction.

As a general

rule, the

temperature coefficient

is

measured

for a

change

of 10 degrees Centigrade, equivalent to 18 degrees Fahrenheit, so that


TEMPERATURE IMEASUREINIENT AND CONTROL if

a reaction, which at 60 degrees Fahrenheit takes 6 minutes,

at 78 degrees Fahrenheit in 3 minutes,

perature coefficient or factor of

we should say

that

is

81

completed

had a tem-

it

the rate of reaction being doubled

2,

for a rise of 18 degrees Fahrenheit.

The temperature

development varies with the develop-

coefficient of

ing agent, being least with the developers of high reduction potential,

such as Elon, and most with developers of low reduction potential, such

There

as hydroquinone.

is

one consequence of this which

is

rather im-

portant, namely, that the behavior of an Elon-hydroquinone developer

depends upon the temperature. is

very

inert,

At low temperature the hydroquinone is not decreased to the same

while the activity of the Elon

if it contained an At high temperatures the activity of the hydroquinone is increased far more than that of the Elon, and the situation is reversed. The difference in rate of development at low temperatures and at normal temperatures is shown in Figure 37. All four strips were given

extent and, consequently, the developer behaves as excess of Elon.

the

same exposure and equal times

It is seen that the lowering of

of development, namely, 4 minutes.

temperature has relatively

little effect

the rate of development of the Elon developer but slows

velopment rate of hydroquinone very greatly. that an Elon-hydroquinone developer will act

developer

A

if

the temperature

is

It is

down

obvious, therefore,

much

like

an all-Elon

lowered considerably.

similar principle applies to the fogging effect produced

opers.

If

development

ers will fog,

by

devel-

continued for a sufficient time, most develop-

but the fog reaction

and apparently has a

much

is

on

the de-

is

different

from that of development,

and one which

different temperature coefficient,

is

higher than the temperature coefficient of the development reac-

tion itself.

Consequently, a developer, which will develop an emulsion

to a satisfactory contrast with

low fog at a normal temperature,

produce very bad fog at the same image contrast

if

may

the temperature

is

high.

From in

the above

photography

is

it

will

be understood that the control of temperature

of great importance.

Whenever

possible,

development

always be carried out at a normal temperature (65째 If the temperature of the developer is too to 7o째F.) (18째 to 21째 C).

and

fixation should

high, then fog, softening,

and

Also, the solution oxidizes gelatin film.

The time

frilling of the

much more

of drying

On

is

material

readily,

may

also increased

by

the other hand,

if

too low, development will be delayed and there

is

cess water in the swollen film.

be encountered.

and tends

to stain the

virtue of the ex-

the temperature

is

danger of under-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

82

development, while the rate of fixation will be slow so that the fixing time must be prolonged to insure thorough fixation.

Acid fixing baths frequently decompose very rapidly with liberation of free sulphur

kept for a few hours to a few days at temperatures

if

over 95°F. (35°C.). temperatures,

it is

Although the rate of fixation

above 75 °F.

rise

for use

being 65° to 70°F. (18° to 2i°C.)-

rately

it

is

(2 4°C.), the

In storing large volumes

hypo and hardener solutions sepathe hypo when the latter is put into the

best to store the

and add the hardener

working tank.

increased at higher

recommended temperature range

bath to

of fixing bath

is

very bad practice to allow the temperature of a fixing

to

made

If cooling coils are used, they should be

of a

metallic material resistant to the corrosive action of these solutions (see

Chapter IV, page 52).

Some strongly oxidizing solutions, when employed at high temperatures

in particular acid

rapidly lose their effectiveness for

photographic use owing to secondary reactions.

work best

at temperatures

permanganate,

Usually these solutions

below 7o°F. (2i°C.).

Some photographic solutions, notably hypo-alum toning baths, are recommended to be used at 120° to 125 °F. (49° to 54°C.), but even these solutions should be watched carefully to see that the temperature

does not rise above that recommended. radation of the tone will result

if

Blistering, staining

and deg-

the temperature rises too high (above

i30°F.).

is

About the best general rule that can be given regarding temperature to mix, store and use the solutions at the temperature recommended

in the instructions of the

Types

of

manufacturer.

Thermometers and Their Application.

scale work, a good-grade glass fairly

— For small

thermometer of the usual type having

wide spaces between the unit divisions and legible figures

Some

satisfactory.

of these are

made

in the

form of a

Mercury

thereby serves a dual purpose (Fig. 38). of the best

known thermometric

liquids.

over a wide range of temperatures,

It

— 40*^^.

is

stirring rod is

quite

which

perhaps one

expands quite uniformly to -)-626°F.

(

— 40°C.

to

-f 330°C.). It is opaque, does not wet the glass, and has a relatively Ethyl alcohol has also large expansion for a given temperature rise.

been used extensively for measuring temperatures and other organic A dark liquids such as toluene have been used to a limited extent.

opaque liquid glass

is

preferable so that

it

may

be seen clearly through the

stem under darkroom illumination.

For the measurement of temperature of solutions automatic machines, the most satisfactory method

is

in

deep tanks or

to place a ther-


TEMPERATURE MEASUREMENT AND CONTROL mometer permanently

The method

in the tank.

of installation

is

83

impor-

tant.

For large storage or feed tanks which are provided with adequate

means

for stirring the solution, the

thermometer may be inserted through

the side, near the base of the tank.

Fic. 38

— Stirring

rod thermometer.

For working tanks or developing machines, practical to use the dial type of thermometer,

more convenient and

it is

which consists essentially

of a bulb, a long flexible stem, a flexible tube,

and an indicating

dial.

The bulb and stem may be placed in the tank from the top and immersed as much as desired, and should be made of a corrosion-resistant material such as 18-8 stainless

any

steel.

By

placing the bulb close to the tank wall

possibility of the bulb interfering with the

tank

is

obviated.

A

pure

gum

movement

used over the flexible tubing connecting the bulb and the

Three common types of thermometers are shown

A

has the scale attached to a short stem but

as type B,

which

is

fitted

of film in the

rubber or lead covered sleeve should be

is

Type

not as convenient to read

with a wall dial which

read at a glance from a distance of several

dial.

in Figure 39.

feet.

if

illuminated can be

Recording instruments

are also available which plot a record of temperature throughout the

day

(Fig. 39C).

For photographic work, an indicating thermometer

should have a large finger tapering sharply to a point.

The

dial figures

should be positioned so that a temperature of i8°C. (65°F.) cated

when the

finger

is

exactly vertical.

Any thermometer

is

indi-

reading less

than 2i2°F. (ioo°C.) which has a stem extending into or fastened to the inside of a tank should be withdrawn

when hot water

is

used to clean

out the tank, so as to avoid damage to the recording mechanism.

Methods

of Heating

Water

for

Mixing Solutions.

— Water

at


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

84

a temperature of

i25^F. (52°C.)

most chemicals, but there the chemicals

if

is

is

quite satisfactory for dissolving

a possible danger of decomposing some of

the temperature of the water

is

too high.

Most photo-

graphic chemicals are only slightly more soluble at i8o° to 2oo°F. (82°

— —

Stem type thermometer. Courtesy Taylor Instrument Co., Rochester, N. Y. Fig. 39B Dial type thermometer. Courtesy Foxboro Co., Foxboro, Mass. Fig. 39A

to

93°C.) than at i25°F. (52 °C.) and the slight saving

solution of the chemicals

is

and the extra time involved

Hot water

is

offset greatly

ture

is

in cooling the solution.

install their

argument against the use of water

own

heaters.

many

In such

at too high a tempera-

it is more economical i25°F. (52°C.) than to 180° to 20o°F. (82° to93°C.).

the increased cost of heating.

to heat water to

in time of dis-

possibility of spoilage

usually available from an independent source for

photographic workers but some must cases, a further

by the

Obviously,


MEASUREMENT AND CONTROL

TEIMPERATl'RE Hot water as follows: heater, 3.

i.

may

mixing solutions

for

85

be supplied from several sources

a water coil in the furnace,

an oil-burner operated heater,

a gas-flame operated water

2.

an

4.

and

electric heater,

5.

a

low pressure steam operated heater.

Fig.

A

â&#x20AC;&#x201D;

Recording thermometer. Courtesy 39c Taylor Instrument Co., Rochester, N. Y.

low pressure steam water heater consists of two essential units,

namely:

a. a

heating chamber and

ing chamber, in turn,

U

ing a group of " 2.

the head, as

is

is

as

fitted into the

chamber

Steam

It

in

The

is

filling

at the bottom.

the length of the

head.

A

The

a thermostatic control.

â&#x20AC;&#x201D;

i.

heat-

a chamber contain-

One end

Figure 40.

open end

sure of 3 to 15 pounds

three sections.

b.

of two parts

exit into

of the cylinder

is

open, and the head, to which are attached the water

the end of the head.

the

made up

shaped pipes having their entrance and

shown

closed, the other

pipes,

''

is

of the

chamber.

A

strong cap

fits

over

chamber under a presthe space around the pipes, and leaving admitted into the

A common

type of head

is

arranged in

incoming cold water enters one section, traverses

chamber twice and flows

into another section of the

then flows out again into the chamber, traverses

its

length

twice again and flows into the third section of the head, from whence flows out into the hot water pipe line.

it


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

86

At the point where the hot water leaves the head, a thermostat bulb This is connected by a capillary line to a valve on a 25- to 30-pound air line which operates the steam valve controlling the steam is

inserted.

pressure entering the heating chamber.

The

largest of the three gauges

STEIKM

Fig. 40

shown

in

— Diagram

Figure 40

is

set

at a desired temperature.

of a

by

low pressure steam water heater.

trial to

The two

operate the valve to deliver water

small gauges,

G^l

and Gg, measure the

pressure of the incoming air and the air which actually operates the

steam

A

line valve, respectively.

by-pass, B, should be provided as

shown

to operate the heater with-

out thermostatic control in the event that repairs are necessary on the

steam

line valve.

Control of Temperatures. \'ariations in temperature of plus or minus 2°F. are not usually important photographically except in the machine development of motion picture film or sensitometric control work. Variations of plus or minus 5°F. are usually serious, however, and in development must be compensated for by a change in the time of development or the image contrast will be affected. This is shown quite clearly in Figure 41,

which demonstrates the

effect of

changing the tem-

perature of a developer from 55° to 75° F. (13° to 24° C), on the con-

when developing for a constant time of 12 minutes. same developer (DK-50, page 288) it is interesting to note that equal contrasts at 55°, 65°, and 75°F. (13°, 18°, and 24°C.) are obtained in 14, 10, and 7 minutes, respectively. Therefore, when the trast of a negative

With

this

time of development

is

10 minutes, a change of temperature from 65°


TEMPERATURE MEASUREMENT AND CONTROL to

75°F. (i8° to 24°C.)

as

if

will result in

87

overdevelopment just as much

the time had been doubled at 65 °F.

The above

discussion serves to emphasize the need for temperature

control, especially in the case of large scale processing

55°F.

it is

often

75°F.

6s°F.

— Effect on contrast of varying the temperature

Fig. 41

when

of developer with con-

stant time of development.

difficult

offset

and sometimes impossible

temperature variations.

velopment in

in

many

to

change the time of development to

Furthermore, changing the time of de-

cases does not entirely compensate for the difference

temperature and at higher temperatures stains are apt to be produced. It is

a comparatively simple matter for the small scale worker to con-

trol the

temperature of his solutions by simply placing the bottle, tray,

or tank containing the working solution in a water bath of cold or

water until the solution has attained the desired temperature. scale work, the

problem becomes somewhat more

Water Mixers.

— The simplest type

of cold

warm

For large

difficult.

and hot water mixer

is

commonly used on household sink plumbing. It consists of a single By adjusting the valve on each line, water outlet fed by two lines. that

at

an intermediate temperature can be obtained.

Fluctuations in line

pressure and in the temperature of the water cause variations in tem-

perature of the mixed water, however, and

if

one of the

lines is

turned


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

88

off, it

permits the other to discharge without any mixing.

of this type

If

a mixer

used to control the water temperature flowing into a tray

is

or water bath containing films or prints, there

is

danger of ruining the

materials with extremely hot water.

42A - Water mixer with check valves on hot and cold Courtesy Fulton Sylphon Co., Knoxville, Tenn.

lines.

Several types of mixers are available which can be attached to the

hot and cold lines and which are not open to the above objections.

Some

of these mixers have been designed for shower bath installations in

Such mixers contain thermostatic

schools, hotels, athletic clubs, etc.

valves which contract or expand to maintain a constant delivery tem-

The Sylphon mixer

perature.

* illustrated in Figure 42A, for example,

uses a liquid expansion thermostat to control the cold water valve, and

a differential valve operated by the pressure change to control the hot

water valve.

In the event that either line

delivered

may

be

set

is

cut

off,

the mixer auto-

The temperature of the water to be by moving the hand lever on the side. Water

matically closes off the other

line.

mixers are supplied in several sizes and capacities according to the temperature requirements and the one illustrated will hold the discharged

water temperature within =t:2째F. of the

set point

with a supply water

temperature variation of 35째F. and a pressure variation of 30 pounds.

Another typical installation Valve (Series * Fulton t

R

is

the

Leonard Thermostatic Mixing

and T).t

Sylphon Leonard Rooke

Co., Knoxville,

Tenn.

Co., Inc., Providence, R.

I.


TEMPERATURE IMEASUREIMENT AND CONTROL The standard connections

for

any water mixer

installation are

89

shown

in Figure 42 B.

GAUGE GATE

^ 1 ^

VALVE

WOT ~^3ieg

.

1^4-

N

[><|

UNJION

CO\-D

WATER

r^^

^-^

— Standard

Fig. 42B

The mixing

STRAINER

^^^ifi^E*^

WATER TO MACHINE MIXER 65°^ OR TANK

pipe connections for water mixer installation.

valves described above are quite satisfactory for ordinary

use where the operating precision

not greater than

is

±2°F.

rate temperature

maintenance

is

In ex-

usually considered necessary.

treme cases the precision required

may

For

more accu-

processing laboratories using sensitometric control, however,

be as great as ±0.2 °F.

Under

such circumstances, more elaborate temperature control devices must

be installed, which compensate not only for pressure changes

in the lines

but also minimize greatly such factors as valve stem friction and hysteresis (friction

When

and

lost

motion) of diaphragms.

precise temperature control

ing equipment,

it

is

is

engineers of the leading firms

who manufacture temperature

equipment.*

Methods

of Cooling Solutions.

of cooling are

necessary on laboratory process-

suggested that the problem be discussed with the

by means

of

i.

— The

cold water,

regulation

three available

2. ice

and

methods

cooled brine or

3.

a gaseous refrigerant obtainable by mechanical refrigeration. I. Cold water is obtained from a faucet, by adding ice to water, or by mechanical refrigeration, and may be applied to the tanks in the following manner:

a.

Place pipes around the tanks.

b.

Place pipes inside the tanks.

c.

Place water jacket around the tanks.

d.

Flow water down

sides of tanks.

Placing the pipes around the outside of the tanks tory method, provided the tank material

is

as stoneware, Alberene stone, or metal.

With

or other poor conducting material, this

scheme

the rate of heat transfer *

See page 345.

list

is

rather slow and

is

a fairly satisfac-

a fairly good conductor, such insulating tanks of is

is inefficient

wood

In any case,

useless.

by virtue of heat

under water mixers and temperature regulators

in

Appendix

C,


90

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

transfer from the surrounding air, unless the pipes are enclosed with

insulating

medium such

Placing the pipes inside the tanks transfer but the pipes

Fig.

Lead

4,-i

must be

cuil

of a

is

a more efficient method of heat

non-contaminating material such as

un rack lor controlling temperature of a solution in a deep tank.

lead or 18-8 stainless steel for developers, and 18-8 less steel or

molybdenum stainThe dis-

hard rubber for acid rinse baths and fixing baths.

advantages of such a scheme are:

a.

the pipes reduce the available tank

space, h. in case of leakage the baths are ruined, fere with

an

as cork.

and

c.

the pipes inter-

keeping the tanks clean.

In the case of small tanks, the tanks which

may

300 gallon capacity sive floor load.

An

it is

feasible to place a water jacket

With

be of wood or stone.

this is usually impractical,

extremely simple method

around

large tanks of 200 to

on account of the exces-

is

to flow the

water down

the sides of the tanks through perforated pipes, but this will necessitate

frequent cleaning to remove the slime which otherwise accumulates on the tank walls.

In case the developer tanks are of stoneware or Alberene stone, a cooling tank It

may

be placed between the developing and fixing tanks.

should be equipped with a steam

in winter

and a brine

coil for

coil for cooling it in

heating the inflowing water

summer.

The

latter installa-


TEMPERATURE MEASUREISIENT AND CONTROL tion

may

be dispensed with

the temperature of the rinse water does

if

not rise above 65^F. (i8°C.) during the

cedure

is

is

surrounding

Cork

warm

insulation, although rather

The temperature

â&#x20AC;&#x201D; Arrangement

of a

quickly a few degrees

a lead

coil

for cooling solution in ice.

deep tank of solution

by using

the device

may

shown

attached to a wooden frame.

water faucet by means of a hose and the

the correct temperature.

of contamination

A

be raised or lowered

in

Figure 43.

It con-

The pipe is connected frame is moved about in

the tank for 5 or 10 minutes until the solution has

cause, unless the

from the

air to the tank.

deep tank with

to the

This pro-

also effective in preventing the transfer of heat

Fig. 44

sists of

summer months.

used successfully by some motion picture laboratories which

develop by the rack and tank system. expensive,

91

frame of stainless

become adjusted

steel

is

to

preferable be-

wooden rack is well lacquered, there is great danger by chemicals remaining in the rack after insufficient

washing.

With an adequate supply of cool water when using cooling coils, the temperature of the baths can be regulated automatically by means of a thermostat which controls the flow of water through the 2.

Ice can be applied by: a. placing

it

coils.

directly in the solution, h. plac-


PHOTOGRAPHIC CHEi\nCALS AND SOLUTIONS

92

ing it

it

in a

in

a rubber bag or metal tank inside the solutions, and

c.

placing

trough around the tank.

Although

ice is

frequently placed directly in the solutions,

tremely inadvisable because the melting ice dilutes the solution. ter method is to place the ice and move this around in the

in a

it

is

A

ex-

bet-

rubber bag or 18-8 stainless steel tank

solution.


TEMPERATURE MEASUREMENT AND CONTROL when very low temperatures

except is

are required.

93

In any case, dry ice

not recommended for cooling developing solutions because the carbon

dioxide gas converts

some

of the alkali in the developer to bicarbonate

and, therefore, tends to reduce the activity of the developer.

For rapid cooling, the dry placed

in a vessel

Fig. 46

â&#x20AC;&#x201D; Two

which,

ice

should be dissolved in alcohol and

in turn, is

placed

in the solution to

general types of refrigerating units.

be cooled.

Courtesy Frigidaire Corp.,

Dayton, Ohio.

Mechanical Refrigeration Methods. systems are readily applicable to

many

â&#x20AC;&#x201D; Mechanical

refrigeration

types of processing equipment.

Their use should be restricted, however, to the cooling of the actual solu-

because the cost of cooling wash water by this means

tions,

One type

prohibitiv^e.

essing (as described later) since

provides,

it

arrangement

is

usually

of installation designed for x-ray negative proc-

by means

for cooling the

may

be regarded an exception to the rule

of a novel supplementary cooling system,

an

working solutions as well as the wash water.

Fundamentals of Design of Mechanical Refrigerating Units.

â&#x20AC;&#x201D; Mechanical the fact that

pands freely,

it

it

becomes

amount

A a.

is

compressed

liquefied.

it

gives out heat

However,

On

if it is

compressed and cooled

allowing the liquid to evaporate

returns again to the gaseous condition but in doing so the gas

becomes cooled the

a gas

absorbs the heat again.

it

sufficiently,

depend on and when it ex-

refrigerating units of the compression type

if

to a

temperature below the surroundings, depending on

of liquid evaporated

and the rate of evaporation.

mechanical refrigerator consists of four component parts, namely:

the compression

pump

static control device,

and

or compressor, b. the condenser, d.

an expansion or evaporating

c.

a thermo-

coil.

Referring to Figure 45, the gas which may consist of sulphur dioxide, or a volatile organic compound is liquefied by compressing in

ammonia,


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

94

the compressor and cooled in the condenser either with an air fan or by

The Hquid

water.

refrigerant

is

then fed into the expansion

coil

through

the expansion valve which must be adjusted for each installation.

operation of the unit the material which coil as

may

On

being cooled.

is

The

be controlled by a thermostat bulb placed

in

evaporating in the expansion

a result of absorption of heat from the surroundings, the liquid

vaporizes and

is

returned to the compressor, thus completing the cycle.

A. Fig. 47

B.

— Direct-Flo cooling unit and section of

pipe showing construction. lor Co.,

Courtesy H.

W. Tay-

Warren, Ohio.

Refrigerating units

may

be obtained either with

cooled condensors as shown in Figure 46.

cooled or water

air

These units are available

in

several sizes which vary in accordance with the requirements of the user.

Refrigerating Equipment for Tanks o£ 40 Liters) Capacity.

made with

of tests

5 to 10

— In 1929 Wilsey described the

Gallons (20 to results of a series

a cooling unit designed for use in conjunction with

x-ray processing solutions

{X-Ray

Bull., E.

K. Co., 5; August 1929,

6: July 1930, page 6). The cooling unit consists essentially of two parts: A. a pre-cooler, and B. a Direct-Flo cooler. The

page

2; also ibid.

coils for

both coolers are made up of two lengths of metal tubing, one

scoped inside the other as shown

in

B

of Figure 47.

tele-

In the pre-cooler

the incoming water flows through the inner tubing and the cooled waste

water from the tank flows through the outer tube.

About two-thirds

the required temperature drop occurs in the pre-cooler.

The

of

partially

cooled water then flows into the outer section of the pipe in the Direct-

Flo cooler.

The

inner section of this pipe constitutes the expansion coil

of the refrigerating unit.

The

efficient

cascade system of washing

is

employed whereby the

water flows from one tank to another and the fresh water flows into the tank in which the films are placed

last.

A

typical installation of such


TEMPERATURE MEASUREMENT AND CONTROL a unit

is

shown

in

fixing tanks is

it is seen that the wash water flows compartment holding the developer and

Figure 48, where

from the wash tanks

fit

95

the

intt)

and then through the pre-cooler

supplied by the Halsey

W. Taylor

to waste.

Co.,

This entire out-

Warren, Ohio, who also

manufacture a compact pre-cooler and Direct-Flo unit illustrated at in

A

Figure 47.

simple thermostat

â&#x20AC;&#x201D; Diagram

\S

cooler.

A

used to control the temperature.

of cooling installation showing pre-cooler and Direct-Flo Courtesy Halsey W. Taylor Co., Warren, Ohio.

In cold weather, provision directly from

is

is

washing tanks

solution compartment.

made

to by-pass the flow of

to the drain

and

The temperature

waste water

to close the outlet

of the solutions

from the

then main-

is

tained by filling the solution compartment with water at the required

temperature.

Refrigerating Equipment for Deep Tanks as Used by PhotoMotion Picture Laboratories, Tanks of 10

â&#x20AC;&#x201D;

finishers or Small to

150 gallon (40 to 600

capacity are generally used

liters)

by photo-

and by motion picture laboratories which employ the rack and tank method of development. Such tanks are usually quite deep in profinishers

portion to their width and are adapted, therefore, to a system of cooling

which involves some scheme of applying a cooling

coil directly

against

the outside or inside of the tank.

A The

refrigerant liquid

may

may

be utilized

in several

ways

as

shown

in

Figure 49.

be circulated through pipes which are placed on the out-

side of the tanks as at

i.

or inside a

narrow tank containing water or a

mixture of w^ater and glycerine or alcohol to prevent freezing which, in turn,

is

placed in contact with the sides of the tank as at

ing tank

may

be immersed

in the

3. are satisfactory and give better heat transfer

2.

or the cool-

Methods 3. than method i.

tank of liquid as at

2.

and


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

96

tank containing the

If a

fixing bath, the

coils

is

actually immersed in the developer or

tank should be constructed of a corrosion resistant metal

preferably 18-8 stainless

and not soldered,

steel,

and should have the seams electro-welded between the solder and

to avoid electrolytic corrosion

the tank.

It is

3

z

I

Fig. 49

— Various methods of applying refrigeration

to deep tanks.

impractical to immerse the compressor coils directly in the tanks

because of the danger of local freezing or crystallization of the constituent chemicals.

An

actual installation on the principle of

The

uses 50 and 51.

30-gallon tank

is

method

i. is

shown

of stoneware | inch thick

in Fig-

and

is

with ^ inch copper coils (22 feet long), front and back, which are bent as indicated and welded or soldered to large copper sheets (20 ounces) held in position tightly against the sides of the tank by small fitted

wooden frames

or metal

bands (Fig. 50).

transfer from the surrounding air, the tank

In order to prevent heat

may

be completely encased

with 2-inch cork board panels or mastic-coated cork board allowing a I

-inch dead air space around the tank.

All exposed

wooden

parts, in-

cluding cork insulation, should be painted with a chemically resistant paint.

The

efficiency of this installation

the user. as follows:

may

be adjusted to

fit

the needs of

In a specific instance, the performance of an installation was

With

a

-^-

horsepower refrigerator unit

in

a room at 8o°F.

(26.5°C.) a freshly mixed developer in a 30-gallon tank at ioo°F. was cooled to 65°F. (i8°C.) in six hours and was easily maintained at this

temperature with a one degree variation. If the room temperature is above 8o°F., a greater time would be required to bring the solution temperature to 65°F. Also, if the initial solution temperature was less

than ioo°F., a proportionally shorter time would be required to adjust The current consumption for three such tanks, each cooled it to 65 °F.

by to

would be around two to room temperatures varying from 75°

refrigerating units of j horsepower capacity

three kilowatt hours per

90° F.

This

is

day

for

considered a satisfactory performance because this


TEINIPERATURE

MEASUREMENT AND CONTROL

97

temperature variation of one degree would not greatly affect the negative

work a more expensive and

contrast although for high precision

precise

thermostat should be installed.

â&#x20AC;&#x201D;

Fig.

50

â&#x20AC;&#x201D; Cooling tank.

installation

51 Cooling installation for Fig. deep tank. Detail showing thermostatic switch and expansion valve with connections to compressor.

for deep

General view.

must necessarily be considered a separate problem by the individual firm working in collaboration with the refrigeration company.* The above method of cooling is applicable only to stoneware or metal tanks which conduct heat fairly well wooden tanks, which have low heat

Each

installation

to be solved

;

conductance, should not be cooled in this way. essary

I

.

to

immerse the cooling

In such cases

it is

nec-

narrow water bath placed

coils in a

in-

and along one wall of the tank as shown in 3 of Figure 49, or 2. to run cool water through coils immersed in the tank, or 3. to circulate the developer as shown in Figure 52. This last named scheme is applicable As shown in the also to large tanks of 100 to 500 gallons capacity.

side

figure, the solution

is

circulated

by means

of a

rounded by a chamber containing refrigerating It is

assumed

in

connection with

all of

pump

through

coils sur-

coils.

these methods of refrigeration

that the solution will receive a normal

amount

* Equipment adapting the above principles Manufacturing Corp., Rochester, N. Y.

is

of agitation during use

supplied by Kellogg Compressor

&


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

98

such as

is

given by moving tilm hangers in and out of the tanks and

agitating the hangers at intervals during processing.

perienced with a temperature gradient, that

is,

If difficulty is ex-

a difference in tempera-

ture between various parts of the solution in the tank,

it

may

sary to install some type of stirrer to agitate the solution.

100 gallons or larger capacity utilized is

by means

is

of square shape

If

be necesa tank of

and external cooling

of coils applied to the tank walls, the use

is

of a stirrer

imperative or uneven temperatures will prevail in different parts of

the tank.

PUMP Fig. 52

REFRIGERATING UNIT

â&#x20AC;&#x201D; Method

of cooling large

tanks by circulating the developer through an external chill box.

Refrigeration Equipment for Use with Large Automatic Large Developing Machines of 100 to 500 Gallons Capacity.

â&#x20AC;&#x201D;

automatic processing machines are essentially of two types, as follows: 1.

machines using the continuous flow system

2.

machines using the recirculation system

for the solution feed,

for the solution feed.*

and

The

problem of temperature control with either type of machine requires some scheme whereby small fluctuations in temperature are quickly corrected.

Machinery

of this t5^e

is

usually installed in rooms which are

equipped with automatic temperature and humidity control of the ventilation system. Solutions are usually fed from the mixing tanks to the circulating or storage tanks *

and then

These systems are discussed more

to the machines.

fully in Chapter

portation of chemicals and solutions, page 210.

IX

The temperature on storage and trans-


TEMPERATURE MEASUREMENT AND CONTROL of the solution in the storage tank

from the temperature required temperature variations

may

is

99

seldom over a few degrees different

in the

machines.

affect negative quality

be given the problem of correcting for fluctuations

Nevertheless, slight

and attention should in

temperature.

In either of the two systems mentioned above, satisfactory cooling

be accomplished in two ways, namely:

may

by flowing cool water through a coil immersed in the storage tank, or />. by passing the solution through a coil surrounded by a refrigerating coil (as shown in Fig. 52) on its a.

passage from the circulating tank to the machine.

Methods of Raising the Temperature of Photographic Solu— The three most common sources of heat for raising the tem-

tions.

-

perature of a solution are:

i.

hot water,

steam, and

2.

3. electricity.

For small scale work, a water bath surrounding the tank or tray Electrical immersion heaters

effective.

schemes described previously

may

quite

is

also be used.

INIany of the

may

be utilized to

for cooling solutions

heat them by using water or steam coils installed in a similar manner.

Although

electric heating jackets

have not been employed to any extent

such heating arrangements should prove satisfactory

in the past,

in

use

providing the jackets are well heat-insulated and protected against the action of the solution. tive

means

ture

is

a

For large processing machines, the most

effec-

of preventing an undesirable drop in the solution tempera-

to recirculate the solution

chamber heated with steam or

and surround the pipe at one point with electrically heated coils.

Wash Water

Importance of

Temperature.

— When

washing

photographic materials, the temperature of the wash water should not

be too high or too low.

If

it is

too high, over i2o°F. (7,8°C.),

it

may

cause blisters to form in the gelatin layer, or softening of the emulsion.

A satisfactory temperature

range is65°to75°F.(i8°to24°C.).

Nega-

on film or plates) do not wash any more rapidly, by hypo elimination, in warm than cold water, but positive materials, coated on paper, wash more rapidly in warm than cold water because the hypo appears to be held less tenaciously by the paper fibers. tive materials (coated

as measured

when washing paper

Therefore, creased

if

prints, the

washing time should be

in-

the water temperature falls below 6s°F. (i8°C.).

Tropical Processing of Photographic Sensitized Materials.

— Where the temperature cannot be

controlled, as

may

be the case in

and plates provided special measures are taken. These involve the use of solutions which have a minimum propensity to swell the gelatin and which act rapidly so the tropics,

it is still

possible to develop films

that the film or plate needs to remain only a comparatively short time in the solutions (see

Chapter VIII, page 180).


:

CHAPTER

VI

EFFECT OF THE WATER SUPPLY ON PHOTOGRAPHIC SOLUTIONS Water

is

the most widely used chemical in the processing of photo-

graphic materials and ties

present in

impurities

it

may

may

important to

it is

know

to

what extent the impuri-

be harmful to the various operations and

how

these

be removed.

Impurities in Water. water from clean, melted

â&#x20AC;&#x201D; Excluding

ice or

distilled water, rain water,

snow, the following impurities

and

may

be

present

Dissolved salts such as bicarbonates, chlorides, and sulphates of

1.

calcium, magnesium, sodium, and potassium.

may

Suspended matter, which

2.

consist of:

a.

Mineral matter such as mud, iron

b.

Vegetable matter such as decayed vegetation, fungus growths,

rust, or free sulphur.

and micro-organisms.

The suspended

particles

may

be of colloidal dimensions

case they are difficult to remove

by

in

which

filtration.

Dissolved extracts, usually colored yellow or brown, from decayed

3.

vegetable matter and the bark of trees.

Dissolved gases such as

4.

air,

carbon dioxide, sulphur dioxide, and

hydrogen sulphide.

EFFECT OF IMPURITIES ON PROCESSING Development.

â&#x20AC;&#x201D;

containing calcium

cium

i.

If a

salts,

sulphite, but with

developing solution

is

prepared with water

a white precipitate consisting largely of cal-

some calcium carbonate,

is

apt to form on mix-

In some cases a precipitate does not form immediately but a

ing.

sludge

^

consisting of fine needle-shaped crystals of calcium sulphite sepa-

rate out on standing (Fig. 53).

Such a sludge or precipitate will settle However, the

out on the emulsion side of the film and cause spots.

harmless

white precipitate or sludge

is

clear supernatant liquid

drawn

is

if

allowed to

off for use.

settle,

Magnesium

and only the salts,

unless

present in excess, are not precipitated.

The

developer, of course,

is

robbed of sulphite and carbonate to the

extent required to form the sludge or precipitate, but except in the case 1

"The Nature

(igi8)

;

B.

J.

of a Developer Sludge" by

Phot. 65, 87 (1918).

J. I.

Crabtree.

Amcr. Phot.

12, 126


EFFECT OF THE WATER SUPPLY ON SOLUTIONS of developers of low alkalinity, this effect

have shown that calcium or magnesium need to be present

is

negligible.

salts

101

Experiments

(chlorides or sulphates)

concentration greater than o.i /c to produce an

in a

appreciable effect on the developing power of developers containing

0.3% sodium

carbonate.

% â&#x20AC;˘".S^iJ^,.... ;.^^ ^.y

W:0

.:.\\

'y^'i^c

â&#x20AC;&#x201D;

Fig. S3 Crystals of calcium sulphite precipitated from a developer pre-

pared with hard water. Artificially

hardened water was used

According

tests.

to

U.

in

preparing developers for the

Geological Survey data

S.

-

on the hardness of

natural waters in different parts of the United States, the hardest water tested

was found

0.04%

to contain only

of

permanent hardness (calcu-

Depression of negative contrast by virtue

lated as calcium carbonate).

of a lowering of the sulphite or carbonate content of a developer

with natural waters found

liable to occur, therefore,

with weakly alkaline developers.

e.xcept, possibly,

in the

is

not

United States

In the case of devel-

opers containing a low concentration of borax, which are very sensitive to slight

changes

of calcium salts

in alkalinity, the presence of

would be

sufficient to

an appreciable quantity

lower the alkali content, and due

allowance for this should be made.

The

precipitation of calcium carbonate can be prevented

sodium metaphosphate (NaPO..) on the hardness, but (30 grains per quart)

fixing

an excessive amount (over

if

apt to form on the film

to the water, in proportion

is

used, a precipitate of

when

bath unless the film

placing in the fixing bath.

is

it is

depending

grams per liter) aluminum phosphate is 2

transferred from the developer to the

rinsed thoroughly in running water before

The

addition of metaphosphate to a fixing

bath containing alum tends to destroy 2

by adding

its

hardening properties.

U. S. Geological Survey Water Supply Paper No. 496.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

102

Salts liable to be present, other than the above, are chlorides

mides of the

alkali metals

carbonate, which

the action of a weakly alkaline developer.

exert

to

any appreciable

With

in the

It is

if

the average developer,

water used for mixing

is

Developers mixed with

effect.

water containing sodium or potassium sulphides fog even

Sodium up

present in certain alkaline waters, tends to speed

is

however, the concentration of the alkali insufficient

and bro-

which exert a restraining action.

bad chemical

will give

the sulphides are present in very small quantities.

customary

to

add copper sulphate

riodic intervals in order to kill vegetable

the presence of

to certain

and

water supplies at pe-

biological growths.

While

part in 10,000 of the copper salt in a developer will

i

cause aerial fog,^ the concentration of the copper salt in the water supply usually 2.

a.

is

much

lower than

this.

Dirt and iron rust suspended in the developer solution often

produce spots and

stains.

In the case of a pyro developer the iron

apt to combine with the pyro, forming an inky

a bluish-red color to the solution although photographically Particles of finely divided sulphur

is

compound which imparts it is

harmless.

which give the characteristic opal-

escence to sulphur waters will cause fog, owing to the formation of

sodium sulphide by interaction with the carbonate present oping solution.

water

whereupon

it

may

is

usually precipitated

developer.

in the devel-

boiled, the colloidal sulphur usually

is

Vegetable matter

coagulates, b.

If the

be separated by settling or

by the

filtration.

salts present in the

Frequently fungus growths and micro-organisms thrive in

a developer and form a slime or scum on the walls of the tank.

Some

types of these growths act on the sulphite in the developer, changing to

sodium sulphide which fogs the emulsion very badly.

is

removed by developing some waste

The

film in the solution or

it

sulphide

by adding

a small quantity of lead acetate to the developer in the proportion of

60 grains per gallon (i gram per

liter)."*

Tanks which show a tend-

ency to accumulate slime should be scrubbed with hot water at regular intervals

and then treated with a

dilute

sodium hypochlorite solution

Chapter XII, page 265). Suspended mineral, vegetable, or animal matter in general has usually no harmful effect on a developer, provided (see

the mixed developing solution

supernatant liquid drawn

wafm 3

off

is

allowed to stand and only the clear

for use.

Preparing the developer with

water tends to hasten the rate of settling of the suspended matter.

"Chemical Fog" by

Pilot. 66,

J.

I.

Crabtree.

Amcr. Ann. Phot.

33, 20

(1920); B.

J.

97 (1919). 4 " Sulphide Fog by Bacteria in Motion Picture Developers " by M. L. Dundon and J. I. Crabtree. Amcr. Phot. 12, 56 (1925).


EFFECT OF THE WATER SUPPLY ON SOLUTIONS

103

Extracts from decayed vegetable matter or the bark of trees usu-

3.

ally discolor developing solutions but are often precipitated

veloper

prepared with

is

warm water and

ing effect of such extracts

Water

4.

is

dissolves about

the de-

if

The

allowed to stand.

stain-

usually negligible. 2""^

of air at yo^F.

developing agent like hydroquinone

is

(2i°C.) and when a

dissolved without the addition of

sulphite the oxygen present in the water combines with the developing

agent, forming an oxidation product which

form of

apt to stain the gelatin and

is

Air in water occasionally collects on the film in the

fog the emulsion.

bubbles or airbells which prevent development and pro-

little

duce characteristic markings ing at high temperatures

causes blisters

'

(see page 188

'^

(see Fig. 70,

(above 8o°F.)

When

page 144).

(26°C.) dissolved

and Fig. 70).

Mineral waters containing carbon dioxide rarely give provided the water dioxide

way

is

boiled

first in

order to drive

off

present in a developer in excessive amounts,

is

as dissolved

air,

developair often

much

the gas. it

trouble,

If

carbon

acts in the

producing bubbles and airbells on the

film.

drogen sulphide gas will cause bad chemical fog in a developer but

same

Hy-

may

be removed by boiling the water or by precipitating with lead acetate before mixing."It is

*

sometimes thought that water treated with chlorine

suitable for mixing photographic solutions.

Any

may

be un-

chlorine present,

how-

would be destroyed immediately by the sulphite or developing

ever,

agents.

The

chlorine content

is

usually so small that the photographic

properties are not appreciably affected

by

virtue of this destruction of

a trace of the constituent chemicals.

— Calcium and magnesuim

Fixation.

sulphites are soluble in acetic

acid and therefore are not precipitated in fresh acid fixing baths. If the

pH

any scum

value or degree of alkalinity of the bath becomes too high,

of calcium sulphite

prints in the developer

is

which

may have formed on

the films or

not dissolved and remains even after washing.

important, therefore, to keep the fixing bath sufficiently acid by

It is

revival or the use of an acid rinse bath. 5

tree 72,

" Rack Marks and Airbell Markings on Motion Picture Film " by J. and C. E. Ives. Trans. Soc. Mot. Pict. Hinj. No. 24. 95 (1925) B. ;

775 (1925) c

tree. '

;

Crab-

J.

Phot.

73, 4 (1926).

The Handling of Motion Picture Film at High Temperatures " by J. I. CrabTrans. Soc. Mot. Pict. Eng. No. 19, 39 (1924); B. J. Phot. 71, 762 (1924). "Chemical Fog" by J. I. Crabtree. Amcr. Ann. Phot. 33, 20 (1920); B. J.

"

Phot. 66, 97 (1919). 8 " Sulphide Fog by Bacteria in Motion Picture Developers " by M. L. J. I.

I.

Crabtree.

Amcr. Phot.

12, 96 (1925)-

Dundon and


104

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

Other dissolved

salts such as bicarbonates, chlorides, and sulphates are Suspended matter such as dirt, iron rust, and certain types of vegetable and animal matter usually will coagulate and settle out on

harmless.

allowing the fixing bath to stand.

(a)

â&#x20AC;&#x201D;

Drying marks on the film emulsion produced by water on the emulsion side; (b) water on the base side.

Fig. 54

Although most suspended substances have practically no

may

photographic properties of fixing baths, the particles film,

locally retarding fixation,

effect

on the

settle

on the

and producing spots and

stains

(see

Chapter XI, pages 248, 255). Extracts from vegetable matter or dissolved gases do not affect the photographic properties of a fixing bath, but are liable to cause stains and

Washing.

â&#x20AC;&#x201D; Dissolved

blisters,

salts often

and

locally retard fixation.

cause trouble by crystallizing on

the film after drying (Fig. 53, p. loi), and although not always visible as crystals to the eye, they detract from

water containing calcium

salts leave a

its

transparency.

Drops

of

white scum after evaporation.

Water which

is

provided

allowed to remain in droplets on either side of the film dur-

it is

free of dissolved salts also will cause

ing drying^ (Fig. 54). all a.

It is

important therefore to remove thoroughly

excess water from the film before drying.

This can be accomplished

by draining thoroughly before applying a current

9 " Moisture Markings on Motion Picture Film " by J. Matthews. Trans. Soc. Mot. Pict. Eng. No. 17, 29 (1923)

IS (1924).

markings on film

of air, h.

I. ;

by swab-

Crabtree and G. E. J. Phot. 71, 6 and

B.


EFFECT OF THE WATER SUPPLY ON SOLUTIONS bing with wet absorbent cotton, viscose sponge, or chamois, and

means

of a

105

c.

by

pneumatic squeegee.'"

Fig. 55

â&#x20AC;&#x201D; Low pressure steam operated water

still.

(Capacity 15 gallons per hour.)

Suspended mineral, vegetable, and animal matter usually produces a

scum on drying. or

film unless the gelatin surface If the

water used

for

filtered before using for

is

washing

wiped carefully previous to run into a large settling tank

is

is

washing purposes, most of the suspended

matter will be removed (see discussion on

filters,

Chapter

III,

page 31).

Dissolved extracts from bark and decayed vegetable matter produce stains

which are very

difficult to

remove.

In

many

cases, however,

it is

by passing it through a filter containing the wash water is warm, dissolved gases

possible to decolorize such water

activated charcoal.

Also,

sometimes produce

will

sufficiently in the fixing

So far as 10

Mot.

"A

Pict.

is

if

blisters, especially

if

the film

is

not hardened

bath (see page 188).

known, any small

Pneumatic Film Squeegee Etig. No. 30, 270 (1927).

"

traces of impurities left in the gelatin by

J. I.

Crabtree and C. E. Ives.

Trans. Soc.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

106

coating of a film after drying, by virtue of the presence of these im-

wash water, are not

purities in the

liable to seriously

impair the keeping

However,

properties of the films over a period of four or five years.

which are

films

be kept for long periods of time should be washed

to

finally in distilled water.

The Preparation

of

Dye

Solutions.

â&#x20AC;&#x201D; Many

dyes are precipi-

by calcium or magnesium salts and alum. The not always immediate and may occur only after standing

tated out of solution precipitation for a

is

The

few days.

properties of dyes with respect to their rate of pene-

tration into gelatin or the rate at

which they are mordanted are affected

considerably by the presence of metallic ions, or acids, or bases, so that in color

photography or when using

desensitizers, impurities in the water

are apt to produce anomalous results.

Dye

solutions should, therefore,

be prepared with distilled water rather than water containing dissolved salts (see

pages 177 and 326).

Distillation.

â&#x20AC;&#x201D;

Distilled water should be used

water by one process only, namely,

which consists

distillation,

verting natural water into steam which, in turn,

The

liquid form.

whenever possible

for

Chemically pure water can be obtained from natural

mixing solutions.

is

condensed

dissolved salts and impurities do not

in con-

to the

over and

distill

are left behind.

Water

stills

are available in sizes ranging from those which deliver

gallons per hour to those of several

to 2

capacity.

Stills

are most

commonly operated with

pressure steam (Fig. 55).

i

hundred gallons per hour low

either gas or

Small units delivering from

i

to 5 gallons

per hour are also supplied with electric heating units but are usually more

expensive to operate unless a cheap source of current

56A). gas

if

It is

not generally considered

the capacity

is

efficient

both small and large capacity

For very large volumes of for

economy.

The

available (Fig. still

with

greater than 10 gallons per hour unless, of course,

a cheap source of gas can be obtained (Fig. 56B). for heating

is

to operate a

Kerosene

is

also used

stills.

distilled water, multiple effect stills are

used

exact type of installation depends on the needs of the

individual photographer, and manufacturers of water

stills

should be

consulted (see Appendix, page 344). Until recent years block tin has been employed extensively as a construction material for pipe lines and fittings to carry distilled water.

In

and storing distilled water. It lends itself to rapid fabrication, threading, and in long pipe Tin-plated lines does not require supporting to the same extent as tin.

some cases aluminum has been used

for piping


EFFECT OF THE WATER SUPPLY ON SOLUTIONS brass or copper as well as of these install if

aluminum

is

used for storage tank linings but

is

an economical precaution to

It is

automatic spring closing faucets on

aluminum piping

num

aluminum

recommended.

is

employed,

107

all distilled

fiber seats

water

lines and,

should be used in the alumi-

faucets.

— Small

capacity water still heated by a storage battery. Courtesy Barnstead Still and Sterilizer Co., Inc., Boston, Mass. Fig. 56A

electrically

Fig. s6b

water

— Small

still.

capacity gas-heated

Courtesy F.

Stokes

J.

Ma-

chine Co., Philadelphia, Pa.

— Unless

Boiling.

solved salts, and it is

if

the water contains an excessive quantity of dis-

the purchase of distillation equipment

usually sufficient to boil the water and allow

natant portion then fine muslin.

Most

may

be siphoned

off or

colloidal vegetable

it

is

to settle.

prohibitive,

The

super-

the solution filtered through

and animal matter, comprising

slimes and scums, coagulates on boiling and certain lime salts are

changed

to

an insoluble condition and

settle out.

not removed but dissolved gases are driven

by

Dissolved extracts are boiling.

Various types of water filters are available commerbut these do not remove dissolved salts or colloidal matter unless

Filtration. cially,

off

the water has been treated previously with a coagulant.


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

108

The

simplest type of water

filter

consists of several layers of fine

cheesecloth or cotton flannel fitted over the end of a hose attached to the

Another type consists of a small metal receptacle

faucet (Fig. 57).

holding a

felt

pad, sand, or other filtering

medium which may be screwed

on the faucet (Fig. 58).

Simple type of water

Fig.

filter.

â&#x20AC;&#x201D;

Fig. 58 Small water filter attached to faucet. Courtesy

Jones

Manufacturing

Co.,

Boston, Mass.

The tubular

filter

shown

It consists of

filter.

guide rod, a

filter

on a flange.

tube,

The

in

Figure 59 represents a useful type of water

an outer metal cylinder, a combination cap and

and a

cylindrical cover

The

filter

minimum

open

consists of an

helical

Water

ward through the wall of this tube. are made by changing the spacing

A this

against a gasket

in

a

alteration in existing piping.

around a circular wire screen.

filter

fits

which permits installation

straight line on the cylindrical cover,

pipe line with a

which

feed and discharge connections are arranged in a

is

winding of filtered

fluffy cotton

by passing

thread

radially in-

Fillers of various degrees of fineness

of the thread or including a layer of

paper inside the winding. reasonable flow of water for most photographic requirements with

type of

filter will

be obtained with approximately 40 pounds water

pressure per square inch.

The

life

depends

in all cases

on the amount of

material to be removed from the water and on the pressure applied.

use of rotary or gear

pumps

rather than piston

pumps

is

The

recommended.


EFFECT OF THE WATER SUPPLY ON SOLUTIONS

Fig. 59

— Small cylindrical

filter

Commercial

Fig. filter.

using cotton

Filters Corp.,

wound

tubular

filters.

Boston, Mass.

Large capacity gravity type water 6o Courtesy Wm. B. Scaife & Sons, Oakmont,

Pa. °f*

Pa.

"^jf

Large capacity pressure type water Courtesy Wm. B. Scaife & Sons, Oakmont,

Fig. 6i filter.

SUPPLY

109

Courtesy


:

PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

110

For sand

filtration in plants using

filter

coal, or a

may

25,000 to 500,000 gallons daily, a gravity

be installed (Fig. 60).

Pressure

filters

using sand, char-

composition material are also available of similar capacities to

the gravity type but in general they have not been found to deliver quite as clear water as the gravity type.

much more compact than much floor space Fig. 61 (

a pressure fioors of

filter,

)

Pressure filters

It is often

.

particularly

if

however, are usually

filters,

and, therefore, do not require as

necessary to

the laboratory

pump

the water into

located on the upper

is

a building.

The choice among which 3.

gravity

of a particular type of filter are:

i.

depends on several factors

condition of water supply,

2.

location of laboratory, 4. floor space available, and

For further

tion required.

details, the

capacity needed, 5.

manufacturers of

degree of filters

filtra-

should be

consulted (see Appendix, page 342).

Chemical Treatment. fication * 1.

may be

â&#x20AC;&#x201D; The

following methods of chemical puri-

adopted

Potassium alum

may

be added in the proportion of

grains) to 4 liters (i gallon) of water. carries

down suspended

particles

and

alum introduced

into the water has

2.

A 10%

solution of

and coagulates the

solution.

may 3.

The

no harmful

effect

on the solution

mixing developers and fixing baths.

sodium oxalate may be added

until

no further

slime, although other dissolved salts are left in

Solutions of sodium phosphate and of sodium sulphite also

be used to precipitate calcium and magnesium.

Most

of the

commercial methods of softening water

may

be em-

ployed although such methods do not remove sodium and potassium

One

Dis-

small percentage of

This method removes the calcium and magnesium

precipitate forms. salts

for

gram (15

clears the solution rapidly.

solved salts are not removed by this method.

when subsequently used

i

This coagulates the slime which

salts.

most satisfactory methods consists in passing the water through a tank containing sodium aluminum silicate (zeolite), which possesses the power of exchanging its sodium for the calcium and magof the

nesium present

in the water.

Sodium aluminum

silicate

(zeolite)

+ Calcium sulphate

Sodium sulphate

=

+ Calcium aluminum

silicate

* Water purified by the treatments described is not generally satisfactory for drinking purposes since these treatments are not intended to kill micro-organisms in the water.


EFFECT OF THE WATER SUPPLY ON SOLUTIONS When

the zeolite thus loaded with calcium and

in a strong solution of

common

and magnesium again the chemical

may

for

(about

salt

sodium and

12%)

it

magnesium exchanges

ill

is

washed

its

calcium

thus regenerated, whereupon

is

then be used for further softening.

Calcium aluminum

Sodium aluminum

silicate

silicate

(zeolite)

=

+

+

Sodium chloride

Calcium chloride

â&#x20AC;&#x201D;

62 Portable water softening Courtesy Permutit Co., New York, N. Y. Fig.

unit.

A

compact, portable water softening unit working on the principle

described above

York, N. Y.

It

is

supplied by the Permutit Co., 440 Fourth Ave.,

may

be attached to any household faucet and

of softening 100 gallons of water before

62).

it

is

New

capable

needs to be regenerated (Fig.

Larger water softening units are manufactured by several different

companies, reference to which

may

ing Catalog," published annually

New York, N. Y. A comprehensive

be found in the " Chemical Engineerby the Chemical Catalog Company,

discussion of the relative efficiency of various meth-

ods of water softening has been published by Mills." 11

"

Modern Water Softening

277 (Sept. 1933).

"

by A.

J.

Mills.

/.

Soc.

Dyers and Colorists

41),


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

112

A method exchange

of removal of dissolved mineral solids

removing the ionized dissolved

It consists of

through a bed

from water by organic

has been described by Bird, Kirkpatrick and Melof.^-

filters

in

which the

salts are

by passing the water

solids

converted to acids, and then passing

the acidic water through a second bed in which the acids are removed

from solution

and

to yield a water substantially neutral

free of dissolved

solids.

The Use

of Sea Water.

â&#x20AC;&#x201D; Sea

water contains a relatively large

proportion of soluble salts (about 3.5%) and should not be used for

mixing photographic solutions except other water

is

chlorides, bromides,

last

may

is

and iodides

When

graphic solution. sea water

This

available.

extreme emergencies when no

because the dissolved salts such as

may

retard the action of the photo-

the supply of fresh water available

is

very small,

be used for washing photographic materials provided a

washing or soaking previous

water. ^^

in

Even

to drying

given in distilled or fresh

is

after thorough squeegeeing a considerable quantity of

magnesium

the constituent salts remains and the hygroscopic

chloride

causes " dampness " and tends to accelerate fading of the silver image.

important therefore to wash or soak

It is

treatment, which

is

effective in

Suitability of the

Water Supply.

water supply usually reveals very fulness.

It

may

pure water after the sea water

little

â&#x20AC;&#x201D;A

chemical analysis of the

concerning

its

photographic use-

be of some assistance in indicating the quantity of lime,

oxalate, etc., to be late slimes.

in

removing the hypo.

added

to

The quantity

remove dissolved calcium

of total solids indicates

marks may be anticipated, while the presence

if

of iron,

is

to

The only

prepare a developer with the sample and actually try

compared with the same developer prepared with

coagu-

hydrogen sulphide,

or metallic sulphides should be regarded with suspicion. test

salts or to

trouble from drying

useful it

Also, a large drop of water should be allowed to dry on a film

the

amount

of residual

scum observed.

the trouble to be expected

if

the water

This is

out

distilled water.

and

will indicate the extent of

not removed thoroughly before

drying.

"

of Dissolved Mineral Solids from Water by Organic Exchange by P. G. Bird, W. H. Kirkpatrick and E. Melof. /. Amcr. Water Works Asso. 29, 1526 (Oct. 1937). " Washing Motion Picture Film " by K. C. D. Hickman. Trans. Soc. Mot. Pict. Eng. No. 23> 62 (1925). 12

Filters "

I-''

Removal


EFFECT OF THE WATER SUPPLY ON SOLUTIONS Practical Recommendations. with

warm water

night,

any

If

developing solutions are mixed

(about i2 5°F.) (52'^C.) and allowed to stand over

precipitate or suspended matter will settle out

supernatant liquid

and other

â&#x20AC;&#x201D;

113

may

salts in the

be drawn

water supply

and the clear

The presence

off for use.

sometimes beneficial

is

of calcium

in so far as

they tend to retard the swelling of the gelatin coating of the film during washing.

This

The only

is

advantage

of particular

in

hot weather.

impurities liable to cause serious trouble with developers are

hydrogen sulphide or soluble metallic sulphides.

With such water, about

60 grains of lead acetate per gallon of developer (i gram per should be added before mixing.

phide and any excess lead

is

liter)

This removes the sulphides as lead

sul-

precipitated in the developer and settles

out on standing.

No trouble may be

anticipated with fixing baths prepared with average

samples of impure water provided the bath

is

clarified

by

settling before

use.

In localities where very hard water

mixing photographic solutions, unit.

These are available

in

it is

is

both small, portable

capacity) for amateur or studio use, and

normally require several hundred for

or

100 gallon

sizes (of

in large sizes for plants

more gallons

of water each

which

week

mixing their solutions.

When

washing photographic materials

pated with uncolored water a.

the only source available for

advisable to install a water softening

remove

all

if

little

trouble

may

be antici-

the following precautions are taken:

suspended matter by

filtering, either

by means

of

commer-

by placing two or three layers of cloth over the water outremove thoroughly all excess moisture from the film before drying. Water which is colored brown even after filtering through cloth or

cial filters or let, b.

sand

is

very apt to cause staining of the highlights.

through activated charcoal

is

effective.

Usually

filtering


CHAPTER

VII

TECHNIQUE OF MIXING AND USING PHOTOGRAPHIC SOLUTIONS DEVELOPERS Photographic developers usually contain four solid ingredients as

fol-

lows:

The developing

A.

or reducing agent

(Elon,* hydroquinone, pyro,

para-aminophenol, para-phenylenediamine, B.

The

C.

The

etc.).

preservative (sulphites, bisulphites, and metabisulphites of

sodium and potassium). alkali or activator (carbonates

tassium, and

ammonium;

and hydroxides

of sodium, po-

also borax, borates, amines, etc.).

D. The restrainer (bromides and iodides of sodium and potassium).

The Developing number

or

Reducing Agent.

of different developing agents

photographer from time

â&#x20AC;&#x201D; In

to time, for general use

perior to Elon, hydroquinone,

spite of the large

which have been offered

and pyro.f

to the

none have proved su-

Some photographers

still

use

pyro exclusively, maintaining that a yellow pyro-stained negative

will

give better prints than an Elon-hydroquinone developed negative.

Ex-

tensive tests have shown, however, that

it is

possible to get just as good

prints from negatives developed with Elon-hydroquinone as with pyro.

Of

same contrast as an more contrasty print usually give a

course, a pyro negative which appears to have the

Elon-hydroquinone negative

will

because of the yellow stain image present.

hydroquinone negative

is

If,

however, the Elon-

developed long enough so that

printing contrast as the pyro

it

gives the

same

negative, the quality of the prints for a

given amount of fog on the negative will be identical.

The presence

of the

pyro stain image can readily be revealed by

ducing a pyro-developed negative in Farmer's reducer, which

mixing equal parts of a

5%

solution of hypo.

5%

is

re-

made by

solution of potassium ferricyanide and a

This treatment removes the

silver

image but

leaves the stain image. * The developing agent, mono-methyl para-aminophenol is sold under various Since the experience trade names such as Metol, Elon, Pictol, Photol, Rhodol, etc. of the authors has been largely with Elon, reference will be made to this trade prod-

As supplied to the trade, Elon is a salt of sulphuric acid and methyl para-aminophenol and when dissolved in water it gives an acid reaction. para-aminophenol t Other developing agents which are used less extensively are (amidol), para-oxyphenyl glypara-phenylenediamine, di-aminophenol (p.a.p.), uct throughout this book.

:

cine

The

(glycine),

chlor-hydroquinone, and pyrocatechol (pyrocatechin or catechol). common developing agents are listed in Table 7, page 216

properties of several


MIXING AND USING PHOTOGRAPHIC SOLUTIONS Pyro has one very valuable property which are formed when the developer fog, the

nature of which

is

in so far as its

is

veloper will prevent this fog, which

is

oxidation products,

exposed to the

A

explained later.

115

air,

prevent aerial

trace of pyro in the de-

the reason for using a mixture of

Elon, hydroquinone, and pyro in some formulas.

E

H

E

H

E

Imin.

Imin.

2min.

2min.

4min.

Fig. 63

The

â&#x20AC;&#x201D; Comparative

rates of

development

of

Elon

vs.

H 4min.

hydroquinone.

addition of pyro to an Elon-hydroquinone developer tends to in-

crease the rate of aerial oxidation of the developing agents so that the

quantity of pyro added should be a minimum. In view of the above objections, namely:

poor keeping properties, of

b.

a.

the staining and relatively

the accelerating effect on the aerial oxidation

Elon and hydroquinone, and

c.

the fact that

it

is difficult

to secure

negatives of uniform printing contrast because the quantity of image stain varies with the age of the dev^eloper,

by Elon-hydroquinone is

for the

pyro has been replaced entirely

development of motion picture film and

being discarded rapidly by professional photographers

in

favor of the

more stable Elon-hydroquinone developers. The difference in behavior between Elon and hydroquinone clearly in Figure 63.

The

test

was made with what

are

known

is

shown

as step-


PHOTOGRAPHIC CHEMICALS AND SOLUTIONS

116

exposed negatives which simply consist of strips of film which have

An

ceived increasing exposures in steps from end to end.

re-

exposed picture

negative likewise consists of a series of patches of irregular shape which

have received increasing exposures so that we

may

consider the lower

density steps in the step negative to correspond to the shadows, and the

higher densities to the highlights of an ordinary negative.

Such step

negatives are to be preferred for testing purposes because they can be

reproduced exactly and can be compared more easily by placing side by side.

Two developers

were prepared, one containing only Elon and the other

only hydroquinone.

Step-exposed strips of film were then developed in

minute, 2 minutes, and 4 minutes, respectively. minute the Elon developer had produced an image of low contrast

each developer for After

I

i

while the hydroquinone had produced only the faintest sign of an image. After

minutes

2

all

the image tones were visible in the case of both de-

velopers but the hydroquinone image was less contrasty than the Elon

After 4 minutes, the two negatives were almost identical.

image.

On

prolonging the development, the hydroquinone image was more contrasty

than the Elon image.

Elon, therefore, brings out the detail quickly but

the hydroquinone builds

The

Preservative.

from oxidizing

sodium sulphite

The

up the

â&#x20AC;&#x201D; In

contrast.

order to prevent the developer solution

in the presence of air, a preservative is or, occasionally,

sodium

added, usually

bisulphite.

sulphite performs a dual function, namely:

i. it

prevents aerial

oxidation of the developing agent, maintaining the solution colorless both

during mixing and storage, and during use.

When

2.

maintains the developer colorless

it

development takes place

sulphite, the developing solution