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Introduction to Printing Technology r e u b e n d s i lva

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“What gunpowder did for war, the printing press has done for the mind.� ~ Wendell Phillips

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This document aims at outlining the process of graphic print production from start to f inish based on the order of my understanding hence far.

_ Timeline

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_ Pre Press Scanning Colour setting, Halftone Paper Imposition Plate production Ink Costing

06 08 11 14 18 26 27 30

_ Press Relief Letterpress Flexography Offset Gravure Screen Unconventional

_ Post Press Methods Binding _ Field Visit _ Reference

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38 42 46 48

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Timeline Printing is an industrial process of duplicating or developing an original for production of text and images, typically with ink on paper using printing press.

0105 Invention of paper by Chinese. 0200 Woodblock printing 0868 Diamond sutra, the earliest printed block. 1450 Johann Guttenburg, The movable type. 1500 Etching invented. 1655 Oldest existing newspaper, The London Gazette. 1798 Lithography invented by Alois Senefelder. 1867 Typewriter was patented. 1871 Monotype by Tolbert Lanston. 1887 Gelatin Bromide dry plate. 1962 Offset was invented. 1969 Laser printing. 1973 Compugraphics/ videosetter. 1977 Linotype introduced Linotron. 1978 Monotype introduced Lasercomputer. 1985 Raster image processor/Desktop computers. 1991 Introduction of Direct Imaging Technology. 1995 Touch screen process control. 2000 Digital work flow.

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Scanning Very often the images to be printed must be lifted off existing originals. The f irst step in digitizing an original is scanning.

The scanner is a device that optically reads images and converts it to a digital image. The maximum resolution of your scanner sets the limitation on how much you can enlarge your image. There are two factors to consider to determine resolution of scanning: the screen frequency and whether or not you require to change the size of the image. Screen frequency is determined by printing method and paper used. The relationship between image resolution and screen frequency is called ‘sampling factor.’ Optimum sampling factor is 2, which means that the image to be printed on 150lpi should be scanned at 300ppi. If sampling factor goes down to 1, pixels will be visible. List of recommended screen frequencies: Paper Newsprint: 65-85 lpi Uncoated: 100-133 lpi Coated matte: 133-170 lpi Coated glossy: 150-300 lpi

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Print method Offset: 65-300 lpi Screen: 50-100 lpi Gravure: 120-200 lpi Flexographic: 90-120 lpi


Scaling factor describes the ratio of the original scanned image to the size at which it is to be printed. Optimal scanning resolution = Screen frequency x Sampling factor x Scaling

Care for originals Never write on the back of photographhs Cover originals with a tracing sheet Do not touch an original with oily hands. Do not clip or staple originals.

factor(%) Scanners most commonly used are CCD flatbed scanners.

After scanning, we must adjust the gamma curve depending on the black/white areas in an image so that details are not lost. Gamma value<1.8 for snow images/ Gamma value>1.8 for dark images. Also, it is advisable to sharpen the image if it apperas slightly soft. This will assure good results when printing.

Continuous tone

Halft one

Types of originals Line art: Black and white mages without tonal variations like a line drawing in pen. Continuos tone: A grayscale or colour image having smooth continuously varying tonal range like a photograph. Originals not suitable for reproduction may contain stains, dust, scratches, matt finish.

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Colour “I’ve handled colour as a man should behave. You may conclude that I consider ethics and aesthetics as one.” ~ Josef Albers

Chromatics or understanding colour is crucial in printing. Every image contains thousands of different colours. It is not possible to use thousand different inks or light sources to represent each. Therefore, we fool the brain into perceiving these colours by mixing three primary colours and approximating the thousands. Additive colour mixing Additive colour moxing involves adding some amount of red, green and blue light to create new colours. If you mix all three at full intensity , you get white. At a lower intensity, an equal mix of all will give a gray. Two colours at maximum intensity without a third gives you following results. Blue + Green = Cyan (C) Red + Blue= Magenta (M) Red +Green = Yellow (Y) Subtractive colour mixing In printing, colours are created by mixing three primary colored printing inks. Cyan, Magenta and Yellow.(CMY). This method is called ‘subtractive colour mixing.’ Cyan ink absorbs all the red light and reflects green and blue Magenta ink absorbs green light and reflects red and blue. Yellow ink absorbs all the blue light and reflects red and green. They are hence known as ‘subtractive primaries’.

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Colour Gamut The colour gamut is the range of coloursthat can be theoretically be created within a particular colour model. Different colour models have different gamuts. The wider the colour gamut, the more colours you can create with that model. RGB has a wider gamut than CMYK. Even though a CMYK file has more bits per pixel, it’s sensitivity range is limited. An extended colour gamut beyond RGB, is called High Fidelity printing(HiFi). These maybe used in multi colour conversions of upto six-colour printing. Spot colour In multi-colour printing (four,five or six colour) the additional channel is often a ‘spot’ colour. This maybe a special secondary colour or gold/ silver. It maybe selected from Pantone shades. Black: theory versus practice If you print cyan over magenta over yellow, the result should be black. In practice, it turns out to be a dark brownish gray. That’s why a black printing ink is added to this model. This black is referred to as ‘registration black.’ It is debated whether K comes from ‘key’ colour or the ‘k’ in black.

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Images exist in different modes digitally. Bitmap Line art consists of black or white pixels but no mid-range tones.

Grayscale An image that has tones ranging from 0% black to 100% black. Usually 256 steps.

Index An image in index colour can display upto 256 colours within a specified palette. This measn that all the pixels in the image have a value between 1 and 256 based on the colour palette. It is often used by saving GIF format for web use to reduce the image size.

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Duoton/Tritone Two/Three printing inks are used instead of one. Usually you print with black plus one spot colour. TIFF format does not support duotones.

RGB This is the system used in colour monitors and photographic imaging.Each pixel on your screen has a value for how much red, green and blue it contains. An RGB image consists of three separate pixel images. RGB gamut of colours is the largest and contains unto 16.7 million colours.

CMYK A CMYK image can be imagined to be separated into four separate grayscale images. Each one of these images defines the amount of each respective printing ink used.

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Memory Bitmap: 1 bit per pixel = 2^1= 2 tones. Grayscale: 4 to 8 bits per pixel = 16 to 256 scale tones. Index colour: 8 bits per pixel = 256 colours. Duotone: 8 bits per pixel = 256 tones. RGB: 24 bits per pixel(8 bits per channel) = 2^24= 16.7 million colours. CMYK: 32 bits per pixel(8 bits per channel)= 2^32= 4.3 billion colours.

Getting the right colours in print! One of the greatest challenges in producing colour for printing is making sure that the colours you choose are the same as that which are printed. The following parameters affect this. Colour model If youâ&#x20AC;&#x2122;re printing in six colours, you will get a larger gamut and better range of hues as compared to CMYK. Hence, your positives can be separated from an RGB image. Paper Most papers have a slight tint. Others maybe gloss coated. Reflectivity of the paper affects its tonal range. Printing process Thickness of inks used in different processes maybe different. More ink , wider the tonal range. Ink In reality. your inks cannot precisely reproduce these colours exactly. The closer the pigments are to the theoretical values, better the colour consistency. 12

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Halftone Halftone is a reprographic technique that simulates continuos tone imagery through the use of dot lines, varying either in size or spacing.

A printing press cannot produce continuos tones like in a photograph with smooth tonal transitions. It can only print with or without colour. Hence, halftone screen is used tocreate an illusion of continuos tone. Halftone screen To reproduce tones in print, you use a halftone screen. Halftone screens consist of small opts in closely spaced rows. Their size varies depending on which tone you want to simulate. The varying dots create an illusion of a continuos tone. It is a sheet of glass or film. Halftone screens are calculated by a Raster Image Processor(RIP). Screen frequency The screen frequency is the measurement of the number of halftone cells per line. It is measured in lines per inch(lpi). The lower the screen frequency, the larger the halftone cell and larger the halftone dot. This means that the size of a dot printed with a 60lpi screen will be 4 times the size of the same dot printed on a 120lpi screen. The variables that help decide appropriate screen ruling are: viewing distance, process of reproduction and type of paper.

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Paper Newsprint 65-85 lpi Uncoated 100-133 lpi Coated matte 133-170 lpi Coated glossy 150-300 lpi

Printing method Offset 65-300 lpi Screen 50-100 lpi Gravure 120-200 lpi Flexo 90-120 lpi.

Output resolution When film is output to an imagesetter, an output resolution must be set. Other setting include no. of exposure points per unit length. Higher the screen frequency, higher the output resolution.

Screen angle The brain can perceive patterns involving 0 and 90 degree angles. Halftone screens are therefore tilted at 45 degrees to make patterns less recognizable. Hence, black which is the most distracting colour is oriented at 45 degrees. Yellow which is the least distracting colour is kept at 0 degrees. Cyan and Magenta are oriented uniformly close to 45 degrees at 15 and 75 degrees respectively. This gives an even displacement of 30 degrees. These angles apply to offset printing. Gravure and screen printing have different angles.

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Moire It is the case in which improperly set screen angles result in formation of patterns. By assigning different screen frequencies for different inks or changing the screen angles, this can be avoided. Rosette Well-registered screens result in a rosette pattern. There are two main types of rosettes: those with an open centre and those with a dot in the centre. The pattern maybe more evident in areas of less coverage and on higher quality paper but less evident on say newsprint. Density It is the measure of tonal values of the original or printed image. It is measured by a densitometer.

conventional flat tint

conventional half tone

first order stochastic

second order stochastic

FM vs Traditional halftone In FM screening, the halftone dots are of the same size but at varying distances. In traditional halftone, the halftone dots are of varying size but at uniform distances. In the FM technique, the exposure dots are spread evenly throughout the cell where as in traditional the dots are collected in the centre. FM screening generally allows for better reproduction of detail than traditional screening. Laserjet uses AM halftone while Inkjet printers use FM halftone.

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Paper The tangible element that has continuously fed into society through print media, advertising, education and other traditional forms of resources, sales and information gathering.

Paper was first used in Egypt and was called so because it was derived from ‘papyrus’. It was also around the same time made in China from bone. The use of wood pulp to produce paper began around 105 AD. The process takes place in the following order: Raw material Chipping Pulping Bleaching Additives Dehydration Paper! Types of paper Construction paper: coloured, coarse, large, slightly rough, ‘chart’ paper. Inkjet paper: weight, brightness, coated surface to prevent ink spread. Photo paper: type of inkjet paper, glossy, matte/semimatte, silk. Glossy photo paper: vivid look, high colour density(DMAX), wide colour gamut, everyday(HP), premium high gloss(Epson), Ultima(Kodak). Paper surfaces Uncoated papers : have no added layer on the surface and are completely natural; however, the surface may be sized with starch. Uncoated papers 16

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receive their smoothness in the calendaring stack, are generally more absorbent than coated papers and are available in many different textures, colors, weights and finishes. Coated papers, in contrast, have a smoother finish, aren’t very porous and may be calendered or super-calendered off the papermaking machine. Ink will, more or less, sit on a coated paper’s surface and take longer to dry - producing sharper, brighter imagines because the ink doesn’t bleed into the paper and blur the halftone screen. Coated paper: Coating produces papers with excellent ink holdout, which is ideal for color reproduction—detail is not lost and fine text holds up well—making them a popular choice for products ranging from books and magazines to annual reports and advertising supplements. Coated papers are often called art papers and are commonly found in glossy art books and textbooks containing photographs or illustrations. They have exceptional runnability and printability, as well as a consistently high-quality surface, stiffness, bulk and opacity. Paper sizes Paper is available in two standards: British and International. In the British system, the following dimensions are followed: Fullscap 13.5 x 17 in Demy 17.5 x 22.5 in Medium 18 x 23 in Royal 20 x 25 in Crown 15 x 20 in Imperial 22 x 30 in

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C0

1000 x 1414 mm

B0

917 x 1297 mm

A0

841 x 1189 mm

By multiplying the shorter side by two and retaining the longer side we can obtain ‘Quad’ sizes. In the International system, there are 3 standards. A size: Used for stationery purposes B size: Posters C size: Envelopes. The proportion of all three are 1:1.414. What changes are their ‘0’ sizes. C0>B0>A0.

Relative sizes

A0

841 x 1189 mm

A1

594 x 841 mm

A2

420 x 594 mm

A3

297 x 420 mm

A4

210 x 297 mm

√2 proportion

A1

A2

A3

A4

Folio division

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Paper qualities Newsprint: Low cost, low quality, nonarchival paper, made by mechanical pulping, brittle with weak bind. Wove paper: Used in bill and record books. Bond paper: Writing paper used in banks and offices, Letterheads and stationery, rag pulp, 50GSM+ Tracing paper: Translucent, oil resistant, impervious to water/gas Map litho: Smooth top side, used for book and leaflets, 80GSM. Offset: Rough on both sides, rag pulp, 80-100GSM. Duplex board: Boxboard used to make cartons Cartridge paper: Most expensive, rag content, can be preserved and hence used in certificate and stamp paper. Chromo paper: One side coated, 80GSM Art paper: China clay coating covers the porous surface giving it a smooth finish,less


absorption of ink, good ink depth,matt/ gloss,100GSM+ Mirror coat: Cast coated with China clay, mirror finish Card: Thicker paper, 210GSM+, sold in gross(144nos.)

Paper weight By Brirtish standard, paper is sold in â&#x20AC;&#x2DC;reamsâ&#x20AC;&#x2122;. One ream contains 500 sheets. The convention followed in specifying paper is as follows: Paper quality. width x length x wt. of a ream in kg.

The weight per ream gives an indication of the thickness of the paper. Since the no. of sheets in a ream are constant, a greater wt./ream figure would mean a paper of higher GSM. The cost per kg. is also specified. Hence, Cost of one ream can be calculated.

Grain Grain refers to the direction of the fibers in a sheet of paper. In long grain paper, fibers run in the same direction as the longest measurement of the paper. In short grain paper, fibers run in the same direction as the shortest measurement. With sheet paper, short grain direction is indicated by underscoring (or bolding) the dimension along which the grain lies, or by changing the order of the numbers.

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Imposition Halftone is a reprographic technique that simulates continuos tone imagery through the use of dot lines, varying either in size or spacing.

Printing presses are known to be the costliest unit per hour in the graphic production process.We can minimize time spent printing my by using optimally large sheets. Most printing presses have a maximum paper format of 4, 6, 16, 32 pages. Imposition can be done either manually or digitally. In manual imposition, every page of the printed product has been output onto a separate film. The pages are placed according to the imposition scheme and mounted onto a larger transparent film with tape. The completed transparency is then exposed onto a plate. Digital imposition means that you impose it in a layouting software. This can considerably reduce cost especially if the product has many pages.

The Makeready A makeready involves all the activities performed until you get the first approved printed sheet. The number of make-readies must be minimized to minimize cost. It includes the following steps: Printing plate makeready Setting the feeder Registering the sheets Pre-setting the ink screws Ink-water balance Registration check Ink coverage check Correspondence to proof colours

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4-page sheetwise imposition (folio)

8-page half-sheet work imposition ( quarto)

12-page imposition (12mo)

24-page imposition (24mo)

32-page imposition

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What affects imposition? 1. Design: The most important factor is the layout which is the format and placement of images. This determines the number of plates needed. Fewer the plate the faster the makeready. 2. Type of Press: Machines have limits on size of sheets they can handle and number of folds they can make. Type of paper/ orientation being used is to be considered if folding must take place. 3. Budget: If you have a strict budget you may be forced to reduce number of plates by changing a 4 page/sheet format to a 16 page per sheet format. This would give you the same content with half the number of plates thus reducing costs considerably.

Types of Imposition One side It is the simplest form of imposition. One printing plate is used to print on one side of the printing sheet.This is common in small offset press operations. Sheetwise The most common method of imposition is called sheetwise or work and back. With this type of imposition, each side of the sheet gets itâ&#x20AC;&#x2122;s own makeready. Hence, two plates per sheet. The side of the sheet containing the first and last page (if the product contains 4+ pages) is called the first form. The sheet containing

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page2 and the second last to be printed on the other side is called the inner form. Halfsheet work This occurs in a situation where the sheet has space for at least twice as many pages as the document contains. For example if i wish to print an 8 page booklet, my sheet must be capable of holding a 16 page imposition. In this method, one plate containing the first form and inner form gives one impression. The sheet is then reversed and the same plate impresses the other side. Hence, two copies are obtained from one sheet and one plate. This process of reversal of the sheet can be done in two ways:

1. Work and Turn: The sheet is rotated by 180 as well as turned over. Hence, a single gripper edge is used for both impressions. 2. Work and Tumble: The paper is rotated by 180 and flipped head over heels. Hence, two gripper edges are used. Work and turn method is preferred because it helps avoid misregistration. Also, gripper edge takes a margin of half inch. By keeping no. of gripper edges at one we allow for more available printing area.

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Ganged-Up Depending on how many copies of the product you place on the sheet, this imposition is referred to as 2-up, 3-up etc. This method is usually used if the product has just one or two printed pages. Signature Here the imposition is decided upon by first folding the paper and labeling the respective order of pages and then imposing the pages. Since the paper is folded into half, signatures are in 4x multiples. For example, 4-page signature, 8-page signature, 12-page signature, 16-page signature.

Creep In the case of a centre-staple bind, the pages of the folded product are pushed outwards causing the image area of the pages in the centre to move further away from the gutter than those in the beginning and end. You have to compensate for this in the imposition process by first making a dummy to measure the creep of the innermost page and then reduce the inner margin by a factor in all the pages proceeding from the innermost to the first form.

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Untrimmed creep

Trimmed


4-page signature

8-page signature

12-page signature

16-page signature

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Plate-making The printing plates used depends on the type of press, the printing method, and quantity of the print run. A plate is prepared for each color used, or four plates in the case of 4-color (CMYK) process printing. It is basically a process by which the digital file positive is transferred onto the printing plate which is then used for printing. The following are some methods of plate making: Image setter An image setter exposes or develops photo sensitive film or paper. It has a higher resolution than the printer. This maybe a negative which would have to be exposed to generate a positive. Offset plate In this the exposed film is developed by an online developer. The image setterâ&#x20AC;&#x2122;s RIP calculates halftone screen creating a large bitmap. A very fine laser beam exposes the areas of the film that should be exposed. This exposure is then developed. PS plate After the plate is exposed and developed, it undergoes gumming. Gumming prevents oxidation of plate and makes non-printing area water receptive. Computer to plate(C2P) This is a more advanced technology where the positive from the computer gives the plate directly. This type was observed at Art-o-print.

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Inks Inks were first made in ancient China as long as 50 centuries ago. They were made from soot suspended in vegetable oil. Eventually, petroleum was used in inks, which made them cheaper and more popular for offset printing. By the 1960s, petroleum-based inks had completely replaced vegetable-based inks in the printing industry. However, petroleum-based inks are not without their costs to the environment. They contain a variety of heavy metals (barium, copper, zinc) that leach into soil and groundwater. Volatile organic compounds (VOCs) are also released by petroleum-based inks. These contribute to smog in addition to being irritating to the human respiratory system. When considering the sustainability of printing, VOCs emitted during the printing process and the use of non-renewable resources and heavy metals in pigments must be considered. Designers should speak with their printer to keep these factors in mind. Nearly all inks can be placed into the following categories. Standard printing inks: Web offset, sheet fed, process ink. Speciality inks: Metallic, fluorescent, security, phosphorescent. Ink Ingredients Pigments: The ingredient that contributes to the colour of the ink. Vehicle: Substance in the ink that carries the

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pigment and binds it to the printed surface. It maybe oil or water. Modifier: They change the properties of inks so that it can fulfill the requirements of different types of print processes and applications. Driers: Speed up drying of ink. Anti-skinning agent: These are agents that keep the ink from drying too rapidly and skinning over the ink fountain. Extenders: Increase the coverage of the pigment ink. Distillers: Improve the flow of ink.

Ink characteristics Body: Consistency of ink. Tack: The stickiness of the ink. Viscosity: The degree to which ink resists flow when it is under force such as when it is in the roller train. Length: Ability of ink to flow. Opacity: The covering power of ink. Tinting strength: Ability of an ink colour to produce a tint with the addition of white pigment and referred to as coloring powder. Permanency: Degree to which printed ink resists the fading power of light. Drying of ink may be done by absorption, heat, precipitation or oxidation.

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Poor binding: Dry ink scraping off the substrate. Ink adhesion: Poorly adjusted press setting. Mottling: Uneven absorption due to inappropriate paper or poor adjustment.

Special Inks Scented Ink: They are are water based and can only be printed on unsealed paper or board. Scented inks come in a wide variety of smells and can also be synthesized to use a specific fragrance. The smells are suspended in a semi-clear base and then screen-printed onto the required substrate. Heat-Sensitive: These inks have a limited range of colors. Black tends to produce the most dramatic results. The heat-sensitive component is suspended in a semi-clear base and then screen printed. The reactive temperature can be changed in accordance with climatic conditions. Like scented inks, heat-sensitive inks are water based and work best on uncoated paper substrates. They can be made to work on plastic after a number of layers are applied. This is a time consuming process making it not cost effective. Heatsensitive ink has the tendency to scuff when not properly. Pearlescent & Iridescent: These inks can be used with a variety of substrates and, depending on proximity, create a different shade of metallic color when viewing. They are most commonly found on gift cards. They can also work well as solid areas with text on top.

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Costing Case1: Offset printing Poster No.of colours: 2 No.of sides: 1 Unfinished size: 23”x36” Finished size: 23”x12” Quantity: 4000(+100 test)= 4100 nos. Paper: Ballapur Offset paper 23” x 36” x 26.6 kg Paper quantity: 3 posters per sheet No. of sheets = 4100/3=1366 No.of reams= 1366/500= 2.8 ream( appx. 3 ream.) Paper cost: Cost/kg= Rs.50/Cost of 26.6kg(1ream)= 26.6 x 50= Rs.1330/Cost of 3 ream= 1330 x 3 = Rs.3990/- ………Cost A Positive: 11”x22” = 27cm x 57cm= 1653sq.com. Cost /sq.cm.=0.75p/sq.cm. Cost of positive= 1653 x 0.75 = Rs.1240/-…….Cost B Plate cost: One plate= Rs.600/2 colour print= 2 plates - Rs.1200/-……………Cost C Printing: No.of plates x No.of copies x Cost per 1000 copies of ONE colour. = 2 x 4000 x 900 (ink, labour and overheads) = Rs.7200/-…………………...…………Cost D Cutting, finishing and folding:Rs.1000/-…...…Cost E Cost = A+B+C+D+E= Rs. 14,630/TOTAL= Cost +10% = Rs.16,093/Cost per poster = TOTAL/4000 = Rs.4/30

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Case2: Offset printing Book No.of colours(cover): 2+0 colour No. of colours(inside): 1+1 colour No. of copies: 200 nos. No.of pages: 48 Paper1(cover): Size +Weight Paper2(inside): Size +Weight Finished book size: l x h cm

Plate: No. of plates= No. of inside plate+ No. of cover plate Plate cost for inside pages= No.of inside plate x Cost for inside plate……….....Cost C Plate cost for cover pages= No. of cover plates x Cost of cover plate…………Cost D Processing

Paper cost(inside): Open size/size of spread= 2b x l 6 spreads/sheet 12 pages/plate 24 pages/sheet. No. of sheets/book = No. of pages/24 = 2 No. of sheets x no. of copies = 2 x 200= 400 + 10% test = 440 nos.

(Image setting/ positive making): No. of positives= No.of pages/2= 24+cover Cost= No.of positives x cost per positive ……………..Cost E Printing: Inside pages: No.of plates x no. of copies x cost of 1000/ colour Cover page: No. of plates x no. of copies x cost of 1000 per 2 colour ........................Cost F

Total no.of reams = No.of sheets/500= 1 ream Cost of paper2 = Cost/ream x 1 ream= Rs.800/-………………..Cost A Paper cost(cover): No.of copies= 440 No. of sheets of paper1= No.of copies/No.of covers per sheet = 200/3 = 66 nos. Art paper/100 sheets= Rs.300/Cost of paper1= 500x no. of packets = Rs.500/- ……………….Cost B

Post-press: Cost per copy Cost = A+B+C+D+E+F TOTAL= COST +15%

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Relief Printing A relief print is an image created by a printmaking process where protruding surface faces of the plate is inked; recessed areas are ink free. It is the oldest known method of printing.

Letterpress printing It is s form of relief printing of text and image using a press with a printing press and movable type, in which a reversed, raised surface is inked and then pressed into a sheet of paper to obtain a positive rightreading image. It was the normal form of printing text from its invention by Johannes Gutenberg in the mid-15th century until the 19th century. It is a process by which many copies of an image can be produced by repeated direct impresion of an inked raised surface to a continuos roll of paper. Letterpress printing exerts variable amounts of pressure on the substrate depending on size and image elements. Chemical used in letterpress are film developers, inks, blankets and roller washes. It uses ink with a thick consistency.

Press methods Rotary press - The plate is mounted onto a cylinder where a roller system applies ink to the raised area of the plate. The paper passes between the plate cylinder and an impression cylinder where the resulting squeeze between the two cylinders produces the printed impression on paper.

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Flatbed Cylinder press - The type or plate is locked into a chase that is then mounted on the press flatbed. Grippers on a rotating impression cylinder pick up a sheet of paper it is pulled around the cylinder as it revolves. The inked flatbed with the letterpress plate then moves under the cylinder. The compression between the impression cylinder and the flatbed creates the printed image on paper. When the impression is complete the flatbed returns to its original position and is inked for the next impression. Platen Press - Movable metal type is locked into a frame called a chase, which is then placed in the press bed and locked into position. During the printing process, grippers move paper sheets from the feedboard to the platen, which is the surface where the print impression is made. A set of rollers applies ink to the type on the press bed, then the press bed and platen are pressed together to produce the image on paper. When the impression is complete, the platen and press bed spread apart and the grippers remove the paper to a delivery tray.

Identification Upon close examination, letterpress print will reveal the following: 1. Ink squashes on edges 2. Minor indentation of paper on the back. 3. High ink intensity Application Letterpress was extensively used but has now been replaced in most applications by flexography. It is used for publishing newspapers, labels or packaging text. However, a more common application o this technology is for decorative effects like embossing, die-cutting, numbering, perforating and foil stamping.

Printing and non-printing areas are hence separated mechanically.

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Flexography The relief plate used for flexography is made of moulded rubber or photopolymer materials with the image area raised and the non-image area recessed. Flexographic plates can be created with analog and digital platemaking process. Flexography is a direct printing method in that the ink plate applies directly to the substrate. An ink roller known as an â&#x20AC;&#x2DC;Anilox rollerâ&#x20AC;&#x2122;, applies ink to the raised portions of the plate which is then transferred to the substrate. The anilin roller has cells that carry a specific amount of ink to the plate. The number of cells per linear inch can vary according to the type of printjob and the quality required. The name anilin is derived from the ink that was usedfro the process until 1950. The ink carrying roller has continued to be called the anilin roller even though the aniline dye inks are no longer used for flexography. The current inks are very fluid and dry rapidly and are most often water based. Itâ&#x20AC;&#x2122;s quality however is not as high. The ink is fast drying which is an advantage. Application Flexography continues to be the fastest growing print processes and is no longer reserved just fro printing specialty items. The ability to print on a variety of substrates allows the process to be used on a wide range of printed products. Food packaging is an important market because of the ability of flexography to print on non-porous substances. This ability is useful fro printing on plastic bags. gift wrap, wall covering, paperback books, telephone directories and business forms. 34

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Offset Printing Nearly 40% of all print jobs are done by offset printing. It is an indirect printing process which means that the image is transferred or offset from one surface to another.

Principle It is based on the principle that oil and water do not mix. The image area and the non-image area of the offset plate are on the same plane and do not mix. The non-image areas of the plate attract a wetting agent and repel ink made from oil base. The image areas attract the ink and repel the fountain solution. Hence, the separation is done chemically.This process is called â&#x20AC;&#x153;offsetâ&#x20AC;? because the image isnâ&#x20AC;&#x2122;t transferred directly from plate to paper, but to a blanket first before finally printing. Because offset printing does not allow for variable repeats in one machine, offset presses are best used in high volume applications such as the printing of newspapers. Plate production First the positive is printed on a transparency. This transparency is placed front-side-down onto a presensitized plate leaving gripper margins preset by the machine and marking the centre. It is then exposed whereby the negative space is hardened. The plate is then washed with a alkali developer(Novatone) diluted 300g/L. Hence, the plate is made ready for printing.

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Process The printing plate is mounted on a cylinder that transfers the image to a rubber blanket mounted on another cylinder. The image is then transferred from the blanket cylinder to the substrate as the substrate passes between the blanket cylinder and impression cylinder. When the image is transferred to the printing surface it becomes right-reading again. Types of offset press Web fed : A web fed press prints on a continuos web of paper fed into the press from a large roll of paper. The web of paper is then cut into individual sheets after printing or sometimes left perforated. Sheet fed: A sheet fed press prints image on single sheets of paper as they are fed individually into the press.The print quality and sheet to sheet registration is often bettter than web-fed printing but it is often more economical to produce very large runs on web presses because of their high speed. Waterless Printing : Offset printing can be made more environmentally friendly by removing water from the printing process. The waterless process uses the lithographic (offset) system while eliminating the fountain solution, or dampening system. Instead of conventional metal, paper or plastic printing plates, waterless offset printing uses a multilayered silicone covered plate and special ink.

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This process still provides high quality and efficiency with low dot gain for enhanced detail, better color saturation and faster make readies. Without a dampening system, waterless printing requires temperature controls for the ink rollers and more frequent cleaning of the blankets. The plate chemistry is solvent based and requires special handling. Because of the solvents used, inks in waterless printing have a higher VOC content than the ones used in conventional lithography. Identification 1. Even image in text and halftone 2. Sharp and clear outline 3. Solid colors are good. 4. Good text reproduction. Application The types of printed materials that can be produced with offset are numerous and varied. Newspapers, books, magazines, business forms, advertising pieces, brochures, posters, greeting cards, business cards, mailers, coupons etc.

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Gravure Printing Gravure is a high quality printing process capable of producing printed images which have a continuos tone effect similar to a photograph.

The image area consists of honey combed shaped cells or wells that are etched onto the surface of a copper cylinder. The unetched area represents the non-printing area. The cylinder rotates in a bath of ink called the ink pan. As the cylinder turns, the excess ink is wiped of the cylinder by a flexible steel doctor blade.The ink remaining in the recessed cells forms the image by direct ransomer to the substrate as it passes between the plate cylinder and the impression cylinder. The major unit operations in gravure printing are as follows: Image preparation Cylinder preparation Printing Finishing Besides being very fluid and thin, the inks used with other process colour applications differ in hue than the inks used with other processes. Gravure also often employs spot colour inks instead of the standard process colours used in four-colour printing. Gravure is a direct printing method so there is no need to utilize fountain solution to keep the non-image areas clean.Printed images with gravure are of the highest quality because the

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thousand of ink cells appear to merge together to form a continuos tone. However the clarity of type in smaller point sizes is not as good as offset lithography. Application Gravure is used to print very large quantity of unto 10-15 million copies. It is used to print packaging applications, magazines and pressure sensitive applications. The National Geographic magazine, a globally circulated magazine that is famous for itâ&#x20AC;&#x2122;s superior photography uses gravure printing. It is also used for items like currency notes, stamps and foils.

Conventional gravure cells have equal area but different depth. Deeper cells hold more ink and make darker impressions.

Cells with differing area and equal depth are used for packaging applications.

Cells with variable area and variable depth are used for high quality applications.

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Screen Printing It is arguably the most versatile of all printing processes. It can be used to print on a wide variety of substrates.

Screen making A stencil is produced on the screen. This is done by first densifying the transparency positive with a solution containing polyvinyl alcohol and ammonium bichromate. The positive is placed on the screen mesh and then coated with Sonakote solution and Lunar sensitizer solution. It is then placed down on a light table and covered with sand for keeping tight contact. The exposure lasts for approximately 8 minutes. The exposed negative space covered by the solution hardens and becomes imporous to ink. The mesh is stretched tightly over a frame made of metal or wood. Printing Screen printing ink is then applied to the substrate by placing the screen over the material. Ink with a paint like consistency is placed over the screen. Ink is then forced through the positive openings using a squeegee that is drawn across the screen from top to bottom. Ink only passes through the unexposed portion thus forming an image on the substrate. The diameter of the threads and the thread count (basically the lip) will determine how much ink is deposited.

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Advantages The advantage of screen printing over other processes is that it can print on material of different shapes, materials and size. The equipment cost for screen printing are less than that of other processes but rate of production is slower. They are hence suitable for smaller quantities of prints. Identification 1.Slightly raised impression due to heavy deposition of ink 2. High and even ink density 3. Text is blurred compared to offset. Applications Products as varied as signs, posters, circuit boards, mugs, clothing and soft drink bottles can be printed using this process. Screen printing is very useful when an inane needs to be wrapped around an object or when they need to be fit onto oddly shaped objects.

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Unconventional Printing The processes discussed earlier are called conventional processes. They all required a master plate and were printed in large quantities. Unconventional processes are those in which there is no master, no impact press and more economical for very small quantities.

The reproduction of digital images on regular paper, photographic paper, and other printable surfaces. Digital Printing differs from offset printing in that the ink does not absorb into the paper, as does conventional ink, but forms a layer on the surface. It requires less waste in terms of chemicals used and the paper wasted during the set up process. Most digital systems do away with the film, plates and ink that are part of offset printing in favor of some sort of electrophotographic process. Particles of dry or liquid toner are attracted to an electrostatically charged cylinder that carries the image. The toner is then transferred to the paper or, less often, to a blanket cylinder and heat is used to melt and set it on the paper. Digital ink jet presses use an electrical charge to guide the placement of tiny drops of ink to create a glossy image that can rival a continuous-tone photograph. Hybrid technologies combine digital and conventional offset technology. Digital Printing is used primarily for small quantity, short-run printing and variable data printing jobs that require a quick turnaround. This option is a cost-effective method for Full Color or B&W booklets, business cards, catalogs, magazines, manuals or multi-page brochures. Books and brochures can be printed on-demand 42

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as they are ordered, eliminating the need to hold large quantities in inventory. Advantages 1. Digital printing is fast and flexible because thereâ&#x20AC;&#x2122;s no separate proofing, no film or plates, and little make-ready time is needed. 2. Digital is very cost-effective for small runs.

They have taken the place of traditionally manufactured with a base made from ground tree sap. There are a wide range of thermographic powders that are capable of producing awed range of effects. The powders come in many particle sizes.

3. Digital technology is constantly evolving. New advances are being made in areas such as in-line varnishes, scratch-proof inks and finishing techniques. 4. Digital printing can vary text and images on a page-by-page basis, allowing for customization. 5. Chemicals associated with film processing and plate making are eliminated making digital more environmentally friendly 6. Electrink systems used in digital printing have less emissions

Methods Thermography This is a process which produces a glossy, raised image by using infrared light. The image is first printed by letterpress or litho using an adhesive ink which is coated with a fusible resin containing pigment on a metallic powder. When passed under light the resin pigment hardens to give a hard raised image. Thermographic powders are made from plastic resins which were introduced in the 1970â&#x20AC;&#x2122;s.

It can add value to many ordinary print applications. Letterheads, greeting cards, invitations, business cards, marketing applications and envelopes. Thermography printing can generally only be used on one side of the paper, as applying the necessary heat to the second side would negatively affect the first side. Thermography should not be used over a fold or within a one fourth of an inch from the edges of the paper, as the raised ink tends to fracture when folded or cut. i n t ro d u c t i o n to p r i n t i n g t e c h n o l o g y

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Ionography A process that makes use of an image wit the use of an electron cartridge which creates a negative charge on a non conductive surface. The non conductive surface attracts a magnetic toner. A static electric charge is used to draw the particles from the drum onto the substrate. A high pressure roller fuses the toner to the substrate. Magnetography It is similar to iconography except that the drum used is magnetic. The electronic image is converted to a magnetic drum charge which attracts a toner containing iron particles. The toners are very opaque so the process is best suited for spot colours rather than process colours that require transparent colours to work properly. Magnetography is used for applications which require variable imaging such as labels, business forms, direct mail pieces, tickets and barcoding. Electrography/Xerography Invented by Chester Carlson in 1937 and developed by Xerox Corporation. Artwork is placed face down on a glass plate and is illuminated by a fluorescent light which travels the length of the image. The reflected image is directed through the lines through the lens to an electrically charged drum. This charge leaks away where light from the image falls on the drum. A resin based powder called toner is transferred to a sheet of paper where it is fixed

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by heat. Laser copiers work like combined scanners and imagesetters by scanning the image digitally and using a laser to write the image onto an electrostatic drum. Inkjet An inkjet printer is any printer that places extremely small droplets of ink onto paper to create an image. Identification: 1. The dots are extremely small (usually between 50 and 60 microns in diameter), so small that they are tinier than the diameter of a human hair (70 microns)! 2. The dots are positioned very precisely, with resolutions of up to 1440x720 dpi. 3. The dots can have different colors combined together to create photo-quality images. In unconventional printing, because there is no single master an independent image is generated on the cylinder for each individual print. Hence, the per cost copy remains the same irrespective of quantity.

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Post Press PostPress is a crucial part of any printing process even though it takes place after the actual printing, since it determines the f inal look, shape and feel of your printed product.

UV coating UV coating provides the final glaze on the printed material and provides fine lustrous effect to the final product. Our machines can also deliver Spot UV effect wherein only specific parts of the printed material are coated to highlight a particular design, font or colour. Advantages Opacity Stability Eco friendly/ non VOC High gloss Sharp graphic Chemical resisting Scuff resistance Deeper and more vibrant Die-cut capable. Lamination Lamination finishing technique is similar to varnish, but it delivers more shine and provides a richer appearance than varnish. The Lamination effect works very well for sophisticated packaging requirements such as cosmetic and perfume packages, invitation cards and designer brochures.

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Die Punching The Hiedelberg Cylinder, Polar Mohr Eltromat etc for different cutting requirements like die punching, cutting, creasing etc. Apart from cutting and punching, die punching machines can also give creased and Embossed effects. Folding Automatic Insert Folding Machines automatically folds any type of paper into different folding patterns, primarily useful for medical inserts, notebooks, textbooks, magazines, brochures, etc. Foil Stamping Foil stamping provides a rich, shining, metallic effect on printed material and paper. Machines like Kluge EHD through which foil is stamped in any desired shape, font and design on the printing material or package. This is very useful in wedding invitations, perfume and cosmetic packages, FMCG packaging etc. Embossing Embossing is another design effect that can be created through machines, giving the effect of raised or deep impression in any preset design.

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Binding Binding is a process of fastening the sheets of a publication in the proper order and most often with a protective cover. Some types of binding: Plastic comb binding Also called GBC binding, plastic comb binding is punch and bind system that is used for many office documents. Its main advantage is that it is inexpensive and easily edited. Itâ&#x20AC;&#x2122;s advantage is itâ&#x20AC;&#x2122;s appearance and the security of the final book. Also, like other punch and bind systems, it requires more labour than tape binding. Spiral Binding It is a punch and bind system that uses a plastic or metal spiral wire that is wound through punched holes on binding edge. It is the type of binding most often used for school notebooks and steno pads. Perfect binding It is a punchless binding method that works by fastening the book block to the cover spine. It is often used for softcover books and paper backs. Tape binding This process places a cloth strip of adhesive tape down the bind edge of the book and wraps around about half an inch onto the cover and back.

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Saddle stitch Wire staples hold the piece together. A machine drives then through itâ&#x20AC;&#x2122;s backbone fold to the centerfold where they clench. Side stitch The pages are cut all the same size and stacked, then staples are inserted down the side of one edge of the bookâ&#x20AC;&#x2122;s front, 2 to 3 times depending on thickness and paper weight. The result is a sturdy binding, however the book will not lie flat when opened. This binding style is generally less expressive than other styles. It has typical uses in notepads, reports and tear-off calendars. Case Bound (Section sewing) This binding style is typically used for books of more than 80 pages, which require a strong, high-quality finish. The pages of the book are collated, and then sewn together with thread. The cover is then glued to the spine of the page block. Case Bound is generally the most expensive style, so are usually only used for books that must withstand constant use. Itâ&#x20AC;&#x2122;s used for hardcover books, text book, novels. Wire-O-binding This binding holds the pages of the book in place by a double-loop wire inserted through holes on the left edge. It does not spiral through the book rather it creates a wire comb. The pages lay flat when opened and can rotate 360 degree. Wire-O bindings are durable, but do not permit printing on the spine. It is used in reference books, reports, cookboooks. i n t ro d u c t i o n to p r i n t i n g t e c h n o l o g y

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Field Visit We visited two printing presses during our course. Here we observed commercial scale printing, diecutting and packaging. We saw the process of offset printing and procedure of itâ&#x20AC;&#x2122;s plate making. The press had four and five colour printing sheet-fed offset machines. UV printing was also carried out. We also observed medicine packaging from folding to sealing. The second part of our trip was a visit to corrugated paper factory where single sheets are passed through corrugating machines to form a â&#x20AC;&#x2DC;plyâ&#x20AC;&#x2122;. These individual ply are then layered one top of each other to form multiply corrugated sheets of greater strength. They were then die-cut, folded and stapled into boxes. On the second visit, we witnessed execution of a calendar and school textbook from start to finish. This was a very valuable experience as we were able to see the press workflow in practice. 8-page signature imposed book printing, gathering and side-stitch bind was done there.

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Practical At the NID Printing Lab we gained practical knowledge in two methods of printing namely offset and screen. For offset printing, we first created an artwork of approximately 11â&#x20AC;?x 8â&#x20AC;?. The aim was to test offset printing by experimenting with extreme point sizes and colour mediums and tones. In screen printing, the artwork was printed on a variety of plane surface materials testing its capacity to reproduce on paper, plastic and metal sheets with a variety of textures. On these two days, we had a step by step understanding of the process followed in execution of the print. I was sensitized to the extreme care and precision required in printing. The effort required to attain even a single colour offset print was considerable. Loading the plate, cleaning the rolllers, dampening and test runs were some of the steps we participated in during these sessions. We also had tutorials in book binding techniques. We covered notepad binding, pefect binding, spiral binding, japanese binding and library binding. It was valuable because we understood the reasons behind imposition methods and what we require to be aware of while designing a document so that itâ&#x20AC;&#x2122;s binding and finishing can be done well.

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References Course notes Process of Graphic Production in Printing, Curwen Printing Effects, Wayne Robinson Guide to Printing, William Cloves A Guide to Print Production, Johansson Lundberg Ryberg www.pneac.org www.internationalpaper.com www.paperrep.com www.heidelberg.com www.agfa.org www.wikipedia.org www.brittanica.org Google Image search Document set in Baskerville / FontFolio 09

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Acknowledgments Bharat Suthar Dr. Tridha Gajjar NID Printing Lab

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C0

1000 x 1414 mm

B0

917 x 1297 mm

A0

841 x 1189 mm


A0

841 x 1189 mm

A1

594 x 841 mm

A2

420 x 594 mm

A3

297 x 420 mm

A4

210 x 297 mm

A1

A2

A3

A4

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Printing Technology Course Documentation  

A documentation of my course learning in semester5

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