hrrili"4p "l UooA T,renfhe?

Bv I. C. McCune

I. H. Bcxter & Co., Los Angeles

Address given belore the annucl convention ol the Ccrlilornicr Retail Lunbermen's Associqtion held in Ocklcmd, October 26-28, 1939

Most of you in the lumber business probably know how wood is pressure treated and what treated lumber can accomplish in resisting termite and decay attack. My purpose, therefore, in this discussion, will be to briefly outline the more important phases of wood preservation merely to refresh your mind as to the fundamentals back of this industry.

In speaking of wood preservation I, of course, refer to impregation of lumber by pressure methods in closed cylinders because it is this sort of material treated by the pressure process which has built up service records of 25 to 50 years and more. As a matter of fact, the pressure method of treatment is the basis upon which the wood preservation industry is founded.

Prior to the development of the system of pressure treating the only way known to protect lumber from decay and insect attack consisted of ,merely brushing preservative materials over the surfaces of the timbers to be protected or even dipping of the wood in preservatives. Although it might seem possible to obtain some penetration with these surface applications, it will be found in practice that rvood offers surprising resistance to penetration by liquids. The small amount of preservative retained on the 'lvood together with the light penetration obtained cannot be expected to render very much resistance to termite attack or more than limited protection against dry rot, especially where the conditions of use are very susceptible to snch attack. Such superficial treatment of lumber is now limited almost entirely to maintenance work around existing untreated wood structures. It should not be confused rvith pressure treated lumber as processed by wood preserving companies and sold by lumber dealers.

Pressure treating of lumber is far from being a new idea. It had its origin over 100 years ago in 1838 when Sir John Bethel was granted a British patent on a method of in- jecting preservatives into lumber in closed cylinders by means of hydraulic pressure. It is interesting to note that this disoovery of our modern day pressure treating process was occasioned by a war problem. It was the great loss of warships in the British Navy due to the destruction of ship timbers by shipworms and decay which stimulated in the early part of the lfth century the intensive study of wood preservation. It required 4O acres of oak timberland to build a warship and the vessels deteriorated so rapidly that it had become a national calamity. The Government sought the aid of the leading chemists and engineers of that day to solve this perplexing problem, with the result that both the types of preservatives in use today, as well as the result of treatment, were developed at approiimately this same time.

Creosote, and oil distilled from coal tar, which at that time was a waste residue in the manufacture of coke for iron smelting, was found to render timber immune to the attack of decay and insects. Certain metallic salts were also found to be toxic to fungus and insects and were utilized even before creosote. Today we find these trvo distinct types of wood preservatives in general use-the oil preservative, coal tar creosote, and the salt preservatives such as Chromated Zinc Chloride and Wolman Salts. It is the treating practice in the case of building lumber to use the oil preservative-creosote-without any mixtures. so that when reference is made to the standard 8-lb. creosoted lumber, it is meant that eight pounds of creosote oil by weight or approximately one gallon has been impregnated into each cubic foot of wood. The poundage of retention in the case of salt preservatives refers to the actual weight of the salt in its dry form, which has been injected into each cubic foot of lvood; such as three-tenths pouncl, three-fourths pound. or one pottnd per cubic foot. The salt preservatives must be carried into the wood in solution form, the principle being that the salt then crystalizes throughout the deeply penetrated area as the wood dries after treatment.

A pressure treating plant consists of one or more long horizontal treating retorts measuring' up to nine and onehalf feet in diameter and 165 feet long. These steel cylinders are constructed with a full gauge railroad track inside to permit tram cars of lumber to be shunted in by a locomotive until io Som€ of the larger retorts a total of three freight car loads of lumber can be inserted in one charge for treatment.

The complete plant required for pressure treating lumber includes a steam plant, compressors, vacuum pumps, condensers, and control gauges, storage tanks and working tanks for preservatives, a chemical testing laboratory, locomotive yard cranes, and a large number of tram cars besides c,onsiderable track and large storage yard space for seasoning. The investment, therefore, in plant and equipment is one of the large items in wood preservation.

The first step in treating with salt preservative solutions is to heat the lumber after it is sealed in the retort, with steam coils or live steam and at the same time draw a high vacuum which will result in the removal of moisture from the wood. After the wood is properly prepared by heating for some length of time, the preservative solution is admitted into the retort while still holding the vacuum. When the wood is then completely submerged in the preservative the vacuum is released and the pump started until up to a maximum of 175 pounds of pressure per square inch is created in the solution surrounding the wood. This pressure is maintained for several hours and actually forces the solution into the wood. After the preliminary vacuum period the wood cells have less than 15 pounds per square inch of air pressure within them and this external pressure of. 175 pounds per square inch of the solution now provides the mechanical means by which pressltre treating is accomplished. The pressure is continued until the gauges indicate that the lumber refuses to absorb further preservative. This point is reached when the air in the wood is compressed into the center until it equals the external pressure of the solution. The amount of salt retained by the wood is regulated by the strength of the solution sp that treatment to refusal can always be accomplished. The Iumber is now removed and stored for seasoning.

From this picture of the process involved in pressure treating I hope that one fact is now more clearly in your mind-that a definite amount of preservative is injected into the wood so that definite results can be expected of such treated lumber when placed in service. There are many opportunities where you can merchandise pressure treated lumber to your customers on the basis of the better service it will render. and at the same time realize a greater profit for yourself and in that respect, those of us in the wood preserving business are always glad to be of assistance to you.

NAMED DIAMOND MATCH CO. MANAGER AT AUBURN

W. Vannote, recently named manager of the Diamond Match Company yard at Auburn, has taken over his new position. He has been with the company for ten years and was formerly manager of their yard at Live Oak.

IF YOU HAVE A PLyWOOD PROBLEM, BRING IT TO US

The experience ol the Hqrbor Plywood Corporotion's Engineers ond Reseqrch Stoll is ot your commqnd when you buy HARBORD PRODUCTS.

TARIS PITU|l|lD C(lRPORATI|lil

Designed for Today's Architecture

This new board moves in cr hclf circle. Just $rling it trround to where it ccm be used. Ironing don+put the hot iron in iron receptccle, fold up board crnd close ccbinet. It's fireproof. Hot iron rest cmd sleeve board included. Ccrbinet is ccsed cnd door hung. Fits crny 2"x4,16" center wall. Good mcngin oI profit. A phone ccll or post card will bring lull pcrrticulcrs.