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Hardwood Record — Veneer & Panel Section 



July 10, 1921 



Controlling Moisture in Lumber and Veneers 



'iiy J. I\ Hirt. 

 Vice-president, Forest Products Engineerinj^ Company^ Chicago 



( ConfiiiH' tl froin ./inir 



Another important factor in our favor is the time required for 

 the finished product to imbibe or give up moisture. A carload 

 of crated panels could ordinarily be in transit for a year or more 

 without any ill effects if they have been treated in accordance 

 with definitely known conditions and correct practice. The rea- 

 sons for difficulties on this score are obviously due to a lack of 

 comparison of conditions in the plant of the veneer and panel 

 manufacturer and his customer, and an efl'ort to reach a satisfactory 

 mean E. M. C. 



Panels, because of their constructions of plys at right angles, 

 set up opposing forces that assist greatly in retarding expansion 

 and contraction. 



The same does not apply with veneers and, therefore, greater 

 accuracy in controlling moisture and more care in shipping should 

 be exercised. In packing high grade figured veneers, especially 

 crotch stock and burls, it may be advisable under some extreme 

 conditions to use a w^rapping of waxed paper. 



Packing veneers under pressure is another way to decrease mois- 

 ture attraction. A simple hand operated plunger press constructed 

 in your shipping department would not only accomplish this but 

 at the same time would reduce your crating costs. The crates 

 are filled under the raised plunger of the press. The plunger is 

 slotted to receive the top slats of the crate so they can be nailed 

 in position while the pressure is on. This method can be used 

 in crating rotary core stock, cross-banding, backs and dimensioned 

 face stock, but would not apply quite so well in crating sliced logs 

 and sawed flitches. 



Other practices tending to assist in relieving the natural con- 

 traction and expansion of wood are in a state of development at 

 the present time, but at best none of them promise to do any more 

 than to contribute in a measure to the full solution of the problem 

 which brings us back to the point of finding our E. M. C. and 

 governing our product accordingly. 



Drying and Shipping Veneers 



One of the most helpful and least costly methods of controlling 

 moisture is the proper arrangement of material storage rooms. This 

 is a matter that has had little attention by both the veneer and 

 panel manufacturer, and a brief resume of what commonly occurs 

 in drying and shipping veneers might be interesting. 



The veneer manufacturer may be using any of the present com- 

 mercial types of dryers or even the old style kiln or dry house 

 in w^hich he piles racks, or hangs the veneer. If he is using the 

 former, he may succeed in bringing his veneer out of the dryer 

 in a straight condition but the stock very often contains an un- 

 known quantity of moisture. If an effort is being made to dry it 

 to a definite moisture per cent, the calculations on which this is 

 based are sometimes incorrect. At any rate, the veneer is seldom 

 at a moisture content in equilibrium with the air when it leaves 

 the dryer and, therefore, it w^ill either give up more moisture and 

 shrink, or it will imbibe moisture and expand; in any case this 

 "working" will not be evenly distributed over the surface of the 

 sheets and local expansion or "buckling" will result. If the stock 

 is piled on trucks and rushed into crates, it will perhaps remain 

 fairly straight until received by the customer. 



In case the more obsolete equipment is used, it is impossible to 

 dry the stock flat and very often without severe checking. What is 

 still worse, an effort to dry to the correct moisture content is very 

 seldom made. Usually the stock is said to "look and feel" dry, and 

 the manufacturer consoles himself w^ith the thought or expression 



*A talk before the National Veneer & Panel Manufacturers' Association in 

 convention at Chicago, June 14, 1^21. 



that it is as good as his connpetitors are doing anyway, which is an 

 assumption that may apply less generally in the near future. 



At our next observation we find the crated veneer or bundled 

 Hitches being unloaded at the customer's plant. We often see 

 oak flitches thrown on the factory floors without even making any 

 effort to arrange them in piles much less making any effort 

 to control the moisture. Crated stock, as w^ell as the veneers, 

 are often dumped into a cool, damp basement, so that even if the 

 stock had been dried correctly by the manufacturer, it would again 

 imbibe moisture with the results previously explained. Then the 

 customer redries the stock when he is ready to put it into panels. 

 Here again he reduces the moisture content to the unknown quan- 

 tity. To overcome the mistake of incorrect drying at this point, 

 the stock is rushed right through the jointing, taping and joint 

 gluing operations into built up bundles w^hen the veneer is con- 

 sidered quite safe, at least from "buckling." If something hap- 

 pens during this regular process, the taped up veneers often take 

 on enough moisture again and buckle so badly that they must be 

 straightened out. In this event they are again redried to the same 

 unknown condition which is usually too dry, and then the regular 

 process is again carried out. 



In drying veneers the general assumption seems to be that the 

 chief requisite is to get them sufficiently dry. This is decidedly 

 wrong as just as bad as not dry enough, providing the moisture 

 has been reduced below^ the danger of mould. Without losing sight 

 of our objective, I would like to point out right here one of the 

 great sources of lost energy and money w^hich is contributed to 

 jointly and perhaps equally by the veneer and panel manufac- 

 turer. It is not uncommon to find veneer manufacturers loading 

 their logs to the limit of moisture they will hold in preparing them 

 for the lathe or slicer through either one of the two methods: 

 boiling, or steaming, at atmospheric pressure. The procedure is 

 then to dry them far below^ the E. M. C, which causes the stock 

 to pick up moisture to this point. Then the panel manufacturer 

 stores the stock w^here it will pick up still more moisture and again 

 redries it to a percentage considerably below the E. M. C. in his 

 plant. After all this procedure, complaints are still heard from all 

 quarters about "buckling" and breakage. 1 am trying to emphasize 

 that each unnecessary drying operation adds just that much more to 

 your unit costs and in addition there is always more or less material 

 lost in handling veneers even under correct procedure. 



By proper storage, veneers w^ill not only be held in perfect 

 shape, but as a matter of fact can be improved and brought into 

 absolute equilibrium with the atmosphere and at this point will 

 remain perfectly flat. Therefore, instead of dumping them into a 

 moist basement or shed or any other room in which the atmosphere 

 is not controlled, why not make these storage spaces into con- 

 ditioning rooms? 



This can be accomplished at surprisingly small expense. It 

 requires proper arrangement for retaining uniform temperature 

 and humidity and means for circulating the air within the room. 



Under these conditions the veneer manufacturer could leave his 

 stock stored almost indefinitely without injury. The panel manu- 

 facturer could do the same, and what is more important, he can 

 forget all about his redrying operation except in cases of stock 

 that must be glued soon after it is received. Of greater importance 

 still is the assurance that stock taken from a properly arranged 

 and controlled conditioning room will remain straight and flat, 

 because it will neither be taking on or giving up sufficient moisture 

 to cause any local expansion or contraction. 

 iVontinuCil on page 44) 



