Glue has made possible much of the design both in furniture and in finish which is now in vogue. The fact that today we can obtain strong glue of uniform quality has an important bearing on all woodworking operations. Glue also has done much toward the economy of timber.
Seasoning the Stock
As shown in previous articles, the elder-day method of making accurate work was to air-season the stock through a period of years, until the internal stresses become equalized. Then, too, the cabinetmaker of two or three generations ago was in no particular hurry to put his product on the market and thus he gave ample time for the parts to thoroughly adjust themselves.
Today we rush the stuff from the log into the finished product in the shortest possible time. While the dry-kiln literally jerks the moisture out of the stock, the lumber remains full of strains and the moisture content in the various parts of the stock is an amount that is more or less irregular in disposition. To over- come these irregularities, it is necessary to cut the stock up into small pieces and then join them with glue in such a way that the strains in any one part will oppose the strains in another, thus neutralizing the warping tendency.
Built-up stock is the order of the day, whether it be built up of heavy strips or of veneering. This has played an important part in the economy of material. The strips and blocks used for the larger constructions can be cut more closely than was possible in the past, and also the material for the body of a piece can be made from wood containing some worm-holes or other imperfections which would not be allowed to appear on the surface, the surface finish being produced by means of veneer.
Both in built-up stock made from strips and in the built-up veneer stock, the resulting compound piece is stronger than a piece of equal thickness made from a single board. This has brought about the use of thinner material for many purposes.
The compound veneered board made up of a body of three or more pieces of rotary-cut veneer with a face of hardwood veneer is another factor which economises timber to a great extent. A log made into rotary-cut stock occasions no loss in sawdust. When this rotary-cut stock is dried under pressure so as to straighten it and then built up into compound veneer boards, the resulting pieces are remarkably straight.
Manufacturers realized this long ago the extent to which stock of this kind can be used and the saving which can be affected through it. Today the backs of bookcases, and numerous other pieces of furniture are made from compound veneered boards from 1/4 to 5/16 inch thick. These being continuous are therefore dust-proof.
The old method of using tongue-and- groove stock took care of the shrinkage, but if an attempt was made to glue the tongues and grooves to keep out the dust the stock was sure to crack or buckle.
Glue for Compound Board
The glue employed in making up this compound stock must be strong enough so that it can resist the tendency of the wood to expand or contract. In other words, the glue must be at the same time strong, tenacious, and flexible.
Rotary-cut stock generally presents a very good surface for gluing. Some woods when finished with a smoother present such a smooth surface that the glue does not adhere well. In certain instances the wood requires scoring or scratching to make a good glued joint possible.
Panels and Their Place
The compound board has not only revolutionized the practice in constructing backs for furniture but it is also used for drawer bottoms and is now even appearing in the finished surfaces of furniture. The panel-less desk or door would be a manufacturing impossibility were it not for the introduction of compound boards. At best the panel is an excuse introduced into construction practice by the woodworker as an acknowledgment of the fact that it was impossible for him to control shrinkage in any other way. Hence, we have the panel in order to allow the material to come and go without destroying the harmony of the whole or permitting the possibility of actually producing cracks through the wooden structure. We have become so accustomed to panels that at first sight the appearance of a door without them does not suit our sense of fitness. In much the same manner the first automobiles and trolley cars appeared unfinished and in no condition to start without a horse in front of them.