The veneer should be cut slightly larger than the wood it is to be placed on, leaving the rough edges to be cleaned up afterwards. With regard to the ground work something must be said, for there are several particulars to be noted if the wood is of any considerable width, such as panels, carcase ends, and so on. At the same time it must be remarked that in details considerable variety of practice is found. Few men who have done much veneering work but have some pet method of their own, and details will be found to differ. Modern practice tends towards increasing simplicity in place of some of the more complicated and cumbersome arrangements which formerly prevailed.
The side of the wood on which the veneer is laid is a matter of some importance. If laid on one side, the veneered surface will become hollow, and if on the other the reverse. That is to say, if the panel or board does not remain flat, as it may do, the tendency will be in these directions. Now in the majority of cases a hollow surface is much more objectionable than one slightly rounded, so that it is best to lay veneers on the heart side of the wood. I may even go further, and say that the contrary should never be done unless from quite exceptional reasons. As novices may not understand which is the 'heart' side of a board, it may be explained as being that which was nearest the centre of the tree trunk. It can easily be detected by noticing the direction of the annular markings on the end grain. If they are not visible owing to the roughness left by the saw the end can be planed, and they will then be clearly seen. To prevent mistakes, Fig. 164 is given. It represents the end of a board, and shows the upper surface as being the heart side, the one on which the veneer ought to be laid. I am particular about this, as the novice may meet with instructions telling him to do just the contrary, and be slightly perplexed thereby. Well, as I have suggested elsewhere, let him follow the practice of good workmen, and that is to lay the veneer on the heart side. Some cabinet-makers may do the reverse, but they will be rather difficult to find, and when found will probably be indifferent specimens.
The back of the wood should be slightly swelled or rounded by damping, and about this it is impossible to give minute directions, for so much depends on circumstances, size, thickness, etc, that very little can be said about it. It must also be observed that the degree of moisture or swelling given by different workers varies considerably. At one time it was considered advisable to soak the wood thoroughly for a day or two - it may be so still, by some, for aught I know - before veneering. It is, however, by some generally deemed sufficient, and rightly so, to simply damp and swell the wood on the back for a few hours beforehand. This may be managed by wiping the wood over from time to time with a damp rag or sponge, or, and perhaps more conveniently, laying some damp sawdust on it. The only objection to this latter course is that if left too long the sawdust may act more than was intended. However, experience alone can determine what is required in each instance.
Fig. 164. - Section showing Heart Side uppermost.
The wood being ready is laid on the bench, hollow or heart side up. Strong, i.e., good fresh hot glue, is then rubbed on it, not on the veneer, which is then laid without loss of time. In the meantime the caul or cauls should have been made hot, and are then placed above the veneer. To prevent this shifting, one or two veneer pins may be driven in where necessary, but it is as well to avoid using them excessively. If carefully inserted and bent over they can, however, easily be withdrawn afterwards, and need not injure the veneer, as the marks will not be noticeable. In the case of panels they can be driven in by the edges, which will be concealed behind the rabbet. If the wood is only thin, it should be laid between cauls to keep the veneer close to the upper one. Pressure is then applied by means of the hand-screws, which should be liberally used. The heat from the caul will strike through the veneer and melt the glue, causing the surplus to run out at the edges and the surfaces to come into the closest contact. From this it will be seen that it is more important that the caul should be slightly rounded if anything rather than flat, so that the glue may be pressed from the middle outwards to the edges. With a hollow caul of course the tendency is to drive the glue to the centre, and this must be avoided. It is also necessary that the caul should be uniformly heated, so that the glue is equally softened all over. If made too hot the glue, instead of being merely melted, might be burnt or spoiled, and the veneer be injured. With wooden cauls this risk is a very small one, and even with metal is not a very serious one, as if made too hot the plate could not be comfortably moved with the naked hands. The novice with these cautions is hardly likely to err except by carelessness. Metal cauls, unless of exceptional thickness, should have a board laid over them to equalise the pressure on the veneer.
Some of the glue will be forced into and perhaps through the veneer. To prevent the caul sticking it should, if metal, be slightly greased, and a sheet of paper be laid between it and the veneer. With a wooden caul one or two sheets of paper will be sufficient. These precautions are specially necessary with a porous open veneer like burr walnut, but may often be omitted with those of closer texture.
As the glue in striking through is apt to discolour very light veneers, a little more care is necessary with these. A colourless glue may be used, but as this is not always convenient the ordinary kind will do perfectly well if mixed with white, such as powdered chalk, whiting, etc. Whatever the material, it should be finely ground and free from lumps. Glue so prepared is used in the ordinary way, or the veneer may be sized with a little of it thinned down sufficiently. When this latter is done the veneer should be allowed to dry before laying. Another method is simply to rub dry chalk on the veneer and on the board, so that the mixture is formed while the glue is being rubbed in. With light veneers it is advisable to use the glue as thick as it conveniently can be, and to lay it on thinly. As some misapprehension may arise from light veneers being mentioned, it may be said that with oak, ash, and such ordinary woods it is seldom necessary to use anything but good ordinary glue, only the finer and whiter veneers requiring chalk, etc. Of course, even oak and ash, if they are to be kept as white as possible, may be laid with whitened glue, which can be used without injury whenever it may seem desirable.