The only adhesive that can be used in this process is Scotch glue. Both groundwork and veneer are given a coat of glue and, the veneer being laid in position, the surface smoothed out with the hands. About one half is lightly dampened with a swab, and a warm flat iron passed over the surface to liquefy the glue. The veneering hammer is worked zigzag fashion over the surface, from the middle outwards, preferably in the direction of the grain. This avoids stretching the veneer and the subsequent risk of pulling the work hollow. The purpose of the hammer is to press the veneer into close contact with the groundwork and squeeze out surplus glue at the edges.
The one half being completed, the remainder is dealt with in the same way. It helps to minimize casting if the back of the groundwork is dampened first. When both sides are to be veneered the second side should follow immediately after the first. If a joint is needed one veneer should be laid first, and the second put down with an overlap of about 12mm. A straight-edge is cramped down over the overlap and a cut made through both thicknesses with a keen chisel or knife. The one waste strip can be peeled off straightway, but to reach the other the veneer has to be lifted as in Fig. 12. When removed the veneer is pressed down with the hammer and a piece of gummed tape stuck down over the joint to prevent it from opening as the glue dries out.
The scraper is used to clean up veneer. Any gummed tape should be lightly dampened and peeled away beforehand. Glass papering follows, the cork rubber being used.
Fig. 10 Pressing the veneer down with the veneering hammer.
Built-up patterns in veneer
The method of .making these varies to an extent with the particular pattern, and there is a certain amount of personal preference in the way the job is tackled. The examples given in Fig. 13 are typical and are fairly straightforward designs.
It is obvious that the direction of the grain must agree in all four quarters, and in the best work they are cut from four consecutive leaves of veneer, so that not only direction but variations in grain are balanced. Hold them together and plane two adjacent edges straight and square on the shooting-board. Cutting a joint when hammer veneering. A cut is made through both thicknesses.Removing lower waste strip when jointing.
The whole can be assembled on a flat board, and if the planing has been accurate the joints will be close. It may be necessary to take a shaving locally from the edges. If there is any serious in-accuracy it is necessary to correct all four quarters rather than plane the edges of just one, other-wise the joints will not be in alignment. Gummed tape is stuck over the joints to prevent opening and the whole is laid with a caul. It is necessary to position the veneer accurately, and two veneer pins should be tapped in to prevent movement.
The design is somewhat similar but rather more elaborate. The diamonds are prepared in packs and it is essential to plane accurately to shape. The best way is to set out the pattern on a piece of paper fixed to the actual panel and take the shape from this. Hold the veneers down with a dab or two of weak glue, keeping closely to the design and making sure of close joints. If any correction is necessary make it as you proceed, but remember that any serious correction affects the other edges, and if it becomes obvious that the shape is badly out it is better to take a shaving from all the diamonds. Again hold the joints with gummed tape and lay with a caul. One important point is to keep all diamonds the same way round as when cut from the leaf. The reason is that some woods when polished vary in depth of colour according to the direction from which they are seen, hence the desirability of retaining the direction.
The triangular pieces are again cut in packs. They are then assembled as for the other examples with gummed tape. Allow the wide ends to extend about lOmm beyond the finished size so that the whole can be trimmed with straight-edge and knife, as shown by the dotted lines. This necessitates cutting the projecting ends square at the sides, otherwise they will overlap. Finally, the end cross-grained pieces are jointed, fitted up and taped.
- Examples of built-up designs in veneer.
- How packs of veneer are opened up for a quartered panel.
- How packs of veneer are trimmed.
- Assembling diamond pattern with gummed tape.