The Technique of FURNITURE MAKING

Protection of edges

Edges of veneers laid with hide glue have a tendency to lift or splinter out particularly in the long grain, and they are, therefore, protected either by applied mouldings or edges, or, as in traditional work, with narrow crossbandings of veneer. The process is described on p. 305-7. The shrinkage pull of face veneers as they dry out must be compensated for by a correspond­ing balancing veneer applied to the underside of the panel, and this is also described later. Veneer edges laid with resin glues do not need protection (287:3, 4), but balance veneering is also necessary.

Trimming edges

Veneers should be laid with a generous overlap all round in case they slip during laying, and should not be trimmed back until thoroughly dry. Cross-grain edges may have to be knife cut across the face before trimming back with chisel and finely set plane, although veneers laid with resin glues have not the same propensity for splintering out. An excellent veneer-trimmer is illustrated in 283 which cuts the overhang tight against the edge even across the grain, and is invaluable if there is much trimming to be done.

Jointing veneers (hide glues)

If the veneer leaf is insufficient to cover the width, one leaf is laid as already described and the next with a 1 in (25 mm) overlap (280:4). The centre-line of the overlap is then cut through with a sharp knife, working against a straight-edge, the edges carefully lifted, fresh glue inserted if necessary, the area reheated and hammered down, and the joint taped with paper to hold the edges together while the glue sets. If the joint subsequently opens it is usually a sign that either too much water has been used or too much pressure applied across the grain, stretching the moist veneer. Built-up patterns, matched curls, etc. are laid in the same way, centre - or guide-lines drawn across the groundwork/substrate and marked on the edges, the first sheet laid to overlap the guide­line, the second sheet laid and knifed through (280:5). Diamonds and quarters, etc. can also be treated in this manner, taking care to cut them the same overall size and positioning them with equal laps so that the grain matching is not lost; but they are better laid as taped patterns between cauls. Burrs, burls and curls with violently contrasted grain which have buckled badly should also be laid with cauls, but the veneers must be flatted or flattened before laying (see Flattening veneers, p. 300). Here again an experienced worker might prefer to soak the burrs in very hot water, using the thinnest possible glue and repeatedly hammering down until the veneer sticks.

Caul veneering (hide glues)

In this method the veneers are cut square, taped together and laid as a single sheet without preliminary dampening. This eliminates stretching, and the method is always used for laying thick saw-cut veneers, complicated patterns and marquetry-work where any swelling of the individual pieces would inevitably ruin the design. The groundwork/ substrate is glued and allowed to cool off, the veneer assembly laid on the guide-lines and held in the correct position with staples or fine veneer pins tapped in and pinched off level. It is then covered with a heated caul of softwood or thick zinc sheet with an interleaving of newspaper to prevent the caul sticking, and pressure is applied with cross-bearers and cramps/clamps (280:6). The bearers should be fractionally rounded in the length to spread the pressure from the centre outwards, and the cramps tightened in the order shown (280:7). Softening, composed of several thicknesses of newspaper, thick felt or rubber sheeting can be used to even out any irregularities, but they must be warmed throughout or the glue will not flow. Modern veneering practice follows the same principles, but cold-setting resin adhesives have eliminated the necessity for heated cauls, although they can be used for great acceleration of the setting time.