If a vacuum-bag press is not available, shapes of double curvature can be veneered with the traditional sandbag techniques. Either a canvas bag or sandbox filled with coarse silver sand is used, and an example of the latter is shown in 293:7. Assuming that a bombe shape has been constructed either of segments, wood bricks, or, in the traditional examples of bombe commodes, a solid panel tongued to a jointed framework and shaped to the curves with plane, floats (coarse files) and scrapers, the box is filled with sifted sand and the shaped groundwork/substrate to be veneered tamped down until it fits exactly. Register-marks should be made on the groundwork and also on the edges of the box so that the curves of the shape will be exactly located in the depressions in the sand, for the sand, being inert, will not slide under pressure. The groundwork is then carefully withdrawn and the veneers fitted, tailoring them if necessary and taping them firmly together to form a self-supporting shell. If hide glue is used the groundwork is then glued and allowed to cool off, the veneers placed in position and held with staples or pins in the waste edges, the sandbox thoroughly heated and the groundwork with its covering of veneers exactly located in the box. It is then cramped down with suitably shaped cauls, applying pressure in the centre first and then both edges simultaneously or the shape will rock over. Resin glues can be used instead of hide glue, and in fact the heat of the box will accelerate the set, although in this case the sand should be warm rather than hot or precuring will result before the cramps are in position. Canvas bags filled with sand (293:8) follow the same principle and are thumped down over the glued assembly and either cramped or weighted.
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