The Technique of FURNITURE MAKING

Foam padding

The original and familiar latex rubber foam was first developed by the Dunlop Rubber Company in the early 1930s, and completely revolutionized upholstery techniques, to be followed later by polyester and polyether synthetic foams. Apart from differences in

performance-,-latex rubber sponge is foamed by chemical additives (originally soap solutions); therefore the cushions can be shaped or

moulded at the time of manufacture, while synthetic sponges generate their own carbon dioxide which blows the liquid, and self- foaming is generally too rapid for satisfactory moulding techniques, although recent develop­ments have overcome this disability to some extent. In practice latex foam is more expensive but more efficient, and does not lose its sponginess unless exposed to damp conditions or direct sunlight. On the other hand, synthetic foams are tougher but yield (bottom) more

rapidly under pressure and the recovery is

slower; therefore the effect is a little dead in comparison. Of the two forms of synthetic

495 Rubber diaphragm seat for loose cushion, showing method of fixing

foam, polyether is more rubber-like and is the form usually adopted for work.

Both latex and synthetic foams can be obtained in sheet form (solid foam) and with cavities which cut down weight and give increased softness, and in a range of thicknesses up to 12 in (305 mm) according to the type. They are also obtainable in a range of densities corresponding to soft, medium, and hard for traffic seating (railway, bus seating, etc.). Pad thicknesses can be built up with rubber adhesives (Bostik, etc.) and can be cut with shears, corrugated kitchen scissors, sharp knives or on the band-saw. They can be glued direct to solid plywood bases or placed direct over resilient webbings. Adequate ventilation must be provided, and if covered with imperme­able materials—leather, leathercloth and PVC - coated fabrics—solid bases must be pierced with 1/4 in (6 mm) holes at 3 in (76 mm) centres, and loose cushions provided with brass eyelet holes sewn in, or potential users will suffer serious embarrassment, as the effect is that of a joke cushion. It is usual to cover foam padding with under-covers of coarse calico if the top covering is leather or PVC, etc. owing to the difference in the recovery rates, but these are unnecessary under open-weave materials except as an added refinement protecting the inner pad from wear.

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501 Light style armchair with head cushion

502 (right) Chancellor's chair, Keele University, in English oak with upholstery in red Niger goat-skins. Designed and carved by Professor D. W. Pye ARIBA, FSIA. Author's workshops

503 (below) Chairs for St Saviour's Girls' School in 1983 of laminated sycamore with upholstered sides. seat and back with the school emblem embroidered on the backs. Made at Bim Burton's workshop

Figures 497 to 500 show the various stages in the upholstery of a drop-in seat for a dining - chair, using resilient webbing, latex foam padding and top leather cover. Figure 497 shows the installation of the webbing with each strap stretched to the pencil-mark and secured with three 5/8 in (16 mm) improved tacks, while in 498 the under-cover of coarse burlap is folded to allow for deflection of the webbing and secured with 3/8 in (9.5 mm) or 1/2 in (12.5 mm) improved tacks. In 499 the foam padding has been cut to shape, the edges roughly chamfered with a 1/4 in (6 mm) overhang all round, and secured in position with upholsterers' adhesive tape firmly tacked to the framework. The final covers are then stretched evenly over the pad, working from the centres of each side out to the corners and temporarily tacking with 3/8 in (9.5 mm) or 1/2 in (12.5 mm) fine tacks which are not driven home until the stretching and shaping is correct. A little horsehair stuffing can be worked in to the under top cover to raise the dome and increase the firmness of dining-chair seats. Figure 500 shows the leather cover cut to fit.