The Technique of FURNITURE MAKING

UPHOLSTERY

This again is a specialist craft, for a good upholsterer capable of stuffover-work, shaped work and deep buttoning in a full range of materials including leather must be part tailor, dressmaker and leather-worker. However, the introduction of foam pads and resilient rubber webbings has vastly simplified the usual run of upholstery in dining and easy chairs, which is now well within the scope of the average workshop.

Resilient webbings

Invented in 1953 by Pirelli Ltd of Italy, these consist of resilient rubber tensioned strips of attractive appearance, and have almost entirely superseded the jute webbings of traditional upholstery. The advantage of Pirelli webbing is that it can be used without sub-frames or spring­ing, and need not be hidden for it is obtainable in various colours and in four qualities for different seating requirements. The webbing is composed of a rayon fabric bonded in rubber and has proved extremely tough, durable and elastic, with negligible loss of recovery over long periods. It is secured by tacks or staples, as with jute webbings, or with special patented metal clips with serrated edges (493:1) clenched to the ends of the strips and slipped into a sawn groove (493:2) in the framework (another form of wire clip is available for metal framing); and it must be tensioned by stretching to a fixed percentage of its original length (plus 5 to 10 per cent) in accordance with the makers' recom­mendations. The strips can be placed 2 in (50 mm) to 3 in (76 mm) apart and need only run one way, with cross-weaving (as with jute webbings) unnecessary except over large areas. Full details, fastening instructions and samples can be obtained from upholstery suppliers.

Four-point platforms

Another development of Pirelli is the resilient rubber diaphragm with triangular steel loops (493:4) engaged in metal bosses screwed to the

494 Detail of chair seat for loose cushion with resilient webbing straps secured by metal fasteners in grooves sawn into rails

framework of the chair (493:3). They are used instead of webbing for loose cushioning, and the four-point diagonal anchorage eliminates distortion of the side rails, hammocking and localized areas of wear in the cushions (493:5). The diaphragms must be tensioned from 8 to 15 per cent maximum, and a simply-made metal stretching device is obtainable for quick assembly work. They are available in a range of seat sizes from 151/4 in (387 mm) to 221/2 in (571 mm), and therefore the chair must be designed accordingly, though the square format can be stretched to fit square, rectangular or tapered seat frames within the maximum permissible tensioning.

In designing chairs and settees, etc. with resilient webbing or platform suspension in mind, both initial and depressional tension must be considered, with wood sections sufficient for the loading. The position of the webbing strips is also important, whether from side to side or back to front, and here again there must be specific understanding of the tensions involved. Booklets are available from the suppliers giving the relevant details.