Plywood’s Role in the Modern Home

Cue (NZERS), Issue 9, 15 October 1944, Page 6

Plywood’s Role in the Modern Home

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PROGRESSIVE / strides/ made * during the war in the uses to which plywood may be put, suggest that in peace, too, there will be greater demands for veneers in the home, office and factory. It is not hard to visualise sweeping changes in furniture designs, with the architectural trend favouring prefabrication of built-in equipment. Veneering is a method of producing pleasing wood-grain effects not obtainable in plain boards. Plywood is built-up. in uneven numbers of veneer sheets 3 to 11 —primarily for strength but also to retain flatness. With even numbers of cross-grain sheets, buckling is more likely to occur. ' When the timber log arrives at the mill it is treated in a hot bath or vat. This process loosens or softens the wood before it is introduced ; to, whichever . cutting machine will be employed One, known as the slicer, cuts ihe log lengthwise into thin layers, like a knife cutting , cheese. Another is the rotary lathe, which operates rather like a vast . pencil sharpener, in paring off the log as it revolves ’ a long thin strip of veneer. — . Pared Like Tissue

If a slicer is used, the log is usually broken down to four quarter-sections. The slicer knife may come up and down or across, cutting thicknesses of from oneeighth to one-hundredth of an meh. The great, continuous sheet skinned off by the rotary lathe, from a-quarter to one-sixty-of an inch in thickness, is further cut into workable strips, generally 72 by 36 inches.

The next process is to dry the veneer sheets in kilns. Fibre saturation* point is reckoned to be 26 per cent of dry weight. After drying, about 5 to 10 per cent of the moisture content remains! -Up to this point, the processes described have not altered inprinciple for years. It is known that ancient Egyptians even produced a form of plywood. However, it is in the next step, where glue is applied, that experimentation has led to definite advancement in recent years. Plastic plywood is a misnomer for resin bonding, the advent of which has revitalised the plywood industry. Direct issues of its discovery have been the development of the sensational Mosquito fighter-bomber and patrol torpedo boat. .

Simply, the advantage of resin bonding lies in the absence of extra water, in mixing the glue. With cold glues, the solids are variously mixed with about two parts of water, whereas in sheet resin no extra water is added to' the ply, eliminating swelling and subsequent shrinkage. As wood, shrinks 40 to 1 across the grain, a sheet of three-ply glued by coldwater glue has one • veneer in; stress. This will cause warping if the sheet is not kept flat for 12 to 14 hours after leaving the

press, so that the « will » to twist is removed. Stronger Than Metal Strength in flat sheets is best obtained by setting the veneers it 50 deg -to the face. Should a curved surface be desired, a 45 deg set is best, but the angle varies according to the percentage of wood in the crossband as against the -total. In strengthweight ratio, plywood holds the advantage over metal, which aeronautic designers have been quick to recognise, but in winning this advantage, plywood still cedes to metal a margin in bulk. Moulding of plywoods calls into play a series of presses, operated by hand, hydraulic and fluid pressure principles. Fluid pressure is a comparatively recent discovery, involving the use of a flexible bag. The plywood to be moulded is shaped according to the required design and placed in a chamber. Heat and pressure are applied simply by pumping steam into a rubber bag, which itself is in a metal chamber. The resin agents are thus forced into the wood cells as the plywood is taking shane. Even pressure on curved structures is assured by the flexible bag process, thereby facilitating the manufacture of such equipment as hulls, fuselages or wings, either in one piece, in halves or in sections. By its new qualities plywood has become a new material — ible, purposeful, reliable. It must be regarded in a new light, for it will surely revolutionise future building and joinery industries.

,New Zealand represents a fertile field for ■ the progressive minds of these allied industries..

' With closer co-ordination among architects, furniture makers and joiners, the development of prefabrication and built-in fittings need not threaten small industries, but rather offer a fresh opportunity for factories large and small to raise the standard and specialise in the manufacture

of home equipment, calling for skilled use of tools.

Blueprint on Trends The cabinetmaker has the chance of preventing his business from pouring into other channels by moving with the trend and accepting it as his right, rather than fighting the idea and perhaps reducing his products in quality and value. Instead of turning out a wardrobe, the cabinetmaker should answer with a new-design product, complete with appropriate hardware, ready to be set in the measured space of the blueprint. Taste will dictate how the product must be patterned and finished. This new aspect brings in its train the need for better understanding among the architect, builder > and cabinetmaker. e designer and constructor of any building should have a fuller appreciation of the cabinetnia er s shop and the furniture factory to meet their needs more harmoniously. Actually as the architect and builder are likely tobe his new customer—not the buyer as of yore— cabinetmaker must make ready to become a sub-contractor, as it were, for there must continue to be an excessive, call on his skill, time and machinery in the production of better-standard, modern, practicable furniture.