Timber and country: Colour and characteristics: Satinwood soft rich yellow, often with fine figure, Ceylon, India gives lustrous finish Silky Oak purplish-brown, shows pronounced Australia rays when quarter-cut Sycamore white to yellow-white, liable to Europe fade to light brown, when dyed grey known as harewood Teak golden brown, dark markings Burma Utile greyish-red Africa
Walnut Europe American; Zebrano Africa, medium to dark brown, often with fine figure dark purple-brown, often with dark markings richly streaked with light and dark markings
Properties: hard, difficult to work durable, stable medium hard, stable; fairly hard, greasy and durable fairly hard, clean working, stable fairly hard, easy working, stable fairly hard, stable
close texture, polishes well. Reddish straw, light yellow, often with dark markings light yellow to white, pale to deep warm brown
These have largely superseded solid wood in many branches of cabinet work, especially veneered work. They have the advantage of being obtainable in large sizes, and of being free from the shrinkage troubles that belong to solid wood. It should be remembered, however, that the quality varies widely in accordance with the purpose for which the material is intended. A cheap quality plywood may be satisfactory for a tea chest, but useless for cabinet work. It will have all the failings of often knot-free, stable when seasoned easily worked, sometimes badly knotted
tough, bends well, stable cheap solid wood and a crop of others besides. We may conveniently divide the materials under plywood, laminboard and chipboard.
Plywood. Most plies have an odd number of layers e.g. 3, 5, 7, and the grain of the alternate layers or veneers as they are called is at right angles. Occasionally there are four layers in which case the grain of the two centre layers runs in the same direction. Three layers is the commonest in the thinner plies, and they may be built up of three equal thicknesses or the centre layer may be thicker than the others to make up for there being only one. In this case it is generally termed stout heart. Five-ply is sometimes made on similar lines. When there are many layers it is generally termed multiply. For all practical purposes the latter is equally strong in both length and width.
The woods used in plywood manufacture vary widely, but the following are the commonest: birch, alder, ash, beech, gaboon, and various pines. Of these birch is widely used in cabinet work. Both this and gaboon mahogany are (in the best grades) excellent for best-class veneered work.
The care taken in manufacture affects the resulting plywood considerably. The cutting, drying, adhesive, and assembling all play their part. It is a thing about which you can do little however, except to buy prime quality. This will be free of knots on one side at least, and it will have been assembled with a good-quality cement. It should also be free from internal defects such as those in
At A the bad core-joint results in the outer layers being pulled in, a defect which shows badly if it is veneered. In the core veneers overlap, resulting in a ridge across the panel.
The construction of this is rather different from that of plywood. There are two outer layers with a core sandwiched between them, the latter consisting of strips glued together side by side, the grain at right angles with the outer veneers, and with heart sides reversed alternately, so that in the event of shrinkage and consequent warping any pull in one direction is countered by the adjoining strips.
There are three kinds of boards here in the order of quality. The strips forming the core should not exceed 7mm. It is the most satisfactory of the built-up boards, and is suitable for veneered
- multi-ply; B stout-heart five-ply.
- Faults in plywood to be avoided in cabinet work.
- laminated board; blockboard; battenboard.
- Simple edgings for built-up boards