More About Woods

Hardwood
Hardwood is a description applied to the wood of trees from the angiosperms group – that is, trees that produce flowers rather than cones. Another generally distinguishing feature is that the trees have broad leaves rather than needles, and, with the notable exception of Australian eucalypts, are generally deciduous.

The term “hardwood” has no reference to the actual hardness of the wood – that is its specific gravity (weight) or resistance to impact or cutting. Balsa wood, with a specific gravity of 0.17, is in fact a hardwood.

Specific Gravity
Specific Gravity is a measure of the weight, based on pure water being 1.0 on the scale. In simple terms a cubic meter of wood with a specific gravity of 1.0 will weigh 1000kgs. Any wood with a specific gravity of more than 1.0 will sink in fresh water.

The wood generally regarded as being the heaviest in the world is lignum vitae with a specific gravity of 1.37, and which is found in the south east United States and the Caribbean.

The lightest commercially sold wood in the world is balsa ( Ochroma pyramidale ), with a specific gravity of 0.17, and which is found in and around the Caribbean .

The specific gravity of some commonly used furniture woods are as follows:

American Mahogany 0.54
American Cherry 0.58
American Walnut 0.64
Teak 0.65
New Guinea Rosewood 0.66
Tasmanian Oak 0.67
American Oak – White 0.76
Jarrah 0.80
Kwila 0.80
Siamese Rosewood 0.85

Wood Colour
The colour of wood is mainly caused by infiltrates into the cell walls and may vary even in the same species growing near to each other, depending on the location of the site, type of soil and soil content; also the colour may vary in the same board or leaf of veneer.

Many timbers fade upon exposure to light, others darken, and most will deepen in colour when lacquered or polished.

Wood Grain
The word “grain” is often misapplied and misunderstood when describing wood. Such terms as “coarse grained” or “fine grained” actually refer to the texture of the surface and not to the grain.

The grain of wood is the natural formation of the wood fibres relative to the main axis of the tree, and there are eight generally described types including straight, curly and wavy.

Wood Figure
The term “figure” is used to describe the pattern of the wood when cut and finished. A variety of figures can be obtained from the same wood by cutting or slicing the wood in different ways, generally to produce veneers.

Commonly known figures include bird's eye, fiddle back, mottled and crotch. Crotch veneers, cut from the juncture of a tree's main branches and the trunk, reveal spectacular patterns, the most beautiful of which is flame produced from mahogany. Antique furniture displaying flame mahogany is highly prized and much sought after.

Burrs, Burls and Butts
Burls (or burrs) are produced from lumpish growths on trees that generally form as a result of parasitic infestation of the tree, but sometimes from injury to the tree, during the early stages of its growth. Usually they appear on the tree trunk, but they also occur below ground. The term is also used to describe woods more properly called butts.

The term butt is used to describe the junction of the tree roots with the trunk, where the patterns are created by changes to direction caused by their coming together and by the sheer weight of the living tree above.

Among the most spectacular burls are those produced from Rosewood and Walnut. These uniquely figured timbers are highly prized and because of this, and the fact that they are very difficult to work, they are expensive.

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