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Softwood and Hardwood

There are some 40,000 known species of trees, but of these less than 30 are in common use. Timber species may roughly be divided into two groups: softwoods nad hardwoods.

Softwoods generally grow in the colder regions of the world, in the northern American states, Canada, Russia and other parts of the former Soviet Union, and in Scandinavia. Most are evergreen with thin, needle-like leaves and are relatively quick-growing. As a group, softwoods are fairly homogenous. They are typically pale in color, soft and close-grained, and often knotty. Softwoods comprise various species of pine and deal, including redwood, Scots pine, Norway spruce and white deal.

Softwood is a basic constructional material, and as such it is widely available pre-cut. The relative softness of these species, together with the presence oof resinous knots, makes them less durable than many types of hardwood. Softwoods are generally much cheaper than hardwoods; the best grades are those with the straightest grain and fewest knots. Softwoods must be treated against rot and woodworm before use.

Hardwoods, as a group, are much more varied than softwoods. They grow in both temperate and tropical areas, may be deciduous or evergreen and comprise a wide range of species that differ spectacularly in color and texture. Most are much more expensive than softwoods. Many species are in serious decline worldwide. Throughout history, hardwoods have been prized for their beauty. strength, durability and resistance to pests, or for the ease with which they could be carved.

Patterns of grain as well as color can be very distinctive: 1-sweet chestnut, 2-elm, 3-Brazilian mahogany, 4-African mahogany, 5-maple, 6-burr maple, 7-moera

Seasoning

Like many materials that originate from a living source, wood contains a high percentage of water, varying from softwoods to hardwoods and from one species to the next. Once a tree is felled, it begins to loose moisture at a rate dependent on the surrounding warmth and humidity. This seasoning continues until the timber has acclimatized to its immediate environment, but it never entirely stops.

During seasoning, wood moves, contracting very slightly along the length, but to a much greater extent across the width. Most commercially available timber for interior use is dried to a moisture content of around 10%, which is the level recommended for use in centerally heated environments.

Even seasoned wood is sensitive to changes of temperature and humidity. It may be necessary to store wood for a period of time in the room where it will eventually be used so that the timber can further adjust to atmospheric conditions.