The equilibration must be controlled to prevent damage to the wood. Damage from shrinkage is not a problem craftsman 10 bandsaw operators manual pdf, and the drying may proceed more rapidly than in the case of drying for woodworking purposes. Moisture affects the burning process, with unburnt hydrocarbons going up the chimney.
Usually the wood is sawed before drying, but sometimes the log is dried whole. Case hardening describes lumber or timber that has been dried too rapidly. When this shell is at a low moisture content it will ‘set’ and resist shrinkage. The core of the wood is still at a higher moisture content. This core will then begin to dry and shrink.
However, any shrinkage is resisted by the already ‘set’ shell. This results in unrelieved stress called case hardening. Case-hardened wood may warp considerably and dangerously when the stress is released by sawing. Wood is divided, according to its botanical origin, into two kinds: softwoods, from coniferous trees, and hardwoods, from broad-leaved trees. Softwoods are lighter and generally simple in structure, whereas hardwoods are harder and more complex. Although there are about a hundred times more species of hardwood trees than softwood trees, the ability to be dried and processed faster and more easily makes softwood the main supply of commercial wood today.
Water has a significant influence on wood. Wood continually exchanges moisture or water with its surroundings, although the rate of exchange is strongly affected by the degree to which wood is sealed. Free water: The bulk of water contained in the cell lumina is only held by capillary forces. It is not bound chemically and is called free water.