Wood drying (also seasoning lumber or timber seasoning) refers to reducing the moisture content of wood prior to its use. For some purposes wood is not dried at all (it is used "green"). Often the wood needs to be in an equilibrium with the air outside or the air indoors. Wood is either air-dried or kiln-dried. Usually the wood is sawn prior to the drying process, but not always.
Wood drying may be described as the art of ensuring that gross dimensional changes through shrinkage are confined to the drying process. Ideally, wood is dried to that equilibrium moisture content as will later (in service) be attained by the wood. Thus, further dimensional change will be kept to a minimum.
It is probably impossible to completely eliminate movement in wood, but this may be approximated by chemical modification. This is the treatment of wood with chemicals to replace the hydroxyl groups with other hydrophobic functional groups of modifying agents (Stamm, 1964). Among all the existing processes, wood modification with acetic anhydride has considerable promise due to the high anti-shrink or anti-swell efficiency (ASE) attainable without damaging the wood properties.
Source: Wikipedia