ABSTRACT
The fibrous and hygroscopic mass of freshly felled trees and recently cut green timbers contain up to 75% of water which affects the wood's physical properties as density, strength, and hardness. Most of this water must be removed to a desirable level of moisture content, usually below 20% before the wood is processed into end-use products. Drying the wood reduces the risk of dimensional changes when the wood is in place and significantly upgrades, sometimes up to 700%, the commercial value of raw timber. In commercial kiln drying of lumber, there are two major drying defects that cause significant losses for wood processors due to rejection or downgrade of the wood products: excessive moisture content variation in the dried lumber boards; and residual drying stresses and boards' distortions after drying. Depending on the lumber being dried, the physical properties of the material, such as density and porosity, are affected by shrinkage during drying at various levels.
