Hygroexpansion in Wood

Abstract

In the living tree, the cell walls of wood are always in the fully swollen condition, at fiber saturation. Therefore no skrinkage or swelling occurs in the living tree except from hydrostatic tensions in the cell cavity water, and normal thermal expansion and/or changes in the fiber-saturation point with temperature. However, when green wood dries, hygroscopic shrinkage takes place, the extent depending on a number of factors. These include: amount of moisture loss, structural direction (tangential, radial, or longitudinal), kind of wood, drying stresses caused by moisture gradients, etc.