ABSTRACT
Many timbers develop gums and resins in the heart-wood, while the moisture content of the heartwood of most timbers is appreciably lower than that of the sapwood in the freshly felled state. The acidity of the wood increases slightly, though certain timbers have heartwood of very high acidity. In addition to determining many of the technical properties of wood, the distribution of cell types and their sizes is used as a means of timber identification. In many timbers, and certainly in most softwoods, the direction of the deviation from the vertical axis is consistent and the cells assume a distinct spiralmode, which may be either left- or right-handed. Certain timbers show a propensity to conduct suspensions of minerals that are subsequently deposited within the timber. Green timber will yield moisture to the atmosphere with consequent changes in its dimensions. The most important factors affecting the diffusion coefficient of water in timber are temperature, moisture content and density of the timber.
