ABSTRACT
The natural living trees, freshly felled timber logs, lumber boards, and wood in service are porous, hygroscopic materials. These materials contain cell wall substance; internal voids; large amounts of moisture, that is, water in forms of liquid or vapor that often constitutes over 50% of the wood's mass; and some extractives. In some cases, moisture may be even in greater proportion by mass than the solid wood materials. The physical states of pure water are defined by two independent properties: temperature and pressure. The properties of free water are very close to those of pure liquid water. The wood's density is a variable parameter influenced by factors. The basic density of wood is defined as the oven-dry mass of a wood sample divided by its green, swollen volume. The wood contains varying amounts of moisture depending on different heights in the tree and growing conditions, as well as on the species, density, degree of seasoning, and many other factors.
