Moisture content and density are two most important properties for woods.
The moisture
content of tree varies with species, age, size, location and so on. Generally, trees
contain water about two times the weight of its solid material.
For softwoods, the
moisture content in sapwood is significantly higher than that in heartwood. As
for hardwoods, the difference could be negligible. When wood went through all
process and ready for construction purposes, it usually achieves equilibrium moisture
content. At this point, the wood may not gain or loss moisture content to the surrounding
air.
The specific gravity
of wood varies with its condition, notably green, air-dry and oven-dry.
Therefore, specific gravity of a wood must be qualified by the moisture content
at the time.
Freshly cut
lumber, which is also known as green wood is heavier than dry wood due to rich
content of water. The weight of sapwood is also greater than that of heartwood.
After drying however, heartwood would be heavier than sapwood.
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