The Nature of Wood

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Unit 3

• The Nature of Wood

Structure of Wood Cambium Sapwood Heartwood
Moisture Content of Wood Effects of Moisture
Content
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• Wood is composed of tiny cells that are held
  together with a natural cement called lignin.
  (The cells are drawn here many times larger than
  their actual size.) Trees grow by forming new
  wood cells, and reach full maturity and stop
  growing when new cells stop forming.

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• Annual rings begin at the center of the trunk and
  continue outward to the bark. Each ring
  represents a year of cellular growth.

4

• The moisture content of wood is the percentage of
  its weight that is water. The oven-drying method
  provides an accurate measure of moisture content.

5

• A moisture meter is a convenient tool to use to
  check the moisture content of wood.

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• Most lumber shrinkage occurs across the grain.
  For example, a 2? 4? 8' piece of lumber will
  shrink more across its 2? thickness and 4? width
  than along its 8' length.