• Green 
  Refers to a freshly cut piece of timber, still containing a high amount of trapped water within
• Moisture Content (MC)
  Moisture content is a ratio of the weight of a given piece of wood's moisture to the weight of that same species of wood once it has had all of its moisture removed.  Example:  If a piece of oak weighed 40 lbs, and that same piece of wood weighed 20 lbs. once all of the moisture was removed, then one would deduce that the original piece of wood contained 20 lbs. of water.  Moisture content would then be calculated by dividing the 20 lbs of water by the 20 lbs the dried piece weighed, giving a ratio of 1/1, or 100%.  Measuring the moisture content of wood in this way can be time consuming, so electrical moisture meters are commercially available which can provide this measurement simply and quickly.
• Free Moisture
  Bound moisture is the moisture that is held within the cells of a tree for storage.  This moisture moves relatively freely, and makes up the bulk of a green piece of wood's moisture content.  This moisture is also the most easily removed during drying.
• Bound Moisture
  Free moisture is the moisture held in the fibers of a wood cell's walls.  This moisture does not move very freely through the wood, as it is somewhat trapped within the cells' walls.  This moisture is more difficult to remove during drying, and is usually the last moisture that will be removed during drying.
• Fiber Saturation Point
  Refers to the point at which all of the free moisture has been removed from a piece of wood, but the cell walls are still saturated with bound moisture.
• Equilibrium Moisture Content
  Refers to the point at which the moisture content within a piece of wood is in equilibrium with the moisture content of the surrounding atmosphere, and no moisture is moving between the wood and its environment
• Oven-dry
  The point at which a piece of wood no longer contains any moisture, which is done by drying in an oven at temperatures above the boiling point of water until all moisture has been removed.  The weight of a piece of wood when oven dried can be used to determine the moisture content of pieces of wood from the same species, as mentioned above.

Movement in Wood

• Longitudinal shrinkage
  Shrinkage of a wood cell along it's length, from end to end.  Typically shrinks less than 0.1% in length, meaning that a drying piece of wood will shrink almost none along its length.
• Radial Shrinkage
  Shrinkage of wood in the direction from the center of the tree towards its outer edge.  The amount of shrinkage varies from species to species, with an average of 4-6%* shrinkage for most hardwoods and softwoods.  Some species, however, may shrink as much as 8% or more*
• Tangential shrinkage
  Shrinkage of wood around the annual growth rings of the tree.  The amount of shrinkage varies from species to species, with an average of 7-8%* shrinkage for most hardwoods and softwoods.  Some species, however, may shrink as much as 12%* or more.

Drying Methods

• Air Drying
  Drying method in which pieces of wood are left to be dried naturally by the atmosphere.  Usually this is done by leaving stacked wood in sheds where air can freely circulate to dry the wood.  This method will allow the wood to dry to moisture contents of around 15-25%, depending upon the relative humidity of the environment in which the wood is left to dry.
• Kiln Drying
  Drying method in which wood is placed in a carefully controlled environment (a kiln) in which to dry.  This allows for greater control of drying rates in order to reduce the chance of degrade in the dried lumber.  This method can dry wood to whatever moisture content the kiln's operator desires.  Kiln drying is necessary in order to reduce the moisture content of a piece of wood to the 6%-12% moisture content that it would dry to when used as for furnishing a house's interior. 

*Percentages taken when wood has been kiln dried to around 12% moisture content.

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