Wood drying is very important to link during the woodworking process. If you want to get quality dried lumber, learning some knowledge about wood water is necessary.
What is the Moisture content?
The weight of water in living trees, freshly cut logs, and freshly sawn lumber can exceed the weight of the wood. The total amount of water in a piece of wood is called its moisture content (MC).
Moisture Content % = (Weight Of Water/ Ovendry Weight Of Wood) X 100%
For example, a freshly cut piece of oak weighed 165 lbs. In its initial green state, and ended up weighing 100 lbs. When fully dried in the oven. That is to say, a total of 65lbs. of water was lost in the drying process. So 65 lbs. (weight of water). divided by 100 lbs. (oven-dried weight of wood) and multiplied by 100% to get the moisture content, we arrive at 65% for a fresh-cut oak.
This moisture exists in two different forms: as free water that is contained as the liquid in the pores or vessels of the wood itself, and as bound water that is trapped within the cell walls.
The free water has little effect on the physical properties of wood (except weight and burning properties). If lower than the fiber saturation point,(FSP), the bound water has a great influence on the wood properties
Drying the wood drying process, when all the free water has been lost and the bound water in cell walls in saturation. The moisture content of this situation, We named its fiber saturation point.FSP is a critical state. It is the turning point of wood properties. It relates to strength, shrinkage, thermal conductivity, and electrical conductivity.
The fiber saturation point varies for different wood species, usually, in the range of 22%-35%MC, and the average FSP is 30%MC. When the moisture is lower than FSP, The strength, and shrinkage will increase with moisture content decrease. So this is very important knowledge, it is helpful to control the wood drying.
Prepared and maintained by Carlos Sheng,
Supplier of high-frequency vacuum wood dry kiln
