Knowledge about the water in wood
2016-06-06 15:36:10 Hebei Shuowei Metal Manufactuering Co.,Ltd
Wood drying is very important link during woodworking process. If you want get quality dried lumber, to learn some knowledge about the wood water is necessary.
What is 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).
For example, a freshly cut piece of oak weighed 165 lbs. In its initial green state, and ended up weighing is 100 lbs. When fully dried in oven. That is to say total 65lbs. of water 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 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 properites of wood (except weight and burning properties). If lower than the fiber saturation point,(FSP), the bound water have a great influence with the wood properites
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 it fiber saturation point.FSP is a critical state. It is the turning point of wood porperites. It relates to the strength, shrinkage,thermal conductivity and electrical conductivity.
The fiber saturation point is vary from different wood speices, usually in the range of 22%-35%MC, the average FSP is 30%MC. When the moisture lower than FSP,The strength,shrinkage will increase with moisture content decrease. So this is very important knowledge, it is helpfull to control the wood drying.
Prepared and maintained by Carlos Sheng,
Supplier of high frequency vacuum wood dry kiln
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