Moisture properties

In the mechanical wood industry indicated the amount of moisture in the wood as moisture content. It is the quotient of the mass in a moist piece of wood and the mass of the dry wood, expressed as a percentage. Moisture content is used for example in agriculture and sometimes even in forestry and wood fuel sector.

The moisture content is determined directly with the dry-weight method or indirectly with other methods. According to the dry-weight method, for example ISO 3130 or EN 13183-1, weighed sample in humid condition after which the samples are dried at 103 + 2 ° C until it is completely dry. Then the sample is weighed again and the amount of moisture output can be calculated.

At first the high drying leaves water in the cell lumen (cavities). This goes on until the moisture content reaches fiber saturation point, approximately 25-30% moisture content, depending on the type of wood. During drying under fiber saturation point departing the water in the cell walls and water vapour in the cell cavities. The wood starts to shrink when drying is done in fiber saturation point.

Direction %
Tangential ≈8
Radial ≈4
In the fiber direction 0.4
Volume Change ≈12

Moisture movements of pine and spruce.
In percent between the fiber saturation point and absolutely dry wood.


 
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