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THE PREPARATION OF TIMBER - KILN SEASONING

V. Ryan 2011

 

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The seasoning time for wood can be reduced considerably through the use of a specialist kiln. Often air seasoning and kiln seasoning are used together. There are different types of kiln. A ‘forced draught’ kiln is seen below.

Kilns are used because the process speeds up seasoning and this method can be used to accurately control the moisture content of the wood.

The wood is carefully stacked inside the brick kiln. Water is heated and the resulting steam allowed to enter the kiln, circulating inside and around the wood boards. Over time, the amount of steam (humidity) is reduced until the wood has the desired moisture content.

 
 
 
 
The timber remains in the kiln for two to five days, depending on the species of tree and the time of year that the tree was felled (Spring, Autumn or Winter). Softwoods season more rapidly in the kiln, compared to hardwoods. This is due to their differences in cell structure
Research is ongoing in to how to season timber, using the minimum of energy and causing as little damage to the timber as possible.

Other forms of seasoning are:

SOLAR SEASONING - A combination of air and kiln seasoning.

MICROWAVE SEASONING - Microwave energy is directed at the timber, driving out the excess moisture. This technique is used in Canada, in some small scale commercial operations.

CHEMICAL SEASONING: This is a specialist technique. It involves submerging the ‘green’ wood in a hydroscopic chemical for twenty four hours. The chemical slows down the rate of water loss, helping to reduce damage such as warping, during the air drying stage.
 
 
 
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