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KILN DRYING

SEASONING TIMBER

Logs just cut from a growing forest of hardwoods when sawn at the mills yield lengths of timber more or less , green, and containing a of moisture. In this connection the tim- ‘ her is unsuitable for manufacturing. I Before it can be used for any work j where some finish is required, such as ’in furniture, lining, flooring, and the internal finish of shops and offices, it must bo perfectly dry. Seasoning involves the changing of the timber from this green state to a dry condition. One method—known as a natural seasoning—is to stack the timber for a lengthy period, allowing it to dry in the sun and wind; the other is artificial, or kiln drying. The former method takes a long time; in many cases the boards warp, crack, and shrink, causing considerable waste. Since the centre of the stack generally contains a larger amount of moisture than the outside, and the circulation of air is less, the method fails to achieve uniformity. In kiln drying, on the other hand, the loss of size in shrinkage is eliminated; moisture is evenly expelled, and the whole process requires less time. For these reasons kiln drying has been adopted to an increased extent. The green timber can bo brought to a condition of commercial use in a few weeks or months, according to the method adopted and the original state of the timber. A successful method is to take timber as it comes from the mill, cut to the required sizes. It is then stacked on the kiln trucks, with cross sticks between each row of hoards to allow the free circulation of air. The timber is then left to stand in the open air for some weeks so as to bring it to the right condition for kiln drying. The kiln is a large airtight chamber, capable of holding a truck loaded with several thousand feet of timber. Air entering the kiln at the bottom passes over a series of steam-heated pipes, becoming warmed as it circulates through the truck of timber. Having taken up I a certain amount of moisture, it passes out through vents at the top. The humidity of the kiln, the temperature of the air, and circulation are regulated by the operator to suit the timber under treatment. After a week or so the dryness of the circulating air affords an index of the condition of the timber, this being ascertained by the wet and dry bulb thermometer. The system known as the moist-air method has given excellent results in drying hardwoods. The moist, humid atmosphere in which the timber is kept prevents checking, twisting, and excessive shrinkage. When treated and dry the timber is mild, light to handle, and it presents a smooth, clean finish. By correctly applied kiln seasoning it is claimed the loss through excessive shrinkage is almost entirely eliminated.

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Permanent link to this item

https://paperspast.natlib.govt.nz/newspapers/ESD19280131.2.11.8

Bibliographic details

Evening Star, Issue 19778, 31 January 1928, Page 2

Word Count
481

KILN DRYING Evening Star, Issue 19778, 31 January 1928, Page 2

KILN DRYING Evening Star, Issue 19778, 31 January 1928, Page 2