Dimensional stabilization of wood in use
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1980 - House & Home - 8 pages
There are two basic types of wood treatments for dimensional stability: (1) those which reduce the rate of water vapor or liquid absorption but do not reduce the extent of swelling to any great degree and (2) those which reduce the extent of swelling and may or may not reduce the rate of water absorption. Terms most often used to describe the effectiveness of the first type of treatment are moisture-excluding effectiveness (MEE), which can be determined in either water or water vapor form, and water repellency (WR), which is a specific liquid test. The term used to describe the effectiveness of the second type of treatment is reduction in swelling (R) or antishrink efficiency (ASE). Most of the type (1) treatments have very low R or ASE values. The R or ASE values can be determined in water vapor tests or single-soak liquid test for water-leachable treatments, or in double-soak liquid tests for nonleachable treatments. In selecting a treatment to achieve product stability to moisture, at least three factors must be considered. The environment of the end product is the most important factor. If the product will come into contact with water, nonleachable--and perhaps even bonded--treatments will be needed. If, however, the product will be subjected to changes in relative humidity in an indoor environment, a leachable or water-repellent treatment might be satisfactory. The degree of dimensional stability must also be considered. If very rigid tolerances are required in a product --as in pattern wood dies--a treatment with very high R or ASE values is needed. If, on the other hand, only a moderate degree of dimensional stability is satisfactory, a less rigorous treatment will suffice.
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