The Place of Water-Repellent Preservatives in Forest Products

In 1938, the National Woodwork Manufacturers Association Advisory Committee set up standards for water-repellent preservatives. To date the solutions which have passed this toxic standard contain 5 percent by weight of either pentachlorophenol, tetrachlorophenol, 2-chlororthophenylphenol, or a combination of these. The chlorinated phenols do not provide water-repellency, so it is necessary to add other materials, Water-repellent preservatives use petroleum spirits as carriers. For millwork the standard dip time is 3-minutes at room temperature. In ponderosa pine sapwood, this gives a penetration of l.5 to 3 inches up to end grain, and 1/16 to 1/4 inch into the side grain. The effectiveness of the treatment was tested by cyclic exposure to wetting and drying in the laboratory. Treatment of windows and frames keeps the joints tight and reduces swelling and shrinking. Water repellency is important for insulation, as wood loses its natural insulating quality when wet. Treated doors will not swell and stick. Treatment protects wood used in home building during construction and provides protection against decay, stain, insects and fungi after construction as well. Porches, flooring, and boxes such as fruit crates can also benefit from treatment.

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