Wood used in above ground applications such as decking undergoes undesired dimensional changes leading to the lumber warping, cupping, splitting, etc. This is a major concern to consumers but it can be reduced by treating lumber with a water repellent. The ability of resin acids, hydrophobic compounds naturally present in southern yellow pines, was examined as a possible water repellent. A waterborne resin acid or a commercial source of resin acids called tall oil rosin or TOR provided similar water repellency in laboratory tests to wax treatments, while minimal water repellency was observed with solventborne resin acids. Leaching partially reduced the water repellency of wood treated with TOR but not with a pure resin acid. Decking or laminated lumber treated with TOR and exposed outdoor above-ground had reduced moisture content, checking, cupping and mold growth than untreated boards. We previously found that southern pine sapwood has a wide natural variation in resin acid content, and untreated sapwood samples had assorted water repellency and decay resistance. The intrinsic water repellency and decay resistance of southern pine sapwood may be correlated to the amount of resin acids present.

Download document (101 kb)
free for the members of IRG. Available if purchased.

Purchase this document