Effect of Alkaline Treatment on Decay Resistance of Wood

Laboratory tests were undertaken to determine if decay resistance of wood could be improved by alkaline treatment without heat and if a short soaking treatment could be effective. The wood was exposed to different types of wood-degrading fungi under both low- and high-decay-promoting conditions to evaluate performance of the treated wood. Aqueous ammonia, sodium hydroxide, and a mixture of sodium sulfide (3 percent) and sodium carbonate (8 percent) were the treating chemicals. Poria monticola (Murr.) (Madison 698) and Polyporus versicolor (L. ex Fr.) Madison 697) were most often used to test the effectiveness of the different treatments in retarding brown rot and white rot, respectively. Resistance to brown-rot attack was increased in tests promoting low-decay conditions if wood was treated with alkaline solutions by vacuum impregnation or by a 5-minute soak with or without heat. With ammonia, however, higher concentrations of the base were required to obtain consistent resistance if the wood was not heated. Alkaline-treated wood was readily attacked by brown-rot fungi when exposed to high-decay-promoting conditions via the soil-block test. Both heated and unheated alkaline-treated woods were degraded by white-rot and by staining fungi in low-decay-promoting tests.

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