Effect of post-treatment processing on ACZA precipitation in Douglas-fir lumber

The effects of air-drying, kiln-drying, plastic wrapping, and steaming on precipitation of ammoniacal copper zinc arsenate (ACZA) in Douglas-fir lumber was investigated at two retention levels over a 288-hour period by expressing residual liquid from the wood and analyzing it for preservative components. As expected, initial ACZA levels in the expressed liquid were higher in wood treated to the marine-retention level, reflecting the higher solution concentration used for these boards. Levels of all components in the expressed liquid declined over the test period in all treatments. Declines were most rapid and complete with kiln-drying, while the remaining treatments produced more variable results. Copper levels were initially higher than the other components in the expressed liquid and, although they declined over the test period, remained higher than either zinc or arsenic 288 hours after treatment. The results suggest that post-treatment processing can play an important role In the deposition of ACZA components in wood.

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