Effect of Prestain on the Treatability of Western Hemlock with Chromated Copper211 Arsenate

摘要

To enhance the appearance of the treated product, a stain is often sprayed onto211u001ewestern hemlock lumber (Tsuga heterophylla (Raf.) Sarg.) prior to treatment with 211u001echromated copper arsenate (CCA-C). There is concern that this stain might 211u001einterfere with the penetration and retention of CCA-C during the subsequent 211u001epressure treatment. This study compared the penetration and retention of CCA-C in 211u001eprestained and nonstained end-matched specimens of western hemlock lumber. 211u001eResults indicate that the weight gain retention of CCA-C soution was slightly but 211u001esignificantly impaired by the prestain treatment. Assayed concentration levels of 211u001ecopper, chromium, and arsenic detected in the treated wood were also slightly 211u001eless in the prestained samples than in the nonstained samples, especially for the 211u001einner assay zone. No significant difference in average penetration was observed 211u001ebetween the prestained and nonstained specimens, although two of the prestained 211u001especimens did have much less penetration than did their nonstained counterparts. 211u001eThe differences in treatability noted in this study were too small to be of 211u001econcern in commercial practice.