Treatability of Young-Growth Redwood

Young-growth redwood lumber was treated with a waterborne chromated copper arsenate (CCA) preservative in a 2 percent solution, using a full-cell, pressure-treating process. The boards were treated in the green and the kiln-dried (approximately 11 percent moisture content) condition. Treatability was evaluated in terms of the following: gross retention of preservative solution, depth of penetration of preservative, percentage of the cross section of the sample board that accepted treatment, analysis of the chemical actually retained by the groups of samples, and overall uniformity of the treatment. Most samples treated dry were rated as permeable and met AWPA Standards for ground-contact exposure. Most samples treated green were rated as refractory and failed to meet AWPA Standards. Lumber obtained from throughout the redwood range reacted similarly to treatment. Heartwood also readily accepted treatment in the kiln dried boards. It appears that young growth redwood dimension lumber can be expected to readily accept treatment with CCA, as long as it is kiln dried before treatment.

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