COMPARISON OF EMPTY-CELL AND FULL-CELL TREATMENT OF RED-PINE AND LODGEPOLE-PINE POLE SECTIONS WITH CCA-PEG

Matched lodgepole pine and red pine pole sections were treated with chromated copper arsenate (CCA) type C by a Lowry empty-cell or a Bethell full-cell treating process. Empty-cell treatment resulted in net solution absorptions 40 to 60 percent of those for full-cell treatment. As a consequence, air-drying time was reduced by 50 percent or more. Method of treatment had no significant effect on pole hardness (by pilodyn) or CCA penetration. The preservative gradient depended on the wood species; it was steeper for the empty-cell treatment in red pine and for the full-cell treatment in lodgepole pine. Solution stability was reduced by empty-cell treatment. Solution pH increased more rapidly in the empty-cell working solution and the rate of hexavalent chromium reduction was higher. Some sludging developed after about 4 weeks of empty-cell treatment.