Effect of treating schedule on double-density incised spruce-pine-fir

An experiment investigated the effect of lengthening the pressure period or increasing the pressure on chromated copper arsenate treatment of spruce-pine-fir incised with a new double-density incisor. Using a 6-hour pressure period at 1035 kPa, unincised white spruce, lodgepole pine, and alpine fir failed to meet Canadian or U.S. standards, but all the double-density incised material met ground contact standards. Increasing the pressure to 1240 kPa improved penetration and retention for double-density incised pine and fir but not for spruce. Increasing the pressure period from 2 through 8 to 16 hours gave a continuous increase in retention in incised material for all three species. The double-density incised pine and alpine fir met ground contact penetration and retention requirements after 2 hours, but spruce took 4 hours to meet the penetration requirement and 6 hours to meet the retention requirement. Alpine fir almost met the Canadian Standards Association preserved wood foundation standard after only 4 hours, but the spruce and pine took 16 hours to do so. When unincised, the species differed in their treatability. When incised and treated with 4 hours or more of pressure, there was no significant difference between the species’ mean preservative penetrations. With the ultra-high-density incising used in this work, white spruce, lodgepole pine, and alpine fir could be treated to meet any of the Canadian Standards Association and American Wood Preservers’ Association lumber standards (under 114 mm minimum dimension) by manipulating the duration of treatment.

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