Treating Ponderosa Pine Millwork By the Vacuum Process

The vacuum procedure for water-repellent penta treatment of ponderosa pine millwork was evaluated and compared to the 3-minute dip treatment; a total of over 2000 samples were used in the tests. The penta retention was evaluated by the lime-ignition method and penetration was measured by the chlorine-peroxide test. Vacuum treatment was found to be superior to dip treatment. Evaluation of both end and side penetration showed that the vacuum treated material was more uniformly treated. Furthermore, retention measurements by weight difference indicated that “sinker stock” was excessively treated by the 3-minute dip process but not by the vacuum process. Overall, vacuum treatment resulted in a 7.48 percent higher solution retention than end-matched material treated by the dip process. The penta content of solution in the work tanks remained constant during daily usage. Analysis of the data indicated that there was no relationship between solution retention and specific gravity.

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