Effect of Chemical Treatment on Seasoning Stain in Redwood

In this study, the potentialities and limitations of chemical and physical surface treatments to diminish the seasoning stain of redwood were investigated. All treatments were most effective at pH 3.5. Experiments were made in boiling water or methanol, either with oxidizing or reducing agents and later with surface active agents. These reducing agents failed to reduce stain significantly, but the observed effect served as the basis for further investigations. Dried and planed samples were used rather than green panels. Removal of the extractives from the surface resulted in diminished staining. The treatment also produced remarkable uniformity in tone of the panels. The grain-raising effect caused by the boiling water or boiling methanol was found to be negligible. On bevel sidings, water/detergent treatment showed lessened bleeding, as demonstrated by tests in the blister box. When acrylic latex paint was applied, no stain appeared on the treated surfaces, even after heavy rain, although the control stained badly.

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