Control of Brown Stain in Eastern White Pine with Alkaline Salts

Freshly-sawn eastern white pine boards (Pinus strobus L.) 6 feet long, 4 to 8 inches wide, and 1 inch thick were cut into 1 foot lengths, dipped in various solutions of alkaline salts and stored for one week at 80?F, 95 percent relative humidity (RH). They were then oven-dried at 160?F dry bulb 140?F wet bulb for 4 days and rated for the extent of brown stain. Sodium carbonate 5 percent, 5 percent sodium carbonate plus sodium bicarbonate (5:1) and 3 percent sodium borate all showed good stain control. 5 percent sodium carbonate plus sodium bicarbonate (1:1) and 3 percent sodium carbonate showed moderate stain control. Untreated boards always stained heavily. One percent sodium fluoride routinely included for reference showed good stain control. These results were confirmed by kiln-drying charges of 500 board feet divided into five treatment groups and using a moderately severe drying schedule. Heavy stain was always obtained in untreated boards. These solutions which range in pH from 9.2 to 11.5 are suggested as effective replacements for sodium fluoride or sodium azide which are hazardous to human health. They are fully compatible with sodium pentachlorophenate used to prevent fungal staining and obviate the need for it to be supplied with buffer.

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