New Treatment to Prevent . . . Brown Stain in White Pine

The samples were treated with 2 and 4 percent sodium fluoride solutions and close-piled for 3, 7, 14, and 24 days. The close-piling temperature ranged from 47?F at night to 91?F during the day and relative humidity from 34 percent to 89 percent. Brown stain was evaluated by kiln-drying and skip planing the boards and observing the amount of stain present. The test results showed that the chemical brown stain in white pine lumber can be reduced by treating the board with 2 percent solution and can be eliminated entirely by treating boards with 4 percent sodium fluoride solution. This study also indicated that heavy brown stain developed in untreated lumber that has been close-piled for 3 days or longer prior to kiln-drying. The darkest stain appeared in material close-piled for 7 days. In lumber close-piled for more than 7 days the discoloration on the surface of the boards decreased slightly but the penetration increased significantly. Boards close-piled for 24 days prior to kiln-drying were still heavily stained after being skip planed and dressed to 3/4- inch thickness.

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