Warp and shrinkage of hem-fir stud lumber dried at conventional and high temperatures

In this study, 2 by 4 hem-fir stud lumber was dried at conventional (180?F, 82?C) and high temperatures (240? to 270?F, 116? to 132?C). Drying wood at a high temperature reduced the average amounts of bow and crook measured against a straight-edge, but not significantly. However, the number of pieces exceeding the limits allowed by the grading rules appeared to be more a function of final moisture content than drying temperature, suggesting that boards predisposed to warp will do so regardless of temperature. Increased thickness shrinkage for the wood dried at high temperatures might necessitate an increase of 0.005 to 0.010 inch in the green target thickness if a similar level of skip at the planer is to be maintained. The value of the product was not significantly different for wood dried at conventional and high temperatures, but high temperatures reduced the drying time by 50 percent.

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