Quality of Studs Kiln-Dried By High and Conventional Schedules

This paper summarizes the effects of kiln-drying by high (240?F) and conventional (140-160?F) temperatures on lodgepole pine and western larch studs dried at a major lumber-producing plant. Included is an analysis of the losses due to degrade using the system of dual-grading whereby all inspection and grading is done after the lumber is surfaced. Degrade losses directly attributed to kiln-drying were about the same in both drying processes for each species, the larch degrade losses being about 1 percent greater than the lodgepole pine losses. Warp and surface checks caused the most degrade for both species in both drying procedures. For both species, warp caused more degrade by drying at conventional than at high temperatures, while surface checking caused more degrade by high temperature drying. Degrade losses that might have been aggravated by the drying method showed the high temperature drying less deleterious for the lodgepole pine. Shake as a degrading defect in larch accounted for about 11 percent loss, with practically no difference between processes. In lodgepole pine, the loss due to shake was 2 percent or less for both processes. Other than shake, the greatest losses in both species were in the categories of thinness and narrowness. In lodgepole pine these defects accounted for the greatest losses in both drying processes, with drying at conventional temperatures causing about twice the degrade as high temperature drying.

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