A Relationship Between Collapse and Extractives in Western Red Cedar

The collapse that occurred during kiln drying of 2-inch western redcedar (Thuja plicata Donn) boards was investigated in relation to the green moisture and extractive contents of the boards and their grain orientation. Both moisture and extractive contents were found to be related to collapse susceptibility of the tested boards. Several never-dried board specimens end matched to specimens that collapsed severely during the aforementioned experiments were sequentially extracted with dimethylsulfoxide, methanol, and acetone in an attempt to prevent collapse during drying. Collapse was measured as abnormally great volumetric shrinkage. These experiments were only partially successful, in that while collapse was reduced it was not prevented. Variability in residual extractive content prevented attaining statistically significant improved drying behavior. The role of extractives in the formation of collapse was not determined, although the relative importance of both water and extractives in collapse susceptible wood was clearly shown.

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