Effect of Prefreezing Upon Hygroscopicity and Shrinkage of Thin Cross Section of California Redwood

Thin sections of redwood were used to study the effect of prefreezing on dimensional change in the absence of gross drying stresses. While prefreezing of redwood boards before kiln-drying has been shown to reduce total dimensional change as much as 40 percent, no reduction was noted in the thin samples. This suggests that the reduction noted in kiln-dried boards is due to some factor other than a change in basic hygroscopicity. Sapwood samples did shrink and swell more than those cut from heartwood. They also equilibrated to slightly higher moisture contents during both desorption and adsorption. Neither sapwood nor heartwood samples showed any apparent effect of prefreezing upon hygroscopicity or shrinkage.

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