Influence of presteaming on kiln-drying of thick hem-fir lumber

Hem-fir lumber, 10.5 by 10.5 cm in cross section and 91 cm long, was treated in a saturated steam environment and one atmosphere pressure prior to kiln- drying. The objective was to determine the effect of presteaming on the drying rates, moisture content profiles, total shrinkage, and the overall quality of the dried lumber. The lumber was divided into two basic density groups and was presteamed for either 5, 10, or 20 hours. The results showed no clear effect of the presteaming on the drying rates when compared to the control. There was a significant reduction in the difference of core and shell moisture contents after-drying as presteaming times increased and a significant increase in shrinkage with an increase in presteaming duration. However, prolonged presteaming decreased the moisture and shrinkage variability within the lumber and did not adversely affect the quality of the dried wood.

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