Moisture distributions in western hemlock lumber from trees harvested near Sitka, Alaska
2003
Nicholls, David L. | Brackley, Allen M. | Allen, Travis
Western hemlock (Tsuga heterophylla) can be characterized by localized regions of high-moisture-content wood, often referred to as wet pockets, and uneven drying conditions may occur when lumber of higher and lower moisture content is mixed together in a dry kiln. The primary objective of this preliminary study was to characterize the frequency and extent of wet pockets (wetwood) in western hemlock lumber sawn from trees harvested near Sitka, Alaska. Nine western hemlock logs were sampled from three trees, ranging in diameter from approximately 10 to 18 inches. Forty-five boards were processed, yielding 225 samples. Sample moisture content ranged from 31.4 percent to 149.7 percent (as a percentage of oven-dry wood weight), with a standard deviation of 30.6 percent. There was no significant moisture variation among sample heights for the three western hemlock trees included in this study. Average moisture content at a given height ranged from about 70 to 85 percent. Moisture contents of approximately 50 percent were not uncommon for pith-centered samples, whereas most samples more than 5 inches from the pith were typically at least 100-percent moisture content. There was considerable variation in overall moisture content among trees, ranging from about 69 to more than 85 percent. Moisture content variation among butt logs was also considerable, ranging from about 58 to 95 percent.
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