The influence of conditioning on internal checking of high-temperature dried Pacific Coast hemlock

The purpose of this study was to evaluate the effectiveness of steam conditioning immediately after drying to reduce internal checking resulting from high-temperature drying of Pacific Coast hemlock lumber. Three different levels of conditioning time, 2, 4 and 6 hours, were carried out on 2 inches wide by 4 inches thick by 3 feet long (51 mm by 102 mm by 0.91 m) , and on 4 inches wide by 4 inches thick by 3 feet long (105 mm by 105 mm by 0.91 m), specimens. For comparison purposes, controls of both sizes of specimens were also high-temperature dried without conditioning. Analysis of the results indicated that internal checking was not significantly reduced by steam conditioning and was more likely to develop afterwards during storage at room temperature, and that total degrade observed in the "4x4" specimens was more excessive than that in the "2x4" ones. The defective "4x4" specimens were found over-dried (below the targeted 12% moisture content) with high core-shell moisture content differences. More internal checking was found when the specimens' final moisture content ranged from 7 to 8%.Forestry, Faculty ofGraduat