Effect of hot-water soaking or freezing pre-treatments on drying rates of two eucalypts

This study assessed two pre-treatments for regrowth jarrah (Eucalyptus marginata Donn ex Sm.) and regrowth karri (E. diversicolor F. Muell.) by measuring drying rates, drying times, and surface checks. Twenty 300 by 100 by 30 mm jarrah boards and 15 karri boards were allocated to hot-water soaking, freezing, or null (control) treatments. The boards were then assembled into a single, balanced bundle and kiln-dried using a mild schedule. Moderate surface checking occurred during drying of the regrowth jarrah boards given the hot-water soaking pretreatment and the karri boards given the freezing pre-treatment. Boards in all other treatments showed only minor checking. In the first week of drying, jarrah boards given the freezing treatment dried 64 percent faster than controls, and those given the hot- water soaking treatment dried 17 percent faster than controls. For the karri in the first week, the frozen and hot-water soaked boards dried 48 and 34 percent faster, respectively. By the seventh week all treated boards dried slower than the end-matched controls. The combined result of these rates was different drying curves for each group. Jarrah boards given the freezing pre- treatment reached 30 percent moisture content (MC) 5 days (or 10%) earlier than controls, and those given the hot-water soaking pre-treatment reached 30 percent MC 10 days (or 21%) earlier than controls. These field results suggest that permeability or diffusion had improved.

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