Book Description

Short-term heating of softwood veneer blocks temporarily softens the wood so that it can be peeled more readily. Heating reduces the depth of lathe checks and the likelihood of splitting and thereby increases the quality and quantity of veneer recovered. The softwood-plywood industry conventionally conditions blocks three ways: steaming blocks in drive-in chambers, deluging blocks in such chambers with hot water, or submerging blocks in feed-through vats of hot water. About 450 to 1,000 lb of steam are required to heat blocks with a veneer volume of 1,000 ft2, 3/8-in. basis. The best wood temperature for peeling falls between 120°F and 140°F, but the heating periods often are too short for the wood to reach the target temperature because blocks are not properly segregated into diameter classes. Furthermore, heated blocks cool rapidly during transfer. An infrared sensor system reported here gives industry a tool to monitor block temperature. The profitability of conditioning will depend on the cost of the installation and cash from increased veneer yields.