A literature review was made of publications on veneer drying. A discussion on the three types of air-circulation dryers, longitudinal, cross-flow and jet dryers is presented as well as other drying methods including platen, steam-press, radiofrequency (RF) and RF/vacuum drying. Good temperature control in veneer dryers such as in jet dryers using high temperatures in the green end and lower temperatures in the dry end will result in higher quality veneer with less surface inactivation. By maintaining a high humidity in veneer dryers, the following benefits result: faster drying rates, lower energy costs, less chance of surface inactivation and less chance of dryer fires. The following veneer drying benefits result by incising veneer on the lathe: faster drying rates and flatter veneer for easier handling on automated lay-up lines. Other important benefits include: fewer spin-outs at the lathe, less curl-up for the veneer near the core, especially spruce, higher veneer yields, reduced "blows" in plywood during pressing and improved preservative treatability of plywood. A drying strategy involving drying incised veneer to a uniform high moisture content and pressing this face incised veneer (15% m.c.) with dry core incised veneer (3% m.c.) using a moisture tolerant phenolic adhesive, could allow up to 30% reduction in pressing time.
The project objective is to provide key data on the laminating properties of Canadian wood species to assist the secondary manufacturing industry to meet domestic and international customer expectations. This is a progress report to March 31, 1999.