Date: 2009-12-08
Gene Wengert
Q: What is the difference between kiln-dried lumber dried to 7 percent MC and air-dried lumber that is allowed to dry to 7 percent in a shop or in storage?
A: Lumber at 7 percent MC is the same, in terms of moisture issues, no matter how it was dried and achieved this final 7 percent MC. However, there are potentially a few other differences. Lumber dried in a kiln at 130 degrees F or hotter is free of any insects, insect eggs and fungi when it leaves the kiln.
Further, in the kiln it is possible to equalize the lumber to achieve a very uniform final MC (if desired) and also to remove any drying stresses. Finally, if the kiln temperature goes over 160 degrees F with softwood species, the resin that would be liquid at room temperature, and possible ooze out of the wood, will be evaporated. This is called setting the pitch.
Gene Wengert, "The Wood Doctor," has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
Updated: Jan 07, 2010
This article appeared in CabinetMaker+FDM, December 2009. ©Copyright 2012, All Rights Reserved.