Effect of kiln conditions on the strength of Douglas fir and western hemlock

Abstract

To test the effects of kiln-drying on strength properties of Douglas fir and western hemlock, temperatures to 230 F, conditions for equilibrium moisture contents of 6 percent and 12 percent, and prolonged heating were investigated. Prolonged heating and choice of conditions for 6 percent or 12 percent equilibrium moisture content had little effect on most strength properties. Temperature was important: the higher the temperature, the greater the reduction in strength. Toughness was affected most, shear almost as much, modulus of rupture and fiber stress at the proportional limit somewhat less, and modulus of elasticity was affected least.