High-Temperature Kiln-Drying of 4/4 Lumber from 12 Hardwood Species

One-inch lumber of 12 hardwood species was kiln-dried by two schedules: 1) 230?F on stock green from the saw to 6 to 8 percent moisture content (MC) in 50 to 55 hours and 2) combination of conventional temperature (< 180?F) from the green condition to about 20 percent MC, then dried to 6 to 8 percent at 230?F requiring a total of 100 to 250 hours. Fifteen thousand board feet (BF) of lumber representing about 1,200 BF for each of the 12 species were dried in 15 kiln charges. The amount of drying degrade present in standardized blanks sawn from 8-foot lumber varied with species. When dried by the first schedule, basswood, yellow-poplar, white ash, sweetgum, and soft maple dried with only minor amounts of drying defects. Black cherry, hard maple, beech, and pecan-hickory had sufficient defects to be considered unsuitable for this treatment. American elm, cottonwood, and blackgum showed intermediate amounts of drying defects. The combination schedule decreased the drying degrade, but increased the kiln residence time over high temperature alone. However, the combination schedule reduced kiln residence for most species over completely drying at conventional temperatures. The most common drying defect was honeycomb or combinations of honeycomb with other defects such as warp or collapse. Drying defects were commonly associated with knots, pith, or mineral streak.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member