Comparing vacuum drying and conventional drying effects on the coloration of hard maple lumber

Abstract

Vacuum kiln-drying, using low temperature in a low oxygen environment, produces light-colored hard maple in a significantly shorter drying time, and with less variability, than does conventional steam kiln-drying. To avoid chemical staining and to maintain light color, drying hard maple requires the use of high air flow at low temperature and relative humidity soon after being sawn. This study compared the color and drying times of hard maple dried in both types of kilns. Paired samples of 1-in. (25.4-mm) flat-sawn boards were dried in either a conventional kiln or a vacuum kiln, and lumber color of each board after drying was measured with a spectrophotometer. Vacuum drying produced industry-acceptable white maple faster than did conventional drying. On average, there were no visual differences in color between the two drying methods but color among boards from the vacuum kiln was more uniform.

Citation

Lyon, Scott; Bowe, Scott; Wiemann, Michael. 2021. Comparing vacuum drying and conventional drying effects on the coloration of hard maple lumber. Research Paper FPL-RP-708. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 5 p.