Erosion Rates of Wood During Natural Weathering. Part I. Effects of Grain Angle and Surface Texture

R. Sam Williams, Mark T. Knaebe, Peter G. Sotos, William C. Feist


This is the first in a series of reports on the erosion rates of wood exposed outdoors near Madison, Wisconsin. The specimens were oriented vertically, facing south; erosion was measured annually for the first several years and biannually for the remainder of the exposure. In the work reported here, the erosion rates of earlywood and latewood were determined for smooth-planed vertical-grained lumber and abrasive-planed and saw-textured flat-grained plywood for an exposure period of 16 years. Lumber species were southern pine, western redcedar, Douglas-fir, and redwood; plywood species were western redcedar, Douglas-fir, and redwood. Erosion rates varied from 34 μm/year for southern pine latewood to 101 μm/year for western redcedar earlywood. Large differences were observed between earlywood and latewood erosion rates during the first 7 years of weathering, but not during subsequent years. A significant change in the erosion rate of just the latewood was observed for redwood, western redcedar, and Douglas-fir after approximately 7 years of exposure, and for southern pine, a significant change occurred after approximately 12 years of exposure. The erosion rates of vertical-grained lumber were higher than those of flat-grained plywood. Only slight differences were observed for saw-textured as compared to smooth plywood.


Weathering;erosion;flat grain;vertical grain;wood properties

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