Wafer Assay for Treatability of Wood

Over rather limited areas, several hundred tree species are easily encountered in tropical forests. This heterogeneity makes the assessment of treatability and other wood characteristics difficult and costly. A simple but highly sensitive wafer assay that can rapidly screen woods for treatability is described. A 7/8-inch diameter bung cutter is used to machine plugs from which 1/4-inch–thick wafers are sawn. Wafers edge-coated with epoxy resin were used to measure side grain treatability and matched uncoated wafers were prepared to represent both an end and side grain flow. A short 10 minute vacuum and 10 minute atmospheric treatment was used with either water or diesel oil as a simulated preservative carrier. Treatment retentions were calculated in pounds per cubic foot. Liquid retentions of edge-coated and uncoated wafers representing 18 species sampled from 78 trees were tested. Varying with species and carrier, absorptions ranged from about 1 to some 40 lbs./cu. ft. Simple regressions relating uncoated wafer absorptions with those of incised posts had correlation coefficients of about 90 percent. The wafer assays, demonstrated that the sapwood of many tropical hardwoods requires incising to obtain an acceptable preservative treatment.

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