An Investigation of Standard Methods for Determining the Shrinkage of Wood

Under existing British (1938) and ASTM (1950) standards, three separate specimens are needed to determine radial, tangential, and volumetric shrinkage of wood. Tests were made on 13 species of Australian and South West Pacific origin. Since no appreciable difference was found between the linear shrink ages determined on a 4 inch and 1 inch dimension, a single specimen 1 inch radially and tangentially and 4 inches longitudinally may be used for standard tests. Volumetric shrinkage may be calculated from linear shrinkages, its direct determination being unnecessary. In the present tests, as in tests done elsewhere, the observed value was consistently greater than the calculated. This difference is due to thermal expansion, as the ovendry specimens were hot when linear measurements were made. Amendment of the standard test to specify cooling of the ovendry specimens before measuring is recommended.

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