Assessment of Longitudinal Shrinkage and Swelling Using the APA and ASTM Methods

Trevor G. Jones, Ian G. Simpson, Jonathan J. Harrington


The APA and ASTM methods of measuring longitudinal shrinkage and swelling were evaluated and compared using radiata pine coupons with a wide range of wood properties and different operators. The two methods gave different measurements of longitudinal shrinkage and swelling as a result of differences in the location of the measurement points, and the ability to correct for out-of-plane distortion. The APA method gave more precise measurements from the use of inserted brass eyelets and the correction of out-of-plane distortion with a vacuum table. The measurements were not affected by wood type or operator. The ASTM method was found to be sensitive to the condition of the transverse surface at the measurement point and to the presence of drying distortion. The measurements varied in response to wood type and operator. The results indicate the APA method is more precise for measuring longitudinal shrinkage and swelling when measurements are made in series along boards and cants.


APA;ASTM;longitudinal shrinkage;radiata pine;swelling

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