Irregularities of Finished Surfaces Caused By Unequal Ray Shrinkage

Red alder furniture containing undesirable, raised irregularities on the finished surface was examined for anatomical characteristics. Inspection revealed that each raised area was associated with large aggregate rays. The furniture had been produced at a high moisture content and the subsequent shrinkage exposed the rays which do not shrink as much as that of the surrounding tissue. Further examination of this shrinkage phenomena involved other species. In all cases, the radial shrinkage of isolated rays was found to be less than that of the wood free of the rays, particularly where the rays are not completely restrained, such as at the surface of finished furniture. The sample with the original finish was brought to equilibrium at different humidity levels at a moisture content between 13 and 19.8 percent. The surface profile was smooth, suggesting this was the moisture content of original manufacture. The anatomical study of this furniture finish problem reaffirmed that wood should be dried to a moisture content as near as possible to that which it will reach in service, if the best finish is to be maintained.

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