Surface Checking in Veneered Panels

The effect of species relative to anatomical structure of wood, veneer thickness, tightness of veneer cutting, placement of the loose side of veneer, and moisture content on surface checking was observed in the face veneers of finished furniture panels. The three species types used, walnut, birch, and oak represented different anatomical structural patterns in wood. The three species differed significantly in their susceptibility to developing surface checks. Checking appeared to be related to size and distribution of pores, width of rays, and arrangement of parenchymatous tissue. Species with uniform anatomical structure, such as birch, offer the most resistance to surface checking. Oak with its large pores and wide rays showed the greatest tendency toward checking. Walnut was intermediately affected. Surface checking did not appear to be significantly affected by the plane of cutting used in producing the veneer. Veneer thickness was found to be a significant factor in face veneer checking. Checking did not occur in birch veneer thinner than 1/8 inch. Checking in walnut face veneer did not occur in veneers thinner than 1/15 inch. Oak face veneer thicker than 1/20 inch did not give good results. The restraining effect of panel crossbands was considered. The restraining effect of the crossbands on the face veneers appears to diminish progressively from the glue line outward so that the dimensional stability near the finished surface tends to be proportionately less in thicker face veneers. The likelihood of having well developed lathe checks in relatively thick face veneers is probably also a contributing factor. Surface checks in the face veneers of furniture panels are, almost without exception, traceable to the presence of lathe checks in the face veneers. Sawed veneers did not develop surface checks in panels faced with veneers up to approximately 1/8 inch thick. The orientation of veneer on the basis of “loose” or “tight” side was significant. Panels in which the lathe-checked surfaces of face veneers were exposed did not develop excessive surface checking, but the panels tended to develop washboard surfaces with ridges and depressions along the grain spaced at the same intervals as the lathe checks. Fewer surface checks developed in panels fabricated at 4 percent moisture content than occurred in panels made at 8 percent or 12 percent moisture content. The range of moisture content from 4 percent to 12 percent used in the study did not have a significant effect on face veneer checking with veneers approximately 1/30 inch in thickness, and even after exposures from 4 percent to 22 percent moisture content differences, only oak showed surface checking.

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