2658 



Chapter 22 



Table 22- 1 6 — Veneer characteristics and allowable defects of Sound, Utility, and Back- 

 ing grades of hardwood veneers (U.S. Department of Commerce 1972) 



LINEAR EXPANSION OF VENEERED FURNITURE PANELS 



Excessive linear expansion and contraction across the grain of veneered 

 furniture panels and decorative wall panelling causes joints to become visible 

 and face veneer to crack as wood moisture content changes. This movement is 

 controlled by the linear expansion coefficients of face veneers and cores perpen- 

 dicular to the grain of the face veneers, and by the ratio of their thicknesses. 

 Suchsland (1971), using an optical comparator, found that panels constructed 

 with platen-pressed particleboard cores had lowest expansion coefficient; the 

 addition of veneer crossbands (five-ply construction) did not further reduce 

 expansion coefficients of such panels. Veneered lumber-core panels crossband- 

 ed with veneer (five-ply construction) were inferior to veneered particleboard 

 core panels. Linear expansion of lumber core panels could be reduced, however, 

 by increasing the thickness of the crossband veneers. Commercial fiber sheet 

 crossbands showed less restraining effect than crossband veneer. (See chapter 23 



