Veneer cracking is a recurrent problem that results in significant annual losses for manufacturers of
kitchen cabinets and furniture. The exact cause of cracking has never been clearly identified, leading to a
great deal of speculation and discussion among manufacturers of veneer, finishes and adhesives. To our
knowledge, no research group in Canada has addressed this problem, other than some private companies.
As such, no concrete, accurate information is currently available on the cause of veneer cracking.
Identifying the conditions and causes of cracking would certainly have a positive impact on reducing the
costs of complaints received by manufacturers of kitchen cabinets and furniture.
The main objective of the project is to identify the factors involved in veneer cracking to minimize
impacts on product quality. The specific objectives are as follows: 1) identify the humidity conditions that
cause veneer surface cracks when veneer is being glued to the substrate, and 2) evaluate the impact of
aqueous finishes on crack formation.
A literature review in the subject field and a review of the practical cases submitted to FPInnovations
industry advisors helped us identify several parameters that may explain the formation of veneer surface
cracks. Among other things, these parameters relate to veneer shrinkage due to a loss of humidity,
inappropriate component storage, gluing process and glue type, wood type, substrate type, veneer
handling, veneer and log quality, peeling method and veneer orientation.
Laboratory tests were conducted as part of the project, with a focus on 1) the impact of humidity
differences between veneers and substrates at the gluing stage, and 2) the effect of aqueous finishes on the
formation of veneer surface cracks. Tests were conducted with 21 scenarios involving the conditioning
and gluing of maple veneer onto three types of substrates. The results showed the negative effects of
gluing humid veneer (conditioned to 80% RH) to substrates. They also showed that the finish selected
(water vs. solvent) does not impact the formation of surface cracks. However, the application of a surface
finish to veneer does attenuate the formation of cracks through changes in weather conditions. The test
results also showed the positive effect of using particleboard rather than plywood on reducing the number
of surface cracks. The use of a Mende board (fibreboard) substrate with veneer that is not too humid (less
than 80% RH) also tends to yield fewer surface cracks. Finally, the results showed a difference in
performance between the two adhesives used to assemble veneer on particleboard, the veneer glued with
UF adhesive showing more cracks.