Adhesives Bleeding Through Wood Veneer

A few simple steps will prevent this veneering problem. July 2, 2005

Question
We are having problems with adhesive bleeding through the veneer. We are using walnut veneer with epoxy in a hot press. We also bag with very little, to no bleeding through. We’ve tried urea, and we had bleed through as well. We’ve also thickened the epoxy. How do we stop this problem?

Forum Responses
(Adhesives Forum)
From Jeff Pitcher, forum technical advisor:
Epoxied veneer is really overkill. Urea resin should work fine provided you use it correctly. Apply the resin/catalyst mixture to the substrate (only) and allow it some open time of about 15 minutes. At this point, apply the veneer and put it in the bag or the press. The decrease in moisture will limit the bleed through. If this still doesn't do the trick, you could look at using a backed veneer, or you could size your veneers with Glue-Size before you glue.

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From contributor C:
Urea recommends a 15% thickening? That isn't very much thickening? Can you do this with walnut shells?

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From Jeff Pitcher, forum technical advisor:
Good point, you can add shell flour or wheat flour to the UF resin. While it may not seem like much, 15% will not only thicken it considerably, but it will help prevent bleed through by clogging the small pores in the veneer with larger particles (shell flour). If you add much more than this you risk interfering with the catalyst reaction.

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From contributor C:
Where can I buy the thickener?

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From Jeff Pitcher, forum technical advisor:
Many adhesive companies stock shell flour. If yours does not, you can buy it from Custom-Pak Adhesives at 800-454-4583.