Fumed Larch Glue Adhesion Issues on Fire-Retardant MDF

      It is the veneer, the adhesive, or the substrate? Probably the adhesive. January 3, 2012

We have been noticing small checks and lifting in fumed larch veneer on fire rated MDF. There is no finish on it yet and we are reluctant to begin. We had a similar problem with fumed oak lifting and splitting off the substrate. Is this a common problem with fumed veneer, or a manufacturer defect? They always claim that the glueup was perfectly orchestrated and it must be us. The panels are still raw so I find it hard to believe.

Forum Responses
(Veneer Forum)
From contributor C:
There are a ton of things that could do this, here are some:

* M/C of the veneer was high
* M/C of core too high
* Too much heat at pressing
* Not enough heat at pressing (residual moisture)
* The core outer surface is loose
* The core did not bond to the veneer (FR care is tough)
* FR core works best with UF glue, PVA is tricky

This is general. I have never worked with fumed larch, but it may have properties that require special attention.

From contributor R:
I agree with one of the suggestions. The FR core doesn't work well with PVA. My glue supplier told me that if we were planning to use FR core we would need a special formulation of their PVA. We just continue to use a UF to avoid any issues. I haven't seen any issues with fumed veneer.

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