I am trying to veneer some particle boards, using a urea resin (Weldwood) and PVC(?) type glue (BetterBond). I am getting adhesion failures in both cases. I had suspected the age of the urea resin, so I tried a different bucket, different glues, and different substrates altogether–same result. The glues seems to set up and cure, but I could peel the veneer right off the substrate. Areas that does bond better instill no confidence. Close examination of the bond shows that it either doesn’t adhere to the substrate, or bits of the substrate comes off with the veneer.
I am now suspecting a dirty surface…stuff came from the local BORG. I had good success with MDF before, but this is unexpected. Anyone had to clean their MDF prior to veneering? And with what? Thanks.
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I use Urea glues all the time and have never had that problem. But I suspect the glue is gone off. Those glues don't last that long. They should last 1 to 2 months maybe 3-6 if you refridgerate them. But you should at least wipe down the surface of the sub straight first. With the Urea glues I also roll on one coat onto the sustraight and let it sink in. Especially MDF. It's pretty pouris. Then I put on another coat before I put the veneer down. The other problem could be that you don't have enough pressure on the veneer during the glue up process. I hope this helps.
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Since you've had failures with two different glues, I'd suspect either you aren't applying enough glue or the surface is contaminated. On some scrap try putting on a whole bunch of glue to eliminate the application quantity theory. On other scrap, clean the surface prior to gluing using the application rate that you've been using. This will test the cleanliness theory.
In my experience, I've only had veneer failure over mdf as a result of insufficient glue.
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