Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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Haven't been able to inspect yet, but have been told table top I applied new veneer to last winter has bubbles everywhere.
It was a mahogany veneered top that had been painted at some time in past. Neighbor with decades of furniture repair/refinishing experience was asked to strip the paint and stain and finish the top. After stripping he found mahogany veneer that had been sanded through in places. He bought raw walnut veneer and asked me to apply.
Had to trim out the oval/arch in the middle of each leaf, then flatten the rift cut strip from each side. Flattened using the same formula I've used for years, clamped and dried in vacuum bag as I've done many times. Taped the leaves together as always, glued to one piece of the table top (two ends, one or two leaves) at a time with heavy canvas over plastic film over the veneer (in case sanded top wasn't perfectly flat). Top caul over the canvas. Workshop temp kept to 74 degrees throughout the process, plus heating blanket on top for good measure. Fresh urea formaldehyde glue that was first used for test pressing of excess from the same veneer on MDF the day before. Constant good vacuum 22-25" each pressing.
For each pressing, some excess glue in zip lock bag to confirm glue rubbery before vacuum bag opened. Let the table top piece dry overnight, then after scuff sanding used sponge to wet surface of the veneer and remove the remainder of the paper tape. No bubbles formed while wetting the freshly glued veneer.
After all the pieces were done, the repairer/refinisher finish sanded, stained, and finished with nitrocellulose lacquer as he has for decades.
Table owner called the repairer/refinisher last week, so the bubbles may have just shown. It has been averaging 70-80 here for a couple weeks, and there's been some rain several days each week, but the condo likely climate controlled every day so internal humidity likely pretty constant.
The small test panel I made first still looks fine, but it was not stained and finished.
At first I thought had to be silicone contamination on the existing mahogany veneer after the paint was removed, but don't know if that would affect urea formaldehyde adhesion. This weekend I started to wonder how flat the tabletop pieces were when brought to me - they had not been wide belt sanded flat, and I did not think to try to check with long straightedge.
The repairer/refinisher wants to sand off the new veneer and re-veneer, rather than starting with a new core.
Any thoughts on what might cause the lack of adhesion?
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