Peeling Failure of a Consumer-Grade Poly Re-Coat

Well, that sure didn't work. Here's why. March 9, 2008

Question
I am trying to help out a restaurant owner we built tables for 15 years ago. He originally finished them with a brush-on gloss poly. They have been lightly sanded and recoated a couple times. Last year the person recoating them used Minwax fast drying poly. This finish is not lasting and peeling off in spots. He did lightly sand before finishing. Is the fast dry poly an inferior product, or is the finish just getting too thick and might be time to strip it?

Forum Responses
(Finishing Forum)
From contributor J:
Anything a consumer can buy in the store is inferior. You need to go to a commercial finishing supply shop. If he never wants to have to mess with them again, get the pour-on finishes - they last forever.

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From the original questioner:
Yes, the commercial finishes are better. We are considering stripping them and shooting CV on them. That will be expensive for him and inconvenient for us, because I don’t want to be in the refinish business. But in the name of customer service that may be what has to be done.

The original hardware store poly held up well. I am trying to determine if the fast dry poly is inferior to the regular slow drying poly available to the consumer. Or if the root of the problem is the thick millage he is building up with recoating.

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From contributor P:
The fast dry poly is less durable than the standard poly. In order to get the fast dry and recoat times, the varnish uses a styrene resin or vinyl toluene resin as the main component and the resulting finish is less durable.

For a quick fix, you can use a random orbit sander to cut the finish way back and then apply another coat of oil-base varnish/poly. Sand the finish back far enough to make sure the last coat or two of finish has been removed.

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From contributor D:
The peeling is indicative of an adhesion problem. Durability is a separate issue. Peeling generally occurs for two reasons, both of which are incurred because of 1). mechanical (vs. chemical) adhesion failure, usually due to incomplete prep, as is the case when cleaning of grime, or schmutz as I tend to call it, is insufficient and/or sanding (mechanical grip) is lacking, 2). incompatibility of coating to coating resulting in (crazing, which would be evident instanter or mechanical) failure.

Excess mil thickness failure would usually show up as cracking in the finish film, although this is still dependant on the type of coating. Quick fix options could include partial removal of the later campaigns (overcoats) by sending the tops through a sanding planer and/or hand sanding or building new tops or new caps for his existing tops if feasible.

If I was faced with this and it was feasible I would present the option of new caps or new tops and finish with a high mil build marine grade polyester for the long haul. Yearly maintenance can then be performed with a sanding and rebuffing operation. From inception to yearly maintenance, this option can be performed off site with no down time for the restaurant operation. (Don't install the caps with Liquid Nails.)

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From the original questioner:
Thanks for the info - just what I was looking for!