Hello,
A friend ask my advice on a problem he had finishing a cabinet. I explained I am a raw neophyte in this but, since he was the first person to ever ask my advice regarding woodworking, I would try to help.
Seem he tried to finish a red oak cabinet in the following steps : 1) sanded cabinet 2) applied one coat Olympic sanding sealer – did not sand this sealer coat 3) applied one coat “Minwax stain” and then rubbed some areas of this stain off but left other areas as coated 4) applied 2 coats of “spray clear polyurethane . He states all looked good until about one hour after the second coat of polyurethane when he noticed “white blotches” in the areas where he did not rub off the stain. He says there was no possibility of water getting near the cabinet.
If anyone could give suggestions , I would greatly appreciate it. I am always asking for help from others and , if I could return the favor , it would certainly make me feel better.
Thanks,
Uncle Ron
Replies
I have a few questions about what your friend did. Was the sanding sealer oil based or waterborne? Olympic makes both. Same question concerning the spray polyurethane varnish. What brand was the varnish? What kind of "look" was your friend seeking?
I don't understand using sanding sealer on oak prior to staining. Oak doesn't have a tendency toward blotching so the sealer isn't needed for that purpose. This method will just leave a layer of stain sitting on the surface, particularly when excess isn't wiped off. Olympic doesn't recommend stain over sanding sealer, presumably for such a reason.
In addition, Olympic doesn't recommend oil based polyurethane over its oil based sanding sealer, citing special adhesion problems, though oil based poly over water borned sealer is apparently OK. In general, sanding sealer and top coat need to be matched for compatibility. Not all sealers work with all top coats, particularly with polyurethane top coats. Without knowing more its just a guess, but I'd suspect that the white blotches are signs of adhesion problems with the top coat getting ready to de-bond from the sealer/stain.
I'd also guess that this problem would have revealed itself with tests of the finish on scrap. Reading the manufacturers instructions are also useful, and there for a purpose.
At this point, I'm afrain the solution is likely to be stripping off all of the old finishing materials down to bare wood and starting over.
Uncle,
In addition to what Steve suggested, it is also possible that the minwax stain wasn't completely cured (dry) and the outgassing solvent from the stain is causing the finish to blush.
Ray Pine
Since we are speculating, here is another possible:
The work was contaminated with wax or lubricant spray (possibly silicone). It was either on the machine tables or guides or it was sprayed in the general area of the work and adhered to it during the finishing process. Solution: strip it down, sand the heck out of it and start over. JL
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