A few spots poly will not stick to

Q: I have been using oil based polyurethane to finish a bar top. I have 6 coats of poly over 1 coat sanding sealer and one coat stain. There are a few spots, one is about the size of a dime, that the poly will not stick no matter what I do.

I have tried sanding just in those spots a little more than the rest, between the coats of poly, but it doesn’t make any difference in how the poly sticks.

What really confuses me is that the rest of the bar, the sides and the arm rest, do not have any of these spots, it is just the top. Do you have any advice on what to do to make the poly stick to those spots?

A: I would think this has to be caused either by some sort of extractive in the wood itself or a contaminant on the bar top from outside sources which hasn’t been removed. Try wiping the spot down with denatured alcohol to remove the contaminant. Or apply a small amount of de-waxed shellac (Zinsser seal coat) to those areas where this is occurring.