Dry Spots with Wipe-On Poly on Bubinga

Finishers discuss ways to get even finish coverage on oily hardwoods like Bubinga. September 27, 2008

Question
We have just built our first Bubinga project and have had finish problems. We used Minwax wipe on poly and while we have used that finish with great success with mahogany and many domestic hardwoods, we are having trouble with "dry spots" with the Bubinga. The finish appears to sit on the surface of this dense material more than other species. We are having trouble getting an even finish on it. Does anyone have any ideas?

Forum Responses
(Finishing Forum)
From contributor J:
Just thinking out loud, but I have read about wood conditioners. I think they are sort of an isolator between the real finish and the wood, and would protect against any reaction issues that appear to be what you’re facing.

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From contributor P:
I have never tried a wiping stain on Bubinga, but I do use dye stain through a pot or cup regularly with wonderful results. I top with post cat CV. The dye stain we use is a cherry color we use to shade up the Bubinga to a sample color and it turns out real nice. I guess this won't help on this project, but maybe you could change your finish schedule on the next one to get more consistent results.

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From contributor S:
You need to keep building finish. Wipe on finish is nice because it is easier than brushing but you have greater issues with woods that have two differing densities. The softer areas have to fill up enough to effectively seal the wood where the denser areas require very little. You just need to keep adding coats until you even out everything.

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From the original questioner:
We usually use a conversion varnish on our work, but this piece had a lot of architectural woodwork and had to be installed and screwed and plugged. Knowing that we had to field finish the last coat, we chose the wipe on which we have used on other species with good results. I don't think it is a reaction issue, it just didn't absorb like it does on most woods, it laid on top more.

We always use natural finishes, so staining wasn't an option. The dry spots were appearing sporadically and building finish over them just compounded the issue. We normally rub down with 600 or 1200 grit between coats of the poly wipe on, but here we used 320 and it would work, but we would get a few new spots in subsequent coats. We have considered buffing or pumice/rottenstone to possibly work over the panels.

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From contributor M:
Bubinga has a lot more natural oils in it than most other woods (similar to rosewoods, ebony, cocobolo). These oils can impede the curing process. I've seen poly on cocobolo take several days to cure.

That being said, I have sprayed Bubinga and nearly every other oily wood that's commonly turned with pre-cats and conversion varnish. All you have to do is wipe the entire surface down with a cloth soaked in lacquer thinner to remove the surface oils. I have things I sprayed three years ago that look great to this day. The thinner-wipe may help with your wipe-on poly, just don't wipe the poly with lacquer thinner - only the wood first.