4

In general I have had good results with:

  • Oil-based stain -> oil-based polyurethane
  • Oil-based stain -> shellac barrier -> polycrylic / water-based polyurethane

I want to keep the look and at least some of the scratch resistance polyurethane/polycrylic provide.

However, I have found that when I apply any poly to vertical surfaces or bottom faces, it drips or becomes uneven as it dries.

Now, I have a piece that I had to assemble before finishing. It has faces of every orientation that I need to finish. I'd also like to avoid a shellac coat because I have trouble working with shellac. This limits me to oil-based polyurethane. All of the polyurethanes I have take 6-8+ hours to dry, and at least a few hours to stop being affected by gravity.

I'd really like to finish this piece in less than 6 (top, bottom, left, right, front, back) separate 6-8 hour steps (do the top faces, wait for poly to dry before flipping piece and doing a side, and so on).

So I'm looking for either a finish with the same look and some of the protection as polyurethane (I only need mild scratch resistance) that sets very quickly or doesn't run at all, or some technique for applying polyurethane to faces of arbitrary orientation without it running / beading / flowing.

What kind of finish can I use over oil-based stain, or how can I continue to use polyurethane but apply it in one or two sittings instead of six?

  • 1
    Thinner coats and more of them. I really am becoming fond of using a pad rather than a brush for transparent finishes; one of the fuzzy-surfaced sponge pads ought to offer similar advantages for paint. – keshlam Dec 14 '15 at 18:53
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Apply the varnish more thinly. Thinly is a pun here, as I mean thinned but this will directly result in a thinner coat being applied to the wood.

A thin coating is automatically less subject to problems due to gravity, and at best there is zero risk of runs, drips or sags. A thin coating also dries more quickly — varnish drying time is directly linked to coat thickness.

However there's no free lunch and there is a downside: this goes hand in hand with the finish building more slowly.

So it's fewer coats and risk some problems due to gravity, or sidestep those problems entirely accepting that more coats are needed to build coverage (6-8 to roughly equate with three full-strength coats of varnish applied by brush or roller).

Now this is not to say you need to apply the equivalent of three undiluted coats of varnish. Many of the people who wipe on poly in very thin coats will only apply three or four coats and they're happy with both the look and the level of protection. Note this is not enough to provide the full waterproofing that poly can provide (which you might want for a coffee table or kitchen countertop for example), but it is more than adequate for many other pieces of furniture.

  • I'm going to experiment a little. What do you think is a reasonable starting range of dilution ratios for poly that's somewhere between no change and basically wiping on a coat of mineral spirits (I'll need to be careful not to strip stain out, too)? – Jason C Dec 14 '15 at 20:09
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    According to Flexner, a 1:1 dilution ratio is the equivalent of commercial wiping polys (obv. some variation here so don't take as an absolute). But elsewhere he recommends thinning by 1/3 to 1/2 so that you're not building coverage slower than needed. There's no technical issue with the 1:1 ratio, even very dilute coats will dry fine, it's just that it builds more slowly than you need while still being able to get the benefits of wiping the varnish on. I've tried lesser dilutions and I think they work great, so I'd try the least dilution ratio (3:1 poly:MS) to start and see how you get on. – Graphus supports Monica Dec 15 '15 at 13:44

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