I want to put the final coat(s) of wipe on poly over a gloss poly next to last coat of material. I previously applied many coats of Gloss polyurethane, but now I need to finish this project today. Can I puddle some epoxy over a few little problem areas, so that I can sand and put on a final cost of wipe on satin poly?
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Any one had this problem before?– Ken StanislavCommented Aug 12, 2017 at 17:50
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I doubt this would do what you want it to do. I had written a more comprehensive Answer but I lost it when I logged off last night! Long story short, this probably won't work as well as you hope in the short term (problems with adhesion and perfect edges) and long term it's likely that the fills will become more and more visible (epoxy discolours with light exposure).– GraphusCommented Aug 13, 2017 at 7:20
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2 Answers
Since it's due in a day, and this is a year later, I suspect that I'm too late. That ship has sailed.
Epoxy I suspect is a lot harder than your other finish, and I think you will find that sanding it without totally destroying the finish around it will be difficult.
Since the problem is a 'hole' fill the hole with the same material you are using to finish it. Water based varnishes something like 30% solids, so you will need to fill it a bunch of times. E.g.: If your defect is 400 microns (.4 mm or about 1/64 of an inch) fill, let dry, it's now 280. Fill let dry its about 200. 140. 100 70 50 35 25 ...
You can get there a bit faster if the earlier coats have some form of bulk additive, such as fumed silica (used in fiberglass finish coats.) Ideally the mix will be close to the colour of your base material.
If you must turn in in a day, just finish your coats, and leave it. You can finish it later. The epoxy trick, may leave you with a destroyed finish that requires stripping and starting over.
Use a small quantity of yacht varnish. I will fill your irregularities and when it is thoroughly dry you can sand it flat and proceed as planned. Polyurethane will not fill holes in itself very well.
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Spar varnish has a reputation for yellowing. I think it would become very obvious over time. Commented Sep 27, 2018 at 18:35
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Possibly. I look at that piece of work every day and have done so for the last 15 years. Polyurethane goes yellow too and there is no sign of a difference. None. Commented Sep 28, 2018 at 20:45
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Good to know! I would have assumed it was worse over that much time. Commented Sep 30, 2018 at 6:24
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@CharlieKilian, you're right to have reservations about this. 'Spar varnish' isn't a thing, it's a class of thing and some are significantly more yellow than a typical oil-based poly right in the can, and they ain't getting any lighter! The rule of thumb is, the more oil in the varnish the more it discolours with light exposure and there's no way around that.– GraphusCommented Oct 27, 2018 at 14:54