How to sand epoxy flush, but not surrounding wood >320 grit?

[Ian Scofield]

I'm filling a void in some walnut and have used West 207 epoxy which cures like glass. Really interesting, I've never used epoxy of this quality. I poured the epoxy just proud of the surface to ensure I could sand it flush. However, when sanding it down flush, you lose this clarity, and I'm assuming you need to sand it up to very high grit to polish the surface again to restore the clarity.

However, the finish I plan on using (OSMO top oil) says to sand the surface to 220 grit. How exactly should I go about this? Is there a step I'm missing to restore the clarity in the epoxy without sanding it to a very high grit?

[Bennett Ostroff]

In my experience, the only way to get this clarity back is to use a clear film-forming finish, like a varnish. Oil finishes and oil varnish blends - anything that's wiped/buffed off - will help hide the scratches, but won't give it the kind of clarity I think you're talking about. It will have more clarity/depth sanded to 120 with varnish than it would sanded to 2000 grit with an oil finish.

If you decide to stick with the osmo oil, you could lightly wet sand the epoxy area by hand with 400-600 when you apply the finish. That should give it a nice clean matte finish.

[Wayne Lomman]

As Bennett says, use a film finish. If not, you will need to polish it. This can lead to sanding the epoxy hollow if you go overboard. Cheers

[glenn bradley]

When I fill walnut with epoxy I generally dye it so my info may not fit your situation. I don't add the epoxy until my surface is near finish ready (mostly surface prep'd). I use a card scraper to bring the surface of the epoxy flush with the softer wood. I then finish prep the entire surface as if the epoxy were not there. The oil/varnish blends I use make the fill visually vanish into the surrounding material. ... darn ... I coulda swore I had a good pic of that somewhere; sorry.

[Doug Hepler]

Ian,

I flatten epoxy with a card scraper. If it is a small spot you can use a single edge razor blade as a scraper (NOT with a slicing action) Do not fuss with it too much or you may call attention to it.

You certainly can sand to a finer grit than 220. I have not used osmo but I assume that the directions mean at least 220 grit. It appears to be a film finish with a respectable concentration of total solids. So it should build a bit. Therefore, if you sand the entire surface to the same grit the osmo top oil should give you a uniform sheen.

Doug

[Prashun Patel]

Don’t worry too much about it. You can sand your epoxy and your wood up to 600 grit (even higher) without any bonding problems, in my experience.

Also, the top coat will restore most of the sheen to the epoxy. Especially a film forming finish will fill in the scratches and restore the clarity and perfect reflection.

[Ian Scofield]

Thanks for the info. As the void went all the way through, I can test with the finish on the inside of the piece with it being sanded and with the OSMO to see how it looks. This was just a practice project to work on dovetails, so if it doesn't turn out flawless, I can chalk it up as a learning opportunity.

[Bill McNiel]

FWIW-I know from multiple projects that WaterLox will fill and eliminate 220 sanding marks in epoxy. BTW-scraping is much faster and easier for leveling epoxy overfills than sanding.

[Ian Scofield]

FWIW-I know from multiple projects that WaterLox will fill and eliminate 220 sanding marks in epoxy. BTW-scraping is much faster and easier for leveling epoxy overfills than sanding.

Yea I’ve been meaning to buy a scraper. Might have to finally bite the bullet