use spar urethane over epoxy finish?

[paul mcellistrem]

I am finishing some outdoor benches with an epoxy (West System) finish and then planning to coat the epoxy with a spar urethane.

Would it be better to use a spar varnish? I couldn't find a product with the words spar "varnish" at the big box store so I was planning to settle with the spar urethane ---- unless I'm told that's a bad idea.

Thanks for your help and time.

[Ed Falis]

I'm pretty sure a "spar urethane" finish is a varnish. You should be just fine. I'm assuming this is for an outside finish, and you want to protect the epoxy from the UV.

[Jim Becker]

Spar varnish is a very soft finish as it's designed to bend...which is what "spars" do. About the only reason I can think to put it on over the West Systems product would be for UV protection, but even then you're going to be refinishing the project from time to time, anyway.

"Spar Urethane" is varnish. It's just a long oil varnish that contains urethane resins...

[Steve Schoene]

Epoxy does need protection from UV but using "spar urethane" varnish is not the way. For UV protection you want a true marine grade spar varnish. Costs more per quart, but less per year of service. The three varnishes that qualify are: Epifanes Gloss, Interlux Schooner, and Pettit Captain's. Consumer grade single-part urethane resin is more susceptible to damage from UV than the traditional resin's. The spar urethane adds the UV protectant additives to get back to "acceptable", while the marine grade uses the additives to increase protection and extend longevity. A good on-line source is www.defender.com since you won't find the real marine finishes at ordinary paint stores or the borg.

[Frank Stone]

I did this on a boat once outside and it worked fine. I used a marine varnish with extra UV inhibitors. If you need to sand the epoxy do it before it gets hard or you will be there all day.

I also did an epoxy seal on an old end table, then used a scraper while the epoxy was green, and finished with polyurethane, wet sanded and buffed for a real mirror finish. It is indoors but has held up now for 15 years and the epoxy will prevent rings from a wet glass refreshment as well. It gets daily use.