Is one better than the other for refinishing seats? Thanks.
Poly urethane does not have UV inhibitors, neither do the big box brands of spar varnish. The best choice is Z-Spar or Petit brands.
That’s not true. While interior polyurethane varnishes for floors and such don’t typically contain UV inhibitors, exterior polyurethane varnishes do. While I prefer natural-resin varnishes - like those you mentioned or Epiphanes - for my particular uses, polyurethane varnishes are generally more durable. For example, they’re commonly used to coat the skins on skin-on-frame kayaks, where they endure a lot of sun exposure and abrasion. They’re also widely available at big-box and hardware stores at reasonable prices.
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As above. Helsman Spar Finish is widely available and is a polyurethane. While it might not provide as deep a finish as multiple coats of Epiphanes can, it is cosmetically very acceptable and holds up well to UV exposure.
Epifanes is good as you can build multiple coats without sanding between(as long as you recoat within 72 hrs)
It builds well and has great UV protection and a glorious amber color
Edit for spelling
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Agreed on Epifanes. The one characteristic of Helmsman that I don’t like is that it’s very yellow.
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I use Epifanes gloss varnish on my sailboat. It is one of the better choices to withstand the UV here in Florida. For another option that is less labor intensive but still has UV resistance you could use Epifanes Rapidcoat or Rapidclear. 2-3 hour recoat time, no sanding between coats and a semi-gloss finish. Rapidcoat is quite tinted while Rapidclear is as the name says, completely clear. You can mix and match - I used both on the interior of my last sailboat, started with two coats of Rapidcoat and then three coats of Rapidclear. I was quite pleased with the results.
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UV resistance is what matters most. I prefer varnish.
A former poster on this message board, who still lurks occasionally, did a test of a variety of marine varnishes, epoxies, and polyurethanes by applying them to wooden panels and leaving those panels out in the open fully exposed to UV rays for many months.
As might be predicted, the epoxies that were not otherwise protected by UV blockers fared poorest. Marine epoxies and varnishes with UV blockers did much better but eventually deteriorated. Of course, for most of us the wood trim on our boats is not exposed to continuous UV for months on end.
The clear winner in the test results so far as durability went was Helmsman Spar Urethane.
“UV resistance is what matters most. I prefer varnish.”
Polyurethane IS varnish.
The difference is that polyurethane products contain synthetic oils and resins, whereas traditional varnishes use natural oils and resins. Other than that, they are identical in function and either one can contain UV inhibitors, or not.
The advantage of polyurethane varnishes is that they are more durable and abrasion resistant. The downside is they can have a more plastic-y feel to them.
For paddles, I blend either type of varnish with an equal amount of pure tung oil, which creates a softer, satin finish, rather than gloss. It’s more durable than plain oil, but probably less so than straight varnish.
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