Thread: Epoxy resin UV question

The general consensus (as far as I've read) is:

If the varnish work is consistently maintained (for Aus, that pretty much means a light sand back and recoat the topcoat each and every year) and of a decent film thickness (6-8 coats minimum - 12 is better) then yes, the clear will be enough to protect the epoxy, as the varnish should deteriorate first. The trick is to keep an eye on the deterioration, and fix it before it's a problem.

A note, however: Not all "Marine" varnishes have UV inhibitors in them, so make sure the one you choose does. Some "Spar" or "Marine" varnishes from well-known brands have little to no UV blockers in them, and even the good ones there is a limit on how UV protective it can be.

In general, it should be fine

For something completely different.......
You may want to look at an Intergrain product called DWD. I use it on the decks of my boat (so, yes, it also gets walked on). Water based, only 1 or 2 coats (after once only cleaning & priming) and will last many times longer than oil or varnish. In terms of ease of use and particularly longevity, it makes oils & varnish totally obsolete.
So, what's the down side I hear you ask??
It's so chokkas full of UV inhibitors etc, that it WILL detract from the original character/grain/colour of your timber.
So it depends on what you're doing I guess, but I love the stuff.

I forgot to mention.
If you were to use this stuff, I imagine you would skip the epoxy.

Originally Posted by redx

Hi,

I'm told that West System's Epoxy Resin is not UV stable, which means it needs to be protected from direct sunlight. I am using epoxy to seal the woodwork on the new cabin I am building and I did not want to coat the trim entirely with paint.
My question is then, would a clear marine varnish give the epoxy the UV protection it needs?

redx.

Check out the various expoxies that they offer. There are definitely some that are UV stable. I used to build and repair surfboard and windsurfers (many years ago), and used WS exclusively.

Regards from Perth

Derek

I use an intergrain product on my 10 year-old Teal (my avatar) but not DWD, & is not so full of UV inhibitors.
Teal mostly lives upside down on a trailer under a poly tarp, but the ends always
seem to stick out. Light sand & re-coat the exposed bits every couple of years.
Dead easy compared with varnish.
Epoxy stabilisation of the timber under it is a quite separate issue/treatment.

John Welsford's reply to the question "What's your favourite varnish?" is
"white paint"

A clear finish of any sort will need more work to upkeep in AU.
But the look is well worth it IMHO..
Cheers
AJ

Just been reading the blurb on DWD, and it sounds like pretty neat stuff. It says "All new or bare timber must be primed with Dimension4 primer prior to application of DWD", is that really necessary?

Thank to everyone for the replies. I am now tossing up if I should go for a clear varnished finish on the trim or just paint it in a contrasting colour. From some of the comments it seems that clear finishes need a lot of maintenance.

redx.

DWD is thick like mayo. So it puts on a good thick coat. The primer is quite thin and is probably necessary to get the penetration. I suspect the primer may just be the topcoat thinned with water, but I'm not sure.
If you want the best protection, you've got the right idea with paint in a contrasting colour!

The water based product you are mentioning sounds (I haven't looked up the MSD) like a water based polyurethane. These are a relatively new player on the market and in their second generation of refinement. The jury is still out, but they have shown to be some what less durable then true single part, solvent based polyurethanes and considerably less durable then the LPU's.

West System sells a more UV tolerant resin system, check their web site for the 207 hardener literature.

All marine epoxies, regardless of formulation and UV inhibitors added, need to be over coated with varnish or polyurethane. Every marine grade varnish (poly, acrylic or alkyd) I've seen has some UV inhibitors in it. It's useless in the marine environment other wise.

On bright work that can't be completely encapsulated with epoxy, you are best advised to skip the epoxy all together and apply several coats of marine varnish or polyurethane. As Asrainox mentioned, 10 mils would be a minimum coating in this regard.

Thanks again to everyone for the informative replies.

The restoration of my boat is going well and is an enjoyable exercise except for the painting stage, which is yet to come. As can be gathered from some of my other threads the problem of choosing the right paint products is where I am most confused (and still undecided). The potential to get it wrong is a worrying one given the high cost of the paints and the time and effort put into preparation.

Therefore, the help and advice I have received through this forum is much appreciated.

Cheers,
redx

Use a single part polyurethane paint, like Brightsides. You can roll and tip with nearly spray booth quality, the cost is modest and you'll look like a pro, with a lot less trouble.

Thanks for that advice PAR. A single part polyurethane paint would be much easier for me to handle in my situation, but it raises one other question on the subject.

With Brightsides it is recommended you first prime with Interlux Pre-Kote Primer. As none of these products are recommended for boats that will be permanently immersed in salt water (as mine will be), I am wondering if I should use a Hi build two pack polyurethane primer instead, such as "Interlux InterProtect 2000E Epoxy Primer", and will this be compatible with a single part top coat like Brightsides?

redx.

If your boat will be immersed long term, more then a few days at a time), then you have no choice but to use bottom paint (anti fouling). Bottom paint can be applied over "toothed" epoxy, but you're usually best off to employ an epoxy primer over the epoxy, just to insure compatibility Yes, epoxy primers are compatible with single part polyurethanes..

Thanks for that advice PAR, much obliged.

Cheers,
redx