UV coating for black epoxy

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UV coating for black epoxy

Postby Tom&Shelly » Sun Mar 01, 2020 5:12 pm

I've been coating some detail on our hatch: the gussets, rain channel, and edges, with black epoxy (epoxy with carbon powder mixed in).

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Almost finished (the way I do it, I applied a coat of clear epoxy, then about three coats of black, all with black foam brushes, letting the coats dry and wet sanding between coats. Probably not the best way, by any means, but it eventually gave me the results I desired--filling in the wood grain for a smooth finish), and I was planning on simply applying three coats of polyurethane varnish for UV protection. But I'm wondering if that is the best way to do that?

Does anyone have any opinions about using some sort of black paint instead? If so, any suggestions on type or brand?

Thanks!

Tom
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Re: UV coating for black epoxy

Postby tony.latham » Sun Mar 01, 2020 6:48 pm

and I was planning on simply applying three coats of polyurethane varnish for UV protection...


Make sure that is a UV varnish of course...

I'm wondering if the black coloring in the epoxy will inhibit it?

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Re: UV coating for black epoxy

Postby Tom&Shelly » Sun Mar 01, 2020 7:45 pm

tony.latham wrote:
and I was planning on simply applying three coats of polyurethane varnish for UV protection...


Make sure that is a UV varnish of course...

I'm wondering if the black coloring in the epoxy will inhibit it?

Tony


Not sure :thinking:

Seems like the carbon probably would protect the epoxy behind the powder, but the surface layer of epoxy might degrade, making the whole thing a dusty mess, leaving black dust on whoever touched the surface. But that's a guess.

Shelly and I experimented last year with the edge on one of our shelves, and found sanding the shiny black epoxy made it a somewhat unattractive dull, but satin varnish restored just enough luster to make it look good. Of course, the varnish will likely turn a little brown with age, and we don't know if that will be noticeable.

I have lots of Helmsman (outdoor) spar varnish, which I like, and it has UV inhibitors. I used it on the Baltic birch in the galley and teardrop cabin and generally like the results. Seem to remember you and some others don't like it, Tony, but wasn't sure of your reasons?

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Re: UV coating for black epoxy

Postby tony.latham » Sun Mar 01, 2020 8:21 pm

Seem to remember you and some others don't like it, Tony, but wasn't sure of your reasons?


For me, it takes forever to dry. But maybe that's just what real varnish does.

I'm glad you brought this up because I need to treat my fiberglassed wall ends in the galley for UV and had forgotten about it.

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Re: UV coating for black epoxy

Postby Tom&Shelly » Sun Mar 01, 2020 8:31 pm

tony.latham wrote:
Seem to remember you and some others don't like it, Tony, but wasn't sure of your reasons?


For me, it takes forever to dry. But maybe that's just what real varnish does.

I'm glad you brought this up because I need to treat my fiberglassed wall ends in the galley for UV and had forgotten about it.

Tony


Ah! It's usually so dry here in New Mexico, that even oil based varnish dries in a few hours. Also, one thing I've noticed about retirement is that I always seem to have things that need to be done, that fill the time between coats! :?

Glad I could help, and thank you Tony!

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Re: UV coating for black epoxy

Postby dogcatcher » Sun Mar 01, 2020 9:37 pm

I also used Helmsman Spar Varnish, but on the wood trim on our boat and on the wooden outdoor furniture,
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Re: UV coating for black epoxy

Postby swoody126 » Mon Mar 02, 2020 8:12 am

pox does knot like UV

¿ have you considered black exterior Rustoleum ?

reasonable price

common in big box stores

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Re: UV coating for black epoxy

Postby noseoil » Mon Mar 02, 2020 8:38 am

If you store the trailer under a cover (garage, carport, etc.) it will not age too quickly with epoxy & a UV varnish. If it's stored in full sunlight, it's going to age fairly fast no matter what you do. The black Rustoleum would be as good as anything for durability, but the UV is pretty "hot" at 5,000' & very little cloudy weather in ABQ. That's why the Tortoise was under a cover in the back yard in Tucson, just too hot & bright in the summer. Glad to be in Raton now & parked inside a garage.

I use cabosil, black graphite powder, chopped strand glass & a pinch of wood dust for stock inletting on rifle builds. Never worry about rain, sun, UV or anything else as the vault is the normal resting place for the builds on these...
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Re: UV coating for black epoxy

Postby Tom&Shelly » Mon Mar 02, 2020 9:47 am

swoody126 wrote:pox does knot like UV

¿ have you considered black exterior Rustoleum ?

reasonable price

common in big box stores

sw


Thanks SW, I like that answer, mainly because I already have most of a can of their flat black enamel:

https://www.homedepot.com/p/Rust-Oleum- ... /100186061

I use it on the exterior lights on our house, and it seems to last a few years. I've been wondering how well it would work on top of epoxy. (We also plan to use it on some white running lights so almost all of our exterior pieces on the trailer are black.)

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Re: UV coating for black epoxy

Postby Tom&Shelly » Mon Mar 02, 2020 9:54 am

noseoil wrote:If you store the trailer under a cover (garage, carport, etc.) it will not age too quickly with epoxy & a UV varnish. If it's stored in full sunlight, it's going to age fairly fast no matter what you do. The black Rustoleum would be as good as anything for durability, but the UV is pretty "hot" at 5,000' & very little cloudy weather in ABQ. That's why the Tortoise was under a cover in the back yard in Tucson, just too hot & bright in the summer. Glad to be in Raton now & parked inside a garage.


Boy, don't I know that Tim! :)

I've noticed the signs for businesses out here only last a few years (red seems to fair worst of all!)

We are in the process (currently permitting) of building a garage for our trailer, and plan to keep it in there when not in use. Of course, we want to use it as much as possible, including month's long trips to various parts of the continent, so it'll still get its share of exposure to the climate that different parts of North America have to offer.

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Re: UV coating for black epoxy

Postby Tom&Shelly » Mon Mar 02, 2020 6:08 pm

Just heard from the boss: Guess I'll go out and buy a new can of gloss black.

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Re: UV coating for black epoxy

Postby noseoil » Sat Mar 07, 2020 9:27 am

Our solution in Tucson was a pop-up shelter, which will last a couple of years then disintegrate in a thunderstorm & shred itself. It's not any kind of permanent solution, but it's enough to keep the sun off in the heat of summer. I did a drape over the west end for those too-hot afternoons & it helped a lot to cut sunlight from the metal skin.

What prompted it was an oven thermometer set inside the galley in July in the afternoon to check things. The galley faced west & had been in the sun all afternoon. I had trouble opening the hatch that day, the latch was bound up, but when I did & looked the inside temperature was about 155 degrees back there! I was worried that things would start coming apart (formica glue, finish & bonds in general). I couldn't get the latch to engage & close until evening, due to the aluminum expansion which actually racked the hatch out of shape temporarily. All's well that ends well & a trip to Home Delay solved the problem. Needless to say, it stayed covered from than point onward both summer & winter.

The moral of the story is, any shade is better than no shade on a hot afternoon in the sun in summer. We recently did a metal carport here in Raton, due to the summer hail storms. Nice to have the snow on the roof instead of the vehicles now as well.
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Re: UV coating for black epoxy

Postby swoody126 » Sat Mar 07, 2020 9:38 am

'taint winter sun/summer sun hot sun/cold sun it'z just SUN... period

rays r rays and UV rays are aways in there amongst 'em

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Re: UV coating for black epoxy

Postby Tom&Shelly » Sat Mar 07, 2020 10:59 am

We're now planning on coating over the black epoxy with Rustoleum's gloss black enamel.

After testing black epoxy on a shelf edge last year, I wasn't happy about the way it would soak into the wood, and show up at the interface with the varnished side. So this time I started with a coat of clear epoxy, which solved that problem. But, for the hatch and galley wall edges, there are some sharp corners, and, with the clear epoxy soaked into the wood, I sometimes sand through the black epoxy to the clear coat, even with 400 grit. So, if I ever do something like this again, for the first coat I'll use the clear on corners with varnished sides, and black everywhere else. Oh well....

I don't really have illusions that the black paint won't wear at the corners and show too, but this seems to be the best solution for now. :shrug:

I can revisit this next Winter. Completing the build (and camping this Summer) won't restrict access to these areas.

Anyway, ready to move on and start building again. Been spreading the epoxy for the past two months!

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