Painting over epoxy..is it really necessary

Finishes, paints and coatings

Painting over epoxy..is it really necessary

Postby kd5edj63 » Sat Oct 19, 2013 7:32 pm

I plan on using a premium Behr exterior paint and primer in one (I usually hate anything "all in one" or "multi purpose") but my local big box store recommended this paint. I was left a little confused as to weather I should somehow seal the wood first. The lady said seal OR paint. Dont do both. Im a bit hesitant to put this high dollar paint right on ply wood without any epoxy, varnish or other sort of primer or protection. What are yalls thoughts. I want to maybe keep a woody look on the inside, but probably not on the outside.
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Re: Painting over epoxy..is it really necessary

Postby Heifer Boy » Sat Oct 19, 2013 9:01 pm

Yes it is important to paint over epoxy if it's subject to the weather. Epoxy will 'yellow' in the sun and eventually break down.

But it doesn't have to be paint. You can varnish/poly over it as this provides UV protection to the epoxy. If you ever see a wooden boat without paint it will have varnish over the epoxy. They call it a 'bright' finish.

HB
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Re: Painting over epoxy..is it really necessary

Postby Esteban » Sat Oct 19, 2013 9:18 pm

Yes it is necessary to have some kind of a coating like paint or varnish over epoxy that is exposed to sunlight.

Here's an excerpt from West Systems Finish-Coatings
Finish Coatings

The function of a finish coating like paint or varnish over an epoxy barrier coat, is to decorate the surface and protect the epoxy from sunlight. In doing so, the finish coating extends the life of the epoxy moisture barrier, which, in turn provides a stable base that extends the life of the finish coating. Together the two form a protective system far more durable than either coating by itself.

Protection from sunlight is a primary consideration in the selection of a finish coating. Long term UV (ultraviolet) protection of the barrier coat depends on how well the finish coating itself resists UV and keeps its pigments, or its shield of UV filters on the surface of the epoxy barrier coat. A high gloss finish reflects a higher proportion of the light hitting the surface than a dull surface. All other thing being equal, a white (especially a glossy white) coating will last the longest.

Most types of coatings are compatible with epoxy. Thoroughly cured epoxy is an almost completely inert hard plastic. This means most paint solvents will not soften, swell or react with it. However, it is still a good idea to build a test panel to assure coating compatibility.

It continues with short descriptions of different coating types that may more fully answer your concerns. It's worth reading.

For the inside consider using epoxy first then varnish.
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Sat Oct 19, 2013 10:09 pm

Thank you. Thank you so much for the assurance. I will most certainly go with an epoxy sealer. As a car painter, I know the disaster of putting a good paint job on a bad foundation :beer:
The problem here is I am working outside the rehlm of my expertise. If I built a tear out of steel it would be way to heavy, So I need yalls help here. But there are some cross overs like, I know yall use "bondo" for filling. I even hate the term Bondo. Its body filler in my world. Made by many a company. I prefer evercoat personally.
But I have that product and have used it on wood, so I know that even low end body fillers are a great way to fill. Keep the help comming. I will be spending some good money in the morning loading up my truck with an early Christams for me :D
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Sat Oct 19, 2013 10:12 pm

I even scoped out my 1st test spot for my tear while hiking today. Well, beyond my yamping test LOLI will Yamp, before I camp
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Re: Painting over epoxy..is it really necessary

Postby fire on water » Sun Oct 20, 2013 11:50 am

Raka makes a epoxy with uv inhibitors in it
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Re: Painting over epoxy..is it really necessary

Postby Tom Kurth » Sun Oct 20, 2013 12:02 pm

Be aware, even with inhibitors, even with some kind of varnish or poly overcoat, epoxy WILL, not may, suffer UV degradation. Paint is a more sure overcoat. If you want a clear coat use a top quality marine (not spar) varnish or an automotive clearcoat. Honestly, I don't know about the automotive for sure. Even with a good marine varnish, it will need to be renewed frequently (understand that as annually.)

Best,
Tom
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Re: Painting over epoxy..is it really necessary

Postby Esteban » Sun Oct 20, 2013 1:04 pm

Tom Kurth wrote:Be aware, even with inhibitors, even with some kind of varnish or poly overcoat, epoxy WILL, not may, suffer UV degradation. Paint is a more sure overcoat. If you want a clear coat use a top quality marine (not spar) varnish or an automotive clearcoat. Honestly, I don't know about the automotive for sure. Even with a good marine varnish, it will need to be renewed frequently (understand that as annually.)

Best,
Tom

I favor paint for its longevity. Probably a one part marine paint like Interlux Brightside Brightside® Polyurethane, Pettit Easypoxy Pettit Easypoxy or a lower cost Rustoleum Topside Rustoleum Topside

Rustoleum has fewer color choices so unless I wanted a white I'd probably choose one of the Brightside or Easypoxy colors.

Oyster White by Rustoleum is an off white that does look appealing...thinking it might not show dirt/dust as much as a pure white.

Interlux has a helpful paint forum yachtpaintforum.com
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Sun Oct 20, 2013 8:36 pm

I wonder if I should have asked, Is it necessary to epoxy UNDER paint :thinking: that is my question
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Re: Painting over epoxy..is it really necessary

Postby Esteban » Sun Oct 20, 2013 9:30 pm

kd5edj63 wrote:I wonder if I should have asked, Is it necessary to epoxy UNDER paint :thinking: that is my question

No, it is not necessary to seal all the plywood with epoxy in order to paint it.

A good idea for extra protection, yes. It seals and stabilizes the plywood so coatings stick on better and last longer (protecting vulnerable plywood).

Even better if you use fiberglass tape and epoxy on all the plywood edges and joints.

Fiberglassing all the plywood adds more long term protection.

Paint by itself may/will be more subject to weathering, possibly cracking and or leaking (because wood expands and contracts with the weather).

The west system finish coating quote up above says in part: "(epoxy) extends the life of the finish coating (paint). Together the two form a protective system far more durable than either coating by itself." If you click on the link and read it all you'll know more about epoxy and paint/coatings issues.

Done right it adds longevity and frees you from some periodic maintenance (or repairs).

It is your teardrop so you get to decide what is best for your wants, needs, skills and budget. :)
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Mon Oct 21, 2013 8:35 am

Thanks. I will probably do a couple coats of epoxy 1st
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Mon Oct 21, 2013 12:44 pm

I am back to contemplating using epoxy primer instead of the clear epoxy. Anyone think thats a bad idea :thinking:
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Re: Painting over epoxy..is it really necessary

Postby CARS » Sun Nov 03, 2013 2:43 pm

kd5edj63 wrote:I am back to contemplating using epoxy primer instead of the clear epoxy. Anyone think thats a bad idea :thinking:


I'm a bodyman by trade and plan on fiber glassing my tear. I'm going to treat it just like a semi hood, boat, snowmobile hood, etc.

Glass, fill imperfections, prime, and paint with urethane paint.

The only thing that is different is that in the past I primarily used polyester resin, but I think I can adapt to using large amounts of epoxy.
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Re: Painting over epoxy..is it really necessary

Postby kd5edj63 » Thu Nov 14, 2013 12:46 pm

I ended up treating it like a house and primed with an oil based primer, and painted it with the best paint Behr makes
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Re: Painting over epoxy..is it really necessary

Postby mgb4tim » Fri Nov 15, 2013 2:05 pm

kd5edj63 wrote:The only thing that is different is that in the past I primarily used polyester resin, but I think I can adapt to using large amounts of epoxy.


Why would would you go through the expense of epoxy over poly if you weren't building a foamie?
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