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Thread: fancy epoxy vs. regular epoxy for coating

  1. #1

    fancy epoxy vs. regular epoxy for coating

    I'm doing a project using 3/4" baltic birch ply. Because it will be exposed to ground moisture, dew, etc., and it must not warp at all, I want to encapsulate the whole thing in epoxy after it's assembled. The coating must be thick enough to hide all the wood grain and seams and whatnot; it must form a flat surface. After that, the epoxy will be sanded and painted black.

    I found several kinds of epoxy by System Three:

    One is called "general purpose", it's a thick amber liquid that looks like honey.

    Another is called "mirror coat". They say it's "a pourable, self-leveling bar and tabletop coating."

    The other is called "clear coat" and they say it's "an extremely low viscosity, water white, penetrating epoxy system."

    Here's what I'm inclined to do, let me know what you think:

    I'd rather use the clear epoxy. It's a bit more expensive than the other two but not by much (22% more than the generic). I don't care about transparency, I'm going to paint it over anyway. But I like the idea of working with a very watery resin, unless there are any hidden drawbacks that I'm not aware of.

    Since it's very fluid, I imagine it will be better at hiding the grain and the seams, and it might be easier to spread it out to form a very flat and straight surface. They explicitly say it's "penetrating", which sounds good - I'd like to use a resin that gets soaked deep into the wood and penetrates all the little spaces and cracks. Unless I'm missing something obvious, it just sounds like a very good thing (if you ignore the price hike). Am I right?

    Also, I assume I could use it instead of carpenter's glue, to assemble the various pieces. It's kind of a waste, to glue wood with the fancy clear resin, but if I'm buying it anyway, I may as well use it, right? The fact that it's watery should not be a problem, if I manage to get enough of it between the dado and the other piece.

    I'm asking all these questions because I never used epoxy, so please let me know if I'm wrong.

    Thanks.
    Florin Andrei

  2. #2
    Any reputable epoxy formulator will have an epoxy designed especially for your application, check out their web-sites. It is also very easy to add colour to epoxy and you might just be able to avoid painting if you go this route.

  3. #3
    Join Date
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    Adding pigment to epoxy doesn't do as good a job of protecting it from UV than a solid paint film. Also, if sun is involved a light color will be considerably more durable than black. Black adds to heating and a wider range of temps creates more opportunities for a finish to deteriorate. For use as a glue you might want to add a filler to increase the viscosity. I'm not so sure about low viscosity as far as hiding grain and seam, though as you recognize it will penetrate more easily. But to hide, it has to build on the surface so you can sand it level before painting. If you really want to run up the cost, start with a couple of coats of low viscosity, and finish with the general purpose. Sanding epoxy can sometimes be a chore, so you might want to check with the manufacturer's tech people if there is a hardener or additive that will make it easier to sand without reducing water resistance. By the way, West Systems is another well thought of maker that offers good technical assistance. System Three is good too.

  4. #4
    The generic will be fine and probably best all around. If you use any of these to glue the pieces you will want to thicken it with a filler. (if all the epoxy runs out of the joint it won't do much good for you).

    I suggest that you look at West Systems materials. They provide tons of information and help with how to use their products.

    http://www.westsystem.com/ss/

    There's nothing wrong with other brands but the level of support you get from West Systems is just amazing and it sounds like it would help you a lot.

    I'm thinking you might want to use a layer of glass cloth and a couple of coats of resin applied before you cut the parts out of your plywood sheets. If you share a drawing of the thing you're making I could give better advice.

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