How to Use Epoxy, Part 1 – Coating Plywood for Paint or Varnish

For your next project, let Eric Blake walk you through using an epoxy buildup coat before painting or varnishing bare plywood.

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19 Responses So Far to “How to Use Epoxy, Part 1 – Coating Plywood for Paint or Varnish

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    Paul Briggs says:

    You can clearly see that the ridges in the paint tray squeeze the epoxy out of the roller producing diagonal stripes when he rolls it on the wood. You can clearly see them on the roller itself and at the 14 minute mark he rolls this saying, “You wanna get the roller nice and even…”

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    Daniel Mydlack says:

    You mentioned some people using auto-refinisher clear coats over the boat finish. How might I find more info on that specific application? I am painting using Alexseal 2k poly and I want a much lower gloss. The flattening agent is not recommended for my situation so I am looking into spraying a 2k poly clearcoat matt finish. I’ve spoken to the auto clearcoat manufacturer and they don’t know of anyone. I’ve spoken with Gold Coast Marine and they haven’t either.

    Thank you!
    Danny in Baltimore

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    John Brame says:

    I used to use the pumps when I first started using epoxy. Made the change to measuring out by weight with a small set of scales. Seems to be working real good. The pumps were a regular pain to use. It is getting up to 38 celcius here in south australia tomorrow. That should make for a viscous brew as I put some coats on the spars. Thanks for the video.

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    Dony Bland says:

    Many hearty thanks Eric, very nicely presented instruction, kudos ,eh?

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    Alan Jardine says:

    Great videos and I’m about to strip and revanish the stern end of a 1958 Baltic cutter built in Denmark. My son sailed her back from Vancouver to here where we live in Australia, via Hawaii, Tuvalu, and Venuatu.
    What is the best method of removing old varnish and would it benefit a coating of epoxy before re varnishing?
    Is there a single pack epoxy available or is it always a mix?

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    Michael Seibert says:

    Just to clarify my description I just posted, before I primed the side the last time, I sanded all of those little glossy low spots out, and, in doing so, sanded almost all of the epoxy off again.

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    Michael Seibert says:

    Hi Eric –

    I am building a wooden Lightning, and am trying to get the topside ready for paint. I had a rough time getting the sides fair, and sanded through my original West epoxy barrier coat. Since I had bare wood exposed, I figured I should do another barrier coat. I used MAS low viscosity for the barrier boat. Bottom line: I did several rounds of two coats of MAS on my sides. I did the second coat about 5 hours after the 1st, when it was tacky. I sanded the epoxy lightly so I didn’t sand it off. Then I primed the side with Epifanes Multi Marine primer. When the low afternoon sun hit the side, it looked like the surface of the moon.

    So I sanded everything smooth again. After watching your videos again, I did one more application of epoxy. I rolled and tipped it in smaller sections, and it seemed better. But, when I sanded it, I had hundreds of little glossy spots that I couldn’t get rid of without sanding almost all of the epoxy off again. I lost my patience and primed the side as it was, and it came great. So now that side in good shape, but it lacks a good barrier coat of epoxy. Any idea what I did wrong?

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    Fred Bender says:

    Eric Thanks for the great instruction video on using epoxy.
    I’m building a Caledonia Yawl Thanks Geoff Kerr. I was interested in finding the 3″ roller with metal frame you use in the video. Thanks,
    Fred Bender

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    Robert Sullivan says:

    I am in the process of building a drift boat,(a stitch and glue) and this video has helped a lot. It has been suggested to epoxy coat the inside of the panels/bulkheads, prior to stitching them together. Why or do I need to varnish after the epoxy coat? My concern is what happens years down the road on having to strip every thing? Thank you again

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    Kyle Stroomer says:

    Great series! Wish I had watched it a couple weeks ago before trying to coat plywood with a chip brush on my initially “cheap and quick” dinghy tender to get us on a mooring ball this year. Live and learn I suppose.

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    Alden Reed says:

    The epoxy videos are great! How does the thin epoxy 207 compare to a penetrating epoxy such as Smith’s CPES? Is CPES better for rejuvenating old wood?

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      Eric Blake says:

      Hey Alden,
      The 207 is thinner than your typical epoxy, but not nearly as thin as Smiths etc. Smiths is like water. I love to use a penetrating epoxy for initial coats on plywood edges, especially plywood lap strake boats like a shellback. It isn’t nearly as durable as a West System type epoxy, but really does an amazing job wicking into end grain. Not sure what you mean by Rejuvinating old wood? I have had good luck driving West Epoxy into funky spots with a het gun, which helps to thin the epoxy and open the poors in the wood.

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        Clifford Spence says:

        My close to 40 years experience in the Polymer industry tells me that you need to be careful applying heat to two-pack materials. Yes, it can help to reduce viscosity initially, but it will add to the exothermic reaction generated by the epoxy itself as its cure mechanism.

        Additionally, while a little heat is good – sometimes it causes more problems than it hopes to cure! I once was coating a really beautiful waney-edged thick oak table. Thinking how smart I was, I decided to add a little autumn sun by coating it outdoors in full sun.
        Oh boy what a really glossy self-leveled finish I had! I stopped for a beverage, hoping that the extra heat would kick the epoxy off a bit faster. Indeed it did! But the major lesson I learned with that application was that wood is porous! It has millions of pores – all with little pockets of air or CO2 or what have you. While the sun was heating the epoxy, it was also heating the substrate and expanding all those little pores – and a bit faster than the epoxy was curing!

        The end result? A beautiful honeycomb of cured epoxy – the whole shebang had to be sanded back to bare wood, the table carried indoors and no more fancy tricks.

        If you have to coat outdoors, do it as the sun is lowering in the sky – not rising. That way the pores will be contracting, and hopefully pulling the epoxy INTO the pores and not expanding and blowing bubbles into the epoxy. As an added caveat, just be aware that lower level epoxies, with dropping temperatures, can throw what is known as an “Amine Blush.” This occurs when the curative side of the two-pack draws atmospheric moisture into the matrix. It appears as a whitish, waxy oil on the surface of your not so great looking finish.
        Epoxies are great! Just be careful and read as much as you can BEFORE you lift a brush.
        I’m all for energy efficiency – especially when it is MY energy we are talking about! That really tough epoxy appears even tougher when you have to remove it all!
        Cliff Spence
        Founder & CEO TEK-SET [International] Polymers Inc.

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    Steven Keller says:

    I am wondering why, when it comes time to restore a varnish on epoxy finish, it would be necessary to strip off the epoxy as well as the varnish. Why isn’t it enough to strip off only the varnish?

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      Eric Blake says:

      Hello Steven,
      We typically strip old varnish back with a heat gun, and this would compromise the epoxy if you are after a varnished finish, requiring you to strip everything back to bare wood. This is a bit more of a job, but can be done you know what you are in for.

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    martin schulman says:

    Thanks for this great video. There are times that we all have to get back to basics. This is a great review of how its done and a really helpful review for any of us who think we know it all.

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    Burton Blais says:

    Thanks for the explanation about how overworking the epoxy produces milkiness in the finish. Lately I’ve been having a lot of trouble with curing Brightsides (one part polyurethane) paints on my epoxy-coated surfaces, no matter how thoroughly I wash the surface to remove amine blush (which would interfere with the paint’s chemistry). It occurs to me after watching this video that perhaps I have been overworking the epoxy and introducing these tiny emulsified bubbles (I have noticed some patches of milkiness, but was never concerned since I was aiming for a painted finish). When you think of it, the internal surface of each bubble would be like any other cured epoxy surface, potentially holding amines which are readily released onto the top surface of the finish (especially when sanded). I shall be much more careful in future!

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    Sean Kelly says:

    You are misleading in calling the epoxies 205 and 207. All West Systems start with their 105 epoxy to which you add 205, 206 or 207 hardener.
    At some point you should caution users to watch for amine blush, especially when using the 205 hardener.
    In order to help the epoxy level out and remove roller stipple or brush strokes you should try waving a heat gun over your wet epoxy. Warming it slightly really makes it flow.


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