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Thread: New paint over new epoxy

  1. #1
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    Default New paint over new epoxy

    Finished the second coat of epoxy on my plywood boat last night. I have heeded the recommendations here and have abandoned the latex house paint plan and was able to at least get Rustoleum Topsides oil based marine paint locally.

    My question is how long do I have to wait for the epoxy to cure before I can top coat it with the enamel? I can sand the epoxy in a day but have read it takes about a week to fully cure. Since it is thixotropic I assume it can cure absent of oxygen but didn't know if I had to wait longer for any other reason.

  2. #2
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    Default Re: New paint over new epoxy

    You really should be waiting a week or more before sanding it. Its health hazard is greatly reduced after it has had more time to cure. Sanding day old epoxy is just asking for trouble.
    Last edited by Todd Bradshaw; 05-16-2017 at 11:24 AM.

  3. #3
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    Default Re: New paint over new epoxy

    And make sure you wipe it down with paper towels and water to remove the blush. Sanding wont do it. Water will.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
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    Default Re: New paint over new epoxy

    You'll want to give the epoxy at least a full week to cure, if not two before painting.
    Steve

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    R.D Culler

  5. #5
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    Default Re: New paint over new epoxy

    OK will do. I've always worn a mask when sanding but point well taken. I'll let it cure a week before topcoating.

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    Default Re: New paint over new epoxy

    Just breathing sanding dust is not the only hazard. Skin contact is just as much of a potential problem when sanding epoxy which hasn't fully cured. Should you become sensitized (allergic) to resin due to getting the dust on your skin, your days of using epoxy are forever over.

  7. #7
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    Default Re: New paint over new epoxy

    I had neglected that issue. I'll stop sanding early. Don't want to lose access to the goo.

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    Default Re: New paint over new epoxy

    Quote Originally Posted by Stein View Post
    OK will do. I've always worn a mask when sanding but point well taken. I'll let it cure a week before topcoating.
    Give it a week and then just do a few test patches. If the epoxy needs more cure time it will be a lot easier to clean off a few square inches than the whole hull. I don't know what is going on chemically but in my experience if the epoxy isn't ready the topcoat will just sit there in a state of stickiness until it gets cleaned off and allowed to finish curing. When I painted Kayli Marie the first time there were patches of tacky paint after days of dry time. I wiped the hull down with mineral spirits and the tacky spots cleaned right off, I let the boat sit for another week before trying again, that worked just fine.
    Steve

    Boats, like whiskey, are all good.
    R.D Culler

  9. #9

    Default Re: New paint over new epoxy

    Quote Originally Posted by Breakaway View Post
    And make sure you wipe it down with paper towels and water to remove the blush. Sanding wont do it. Water will.

    Kevin
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  10. #10
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    Default Re: New paint over new epoxy

    It's the water that is doing the job of liquefying the blush so that it can be removed. The paper towels (and plenty of them) perform the function of lifting the liquefied blush off of the surface. Using enough of them makes sure you're actually removing it, not just smearing it around. Dry paper towels have little or no effect on blush. The best bet is usually water and a Scotchbrite pad, followed by paper towels. It will do the job quickly and get you ready for the next step. Even for non-blushing resin, if it's been sitting there curing for a week or so, there is probably something which has settled on the surface that you don't really want there. The same water/Scotchbrite/paper towel routine is quick and a good idea before proceeding to the next step.

  11. #11
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    Default Re: New paint over new epoxy

    my experience seconds that.
    I used hot soapy water with a deck scrub, keeping the working area as wet as possible. i worked it so the blush was being mixed into the water.
    then lift the water off with rags or paper towels quickly before it runs off or dries. section by section.

    Soapy because that's what i read, but i'm not sure it matters.

    Not sure if its coincidence, but the last time i used epoxy i used a superior marine branded product (Intercontinental I think) and i never experienced any blush. And it gets humid where i live particularly in summer.
    Why is 'Politically Approved' speech better than 'Politically Correct' speech?

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    Default Re: New paint over new epoxy

    I'd skip the soap. Any time you can avoid putting another substance, chemical, or mix of chemicals on your epoxy it is a good idea to do so. They aren't needed for adhesion, bonding, etc. and even products designed to clean can be an unwanted source of contamination. They may not be washing off as well as you think they are. New users screwing up perfectly good epoxy work, all in the name of "cleaning" the surface and actually ending up with contamination problems which are hard to fix tend to be a pretty common problems.

    It's also usually a good idea to avoid the really cheap paper towels. Some paper products are treated with silicone. It repels water to an extent, to help keep them from falling apart so fast when they get wet. Ever notice that a lot of Kleenex is actually rather water repellent? Well that's why, and some cheap paper towels are similar.

  13. #13
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    Default Re: New paint over new epoxy

    Oil causes​ fish eyes and wax is a mold release agent. I wonder if the soap would remove these, and not be a problem if thoroughly rinsed off.

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    Default Re: New paint over new epoxy

    I use RAKA Blushless epoxy. I read about BLUSH but I don't see it, or recognize BLUSH.
    How do you know if you removed the Blush ??
    How do you know if you have blush ???

  15. #15
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    Default Re: New paint over new epoxy

    You can see and feel blush. It's kind of a very thin, waxy film that forms on top. It's pretty obvious, and it's similarly obvious when it has then been removed.

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    Default Re: New paint over new epoxy

    Not sure if Marinepoxy brand is blushless but I can't see or feel anything after curing a couple of days. Even stuff like the graphite filled epoxy bottom that has cured two weeks has nothing on it. I'll try washing it in a section to see if anything changes. If not does the whole boat need to be washed down inside and out if there isn't any perceptible blush?

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    Default Re: New paint over new epoxy

    I've just applied a 2-part primer over epoxy on my deck. The Raka non-blush epoxy had cured for several months. After removing residual dust I cleaned the surface using a two bucket method. I used scotch bright, a small amount of Simple Green and many rags. Prior to cleaning, the surface looked and felt clean. I'm familiar with blushing and non-blushing epoxies and also familiar with the feel of amine blush. It was totally surprising to see how "dirty" both the washing and rinsing water became. I don't know if the material being removed was amine wax. Following the paint manufacturers instructions I did a final wipe down of the deck with alcohol prior to painting and those rags found nothing.

  18. #18
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    Default Re: New paint over new epoxy

    If not does the whole boat need to be washed down inside and out if there isn't any perceptible blush?
    Technically, no it doesn't. However, the consequences of contamination problems, either from within (blush that wasn't removed), from settled stuff (auto emissions, dust, etc.), or from chemical contamination (usually "cleaning" solvents which should have been left in the can on the shelf and which should have never gotten near your boat) - can create project-ruining situations that are a tremendous pain in the ass to fix. Paint or epoxy that won't harden, fisheyes, delaminations, failed structural bonds and other undesired problems happen frequently on these forums, and nearly all of them can be avoided by simply working cleanly. Plain clean water and a Scotchbrite pad are adequate to clean nearly any epoxy surface in preparation for the following steps in your building process, and are by far the least likely to screw something up. Whether your particular resin blushes or not and whether you believe the surface is clean or not, the small amount of time needed to go over the hull with water, the pad and then paper towels or clean rags is nothing compared to the time and hassle involved in finding out that you just covered your hull with paint or resin that is never going to harden or stick properly.

  19. #19
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    Default Re: New paint over new epoxy

    Thanks Todd. Hopefully the last question on this. I'll need to sand the epoxy for a smooth finish, stray runs, etc. Should I wash before to prevent "moving around" any blush, sand, then wash again or just wait until after I sand and wash once before paint? Just want to do it right the first time.

  20. #20
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    Default Re: New paint over new epoxy

    Washing before sanding is good. It keeps you from grinding blush down into the surface when sanding, and also helps to lengthen the effective life of your sandpaper. I have both vacuumed and painted within a day or so of doing the sanding, and on other occasions washed again before painting if it's been sitting for a few days after sanding. Both have worked OK, so I think you just need to look at the situation when it arises and make the call. If there is any doubt about cleanliness, it may be worth washing again.

  21. #21
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    Default Re: New paint over new epoxy

    Sounds like a plan. Scotch brite and water, dry, sand, Scotch Brite wash again after sanding before paint. Thanks for the help.

  22. #22
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    Default Re: New paint over new epoxy

    why would anyone use a bushing epoxy when non blushing epoxies are available for about the same price? makes no sense.

  23. #23
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    Default Re: New paint over new epoxy

    Because dealing with blush is a very minor thing, which is continually blown way out of proportion on forums like this one, mostly by folks who don't know what they're talking about - many of whom who actually have little or no experience with it (or with boats). I've been using WEST Epoxy (which usually blushes) ever since it first came on the market and it has never failed me. I stick with it and support the company and people who developed it, as well as the vast majority of the techniques used these days for wood/epoxy boatbuilding. They have spent drastically more time and energy teaching, testing and pioneering techniques for using epoxy on boats that anybody in the industry.

    I want the folks developing the epoxy that I use on my boats to clearly know more about both resins and boatbuilding than I do. If they obviously don't, then they're not getting my business.

  24. #24
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    Default Re: New paint over new epoxy

    Quote Originally Posted by Todd Bradshaw View Post
    Because dealing with blush is a very minor thing, which is continually blown way out of proportion on forums like this one, mostly by folks who don't know what they're talking about - many of whom who actually have little or no experience with it (or with boats). I've been using WEST Epoxy (which usually blushes) ever since it first came on the market and it has never failed me. I stick with it and support the company and people who developed it, as well as the vast majority of the techniques used these days for wood/epoxy boatbuilding. They have spent drastically more time and energy teaching, testing and pioneering techniques for using epoxy on boats that anybody in the industry.

    I want the folks developing the epoxy that I use on my boats to clearly know more about both resins and boatbuilding than I do. If they obviously don't, then they're not getting my business.
    Todd - when a thread is being handled just fine by the various contributors, and an accurate picture and good advice is developing... I generally find no reason to jump in. I only do so now in recognition that you have been largely carrying the ball on this thread, and have been doing so admirably. Good facts. Accurate levels of emphasis. Remarkable restraint in the face of bloviation. So... thanks.
    David G
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  25. #25
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    Default Re: New paint over new epoxy

    Print out Todd's posts and take them to heart.
    Green epoxy is a potent carcinogen.
    The blush is very water soluble.
    Maybe wash, then wet sand, wearing gloves and safety glasses.
    Can you buy/borrow a vacuum sander like a Festool?
    Good luck

  26. #26
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    Default Re: New paint over new epoxy

    I have a 3M random orbital 6" sander with vac attachment. I haven't seen the Festool unit is but the 3M unit is a really nice $300 sander, albeit for professional autobody work. I assume it should work adequately.

  27. #27
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    Default Re: New paint over new epoxy

    Quote Originally Posted by Stein View Post
    I have a 3M random orbital 6" sander with vac attachment. I haven't seen the Festool unit is but the 3M unit is a really nice $300 sander, albeit for professional autobody work. I assume it should work adequately.
    It'll be peachy.
    David G
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    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  28. #28
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    Default Re: New paint over new epoxy

    What Todd said.
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  29. #29
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    Default Re: New paint over new epoxy

    Yep, that should work great. Keep in mind that power sanding creates a certain amount of heat from friction. The heat tends to soften epoxy and softer epoxy tends to plug-up sandpaper faster. Plugged-up sandpaper creates even more heat. This excessive heat can damage the resin and even smear hardened epoxy, as well as cause fiberglass weave texture to telegraph to the surface where there was none before, or even cause visible micro-fractures down in the glass-cloth.

    What all of this boils down to is that you want to avoid the temptation to push your sandpaper past the point where it is no longer cutting well. The cost of a fresh disk is always a lot less than the hassle of fixing problems which were easy to avoid. One trick is to search your closet (or that of your wife ) for an old natural crepe-soled shoe. The tan crepe rubber sole will act like a big eraser and can be held against a moving disk to help clean and extend the life of the grit. You can also buy blocks of crepe rubber for cleaning disks and sanding belts at hardware stores if your wife catches you going through her shoe closet.

  30. #30
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    Default Re: New paint over new epoxy

    One of the nice things about this sander is the variable speed. Most air powered sanders have very little power at low CFM but this thing has good power at virtually any setting. I'll look into the "eraser". I'm very liberal when it comes to replacing paper. When purchased in bulk rolls of discs it isn't worth the effort to limp along a marginal piece. Let the tool cut.

  31. #31
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    Default Re: New paint over new epoxy

    "Should you become sensitized (allergic) to resin due to getting the dust on your skin, your days of using epoxy are forever over."

    I've been lucky with this, knock on wood! Probably jinx myself here, but after many years of working clean, not all of those splash free, I had a brief reaction after smearing some on my belly unnoticed during an extended lamination session couple of years ago. By shower time that night this had become inflamed and itchy over a one square foot area. Although scheduling required my continued use of epoxy over the next two weeks, by taking great care I was able to have the rash disappear within the following month.

    Having been given a second chance, I'm trying not to blow my access to this option. I've got a bit more to do yet. / Jim

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