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Thread: How long does applied epoxy need to be kept warm?

  1. #1
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    Default How long does applied epoxy need to be kept warm?

    My boat building has been on hold al winter due to my shop being too cold for epoxy work. I know that epoxy applied at cold temperatures will eventually harden, but apparently the properties are compromised. We're going to have a very warm week; lows in the 50's and 60's F., highs near 80. If I apply epoxy with the shop at say, 70 F., how long do I have to keep the shop at 50 or better?

  2. #2
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    Default Re: How long does applied epoxy need to be kept warm?

    You can warm the epoxy before mixing. Sit it by the heater overnight (not to close) and good to go the next day.
    It will kick off a lot faster.

  3. #3
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    Default Re: How long does applied epoxy need to be kept warm?

    Just until the epoxy hardens up. Probably a day. After that it'll finish hardening no matter what, over the course of time.

    But if you want to get to sanding it ASAP, or remove temporary forms and fasteners, keep the heat on to speed it all up.

  4. #4
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    Default Re: How long does applied epoxy need to be kept warm?

    Depends on how big a hurry you're in. Epoxy cure will just slow down as the temps dip. Won't affect the final cure or ultimate strength as I understand it. But if you're in a big hurry to do the next step, you can do some localized heating. Two common methods are: Electric blankets draped over the epoxied area; throw together a temporary tent just big enough to enclose your workpiece and heat the area inside the tent.
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  5. #5
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    Default Re: How long does applied epoxy need to be kept warm?

    You could try a fast cure catalyst/fast hardener. I’ve not had the issue of worrying about cold weather while using epoxy but I see (on Youtube) a couple in Sweden about to build a strip planked hull are proposing to use fast hardener with some element of shop heating as their solution to overcoming the issue.
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  6. #6
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    Default Re: How long does applied epoxy need to be kept warm?

    I was told at least 3 days at room temp before going colder and 7 days for full cure, with cure stalling below 50 degrees F by my latest vendor of 2:1 epoxy. Since my repair job is keel-supporting framing I do not want to shortchange any recommendations.

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    Default Re: How long does applied epoxy need to be kept warm?

    Yeah, what I've read is that it will eventually cure at low temperatures, or will cure once it warms up, but strength will be permanently compromised. I guess if I apply it tomorrow at 70 F., I should be able to keep it above 60 through the week. It's not a critical structural application, either. Just making epoxy putty to fill the screw holes. It does need to keep the ocean out, though!

  8. #8
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    Default Re: How long does applied epoxy need to be kept warm?

    Quote Originally Posted by MushCreek View Post
    Yeah, what I've read is that it will eventually cure at low temperatures, or will cure once it warms up, but strength will be permanently compromised. I guess if I apply it tomorrow at 70 F., I should be able to keep it above 60 through the week. It's not a critical structural application, either. Just making epoxy putty to fill the screw holes. It does need to keep the ocean out, though!
    Just carry some spare screws :-)


    p.s. I reckon it will cure fine at your temperatures, might take a couple of weeks to cure fully. I've had to stop work because it's too hot......................

  9. #9
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    Default Re: How long does applied epoxy need to be kept warm?

    And put neat epoxy in the holes first before adding thickened

  10. #10
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    Default Re: How long does applied epoxy need to be kept warm?

    Different brands of epoxy formulations will have different cure rates for temperatures during cure. Choice of hardener will have a significant effect as well both on cure time as well as 'open' or working time.

    If you want reliable advice for the brand you're using, contact the manufacturer/vendor for their specifics on the product you're using.

    More generally, epoxies we use will work best between 60° - 70° F; the higher end for application (mixes easier, spreads more easily, wets out fiberglass better), the lower end as a guide for the minimum temperature to be maintained during the first half of the cure time.

    If you can maintain 60°F for the full cure period (days for some formulations) you can expect the maximum strength achievable.

    I'm most familiar with the MAS LV products these days. They don't recommend uisng their slow hardener for temps under 50°F.:

    Screenshot 2023-02-20 at 8.14.54 PM.jpg

    Mix slow and fast at 1:1 ratio (this is what they sell as Medium) you can get a full cure in 10-1/2 days @ 50F, 14 days if you don't go below 41°. Using the fast hardener, for those cure temps you get 6 days or 8 days respectively.

    Hope this helps!

    PS - And please do remember that until the epoxy has fully cured the stuff shouldn't be machined or sanded without proper attention paid to use of adequate PPE. Hardeners have very active chemistries due to the rolls they are to play, frequently quite caustic and do not play well in contact with our bodies. Once you've found you've become sensitized to epoxy chemistry, you can pretty much give up even being in close proximity to much of anything made with it for the rest of your life.
    Last edited by sp_clark; 02-20-2023 at 09:23 PM.
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  11. #11
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    Default Re: How long does applied epoxy need to be kept warm?

    properties are not compromised if temps drop. - Why not use a no blushing solvent free epoxy with an accelerated winter curing agent that works and sets up quickly in temps below freezing? Mix the different curing agents for whatever pot life - working temps you need - paul - CEO progressive epoxy polymers, Inc

  12. #12
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    Default Re: How long does applied epoxy need to be kept warm?

    I have recently been working with WEST 105/205 at temperatures between 40 - 50 degrees f. My boat is outdoors and is not heated in any way. According to the folks at Epoxyworks, this is nothing to really worry about:

    https://www.epoxyworks.com/index.php...ture-adhesion/

    The relevant data are here:


    More here: https://www.epoxyworks.com/index.php...ather-bonding/

    I am reassured by those numbers.

    James

  13. #13
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    Default Re: How long does applied epoxy need to be kept warm?

    I keep my resin in a warm cupboard / box before use, the cupboard, has a reptile aquarium heater mat in the bottom, temperature controlled to 25C max. The cupboard / box is not much bigger than the resin and catalyst containers.
    These heaters use no more power than a light bulb.
    I find keeping the work warm with a fan heater for several hours is enough, you don't need to heat the whole workshop.
    Just an amateur bodging away..

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    Default Re: How long does applied epoxy need to be kept warm?

    We were lucky enough to have a full week of warm weather. It still continues, in fact. I was using slow epoxy, because that's what I have left over from summer building. It was about 65-70 in the shop, and it kicked in a few hours, and was quite hard by the next day. The shop hasn't dropped below 55 the entire time, so I'm in good shape. It'll be weeks before I get around to sanding, and I wear a respirator mask anyway. I'm getting tired of all of the dust in the shop, so I think I'll roll her outside on nice days to sand outdoors. According to my supplier, the epoxy I'm using should be good above 40 F.

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    Default Re: How long does applied epoxy need to be kept warm?

    I am working on repairing structural bulkheads on a Sabre 38. The engineer overseeing the work for the insurance company told me I need to maintain 50 degrees for a minimum 24 hours for the epoxy/glass work for him to sign off on the repair.

  16. #16
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    Default Re: How long does applied epoxy need to be kept warm?

    Is there actual data showing weakened ultimate cure? Or is it just that some formulations have only been tested at higher temps, and as a result, they will only make claims as such? (that kind of behind covering sounds like what the aforementioned engineer is doing...).

    It seems like whenever this comes up, there are some people who say it doesn't matter, and some people who say it does matter, and the closest to data that I've seen is what James posted above, which seems to come down on the doesn't matter side.

    (I'm somewhat an interested party, since I did a lot of my work in an unheated northeast garage over the winter... using System 3 Silvertip Fast, which is spec'd down to 35, but I'm sure _overnight_ it often went lower when it was in the high 30s and 40s during the day).
    Daniel

    Building a Campion Apple 16 & a Duckworks Scout

  17. #17
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    Default Re: How long does applied epoxy need to be kept warm?

    Quote Originally Posted by Geftb View Post
    You can warm the epoxy before mixing. Sit it by the heater overnight (not to close) and good to go the next day.
    It will kick off a lot faster.
    Better to keep the wood to be joined warm, a thin film of glue on cold wood loses its heat pretty much instantly.

    John Welsford
    An expert is but a beginner with experience.

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