How to get your resin to cure in cold weather

cold weather resin curing tipsThanks to Jason Bell of Ballistic Impressions for sharing this tip.

I was having curing issues with the polyester, polyurethane, and epoxy resins I use when casting during this time of the year in my garage. I realized it was pretty much all around the heat or lack thereof during the complete curing process. It would start fine as the heat built up.  But, once the warmth began to dissipate, that’s when the problems would start. So, if you are asking yourself how to get your resin to cure in cold weather, here’s what I do.

Take my “Bullet Spheres” for example. These are made with a two-layer pour in 2 part molds I make myself.

mold base

I heat whichever resin type I’m working with in a water bath.  I want to get it to about 77-80 degrees F when I’m ready to pour.

mold cover

After I pour the first base layer into my silicone mold, I cover it with a container.  This seals off any dust from entering and retains the heat as the exothermic reaction takes place.

mold with hot hands


After I add what I embed/pour in the second layer, I cover the complete mold to let it cure. But before I cover it, I activate a HotHands hand warmer about 15 minutes before the final pour so it gets up to max temperature.  Then, I place it next to the mold and cover it with a container.

covered mold curing

I put some weight on top to help retain heat and prevent dust, etc. from getting into the resin.

This technique has not only improved the quality of the castings, but it has also dramatically cut down the cure time.

I’m a night owl, so I generally cast late. Before using the warmer during curing, if I came back about 12 hours later, the resin would still be sticky and not ready to handle. By using the HotHands and sealing the mold from the 55-60 degree working temperature in my garage during the winter months, all of my castings since have come out perfect and cured FAR quicker.

I’ve been casting for a while now.  This is going to be my method moving forward when my garage is under 70 degrees F.  I’ve used this process with fourteen different epoxy, polyester and polyurethane resins and gotten better results every time.

before and after using heating pad to cure resin

This shows how my castings were coming out from curing in cooler conditions versus using the new method. It’s a night and day difference!


If you like Jason’s article these may interest you too:

Resin casting in cold weather
Casting resin in cold temperatures


What other questions do you have about how to get your resin to cure in cold weather?

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13 thoughts on “How to get your resin to cure in cold weather

  1. Mmm I am having a very hard time this winter! Our house is seldom more than 68 degrees and very little I do can get it warmer (eastern WA, drafty windows.) The only resin I can get to cure bubble-free is easycast epoxy, and then only if I mix it in hot water and cure it on a heating pad. The nicer ones I’ve bought are 100% useless rn. I wish someone would come up w a good cool-weather resin!

    1. In my experience, it’s all about retaining the heat from the exothermic heat reaction. As Katherine said, a hot box of sorts is an easy solution. For most of my pieces, I just use an external heat source and seal the mold with a plastic container. The heat mat is a creative way to do this as well. I just purchased one off Amazon last week, along with a thermostat to control the temperature. Once I run out these heat pads I have on hand, I’ll try out that method. I like the idea of being about to control the heat temperature and duration each piece is exposed to that heat. Happy casting! Jason

  2. Sigh, yes. I might try the hotbox, though I might just scale down production until summer. (My family would thank me for that anyway!)

  3. I preheat the resin also. I coat my 18x 24″ works of art. I use a space heater and make a tent with my tarp. I turn the space heater toward the tarp, away from the resin, to prevent the fan of the space heater from rippling the surface.

  4. I have warmed the two products in hot water for about 20 and tested the temp of the water, before mixing. I wonder if using a heating pad on the surface under the pour would work?

      1. I’m curing them on heating pads, yep. I also warm the resin up in hot water first. Still, the only one I can get all (okay most of!) the bubbles out of is easycast. The others I have are the resin obsession brand, which I really like if I’m not trying to do something clear, and the jewelry grade one sold on here (forget the brand.) That one has kind of been a disaster. I mix very carefully, but sometimes it cures hard, and sometimes it never gets beyond the goo stage, and it *always* has tons of bubbles. Abandoning that one till summer!

        Oh and I actually bought a heat lamp yesterday to try to warm the area up more. The guy that sold it to me was like, “Are you trying to blow yourself up?” XD

  5. Hi
    After reading this great tip I made a wooden box out of MDF lined it with silver foil which I place over my resin project. Under the project I have a reptile aquarium heating mat bought really cheaply on line and it works a treat. I use the warm water bath to mix my resins to begin with.
    Thanks Martin

  6. I have an oil filled heater which I used to heat up the room if needed. I can also put the resin on top of the heater on a metal pan while mixing
    Seems to work well
    Will add a covering after reading the comments

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