Working with Epoxy in Cold Weather

If cold weather has turned your workshop into a winter wonderland, as in, “I wonder if my resin will cure in cold weather?” or “I wonder why my epoxy is cloudy and chunky?” – you’re not alone – and we can help. So turn up the heat in your workshop, grab a cup of coffee, and read on!

How Does Cold Affect Epoxy?

Without a doubt, colder temperatures affect the way epoxy mixes, pours, spreads, coats and cures. Here’s what you can expect when the temperature drops:

  • Higher (thicker) viscosity: Components are harder to mix, pour, and spread, and bubbles can stay trapped in the thicker material
  • Crystallization: Components become cloudy or form crystals
  • Gelling: Beginning stages of crystallization, microcrystals start to form and the material starts to turn hazy
  • Longer cure times, or no cure at all
  • Cured epoxy may not achieve optimal physical properties, such as hardness and strength

But there are some simple ways to make epoxy resin and hardener easier to work with, and to ensure a proper cure.

How to Store Epoxy in Cold Weather

At any time of year, not just winter, the best place to store your epoxy resin and hardener is in a place that’s cool, dark and dry. Excessive cold can cause crystallization, overexposure to UV light can make the resin and hardener turn yellow in the bottles, and an environment that’s too damp or humid, can contaminate the components, causing cloudiness, crystallization, and a failed cure.

You can help prevent epoxy crystallization and improve shelf life by storing epoxy resin and hardener components in the optimal conditions specified by the manufacturer.

What Does Crystallized Epoxy Look Like?

Above: Note the cloudy appearance and noticeable chunks in this sample of crystallized epoxy resin.

Any sign of cloudiness in the resin or hardener is an indication that crystals are starting to form. These crystals turn the resin from a flowing liquid into a cloudy, lumpy, or completely solid material. Thickened epoxy adhesives can also be affected, and will form chunky crystals that make it difficult to dispense from the mixing tip. Common causes of crystallization include repeated freeze/thaw cycles, prolonged storage in temperatures colder than recommended, or cold temperatures during shipping/delivery.

How to Fix Crystallized Resin

If your resin or hardener gels or crystallizes – not to worry – it’s still good. Before using it, all you need to do is heat it gently to return it to its liquid form. Place the tightly sealed container of gelled or crystallized material in a warm water bath heated to 125°F-140°F. Gently stir or agitate the material, as needed, until it returns to its liquid form, with no sign of crystals.

Cold Weather Techniques for Applying and Curing Epoxy

Above: When epoxy gets cold, it gets thicker and harder to work with. A warm water bath helps components flow more easily.

Making Cold Epoxy Easier to Dispense, Mix, and Apply

As mentioned earlier, when epoxy gets cold, it gets thick, like molasses. This makes the material harder to dispense via pumps, and harder to mix, pour, and spread evenly. There’s a possibility that the molecules won’t be able to cross-link completely because the components don’t get mixed thoroughly. If that happens, the epoxy won’t cure properly and will not achieve maximum strength.

To make cold epoxy resin and hardener flow better and mix more easily, there are a couple of things you can do:

  • Store the resin and hardener bottles in a warm room several hours before using.
  • Heat gently by warming the material in the bottles. Place tightly closed containers of resin and hardener in a warm water bath, and heat to 80°F. Don’t heat the material to more than 80°F because it’ll make the epoxy too hot and it will start curing as soon as you start mixing it.
  • Make sure the ambient air in your work space is within the epoxy manufacturer’s specified temperature range for application and for the entire curing process.
  • If you’re casting resin in molds, before filling them with the warmed resin, wave a heat gun over the molds to warm them, too.

Making Epoxy Cure Faster in Cold Weather

A thin film of epoxy takes longer to cure at room temperature – and even longer in cooler temperatures. To help expedite the cure, use a fast speed hardener, if available for the epoxy system you’re using. TotalBoat High Performance Epoxy Fast Kit provides the fastest cure and shortest working time at room temperature, or achieves an overnight cure in low temperatures (minimum 55°F). To help the epoxy cure faster, you can also warm the surface before applying epoxy, and warm the air in your workshop.

Most importantly, always use the mix ratio required by the epoxy manufacturer. It might be tempting to add more hardener, with the intention of speeding up the cure, but it won’t work.

And in case you’re concerned that the mix ratio might be off if the densities of the resin and hardener are different in cooler temperatures, don’t worry. As long as you use the recommended mix ratio, you’ll be fine.

Removing Amine Blush Before Overcoating with Epoxy or Paint

Amine blush is a waxy film that forms on the surface of curing epoxy. Even epoxies that typically do not blush, can form blush on the surface because of the slower cure rate in cold temperatures. If any amine blush is present, remove it with warm water and a 3M Scotch-Brite™ pad. Rinse the surface thoroughly to remove residue and dry with a clean, lint-free rag or white paper towels.

It’s important that you only use clean, fresh water to remove amine blush. Do not use solvents or attempt to remove amine blush by sanding.

Ensuring Maximum Adhesion of Epoxy Bonds in Cold Temperatures

Strong epoxy bonds take longer in cold weather, so allow extra cure time before removing clamps or putting stress on bonded joints.

Ensuring That Epoxy Cures Completely in Cold Weather

In warmer conditions, it’s easy to cure epoxy at room temperature. But in cooler temperatures, any lack of heat during the curing process can cause problems. Everything is fine during the initial cure, when the exothermic reaction is generating heat, but once this warmth dissipates, the curing can slow down or stop completely.

To ensure a proper cure in cold weather, after the epoxy has partially cured at room temperature, you can help it cure completely and achieve its maximum physical properties by raising the temperature of the epoxied surface and the air surrounding it. This is known as post-curing. Space heaters and curing blankets are just a couple of ways to raise the temperature.

Minimum Recommended Temperatures for Using TotalBoat Epoxy Systems

As mentioned in Which Epoxy Should I Use for My Project? – all epoxies are not the same, and that’s especially true for the temperature ranges recommended for application and curing. Here are the minimum temperatures for using TotalBoat epoxies.

TotalBoat Epoxy System Minimum Application Temperature
TotalBoat TableTop Epoxy 70°F
TotalBoat MakerPoxy Artist’s Resin by Jess Crow 70°F
TotalBoat ThickSet Epoxy 65°F
TotalBoat ThickSet Fathom Epoxy 65°F
TotalBoat High Performance 2:1 Epoxy 55°F (all hardener speeds – fast, medium & slow)
TotalBoat Traditional 5:1 Epoxy 40°F (fast hardener); 60°F (slow hardener)
TotalBoat Penetrating Epoxy 40°F (cold weather formula); 65°F (regular formula)
TotalBoat FlexEpox Flexible Epoxy Adhesive 40°F
TotalBoat Thixo Thickened Epoxy Adhesive 40°F
TotalBoat Thixo Flex Thickened Flexible Epoxy Adhesive 40°F
TotalBoat Thixo Fast Cure Epoxy, TotalBoat Thixo Low Viscosity (LV) Epoxy, TotalBoat Thixo Wood 2.0 Epoxy 55°F
TotalBoat Aluminum Boat Leak Sealer 40°F
TotalBoat TotalFair Epoxy Fairing Compound 50°F

Now that you know how to make sure your epoxy projects turn out delightful when the weather outside is frightful – we’d love to see what you’re working on! So please tag us on Instagram and Facebook using @totalboat, #totalboat and #totalboatepoxy! And if you have any questions about using these products in cold weather – or you need hot weather epoxy tips – be sure to call our helpful TotalBoat Tech Support Team at (800) 497-0010.


Does the use of a pressure tank for curing impact the cure time and temperature requirements?

Arthur Busby III

Can I use your epoxy over a tiled shower floor which has some high sports that are painful to step on.

Pete fotler

Leave a comment