Wednesday, May 12, 2021

How to Work with Resin in Cold Weather

During the colder months of the year, resin behaves a little differently to how it does in the warmer months. Both heat and cold have an effect on the way resin mixes and cures. But it's the cold that causes the most problems for people new to working with resin.
Thermometer with blue bulb sitting alonside thermometer with red bulb

Resin is very finicky when it comes to temperature (and humidity... but that's another story!).

For most epoxy resins, that temperature is around 21-25°C or 70-75°F but each resin is slightly different so you need to check the instructions in your kit to find the optimal curing temperature for your resin. If it's not in your instructions, contact the manufacturer and ask.

Epoxy resin is happiest when you get the temperature just right. It's a bit like Goldilocks...
Not too hot... Not too cold...
It needs to be JUST RIGHT!


If your resin is below these temperatures, it will affect the curing of the resin.

We'll get into the effects that cold has on resin in a moment but before that, let's look at what makes resin turn from a liquid state into a solid.

Once the resin and hardener are measured out in the right ratio and mixed together, a chemical reaction occurs. This chemical reaction produces heat (known as an exothermic reaction), and it's the heat that's generated that causes the resin to cure. Without heat, the two parts would stay liquid

So if you're working in a space where the temperature is way below the recommended room temperature, the heat generated from the exothermic reaction will dissipate from the resin and the curing process will slow down or STOP

And if the room is warmer than the optimum temperature, the curing process will speed up. And this is why getting the room temperature right is so important!

But it doesn't end there. There are other issues caused by working with resin in cold temperatures and mixing cold resin: 

  • The resin and hardener will become more viscous (thicker), making it much harder to measure the two parts accurately, especially if one part is thick like honey. 

  • When you mix cold resin and hardener together, you'll stir in a LOT of bubbles (and nobody wants bubbles!)

  • Mixing cold resin also creates microscopic bubbles. They're so small and light that they can't rise to the surface in the thicker resin, giving the resin a cloudy or foggy look.

  • The resin will take a lot longer to cure. Or worse, it might not cure at all! 

  • On artworks, it can cause surface imperfections like dimples, instead of a smooth, glossy finish.


Tips for Avoiding Cold Resin

But that doesn't mean you can't work with resin in the colder months. You just need to find ways of controlling the temperature. Here are 5 SIMPLE (and practical!) things you can do to get the temperature right.
  1. Store your resin in a warm place inside the house rather than in the garage or shed where the resin would be exposed to cold temperatures. 
  2. Keep it off cold concrete and tiled floors too. 
  3. If your bottles of resin feel cool or cold to the touch, place them in a warm-to-hot water bath for 10 minutes (see how to do it down below). 
  4. Use a heater to increase the room temperature for the whole of the curing period (not just while you're working with resin).
  5. In the winter months, you might find your epoxy has crystalised and it has a grainy or milky look. Or it may have even solidified completely. This is a normal occurrence for epoxy that has been exposed to extremely cold or freezing temperatures for an extended period of time. 

Don't panic if this has happened to your resin because warming it up will bring it back to a pourable consistency. 

Try placing the resin in front of a radiator or space heater to bring it back to room temperature. Check on it frequently to see how it's going.

To prevent it from overheating, keep some distance between the heat source and the resin.

How to Get Resin Temperatures Right 👌

There are 2 gadgets I keep in my work area so that I can make sure that my resin is at its optimal temperature: 
  1. a digital thermometer to check the room temperature; and
  2. an infrared thermometer so I can measure the temperature of the resin and hardener before I mix them together.
I highly recommend getting a small digital barometer similar to this one: it not only measures the room temperature but also the humidity levels (because resin is not a big fan of humidity!).
Digital barometer displaying temperature and humidity readings

If you're thinking about getting an infrared thermometer to check the temperature of your resin, then look for one that has a distance-to-spot ratio of  8:1 or 12:1. That ratio simply means that you can measure a spot that is 1" wide from either 8" or 12" away from the object being measured.

Let's test out the infrared thermometer to see how it can be useful.

The brand of epoxy resin that I'm testing is happiest at 25°C.

When I point the infrared thermometer at the resin, you can see that it's a little on the cool side. When I hold the bottle in my hand, it definitely feels cool to the touch. And we already know that if we mix cold resin, we'll stir in lots of bubbles.

So, how do we avoid the bubbles?

The quickest and easiest method is to warm the resin up in a warm water bath.

Just fill a container that's tall enough for your bottles with hot tap water. 

How hot? Well, it should be hot enough that you can put your hand in it for a few seconds without burning yourself. 

Make sure the caps are tightly screwed on and place the bottles in the container. After 10 minutes, dry off the bottles and let them cool for a minute or two so that the plastic can cool down (because you want to measure the temperature of the resin, not the plastic bottle). 

Now you can see that the resin is much warmer. The bottle now feels slightly warm to the touch. And the resin will be less viscous making it easier to measure, easier to mix and it will have dramatically fewer bubbles.

Caution: Mixing HOT resin can be dangerous. If the resin feels hot, let it cool down before mixing.

Now that you know how to adjust the temperature of both your resin and your working area, you'll be able to avoid the challenges that the cold brings and work with resin right throughout the winter months.

Pin this for later!
Gloved hand stirring pink and white pigments into resin that has bubbles

Happy Resining!

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Would you like to comment?

  1. Very informative. I'm new to this craft so any info is great.

    1. Glad it's helped.
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  2. I am getting lines on the fronts of my resin pieces that look like cracks. Any idea what I may be doing wrong? Would cold weather have something to do with it?

    1. It is possibly an amine blush which is caused by low temperature and humidity. Or the crazing can be caused by over-torching the resin to pop surface bubbles.


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