Something happened to me recently that hasn’t happened in a long time. About 90 seconds into mixing my resin, it got very hot and started smoking. (No, not the cigarette kind. The kind where you know a fire is coming.). While resin getting hot is normal, my epoxy resin overheated and cured in its cup in about 90 seconds. Yes, it can happen to even the most experienced of resin crafters. Here’s your chance to learn from my mistakes and what to do to keep it from happening to you.
Let me set the stage:
After warming my resin kit, I mixed three ounces of Resin Obsession super resin to pour into three different molds. I poured the first two projects, but by the time I tried coloring the resin for the third project, it started to smoke. Within a minute, the resin heated significantly and fully cured.
So why did the epoxy resin overheat?
There are several reasons why my epoxy got hot, smoked, and cured quickly.
Resin kits have a minimum and maximum mixing amount. The minimum amount ensures enough heat is produced to start resin curing, but there can be too much of a good thing. Paying attention to the maximum mixing amount is essential to make sure the resin doesn’t heat up too quickly. In this case, I mixed three ounces of the Resin Obsession super clear resin, which is the maximum mixing amount for this resin.
While warming resin is excellent for reducing bubbles, that heat also adds to the heat of the reaction. While I usually warm my epoxy resin in a hot water bath for five minutes, I went a little squirrel and got distracted. My resin sat in hot water for at least ten minutes before I used it.
I live in Florida. Even though it’s only March, it has been warm for the last three weeks. The humidity hasn’t been bad, though, so my studio has the windows up and fresh air breezing through. Even though it was late afternoon, it was 80 degrees inside.
When heat is produced in a cup of mixed resin and hardener, it builds upon itself. The more resin and hardener that is heating up, the quicker the heat builds. I only used about 1/2 ounce of the 3 ounces I mixed in my first two projects and let the other 2 1/2 ounces sit in the mixing cup, producing heat.
So what did I do wrong that my epoxy resin overheated — and what should I have done differently?
1. Even though I didn’t mix more than the maximum mixing amount, the extra heat from the resin sitting in the hot water bath too long added too much to the reaction. I should have paid closer attention to the amount of time the resin sat in the water instead of multitasking.
2. I didn’t consider my room temperature. I should have turned on the air conditioner or waited until later in the day to pour resin when things were cooler.
3. I should have used the resin for the ‘big’ project first. That way, there would have been less heat building up in the cup to cause it to overheat and cure. For bonus points, you can read about thermodynamics and the science behind this.
So what should you do in case you find your epoxy resin overheated?
Situations like this are why I always recommend having excellent ventilation when working with resin. In my case, I work underneath a ventilation hood, plus had the benefit of airflow from the open windows. At the least, you should have air circulating to allow the fumes to move away from you in a case like this.’
Use cups that are designed to mix resin. Even though my cups got very hot, they didn’t leak, melt or crack. You can’t always count on that with other paper or plastic cups. Worrying about resin smoking is bad enough. You don’t want to worry too about the cup leaking resin everywhere.
Have a metal container handy when you are mixing resin. If your resin overheats and smokes, you do not want to put it into a plastic or cardboard container. These can leak or worse — catch fire.
Do not throw the hot resin in your trash! The reaction is still occurring and can melt your trash can or start a fire. Instead, take it outside where it can sit on a surface while things cool off. In my case, I walked 10 feet through the front door and set my smoking hot resin on concrete to cool off.
Have a fire extinguisher close by. While this is the worst-case scenario option, it never hurts to be ready should you find your epoxy resin overheated.
Want to see more about what happened? Enjoy a close up of the bubble-filled, overheated epoxy resin in this video:
Want to learn more of the resin basics so this and other mistakes don’t happen to you?
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