Something happened to me recently mixing resin that hasn’t happened in a long time. While resin getting hot is completely normal (and should happen to make sure resin cures), 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. I want to make this a teachable moment for everyone who creates with resin.
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 without any problems, 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 resin smoke, get very hot and cure?
There are several reasons when combined, that caused my resin to heat up quickly and cure.
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 resin in a hot water bath for five minutes, I got distracted this time. My resin sat in hot water for closer to ten minutes before I used it.
I live in Florida. Even though it’s only March, it has been unseasonably 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.
While I can’t explain in technical terms, 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 made sure not to mix more than the maximum mixing amount, the extra heat from the resin sitting in the hot water bath too long added too much extra heat to the reaction. I should have paid closer attention to the amount of time the resin sat in the water instead of multitasking.
2. Because my room was warmer than what is ideal for resin curing (resin likes a temperature in the low 70’s F), I should have either turned on the air conditioner or waited until later in the day to pour resin after things cooled off inside.
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.
So what should you know in case this happens to you?
Situations like this are why I always recommend having excellent ventilation when working with resin. In my case, I was working underneath a ventilation hood, plus had the benefit of airflow from the open windows. At a minimum, 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. That always can’t be said for other paper or plastic cups. Worrying about the 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 also 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 fully prepared should you find your epoxy resin overheated.
Want to see more about what happened? Enjoy a close up of the bubble-filled, cured resin in this video:
Unpublished Blog Posts of Resin Obsession, LLC © 2020 Resin Obsession, LLC