Resin can be a fussy beast. Like on a scale of changing a light bulb to growing orchids, resin is in the changing a tire range. It’s pretty straightforward, but leave something out. Or cut a corner. Or, as in this case, fail to follow good procedures, and your resin time suddenly turns into a blowout. While resin getting hot is normal, it shouldn’t get hot and cure quickly (unless it’s a resin designed to do that). So when my epoxy resin overheated and cured in its cup in about 90 seconds, I turned it from a mistake into a teachable moment. Here’s your chance to learn and keep it from happening to you.
Let me set the stage:
After warming my resin kit, I mixed three ounces of epoxy resin to pour into three separate resin molds. I poured the first two projects, but by the time I tried coloring the resin for the third project, it started smoking. Within a minute, the resin got super hot and fully cured.
And if you’re thinking, ‘What’s the big deal? I’d love for my resin to cure faster!’
It’s because that resin cures full of bubbles and is unusable. Like this…
So why did the epoxy resin overheat?
There are several reasons why my epoxy got hot, smoked, and cured quickly.
Factor #1: Resin kits have a minimum and maximum mixing amount.
A minimum mixing amount ensures enough heat is produced to start resin curing, but there can be too much of a good thing. When you go above the maximum mixing amount, the resin heats up too quickly. I mixed three ounces of clear resin, which is the maximum mixing amount for this resin.
Factor #2: 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.
Factor #3: It was 80 degrees F inside my studio.
I live in Florida, so I had the windows open to allow for cross-ventilation. (an important part of resin safety)
Factor #4: Heat builds on itself
The more resin and hardener you mix, the quicker the reaction 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. For bonus points, you can read about thermodynamics and the science behind this.
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 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. 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 casting resin for the ‘big’ project first. That way, there would have been less resin (and less heat building) in my main resin mixing cup.
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 I 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 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 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 mess:
Want to learn more of the resin basics, so this and other mistakes don’t happen to you?
Be sure to grab your copy of the instantly downloadable PDF book, Resin Fundamentals. The book gets you to resin expert status in only a couple of hours, even if you have never worked with resin before. Buy now, and the ebook is yours to read in minutes.
Unpublished Blog Posts of Resin Obsession, LLC © 2023 Resin Obsession, LLC
I’d like to know the guidelines on the amts that you can mix safely, as I know there is a big difference in casting, coating, doming resins. …and how much mixed resin does one need per sq. ft., please. Doming resins for coasters I mix no more than about 6 oz. (3 oz. ea.resin and hardener) for instance. Casting resins for a large cabachon…how much TOTAL should you mix safely…or a geode before dividing up into smaller cups for diff colors? Even a link to a chart would be helpful.
This is a great question Karen! Unfortunately, there is no one size fits all answer. If it’s a resin sold in the Resin Obsession store, we have all of that information in a PDF for you in this article: https://www.resinobsession.com/resin-frequently-asked-questions/resin-casting/
Otherwise, you will need to ask the manufacturer directly.
I have a ruined carpet in my craft room from using a cheap plastic cup that melted and leaked when I wasn’t looking.
Lesson #1 – Don’t use cheap plastic cups!
Lesson #2 – If you have carpeted flooring, lay a plastic sheet down to protect it, like a painters tarp.
Lesson #3 – Don’t leave your resin until it’s poured and covered!!
I really like your #2 comment Rhonda. A cheap plastic tarp is a great protective surface.
Thank you for posting about this hardening issue in Florida! I spent all day prepping and waiting until midnight to try my 1st big pour last night… epic failure! I’ve been flabbergasted over how instantly the entire project went horribly wrong… and how I managed to mess it up so badly??!! Of all the projects I’ve taken on, the spectrum of materials I’ve used… epoxy resin is the first to kick my butt!
After being upset over it for 12 hours now, you’ve made me feel better about things going wrong sometimes. .. but now what do I do?!
It’s around 100 degrees, humid and gross… no avoiding this dilemma…
Mixed great, had all my colors ready, randomly poured the 1st color, turned around to grab trowel and saw 2 melting cups that were half hardened already, other 2 cups about to do the same, so hot I really thought would catch fire! Grabbed bucket, water, got everything safe asap… of course the poured epoxy was basically cured in those 2 minutes also… wasted hours, materials and have a piece of my patio table out of commission, looking like a volcano puked on it in the garage….
Eek!
There’s no hope for a 70 degree day anytime soon. Its July, I’m in southern Florida… taking on the impossible!
This just happened to me and I had never seen this before. I lost a lot of product and couldn’t figure it out and then I saw your hot water bath comment and had my ah ha moment. Thank you so much
I’m so glad it helped Shannon. 🙂
Katherine – Would a fire extinguisher be effective for a runaway resin / catalyst reaction? I have read in the past that the most effective method of dousing a uncontrolled reaction like that is to use sand to effectively smother the resin and allow the reaction to eventually cool. What’s your thoughts on that approach?
Hi Mike, I do keep two fire extinguishers in my studio should things get out of control.
So I am been doing resin shot glasses I’ve noticed that I’m getting a lot of bubbles in them. The fuel oil went out of the furnace yesterday but I did not realize it until after I had started pouring one ,poured in my silicone mold I put it in the oven on 210 for 10 minutes. Then I pulled them out to cure until today when I pulled them out it feels like shards of glass are running all up and down them. I’ve realized the oven is not the best way to keep up to get the bubbles out What else do you suggest?
Hi Jackie, we have an article about handling bubbles in resin here: https://www.resinobsession.com/resin-frequently-asked-questions/resin-bubbles/
Reason 4, the fact that the hotter the resin gets the more heat that is produced, it’s pretty easy to explain in fact. The chemical reaction produces heat. The fastest the reaction, the more heat, and the rate of the reaction is dependant on the temperature,vso the hotter it gets he faster the temperature changes. In chemistry and physics these sorts of phenomena are common, where the rate that something changes is proportional to the total amount of that thing. In this case the rate that heat is produced, is proportional to the total amount of heat in the cup. The total amount of heat times a constant is the temperature in the cup. The solutions to such equations are exponential. Chemical reactions are known to runaway like that. Depending on the chemicals involved it can catch fire or even explode.
In fact, items 1-3 are also related to this. The total heat as a function of time is an exponential curve. By starting with more heat, your starting further along the exponential curve, closer to the part where it runs away out of control.
Thanks, Michael for the scientific explanation here!
This just happened twice to me. im also in FL and it’s now, Aug summer rainy humid and I know this has happened to people before but, I thought I might had just mixed wrong but duh! it;s hot in my house I am now cooling my home down which is hard with windows open but oh well I will also pour wayyyy less it may take more time but it’s better then waisting resin that can get very pricey as I am sure everyone can agree with =)
I am new to resin and just did my first pour tonight. My one is extremely warm. The bottom is hot. The other pour feels normal. I sat them near my fan that’s in my window. Will this help? I didn’t know that the temperature made a difference. My house is in the 80s and just now dropping a little because it’s 230a 😅 do I take the one that’s hot out of the mold?
Hi Kristyl, don’t bother anything until the resin has completely cooled.
I had this happen when I was adding dried flowers to a piece.
It smoked. It bubbled up into very a interesting form.
I let it cool and then added more 3 dimensional flowers and did a few more thin coats.
It is awesome and very unusual. Really like it.
Have not repeated.
Hello,
I am new to resin and want to make a crystal-shaped piece with some flowers. What would be some good advice? These are the dimensions 6 x 2.4 inches, 5.8 x 2 inches and 5.5 x 1.9 inches.
Thank you
Hi Lacey, welcome to the world of resin! We’ve got a bunch of beginner articles to get you started here: https://www.resinobsession.com/tag/beginner/
Oh my I crafted with resin for the first time and two of my very large pieces smoked, bubble and needless to say those projects are no good. I wish I had watched your video beforehand. Living and learning is a good teacher. I am glad nothing burned up here…LOL
I am too!
I am told for large deep molds i need to use a deep mold solution?
Hi Marsha, yes, using a deep pour epoxy is best for deep molds. We have some in our store here: https://shop.resinobsession.com/collections/resin/resin-obsession-deep-pour-resin
Help!
This has happened to me! I had an order to preserve fondant wedding toppers. But now my resin has overheated and gone rock solid. I’m going to leave it over night but any suggestions on how I can save the fondant toppers? (If they haven’t burnt as well)
Hi Maisie, I’m afraid you’ll have to cut the topper out of the resin, then sand as much off as possible before recasting.
just happened to me today and it made me sick to my stomach. I wasted $300 worth of product. I had mixed my resin then the colors and it said I had a longer working time because the product is specific for countertops. Nope. Then my iPhone fell off the ladder and broke the back glass ( it was delivered 2 days ago) and then one of the horses got sick, refused to load in the trailer to go to the vet, reared up and cracked his head. The vet came here and had to put a drain in and stich him up. It’s all the darn epoxy’s fault! …. But seriously , now I feel like I’ve lost my confidence to finish my 81 year old moms countertop. That’s all that’s stopping her from moving in the tiny house we built for them. I can’t believe epoxy is kicking my butt.
Oh goodness, Melissa, I’m sorry to hear this. 🙁
I mixed and poured my epoxy into my project I’ve been working on in my shop and waited around for about 15 to 20 minutes to make sure I got all the bubbles out then went inside the house for probably a half hour. When I went to check my project the epoxy was hot and hardened up and it has a crap load of micro bubbles in it causing it to look cloudy. What did I do wrong. I’m gonna try to cut as much of the epoxy out and try it again. If anyone can help out so that doesn’t happen again I would appreciate it.
I found this article about overheated epoxy resin! It was very helpful in understanding the potential risks of using epoxy resin, as well as steps to take if you encounter an issue. This information is invaluable and has saved me from some unfortunate accidents!
Also why did it turn a reddish yellow colour when it hardened? That is pretty weird.
The red and yellow colors are from the flowers I included in the project.
Had the same situation today and I was baffled. When I first started working with resin I did not have the same reaction…I had about 10 min window to work with it and it was fine…but today when I started with a project again the resin started smoking and getting really hot. I was informed beforehand that it may do this so I did not panic, and took the cups outside to cure.
So I searched in Google and came across your site. And now I may have an insight on what may have caused the overheating. I guess the hot weather may have played a huge role, cause it’s summer here and I live in Cyprus so it gets pretty hot. So I just wasted a good amount of resin and money. :S
Next time I will have my AC open or just work in the evenings.
Previously I was working with my resin in the winter months so understandably the weather was way cooler and this did help keep the resin cool untill pouring.
Well now I will be more prepared. 🙂
I saw my resin start smoking so I picked it up and put it in front of an AC. I live in nj and I had my door open for ventilation, I didn’t realize my room was 80°. After setting it in front of the AC for about 5 minutes the resin cooled back down to a normal temperature. The middle completely cures in about 10 minutes when it overheated but the outside is now curing at a normal temperature. This was my first time deep casting flowers so I think the layer was too deep and the room was too hot which caused the resin to overheat. Learn from me! Lol
How do you get bubbles out of a resin that is having an exothermic reaction? The previous resin I used didn’t get hot and I was able to use a heat gun on low setting to get bubbles out. I’m now using superclear resin and it seems to get hotter so I’m not sure the best way to get bubbles out??
Hi Valerie, if the resin is heating too quickly, you won’t be able to get the bubbles out quick enough. How much of the super clear resin are you mixing at once?
Hello,
I have been trying to find what temperature the mixed resin will reach during the curing process. I have contacted the resin maker but all I get from them is that the working area should be in this xxx xxx range. That is NOT what I am trying to find out.
I would like to know at what temperature the mix should be when I start to pour in order to be able to maintain colour separation.
Even the supplier is unable to tell me!
Would anyone out there have this information?
Many thanks,
Barry.
Thank you for sharing your experience with epoxy resin! It’s indeed crucial to follow proper procedures to avoid overheating and ensure successful curing. Learning from mistakes is valuable, and your teachable moment serves as a reminder for all resin enthusiasts. Keep experimenting and creating! 🌟🔥🎨
Thanks for the support!
My resin went very hot got it out of pot, and put on to a mold to cool down. What I want to know can I put the hot resin into cold water as I felt scared, that it would go on fire.
You can definitely put it in cool water! I’ve had epoxy get so hot to the point it started bubbling and smoking but no fire, so don’t worry. Unfortunately, the epoxy is no longer going to give you the results you wanted. Discard that epoxy once cool and try again making sure to use the correct amounts and only pouring the recommended amount at a time!