Why is my resin hot? – Reasons for hot resin – Resin getting hot

why is my resin hotIf you are wondering ‘Why is my resin hot?’, let me assure you that it is a perfectly normal occurrence. It can be a little concerning to feel your resin mixing cup warm up in your hands, but this should be expected. In order for a resin and hardener mixture to cure, an exothermic reaction takes place when the two liquids are combined producing heat, which allows the blend to solidify. However, there can be too much of a good thing and resin that gets too hot will cure in unexpected ways.

How will you know if your resin is too hot?

*Pot time is shorter than expected.
*The cured resin mixture cracks.
*The resin fills with bubbles (it can look very foamy), smokes and/or melts your mixing cup.
*You notice excessive shrinkage of your resin casting after filling a void or removing from a mold.

How does resin get too hot?

1. You mixed too much resin and hardener at once. Resin kits have a minimum and maximum mixing amount. Too much resin and hardener mixed together produce too much heat too quickly.

2. You added something to the resin and hardener mixture to cause it to heat up too rapidly. While it’s always fun to try different things to color resin, we don’t know every possible outcome. When using paints and other solvent-based colors in resin, these can sometimes speed up the resin curing reaction and cause the mixture to heat up too quickly.

3. Your resin and hardener components were too warm when you started working with them. I am a big fan of warming your resin kit bottles before use as it helps to reduce the bubbles in your resin mix. However, adding this extra warmth to the bottles ‘jumpstarts’ the resin reaction and can make your resin mix get warmer much sooner than expected.

4. You applied too much heat with a heat gun, torch, etc. to remove bubbles. That heat also adds to the heat of the resin reaction.

How can you keep your resin from getting too hot?

Mix no more than the manufacturer’s recommended mixing maximum. This information can sometimes be hard to find. You may need to contact the resin manufacturer directly to get this data. Note: For all the resins sold on Resin Obsession, we have that information for you in the PDF in this article on resin casting.

Mix and pour several batches of resin if necessary. If the amount of resin you need for your project is more than the maximum recommended to mix at once, mix and pour smaller amounts several times. Note: The heat from the mixes is additive. If the layer you just poured is hot, that heat will transfer into the next layer. You may need to wait several minutes to allow the heat to escape from the first layer before pouring the next layer.

Use a slow curing resin. Some resins can take hours to days to cure. They generate heat slower and are less likely to give you the problems listed above.

Maintain a cooler than normal ambient temperature in your work area. While the low 70’s F is the ideal working temperature for casting resin, you may want to work in temperatures in the 60’s F if you are worried your resin mix will get too hot.

Find something that you can use to absorb some of the resin heat. Metal objects can serve as a heat sink which means it will absorb some of the resin reaction heat. This is a great option if you are casting into a vessel. A metal trivet can not only hold the project, but can help to absorb some of the heat.

Confused about why is my resin hot and other things when it comes to creating with resin?  I get it.  I’ve been there too!  It’s why I wrote the book Resin Fundamentals.  I’ve taken my fourteen years of resin experience and turned it into an easy to read book that details the important factors you need to know to make something amazing with resin.  Buy a copy of the PDF ebook and it arrives to your email inbox in minutes!

Unpublished Blog Posts of Resin Obsession, LLC © 2021 Resin Obsession, LLC

Like this post? You may be interested in  Tips for working with epoxy resin

37 thoughts on “Why is my resin hot? – Reasons for hot resin – Resin getting hot

  1. What is hardner n what can I use to make resin is it clear vanish n what please help i want to start mine thank you

  2. The very first time I kept it very simple. I did add a tiny bit of teal green to it though. I had no idea how much to use since this was my first time. The heat startled me at first. I read everything you post and all your tutorials and tips and remembered it was to be expected. It has also been my best one so far, believe it or not. Lol…I am finally starting to get a few orders from some classmates. One lives out of town and wants me to mail her the earrings. I did let her know that I will wait over a week before I send them because they go in and out of the heat and I want to be sure they won’t droop in the heat. I need to make another order but I will have to wait for my payday. I ran out of small cups. Our local CVS pharmacy gave me ten to tide me over. I also want some of the shaved glass to attempt more druzies.

  3. I mixed a large amount of resin to cover a 4 x 5 foot painting. I had the resin in a warm water bath be cause it was a cool day and I was working outside. The water must have been too warm because I felt as soon as I was mixing the two it was getting hot. it was hardening as I poured it. The resin was smoking and it poured out of my mixing bucket in a big clumpy mess. I ruining the artwork. Lesson learned, if you are going to warm resin in a water bath keep it luke warm.

  4. How do I keep things that I insert into resin from floating and/or moving. Toobies rise, won’t stay where I want them

    1. Hi Nancy, you will either need a more snug fit on the toobies or pour in layers, embedding the toobie in the layer of resin where you want it to stay.

  5. I’m resining boxes so I need to tape the sides I don’t want resumed. I use good blue tape and go around the edges twice. The resin still leaks sometimes and ruins other sides of the box. Any suggestions for the type of tape and what I lm doing wrong?

    1. It sounds like the tape isn’t getting a good adhesion. Make sure the surface is clean before applying the tape.

  6. I am making a paperweight but ran out of epoxy resin so by the time I bought more (2 days) the resin in the mold had gone hard. I added another layer but forgot to sand the hard resin first. Will it cure okay?

  7. I’m trying to save flowers from moms memorial and it keeps burning the flowers what am I doing wrong plz plz plz help me

  8. This is my second attempt and second mold ruined. Initially, everything looks fine with minimal bubbles, but when I check back in about 30 minutes, there is significant bubbles and the mold has deformed/melted. I am making 8 paperweights with wedding flowers as thank yous for my bridesmaids so I would like to get the process down. I only mixed 3 ounces of your super clear resin at a time as is recommended. I am using your 8 ounce paperweight mold. I made sure the room is not too cold and sprayed the flowers with spray resin first. What am I doing wrong? I’m about ready to give up.

    1. Hi Meghan, I’m glad to hear you only mixed three ounces of resin at once. That’s good. It still sounds like everything is getting too hot though. How much did you put in the mold at once?

  9. I was mixing and pouring some resin into molds. I had put 4 drops of food coloring and about .5grams of micah powder. I had done this previously with excellent results but this time about 45 minutes into pouring my mix heated up to the point that it melted the pipettes i was using and burned my fingers. Being so hot hardened the mix instantly to an unusable state. What exactly did i do wrong?

    1. Hi Cristina, I’m sorry to hear this happened to you. There are several reasons why this could have happened. Do you know the maximum mixing amount for the resin you are using?

  10. I have just started using art resin and somewhere i read that using a little extra hardner can make the resin rock hard. I wanted that for my coasters and ended up adding a little extra hardner. All my coasters are cracking from the bottom now. The designs are stunning yet they are all cracking nd i dont know wot to do. The top is fine. I have no idea if its because i didnot use exact volume. Can you please advice me on this?

  11. I put small drops of acrylic paint into my resin and mixed it before pouring into a mold. Within an hour, the molds were hot (as they normally are) but this time very hot. I then realized I could remove them from their molds. After reading your tips/suggestions, I’m wondering if the acrylic caused it to a flash reaction and cured it? I’ve done this before (using acrylic) with a few molds and had to wait a whole day for it to cure. I’m wondering if it’s the outdoor temperature or perhaps the speed I mixed the components?

  12. Hi our Granddaughters husband built a farm table they are using resin on the top but there are small parts the resin wouldn’t cover. Any thoughts?

  13. Hi I am trying to make a 85mm paperweight with cremation ashes added I’ve been working on it all day doing 1.5cm layers I’m about and inch from top have just put another layer about 2cm and the whole thing has heated up and is rock hard Is it now ruined ? Do I carry-on doing my last layers. I’ve added next layers at Gel stage.
    Any advice most welcome

  14. I am building a 1/35 scale plastic World War 2 tank which will be partially submerged in a “pond” diorama. The cured resin will be the “water” in the pond & around the tank.
    The pond will be XPS foamboard covered with a thick coat of spackle, mod podge & paint. I was told to use floral epoxy & to pour several small layers to minimize excessive heating. Do you think this will work without damaging the plastic tank or melting through the bottom of the “pond”? Thanks

    1. Hi Jeffrey, while I haven’t done anything exactly like this, I wouldn’t expect the resin to heat up so much that it damages the tank.

      As for the resin, For pours of 3 ounces or less, the Resin Obsession super clear resin is what you want: https://shop.resinobsession.com/collections/resin/resin-obsession-super-clear-resin

      For pours of 3 ounces or more, the Resin obsession deep pour casting resin works great: https://shop.resinobsession.com/collections/resin/resin-obsession-deep-pour-resin

  15. Hello. I’m manna and I’m attempting a floating shelf with epoxy resin. Any suggestions to keep it from cracking or melting my mold?

  16. Hi! I’m new to resin and have been reading and researching up on it for ages and I’ve finally begun 😊 my first project was a book mark and it came out alright. My second though, I’m trying to make a coaster and I mixed in some acrylic paint to it as well as dried flowers. I let the resin sit for about 10 min after mixing before pouring and I noticed the cup was getting very hot and when I poured, the resin was was thick and had a honey consistency. My paint didn’t mix in the way I wanted it to either.😢 I tried to add the recommended amount of paint 1 :10 ratio but it didn’t colour my resin completely
    finally, although I torched it as much as I could, there were still many bubbles left inside. I also tried to burst them with a pin and a toothpick that’s been sealed with resin. Please help me… What did I do wrong 😥

    1. Hi Nihla, have you had a chance to review this article yet? There are several things that could have gone wrong.

  17. I made a large amount and put it in a glass vase. It has got very hot. Is this likely to crack the vase. How can I cool it down

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