Epoxy resin cracking – Why does resin crack?

why is my epoxy resin crackingYou created a fantastic resin casting only to check on it later to find spider-like veins running throughout. Your resin has cracked! Unfortunately, epoxy resin cracking happens most commonly when resin gets too hot, then cools off quickly.

Why does epoxy resin get hot?

For two-part resin to harden, you must mix the Part A resin with the Part B hardener. Once combined, the resin mixture heats up and eventually hardens into a solid mass. While a little bit of heat is standard, too much heat can cause epoxy resin cracking.

How do you fix epoxy resin cracking?

Wait for the resin to cure and cool down fully. Then, sand the resin down to the level of the crack. You can then coat it with a tabletop coating resin or polish the resin through other methods. You can also cut out the area of the damage and refill it with resin.

What if you don’t fix the resin cracks?

If there is only a crack or two, and you don’t mind the look, you can leave the resin cracking as is. Many people won’t notice. If there are multiple cracks, or if you’re worried the piece’s structural integrity is compromised, then scrap the work and start over. You don’t want anyone to use what you’ve made with resin, only to have the piece fail later.

How can you prevent epoxy resin cracking?

Controlling epoxy resin cracking means controlling the heat of the resin reaction. To do that, there are three things you need to pay attention to:

1.  Don’t mix too much resin and hardener at once

Resin kits have a maximum mixing amount. This is the maximum amount of resin and hardener you should mix together in one cup at one time. Mix more than this, and the resin will overheat and crack. For the resins sold in the Resin Obsession store, we share the maximum mixing amount for each formula in our resin buying guide.

2.  Don’t pour too thick

The thicker you pour resin layers, the more heat that builds up in the resin mass. If you need to pour in thick layers, use a resin designed for that purpose. The Resin Obsession deep pour epoxy resin cures slowly, allowing heat to build up gradually. Because of this, you can pour it up to two inches thick at once, which makes it an ideal resin choice for epoxy river tables and memorial flower paperweights.

3.  Cool the resin

While it seems a little odd to say this, cooling epoxy resin may be necessary during the curing phase. You can do this by elevating the mold surface and allowing cool air to circulate underneath. You can also lower your room temperature.  We have deep pour epoxy resin tips to help you with this too.

Lastly, you should always be prepared for epoxy resin cracking. In extreme cases, your resin may get hot enough to smoke or catch its container on fire. You can see what happened to me when my epoxy resin overheated and cracked.

Stop making resin mistakes!

For less than the cost of an epoxy resin kit, you can get a copy of my eBook, Resin Fundamentals. I’ve condensed my fourteen years of resin experience into the essential details beginners need to know about resin to have success from day one! Buy the book now and get a download link in your email inbox in minutes.


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

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4 thoughts on “Epoxy resin cracking – Why does resin crack?

  1. I’ve been doing large or 4×6 photos cubes and my constant battle is bubbles micro now after being advised to pour in small amounts. I also notice the lines between pours that are driving me nuts. I’m more concerns with the micro bubbles. I’ve research and what I’m finding is something about a pressurized process which seems to be a bit much. please help.

  2. Hi I have been making tumblers and I bought the amazing brand resin epoxy. I tried the 2 small bottle and the epoxycame out nice and shinny. I purchased the half gallon jugs the epoxy dries with fine cracks all through the epoxy like shattered glass. We cant get it to stop doin it no matter what we try. Any help would be helpful. Thank you

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