Is Your Epoxy Smoking? Here’s What You Should Know


Blue and Red Resin Smoke

Working with epoxy resin can be incredibly fun as well as mesmerizing. Whether I am pouring a cast or adding to a river table I love the process all around. When pouring epoxy, it is important to stick closely to the directions. Similar to the precise requirements for baking, most epoxies have temperature, mixing, and pouring requirements – and they are very important to adhere to. Otherwise, your end product could be a disappointing flop which can be incredibly frustrating.

Why is your epoxy smoking? When epoxy and a hardening agent are curing it generates heat. If there is a large quantity of epoxy poured, the heat generated builds upon itself and can reach temperatures of 400°F (205°C) or even higher. This is likely to cause smoking, and it can also melt its container, foam, and let off (potentially) dangerous fumes.

This heating of the epoxy is what is known as an exothermic reaction (or just “exotherm”). (A standard exothermic reaction is a chemical reaction in which heat or light is released.) Exotherm is a desired chemical reaction to cause curing of epoxy, however it can go too far when not managed or controlled. Below I will examine the causes of uncontrolled exotherm and how to avoid them. 

Why Does Epoxy Get Hot?

Anytime you work with epoxy in large quantities, you are likely to experience noticeable levels of heating. It may be as simple as just the cup you mix your epoxy in getting warm, or it could be as detrimental as melting and ruining the mold or container. 

The main reason that epoxy gets so hot is due to the exotherm during the curing process. When base epoxy resin and the hardener (curing agent) are mixed, there is a chemical reaction that causes them to heat up. This helps with the curing process itself. Too hot of temperatures can add to the issue, though, which is why you should be mindful of when and where you are pouring.

The heat should not exceed high temperatures that could damage your mold or container. In general, you want to make sure that your curing epoxy stays cooler than 100°F (38°C) or thereabouts. However, each brand should have a specific temperature that it should not exceed, so be sure to pay attention to your product’s specifications. Even if it is not smoking or foaming, too hot of a cure can cause your epoxy to crack. In order to prevent this, follow best procedures and read our tips below. 

Other Reasons My Epoxy Resin is Smoking

While the most common reason your epoxy is smoking is from the exotherm during the cure, there are a couple of other reasons you may be experiencing the smoking effect. Consider the following:

  • You mixed too much epoxy at once.
    All epoxies have their minimum and maximum amounts to be mixed. If you exceed the maximum amount, there is a good chance that the exotherm will set in too quickly resulting in an exponential heat increase. This means that you could see smoking or even melting of the container that it was mixed in.
  • Using a torch to put out the bubbles.
    A common practice for removing the bubbles that appear on the top of epoxy is to use a small propane torch or heat gun. While this works well for this purpose, if it is done improperly, you can cause the epoxy to smoke. When applying the heat from the torch, you likely applied it too slow which caused it to heat up a small part of the epoxy and, thus, cause smoke. While this can occasionally ruin the cure, it often does not if it was only smoking for a second. 

Can Curing Epoxy Start a Fire?

If you have experiences of smoking, foaming, or fuming epoxy during the curing process – you may be worried about the possible repercussions of using it. While there are some dangers involved, you should not fear if you simply follow safety procedures. Even when being as safe as possible, it is best to be aware of what can happen. This can help to prevent the more serious repercussions that you may be concerned about.   

Can curing epoxy catch on fire? It is unlikely that the curing epoxy can get hot enough to catch itself on fire; however the high temperatures could cause the wood or mold that it is setting in to catch on fire. This means that there are fire hazard risks when working with epoxy.

Do not worry about the fire hazard too much, though. This is a very uncommon situation, although there have been reports of it occurring. As long as you are following directions and paying attention to the information provided here, you can remain worry-free.

How to Stop Epoxy From Smoking?

You just poured your epoxy. After a few minutes, you begin to notice that it is smoking a little. This can be one of the most mind-boggling and worrisome things for someone who has not experienced it. All of your hard work, time, and concentration literally up in smoke? Do not fear- there are measures you can take to fix this problem. 

How to stop your epoxy from smoking? The best way is to prepare ahead of time with appropriate setting, temperature, amounts, and tools. If your epoxy is currently smoking, do what you can to lower the temperature. On the off chance that it is a small cure, bring it to a fridge or cool basement or garage. For a large cure, try adding fans around it and turn on the air conditioning. 

If you have not already poured, here is how to prevent epoxy from smoking:

  1. Read all directions thoroughly. Reading directions is the first and easiest precaution to take. A manufacturer will have very specific instructions with amounts and temperature for epoxy pours. Following these specifications precisely will help to prevent any issues.
  2. Use a wide container for mixing. While you may be following the amounts suggested by the directions, tall and thin containers still cause too much epoxy without enough ventilation and space. Using something like a plastic, gallon ice cream bucket for a small pour or a 5-gallon bucket for a large pour can help spread it out so you do not have too much material in one area.
  3. Using multiple pours. It is recommended that you pour the epoxy in short layers, usually ⅛” – ¼” to help minimize the exotherm. Make sure to not let it fully-harden between pours, or it will have an insufficient bond. Again, precision is a critical component here.
  4. Work at cooler temperatures. A great way to prevent a high exotherm is to keep a low temperature. While many epoxies will say the range should be 70°F (21°C) to 80°F (27°C), if you know that your epoxy gets hot, keeping the area around it cool can help. I have personally never had issues curing around 60°F (15.5°C) or even slightly less. 
  5. Run fans if needed. Many large shops, such as Black Forest Wood Co. will run fans around their epoxy tables as they cure. This is a great way to keep the epoxy cool and reduce heat-related incidents. The only downside to this is the risk of dust mixing with your product, so make sure to monitor for that as well. 
  6. Apply epoxy on a cool, dense surface. While wood and HDPE are common for making epoxy molds, you may want to reconsider. Using a sheet of metal can help control the heat by transferring the extra heat. This is similar to the way food thawing trays work. Just be sure not to apply heat directly to the metal, as this would defeat the purpose. Rather, find an insulating material (like a cloth towel) that can rest on the metal without touching your epoxy mold which will help to keep the product and tray at an even temperature.
  7. Use an epoxy made for deeper pours. Many epoxy resins are now being manufactured to allow for thick pours. This means that the traditional partial-inch pour is able to be abandoned by using these epoxies. Below I will include some of the top epoxies that will not get as hot when curing. 

This may not be an entirely comprehensive list for controlling exotherm in epoxy, but it is definitely a great place to start. Be sure to follow the manufacturer’s instructions closely, but also reach out to other, more skilled, workers if you are having any issues with these steps. 

If you have already poured, here is how to prevent smoking

  1. Get the curing epoxy to a cool area. If the smoking has started, and it is a small mold, you might be able to run it outside (if it is cool out there), to a fridge, or down to a basement/garage that is cooler. This will help the transference of heat and dissipation of smoke.
  2. Bring in fans and know when to use them. Fans were stated before as a precautionary item to have on hand. One way to know if you should run them (and risk the dust) would be to use a temperature gun to monitor the temperature. If you start getting high temps that you are worried about causing smoke, begin using fans to moderate the temperature. 

Will Epoxy Getting Too Hot Ruin the Cure?

If your epoxy is getting hot, you may begin to get worried about the state of the epoxy. The most important thing to do is bring the epoxy back down in temperature. After you have stabilized the curing epoxy, then you can worry about the future of the project. It is much better to resolve small issues quickly than to wait until they are more catastrophic.

Does heat ruin epoxy curing? The only answer is: sometimes. If your epoxy was too hot for a prolonged period of time, there are likely going to be some ramifications. The main problem that users see is a cracking in the epoxy. This happens when part of the epoxy gets cured and the other half is hot – causing a heat differential (similar to how ice cracks in warm water). 

Overall, heat will not ruin your epoxy cure unless it causes a fire or is left to smoke for too long. Most of the time, though, cracking is a fixable mistake. Do not worry about the heat coming from epoxy unless it is much higher than expected. Moderate amounts of heat are a natural part of the curing process.

Epoxy Resin Curing Temperature and Time

With all the worry about overheating during the epoxy curing process, I wanted to add in a short section about appropriate curing temp and times. 

The ideal curing time for epoxy varies quite a bit from type of epoxy, brand, and depth of pour. In general, you should keep the temperature around 70°F (21°C). The time will vary depending on your product, but in general it is hard after sitting for 24 hours, but to be fully cured can take anywhere from 2-5 days. 

With all this variation, the most important thing to remember is to know your epoxy. It is critical to read the labels and to purchase the epoxy that works well for the requirements you are able to meet. 

Epoxies That Will Not Get as Hot

It can be hard to know what epoxies will work well with deep pours. Below are my top two recommendations for projects that require deeper pours. This could be river tables, casting, or anything else that you might be able to think of. 

EcoPoxy FlowCast

EcoPoxy FlowCast is one of the latest updates to the EcoPoxy lineup. It boasts anywhere from a 1.5” – 2” pour thickness, allowing you to work with most home pours. It can be best worked on at 70-80°F (21-27°C) which should also be easy to maintain in your home or shop. FlowCast also has no VOC’s, making it safe to use and a low viscosity which allows for bubbles to easily rise to the surface without coaxing. 

EcoPoxy, as the name suggests, is also a highly sustainable company. They are working towards a completely natural product. It is currently the most bio-friendly and I assume that it will keep that title for the foreseeable future. Using a product that is both suitable for deep pours and safe for the environment will surely put your mind at ease as you create lasting projects with killer designs! 

Chill Deep Pour – Polymeres Technologies

Chill Deep, as the name suggests, is a deep pouring epoxy. This particular epoxy is rated for 2”-2.25” deep at 68-72°F (20-22°C). This is one of the deepest pouring epoxies on the market. Polymeres Technologies is an amazing brand – they supply top grade epoxies for tons of markets. They have the chemistry and labs to back up everything they do.
While I love everything that this epoxy has to offer, there is one downside. It is rather difficult to find this epoxy. Sometimes you can find it on Etsy or Ebay, but likely you will need to contact them to get either a referral to a local realtor or order directly from the company. This may make using this product consistently a bit challenging, but the quality is so worth it.

Related Questions

How to Cure Epoxy Resin Faster?

It is not suggested that you try to expedite the curing process by too much. That being said, if you are working at room temperature, you are able to heat up the epoxy to increase the cure time. This is best done by raising the temperature, whether that is by heating the room, using a heat gun, a space heater, or even placing a warm light around it. 

If you are working in hot environments, it is not advisable to speed up the curing process or it could cause smoking and cracking. While there are plenty of reasons you could come up with for wanting to speed up the curing process, these are the kind of projects that are worth the wait.

Why Is My Resin Still Sticky?

Resin that is still sticky is caused by the chemicals not curing well. The most common reasons are:

  1. An improper ratio of epoxy to hardener
  2. Not mixing the curing agent and epoxy well enough
  3. Cold curing temperature that did not exotherm properly during the process

You are able to fix this, first, try giving it extra time – thin epoxy coats often don’t heat as well and need the extra time. You can also scrape off any sticky spots, sand any hard spots, and then pour another coating of epoxy over it to get a proper cure.

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