Why does my epoxy resin get hot and start smoking?
Working with epoxy resin can be very rewarding and creative, but when the epoxy resin gets hot or starts to smoke, it's often a cause for concern. Understanding why epoxy resin generates heat or smoke is important for achieving safe, high-quality, and durable results.
Understanding the exothermic reaction in epoxy resin
Understanding the exothermic reaction in epoxy resin is crucial for safe and successful processing. During curing, the resin and hardener react chemically , releasing heat —this process is called an exothermic reaction. The larger the amount mixed or the thicker the layer, the more heat is generated. If the temperature is too high, the epoxy resin can overheat, form bubbles, or even smoke.
Common causes of overheating and smoke development in epoxy resin
1. Too large a mixing quantity:
Mixing large quantities of epoxy resin can trap the heat generated in the mixture, accelerate the curing process and cause the resin to overheat. It is therefore advisable to mix smaller batches to allow the heat to dissipate more easily. If too much resin is mixed at once, the heat builds up in the cup, causing the epoxy resin to heat up very quickly, smoke or cure prematurely.
2. Incorrect mixing ratio:
An incorrect mixing ratio of epoxy resin and hardener can also lead to problems. If too much hardener is used, the chemical reaction accelerates significantly, causing the resin to heat up faster, overheat or even smoke. On the other hand, too low a ratio can prevent the resin from curing properly, leaving it sticky or soft. It is therefore crucial to mix exactly according to the manufacturer's instructions to ensure safe and even curing.
3. High ambient temperature:
Working in a warm environment can intensify the exothermic reaction of epoxy resin and increase the risk of overheating. To better control the curing process, the room temperature should be kept as constant as possible at around 22–25 °C, ideally with low humidity. This reduces heat generation and ensures uniform, safe curing of the resin.
4. Excessive layer thickness:
Pouring epoxy resin in layers that are too thick can lead to significant heat build-up, as the heat generated during curing cannot escape easily. This can cause the resin to overheat or even smoke. Applying thinner layers ensures better heat dissipation and safe curing.
The various types of Artline epoxy resin each have recommended maximum casting thicknesses to prevent overheating and achieve optimal results:
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Casting epoxy resin: maximum layer thickness up to 2 cm per layer
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Deep casting epoxy resin: maximum layer thickness up to 5 cm per layer
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Deep pour epoxy resin: maximum layer thickness up to 12 cm per layer
By adhering to these guidelines, you can avoid bubble formation, smoke development and unwanted heat effects and achieve a clear, stable result.
5. Unsuitable mould or mixing container:
Deep, narrow beakers retain heat and intensify the reaction. Use shallower mixing vessels to allow the heat to escape.
Signs that your epoxy resin is overheating
If epoxy resin becomes excessively hot during curing, this can lead to problems. Typical signs of overheating are:
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Significant increase in temperature
The resin feels unusually hot in the beaker or on the surface.
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Smoke or vapour:
The resin begins to smoke or emit vapours, indicating that the reaction temperature is too high.
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Rapid curing:
The epoxy resin cures much faster than usual and is difficult to work with.
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Yellowing or blistering:
Overheated resin can yellow, become cloudy or form blisters, especially in the case of clear resins.
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Sticky or uneven surface:
The surface remains soft or sticky, while the underlying layers are already hard.
These signs should be taken seriously, as overheating not only affects the quality of the result but also poses safety risks.
Tips to avoid overheating with epoxy resin
Mix smaller quantities
Limit the amount of epoxy resin mixed at one time to reduce heat buildup. Follow the manufacturer's instructions for recommended batch sizes.Pour in thin layers
Apply the resin in layers no thicker than recommended, allowing each layer to fully cure before applying the next. This will control heat buildup during curing.Control room temperature
Work in a well-ventilated area with a stable, moderate temperature to prevent external heat from accelerating the curing process.Monitor resin temperature
Use a thermometer to monitor the temperature of the epoxy resin during mixing and curing. If the resin gets too hot, you can cool it down, for example, by spreading it in thin layers.
Quick measures in case of overheating of epoxy resin
Move resin to a cooler place
Move the resin to slow down the curing process and lower the temperature.Spread the resin thinly
By spreading it out in a thinner layer, the heat can be dissipated more effectively.Do not add any additional components
Do not add more hardener or resin to the mixture, as this would further accelerate the reaction.Be careful when there is smoke
Ventilate the area well and allow the resin to cool completely before touching it.
Why Crystal Clear Epoxy Resin is the Best Choice to Avoid Overheating
At Crystal Clear Epoxy Resin, we know how frustrating it is when your project overheats or smokes during curing. That's why our products are designed with advanced temperature control technology to minimise the risk of exothermic reactions.
That's why Crystal Clear Epoxy Resin is ideal for beginners and professionals alike:
✔️ Controlled curing time
Our resins offer an optimised working time, giving you more flexibility when mixing, pouring and layering. This controlled reaction helps prevent overheating, even on larger projects.
✔️ Perfect for thin and medium pours
Our specialised formulas adapt to your project requirements:
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Art & Craft, Artwork & Topcoat, Ocean Wave and Super Gloss are ideal for thin to medium layers up to 1 cm, perfect for art, jewellery and surface coatings where clarity and detail are crucial.
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Deep Casting and Deep Pour epoxy resin are designed for thick castings. The slow-curing formula minimises overheating, cracking and bubbling, even with large volumes.
✔️ Safety tested
Each batch undergoes rigorous quality and heat testing to ensure safety, consistency and minimal smoke emission – even in warmer conditions.
✔️ Expert support
Our team advises you on best practices such as layer casting, selecting the right resin and safely handling additives and pigments.
Whether you are creating artwork, jewellery, table tops or deep casting projects, Crystal Clear Epoxy Resin helps you avoid the most common mistakes, especially overheating, and guarantees perfect results.