If you've ever found yourself with cloudy resin and you're not sure what caused it, you're not alone. Cloudiness can happen in both liquid and cured resin, and there are several possible causes.
In this blog, I'm going to look at 6 common reasons resin becomes cloudy, how to prevent it and what you can do to fix it, when possible.
Understanding The Resin Curing Process
First, let's get back to basics. Epoxy resin starts with two liquid parts: resin and hardener. When they're properly measured, thoroughly mixed and allowed to cure under the right conditions, they react and transform from a liquid into a clear, hard, glossy solid.
But when something interferes with that process, you can end up with problems like sticky resin, bendy resin, a greasy film on the surface, and ... you guessed it ... cloudy resin.
Common Causes of Cloudy Resin - Liquid
| Cause | Description | Prevention / Solution |
|---|---|---|
| Cold Temperatures (Liquid Resin) | Cold resin creates microbubbles and becomes cloudy and thick like taffy. These bubbles cannot be removed with a torch. | Use resin at room temperature (23–30°C / 72–85°F). Warm sealed bottles in a warm water bath before mixing. Never warm already mixed resin and hardener. |
| Under Mixing | Cloudy streaks remain if resin and hardener are not fully combined, leading to improper cure and soft, sticky resin. | Mix thoroughly for at least 3 minutes, scraping sides and bottom of the container until streaks disappear. |
| Whipping While Mixing | Whipping introduces excessive air, creating frothy, cloudy resin with lots of bubbles. | Stir slowly and methodically to minimize bubbles. Always scrape the sides and bottom of your mixing cup. |
| Matte Silicone Mold (Cured Resin) | A matte mold creates a matte finish on the cured resin surface, affecting glossiness. | Use molds with a glossy interior for a shiny finish. For matte molds, apply a clear resin topcoat after curing to restore shine. |
| Moisture Contamination | Cloudy or hazy areas caused by water content in tools, inclusions, or air. | Ensure all materials and inclusions are completely dry. Avoid working in humid or wet conditions. If damage occurs, sand down affected area and apply a fresh coat of resin. |
| High Humidity | Humidity above 80% can cause amine blush—an oily film and cloudiness on the surface. | Keep humidity below 80%, ideally around 50%. Use a dehumidifier or air conditioning before and during your project. Avoid resining during humid or rainy days if control isn't possible. |
1. Cold Temperatures
Resin that's colder than standard room temperature has a cloudy, milky appearance once mixed. That's caused by thousands of cold-induced micro bubbles. They're so small, you'll never be able torch them out - believe me, I've tried.
Cold resin also becomes thick and taffy-like, making it difficult to mix, pour and spread.
To prevent cold-induced cloudiness:
- Use resin at standard room temperature or slightly warmer (between 23ºC / 72ºF and 30ºC / 85ºF.)
- If the resin is cold, place the tightly sealed bottles in a warm water bath before measuring and mixing. This is really important! If you place mixed resin and hardener in a water bath, the warm temperatures will prompt it to flash cure.
- Store resin and hardener tightly sealed at room temperature.
2. Under Mixing
When you first mix the resin and hardener, it's normal to see cloudy streaks as the two parts combine. Keep mixing until those streaks disappear.
But if the resin is under-mixed, those cloudy streaks will remain, and you'll likely end up with sticky resin as well.
3. Whipping The Resin
It's important to stir the resin and hardener thoroughly, but there's no need to whip or beat it like a cake batter.
Vigorous stirring introduces a lot of air, creating a cloudy, frothy looking resin, with far more bubbles than necessary.
To prevent excess bubbles, stir slowly and methodically, scraping the bottom and sides of the mixing container as you go, until the resin is clear and there are no more visible streaks.
Common Causes of Cloudy Resin - Cured
4. Matte Silicone Mold
If you plan to pour resin into a silicone mold, pay attention to the interior finish.
Now, if your favorite mold has a matte interior, don't worry; you can still use it but you'll need to take an extra step: after removing the cured resin from the mold, either pour or brush on another layer of clear resin for a glossy finish.
5. Moisture
Moisture can cause resin to develop cloudy, white, or hazy areas, affecting its clarity and visual appeal. It can come from several sources including:
- Paint, glue, or sealant that hasn't fully dried
- Wet inclusions, such as flowers or leaves
- Water from wet tools or drips from a warm water bath
- Moisture in the surrounding air as the resin cures
The best prevention is simple: keep everything dry. Make sure all your materials and tools are completely dry before introducing them to resin.
Unfortunately, cloudiness from moisture is very difficult to fix because it's usually deep within the resin layer.
You can try carefully sanding down as much of the affected resin layer as you can, followed by pouring a fresh coat of resin, but there's no guarantee you'll be able to remove all of the cloudy resin, and you could damage the artwork below.
💡 TIP: To learn more, see our blog How Does Moisture Affect Epoxy Resin?
6. Humidity
High humidity can cause amine blush, characterized by a tacky or oily film and a cloudy appearance on the surface.
- Keep humidity levels below 80%, and ideally at 50%
- Use air conditioning or a dehumidifier to help reduce humidity
- Avoid working with resin in rainy or humid weather
Amine blush must be removed before attempting to apply a fresh coat of resin. Here are the steps:
- Amine blush film clogs sandpaper, so remove it by wiping the resin surface with a soft cloth and warm, soapy water made with a grease-fighting dish soap such as Dawn. The sticky amines are water soluble and should wipe away easily. Allow to dry and inspect for any remaining residue.
- If the film remains, you will need to wipe with something more abrasive like a Scotch-Brite pad. Allow the surface to dry completely and inspect: the scouring pad will likely have scuffed the resin surface and you will need to apply a fresh coat of resin.
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Use coarse sandpaper to rough up the cured resin surface, wipe away sanding debris with a clean, damp cloth, and pour a fresh coat of carefully measured and mixed ArtResin to restore the clarity. Cover and allow it to cure.
💡 To learn more, see our blog How Does Hot Weather Affect Resin?
6 Expert Tips To Prevent Cloudy Resin
For the clearest, glossiest results:
2. Use a Water Bath: If the resin is cold, bring it up to room temperature or slightly above with a warm water bath.
3. Warm Temperatures: Maintain consistent curing temperatures no lower than 23ºC / 72ºF and no warmer than 30ºC / 85ºF.
4. Dry Environment: Aim for around 50-80% humidity and avoid working in very humid conditions.
5. Keep Moisture Away: Ensure all materials are completely dry before introducing resin.
6. Check Your Silicone Molds: Use a glossy mold for a glossy resin cure.
These preventive measures will significantly reduce the chance of cloudy surfaces in your resin projects.
Fixing Cloudy Resin After Curing
If your resin has already cured cloudy, the best solution depends on what's causing the problem:
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Sand and Re-Pour: If the cloudiness is in the surface layer, carefully sand the affected area and apply a fresh coat of resin.
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Sand and Polish: For minor surface cloudiness, sanding with progressively finer grits and polishing may restore the clarity and shine.
Unfortunately, fixing cloudy resin may require multiple attempts or you may need to start over altogether, depending on the underlying causes and how deep the cloudiness is. Practice and experience will help you master the art of resin curing.
Cloudy resin can be frustrating, but once you know what to look for, it's usually easier to prevent.
For the best chance of a clear, glossy cure, follow the label instructions, keep your resin warm, work in a warm and dry environment, and take your time when mixing.
I hope this helps to clear up the mystery behind cloudy resin!
Do you want to learn more about troubleshooting epoxy resin? Read our guides below:
- Epoxy Resin Troubleshooting
- Why Is My Epoxy Resin Still Sticky?
- How To Harden Sticky Resin
- Amine Blush: What Is It & How To Prevent It
ArtResin: The Original Epoxy For Resin Art.
