Fish Eyes in Epoxy: Causes, Fixes & Prevention

You pour your epoxy, everything looks smooth, and then small craters start opening across. the surface. Those are fish eyes in epoxy. 

Fish eyes, sometimes called craters, happen when epoxy pulls away from certain areas instead of flowing evenly across the surface. They're frustrating, but the cause is usually pretty simple: something is interfering with epoxy's ability to properly coat the surface. 

Here's what causes fish eyes, how to fix them, and how to prevent them on your next pour. 

Start With The Right Epoxy

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What Causes Fish Eyes in Epoxy?

The most common cause of fish eyes is surface contamination. Even a small amount of residue can cause epoxy to separate. Common culprits include:

• Oil or grease
• Wax or furniture polish
• Fingerprints
• Cleaning-product residue
• Dust
• Uncured stain, paint, or sealer

Fish eyes can also happen if the surface is too smooth or if the epoxy coating is applied too thinly. If the epoxy keeps pulling away from exact same spot after you move resin back over it, contamination is a strong possibility.

Fish Eyes vs. Bubbles

Fish eyes and bubbles may look similar, but they're different problems. Bubbles are pockets of air trapped completely in the resin. Fish eyes look more like small craters where the epoxy has pulled away from the surface underneath and ruin the smooth glass like coating. Heat can help release bubbles, but it usually won't solve a fish eye caused by contamination. 

How to Fix Fish Eyes in Epoxy

If fish eyes have already appeared, avoid repeatedly pushing wet epoxy back into the crater. It may fill temporarily, only to open again. For a more reliable repair:

1. Let the epoxy cure according to the product instructions.
2. Sand the affected area until the surface is smooth and level.
3. Thoroughly remove sanding dust and any possible contamination.
4. Make sure the surface is completely dry.
5. Apply a fresh coat of epoxy at the recommended thickness. 

The key is fixing the cause underneath the fish eye, not just filling the crater. 

How to Prevent Fish Eyes

Most fish eyes can be avoided with good surface prep. Before pouring epoxy:

• Start with a clean, dry surface.
• Remove grease, wax, polish, oils, and other residue.
• Allow stains, paints, and sealers to fully cure.
• Sand surfaces appropriately before recoating.
• Wear clean gloves after your final surface prep.
• Avoid silicone sprays and polishing products near your workspace.
• Use clean mixing and application tools. 
• Apply your epoxy at its recommended coating thickness. 

Previously finished furniture or wood deserves extra attention. A surface can look clean while still holding. 

Can You Pour Another Coat Over Fish Eyes?

Yes, but simply pouring more epoxy over the problem usually isn't the best fix. Allow the original coat to cure, sand the fish eyes completely level, properly prepare the surface, and then pour another coat. If the contamination is still there, the fish eyes may come right back. 

The Bottom Line

If you're seeing fish eyes in epoxy, start with your surface prep. Oil, wax, fingerprints, previous finishes, and other contaminants can all cause epoxy to pull away to form small craters. Let the affected coat cure, sand it smooth, clean the surface thoroughly, and recoat. 

A little extra prep before the pour can save you a lot of sanding and epoxy resin in the long run. 

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