Fish Eyes in Epoxy: Cause, Fix, and Prevention

Short answer: Fish eyes are usually caused by contamination: silicone, oil, wax, grease, or a dirty tool or rag. Clean the surface thoroughly, use clean dedicated tools, keep silicone products away from the work area, and do not recoat over a contaminated surface and expect it to fix itself.

Close-up of fish-eye craters in the clear epoxy coating on a wood tabletop

How to tell fish eyes from bubbles

Bubbles are round air pockets, on the surface or just below it.
Fish eyes are shallow craters where epoxy pulls away from a contaminated spot, often with a small bare spot or speck in the center.
If the defect repeats in the same spots after a recoat, suspect contamination, not air.

What causes them?

Silicone. Silicone sprays, polishes, mold release, and some lubricants are the classic cause, even in small amounts, and even from nearby spraying.
Oil, wax, or grease. Skin oil, oily wood, wax finishes, and greasy tools can all create bare spots.
Contaminated tools or rags. A rag or stir stick used with another product can carry the problem into a clean pour.
An incompatible previous finish. A surface that was not prepared, or that still carries an old finish the epoxy cannot bond to, can reject the new coat in spots.

Fix: after it has cured

Gloved hand wiping a sanded epoxy river-table surface with a cloth

Clean the affected area first with a lint-free rag, so sanding does not spread contamination.
Once the epoxy is hard enough to sand, sand the affected area smooth, so the craters are opened and level, then clean again. For Bar & Table Top Epoxy: if more than 10 hours have passed since the previous coat, lightly scuff with 220 to 320 grit, then clean with a lint-free rag and denatured alcohol or acetone, and let the cleaner evaporate fully.
Check the surface is fully clean and dry before recoating. If a spot still looks oily or waxy, clean and sand again.
Apply the approved recoat for the product and watch it. Bar & Table Top Epoxy flood coats are poured at 1/8 inch. Deep Pour Epoxy must not be applied thinner than 1/4 inch. If fish eyes return in the same spots, stop adding epoxy and contact UltraClear before another repair. Do not sand epoxy while it is wet or soft.
Test on a small area first if you are unsure whether a previous finish is compatible.

Prevent them next time

Keep silicone sprays and polishes out of the work area while you pour and cure. If a Deep Pour mold needs a release agent, use it only on the mold, keep it off the wood and off any surface epoxy must bond to, and let it dry before pouring.
Use clean, dedicated mixing and spreading tools for epoxy only.
Use clean lint-free rags, not shop rags that may have held oil or silicone.
Prepare the surface fully: sand, remove all dust, and clean before the first coat.
Wash and dry your hands, or wear clean gloves, before handling a prepared surface.

Questions about fish eyes in epoxy

Why do fish eyes return in the same spots after recoating?

The surface may still contain silicone, oil, wax, or an incompatible finish. Another coat does not remove that cause, so the epoxy can pull away in the same places again. Correct the contamination or finish compatibility before recoating, and test the prepared area. If the problem continues, contact UltraClear before adding more epoxy.

Can a heat gun fix fish eyes like it removes air bubbles?

Treat fish eyes as a surface-preparation problem. Brief, moving heat can remove air bubbles from liquid epoxy, but it does not replace removing silicone, oily residue, or an incompatible finish. Before recoating, identify why the epoxy is pulling away and correct that cause instead of repeatedly heating the crater.

Can tack cloths or mineral spirits cause fish eyes?

Yes. Tack cloths can leave oily residue that interferes with adhesion, and mineral spirits or paint thinner are not the recommended cleanup products before recoating. Use a fresh lint-free rag with denatured alcohol or acetone as directed for your epoxy. Remove all dust and residue, then let the cleaner evaporate fully before coating.

Can water-based polyurethane or polycrylic make epoxy pull away?

Yes. UltraClear Bar & Table Top Epoxy should not be poured directly over water-based polyurethane, polycrylic, or acrylic clear coats. UltraClear recommends three coats of an oil-based polyurethane barrier first, followed by at least 24 hours of drying before the epoxy seal coat. Follow the existing finish’s preparation instructions and test a sample. Water-based paint is a different category.

What if my wood already has an oil-based stain or paint?

Do not apply Bar & Table Top Epoxy directly over oil-based stain or paint. UltraClear recommends a barrier of at least three coats of oil-based polyurethane before the epoxy seal coat. For stained wood, wait at least 24 hours after the last polyurethane coat. The finish must be properly dry and prepared; confirm compatibility before coating the whole project.

Are dry patches in a seal coat always fish eyes?

No. Porous wood may absorb the first seal coat and leave dry-looking areas that need another seal coat. Fish eyes involve epoxy beading up or pulling away from particular spots. If the coating is separating, correct the residue or incompatible finish before proceeding. Extra seal coats help absorption; they do not solve an adhesion problem underneath.

Can silicone sprays or mold release cause fish eyes?

Yes. Silicone contamination can stop epoxy from bonding, and release products belong only on mold surfaces where adhesion is not wanted. Keep silicone sprays, polishes, and release residue away from wood and any surface the epoxy must bond to. Follow the mold-release instructions and use clean, dedicated tools and rags around the prepared work.

Can vinyl stickers or decals make epoxy separate?

Yes. Vinyl decals need to be sealed with Mod Podge before applying the epoxy seal coat and flood coat. Let the Mod Podge dry for at least 24 hours. Test the complete combination of decal, substrate, and finish first. This guidance is for smaller decals with surrounding wood; a single decal covering the entire top is not suitable for the same method.