Epoxy Floor Fisheyes & Craters: Causes and Fixes

You roll out a smooth coat of epoxy and within minutes small round craters appear, as if the coating is pulling away from invisible spots on the floor. Those are fisheyes, and they are one of the most common DIY failures in Katy garages. They are caused by surface contamination, and they are entirely preventable with the right prep.

What a Fisheye Actually Is

A fisheye is a small circular crater where the liquid epoxy refuses to wet out and instead beads away from a contaminated spot. The cause is almost always a difference in surface tension: a trace of oil, grease, silicone, wax, or even floor-polish residue sits on the concrete, and the epoxy — which wants to flow evenly — pulls back from it like water off a waxed car. Each speck of contamination becomes the center of its own little crater.

The Usual Culprits in a Katy Garage

• Automotive fluids. Years of oil drips, transmission fluid, and brake cleaner soak into bare concrete. Even after the surface looks clean, oil remains deep in the pores.
• Silicone overspray. Tire shine, WD-40, and aerosol lubricants contain silicone, which is the single worst enemy of a coating — a tiny amount ruins adhesion across a wide area.
• Cleaning products. Mop-and-shine cleaners and some degreasers leave a waxy or surfactant film that triggers fisheyes.
• Skin oils and dust. Touching the prepped slab or letting it sit and collect dust before coating can be enough.

How Professionals Prevent Them

The fix starts before any product is mixed. We diamond grind the entire slab to mechanically remove the contaminated top layer rather than relying on a chemical wash that can leave residue. On heavily oil-stained concrete — common in older Katy garages — we degrease and, if needed, use an oil-stop primer before the build coats. Doing the prep right is the difference; it is the same reason we walk customers through the most common DIY epoxy mistakes and our full installation process.

Fisheyes vs. Bubbles — Don’t Confuse Them

Fisheyes are craters that form from contamination as the coating goes down. Bubbles or pinholes form when air or vapor pushes up through curing epoxy — a different problem with a different cause. If your issue is rising air rather than beading, read our guide on epoxy outgassing and bubbles.

Fixing a Floor That Already Has Fisheyes

Once a coat has cured with fisheyes, you cannot simply paint over them — the contamination is still there and will telegraph through. The repair is to abrade the affected coat (sand or grind), remove the contamination, and re-apply. For a small area this means feathering in a patch; for a widespread failure the coat is ground off and the floor re-prepped properly. A professional re-coat over correctly cleaned concrete cures out smooth and crater-free.

Frequently Asked Questions