Fisheyes are small, round craters that form when a coating pulls away from a contaminated spot. Oil, silicone, wax, and some lubricants are common causes. The coating can’t wet out and bond over the residue. Careful cleaning and grinding before coating prevents them.
Why Fisheyes Matter for Your Floor
Fisheyes are a looks problem first. You’ll see little round dimples or craters, sometimes with a raised ring around the edge, where the coating seems to have run away from the spot. Think of water beading on a freshly waxed car: the liquid won’t lie flat on something slick.
They’re also a sign of trouble underneath. Whatever pushed the coating away is still sitting on the concrete, and the coating isn’t bonded well in that spot. On a garage floor, those weak points can be where chipping or peeling starts later.
What Causes Fisheyes in Epoxy and Floor Coatings
Fisheyes form when the coating lands on something it can’t stick to. Painting over oil, wax, silicone, or grease is the classic cause. On concrete floors, common culprits include:
- Oil and fluid drips that soaked into a garage slab over the years
- Silicone sprays and tire shine used near the floor
- Old sealers, waxes, or cleaners that leave a film
- Dust or residue left behind after grinding
Garage slabs are the most likely to have fisheyes because oil soaks deep into concrete. A surface wipe can look clean while residue is still below the surface.
How Contractors Prevent and Fix Fisheyes
Good prep is the main defense. Grinding removes the top layer of concrete along with most surface contamination. Heavy oil spots may need degreasing or extra grinding. A good crew vacuums thoroughly before anything goes down.
If fisheyes show up while the coating is still wet, the contractor can sometimes clean the spot and reapply. Once the coat has cured, the usual fix is to sand the area smooth and recoat. A small test patch on a stained area of the slab can show whether contamination is a problem before the whole floor is coated.
If you’re planning an epoxy or polyaspartic floor, our guide to concrete floor coatings walks through what good prep looks like.
Fisheyes FAQ
What are fisheyes typically caused by?
Fisheyes are caused by contamination on the surface, most often oil, silicone, wax, or grease. The coating pulls away from the contaminated spot instead of lying flat. On concrete, old oil stains and silicone sprays are the usual suspects.
How do you fix fish eyes in epoxy?
Once the epoxy has cured, the affected area is sanded or ground smooth, cleaned, and recoated. Simply rolling another coat over fisheyes usually doesn’t work, because the contamination can come back through. The goal is to remove the residue, not just cover it.
What do fish eyes in a coating look like?
They look like small round craters or dimples, often with a ring around the edge, a bit like a fish’s eye. They often show up in clusters where a spill or spray landed.
Can you prevent fisheyes on a garage floor?
Yes. Thorough grinding and cleaning before coating removes most contamination, and deep oil stains may need extra treatment. Keeping sprays and lubricants away from the floor before the job helps too.