The fisheye pattern is one of the most visible and frustrating defects in epoxy finishing. It appears as small, circular craters or spots where the wet epoxy has receded, leaving a void that exposes the substrate underneath. This is caused by surface tension contamination, where the liquid epoxy actively pulls away from a foreign substance.

The Mechanism: Surface Tension Repulsion

1. Contaminant Barrier: Substances like silicone, oil, grease, wax, or residual cleaning agents create a microscopic layer on the substrate. These contaminants have a much lower surface tension than the liquid epoxy resin.
2. Epoxy Repulsion: The liquid epoxy, attempting to achieve a uniform surface tension, reacts strongly to the low-energy contaminant spots. The resin molecules pull away from the contaminated area toward the surrounding clean epoxy, leading to a void or crater—the fisheye.
3. Causes:
   • Silicone: This is the most notorious culprit. Traces can come from furniture polish, silicone caulking, release sprays, or even hair/skin products.
   • Oil/Grease: Fingerprint oils, machine oils, cutting fluids, and wax/polish residue.
   • Moisture: Excessive moisture or condensation can also cause a less severe version of this effect.

Genuine Solutions for Prevention and Repair

Prevention through meticulous cleaning is the only reliable way to stop fisheyes.

1. Prevention: Decontamination is Crucial

• Aggressive Cleaning: Before the pour, the substrate must be aggressively cleaned.
  • Sand and Vacuum: First, sand the surface (e.g., wood or metal) to create a mechanical profile and remove the bulk of any surface film.
  • Solvent Wipe: Wipe the entire surface with Acetone or high-purity Isopropyl Alcohol (IPA) to dissolve any residual oils or grease. Use a clean, lint-free cloth and discard it after one or two passes. Do not touch the cleaned surface with bare hands.
• Isolate Silicone: Remove all silicone sources from the work area, including any sprays, caulking, and tools that may have been exposed to them.

2. Repairing Fisheyes (The Fix)

If fisheyes appear in your wet epoxy:

• Torch/Heat Gun: For minor cases, immediately apply a quick, sweeping pass with a torch or heat gun. The heat lowers the epoxy’s viscosity, allowing it a brief moment to flow back and fill the voids. This is often only partially effective.
  
• The Second Coat Method (Post-Cure): If the fisheyes persist after curing:
  1. Decontaminate: Thoroughly clean the cured surface to remove any remaining oil or silicone barrier. Use a warm, mild detergent wash, followed by an Acetone wipe.
  2. Sand: Sand the entire surface lightly with 180-220 grit sandpaper.
  3. Apply a Fresh Coat: Pour a new, thin coat of epoxy. The sanding and cleaning should provide enough surface energy and adhesion for the fresh epoxy to “wet out” and fill the craters left by the first coat.
     
• Using a Defoamer/Fisheye Killer (Controversial): Commercial additives called “Fisheye Killer” or “Defoamer” can be mixed into the epoxy. These are essentially low-surface-tension additives designed to make the entire batch of epoxy compatible with the contaminant. However, they can weaken the final cured surface and should be used with extreme caution and only as a last resort.