How to avoid or fix fisheyes, pin holes and separations
Fisheyes, pinholes, and separations are surface defects, not bubble problems — they're caused by contamination or surface tension rather than trapped air, so the fixes are different from general bubble troubleshooting. This guide covers what each one looks like, what causes it, and how to prevent or fix it.
What each issue looks like
| Issue | What it looks like | Common cause |
|---|---|---|
| Fisheye | A circular crater or dimple where resin has pulled back from a spot on the surface | Contamination on the substrate — oil, wax, silicone-based mould release, fingerprints, or residue from cleaning products |
| Pinhole | A tiny pit or hole at or just below the surface | Trapped air escaping from a porous substrate (wood, some papers, dried flowers) as it off-gasses into curing resin, or dust and debris that broke the surface tension |
| Separation | A gap or bare strip where resin has pulled away from the edge of the artwork or mould | Similar root cause to fisheyes — contamination at the edge, or resin surface tension pulling inward before it keys into the substrate |
Preventing them
- Keep your work area clean. Dust, hair, and airborne debris are a common trigger for all three issues. Avoid people walking through your workspace while you pour, and cover your piece loosely while it cures — without letting the cover touch the surface.
- Clean and dry the substrate before pouring. Wipe mugs, tiles, wood, and moulds down with isopropyl alcohol and let them dry fully. Any oil, wax, or mould-release residue left behind is the single most common cause of fisheyes and separations.
- Seal porous substrates first. Wood, canvas, and similar materials can trap air and moisture that escapes as tiny bubbles once resin goes on top, showing up later as pinholes. A thin seal coat, cured before your main pour, gives that trapped air somewhere to go without disturbing your final layer.
- Don't touch or move the piece while it's curing. Fingerprints and stray hairs landing on a curing surface are a common source of both fisheyes and pinholes.
Fixing fisheyes or pinholes while the resin is still workable
If you spot one while the resin is still liquid and within its working time:
- Try heat first. A heat gun or torch passed briefly over the spot can help the resin flow back in and self-level before it gels — see our Bubbles article for the technique.
- A light isopropyl alcohol spritz can also help resin re-level into small imperfections without disturbing the rest of the pour.
- Leave it to self-level rather than poking at it. A tool dragged across still-liquid resin tends to leave its own mark. Give the surface a chance to close on its own first.
Fixing separations
If resin pulls away from an edge while curing:
- Don't try to spread or drag the existing resin back over the gap — that tends to leave streaks or introduce bubbles.
- Mix a small, fresh batch of resin at the correct ratio and apply it directly over the gap. It will self-level and merge with the resin still curing underneath.
- Let it cure fully before deciding whether a second application is needed.
Fixing pinholes or fisheyes after full cure
Once resin has fully cured, a crater or pinhole won't correct itself — the fix at that point is mechanical: sand the affected area smooth, then apply a fresh topcoat layer to restore an even finish.
Related articles
- Bubbles — Why They Appear and How to Remove Them
- Cloudy or Milky Result — Causes and Fixes
- Mixing Ratio — How to Measure Resin and Hardener Correctly
Aug 23, 2026
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