Why have holes appeared in my resin project?

Holes, craters, or bare patches in cured resin are different from bubbles. Bubbles are trapped air that rises and pops. A hole or bare spot is an area where the resin never bonded to the surface in the first place — it pulled back, or never flowed over that spot at all, usually because something on the surface repelled it. This guide covers why that happens and how to stop it.

What causes it

Resin needs a clean, dry, contaminant-free surface to bond and self-level evenly. Anything that creates a barrier between the resin and the surface can cause it to pull away, leaving a crater or a completely bare patch once cured. Common causes:

• Silicone contamination. Silicone-based mould release agents, silicone caulk residue, or even cross-contamination from silicone kitchen tools and mats are the most common culprit. Silicone actively repels resin, and even a trace amount is enough to cause a visible crater.
• Oils and lotions from your hands. Hand cream, sunscreen, or natural skin oils transferred onto the surface while handling your piece will interfere with adhesion in that spot.
• Dust, wax, or polish residue. Furniture polish, wax coatings, or a dusty work surface can all sit between the resin and the substrate.
• An uneven or under-prepped surface. Wood with unsanded low spots, or a surface that wasn't levelled before pouring, can cause resin to pool away from certain areas rather than spread evenly — this can look like a hole even though nothing repelled it.
• Pouring over a surface that isn't fully cured or dry. A base coat, primer, or previous resin layer that hasn't fully cured yet can behave unpredictably under a new pour.

How to prevent it

1. Clean the surface thoroughly before you pour. Wipe it down with isopropyl alcohol on a lint-free cloth immediately before mixing your resin. This removes dust, light oils, and most everyday residue.
2. Check for silicone specifically. If you suspect silicone contamination — for example, the surface has ever been near mould release spray, silicone mats, or silicone-based sealants — clean it again with isopropyl alcohol and let it dry fully. Avoid silicone products in your workspace altogether where possible, since even airborne residue can settle on a surface.
3. Handle the piece with clean hands or gloves. Once the surface is cleaned, avoid touching it with bare hands. Use nitrile gloves or handle the piece by the edges.
4. Let the surface dry completely. Any cleaning liquid needs to fully evaporate before you pour — pouring onto a damp surface can cause its own adhesion and clarity problems.
5. Level your work surface and your piece. Use a spirit level or levelling feet so the resin can spread and self-level evenly across the whole surface instead of pooling away from high spots.

If a hole has already cured in

You generally can't fix a hole by pouring more resin directly into it and hoping it bonds — if the original spot was contaminated, a second pour is likely to repel in the same place. Sand back the affected area (following standard safety precautions for sanding cured resin), clean it thoroughly, and re-coat. For a hole caused by an uneven surface rather than contamination, a light sanding and a fresh, carefully levelled coat is usually enough.

Related articles

• Bubbles — Why They Appear and How to Remove Them
• Cloudy or Milky Result — Causes and Fixes
• Using Epoxy Resin on Wood — Tables, Charcuterie Boards & Live Edge