How to Fix Epoxy Bubbles: Causes, Fixes and Prevention
Updated 2026-10-16
Bubbles are probably the most common complaint in epoxy projects. A few tiny bubbles in a coaster might not matter, but a constellation of them frozen into a bar top is frustrating. The good news: most bubbles have predictable causes, many can be removed while the epoxy is still wet, and even cured bubbles can usually be repaired. This guide covers both the fix and the prevention.
Where bubbles come from
Understanding the source tells you which fix to use.
- Mixing. Stirring folds air into the resin, especially when stirring fast or whipping. Drill-mounted mixers at high speed are a frequent culprit.
- Outgassing from the surface. Porous materials — wood especially, but also concrete and some fabrics or paper — contain air. As epoxy fills the pores, that air escapes upward into the resin. Warmth can make wood release more air.
- Cold epoxy. Resin is thicker when it's cold, so bubbles rise more slowly and get trapped. Many manufacturers recommend warming the bottles to room temperature before mixing.
- Pouring technique. Pouring from a height or pouring fast can trap air, especially in molds with detail.
- Molds and embedded objects. Fine mold details, undercuts and embedded items (dried flowers, shells, electronics) trap air pockets.
- Thick pours of the wrong product. When a coating epoxy is poured too thick, the heat of the reaction can create bubbles and other defects. See deep pour vs tabletop epoxy.
Fixing bubbles while the epoxy is wet
1. Use heat to release surface bubbles
Gentle heat thins the epoxy at the surface so bubbles can rise and pop. Common tools are a heat gun or a small torch, passed quickly over the surface a few inches away. Keep it moving; holding heat in one spot can scorch the resin, cause ripples, or damage the substrate and tape. Torches are open flames — keep them away from solvents and flammable materials and never use them near the vapor of other products. Follow your epoxy manufacturer's guidance on which tool they recommend.
2. Repeat during the working time
Bubbles from wood can keep appearing for a while after the pour. Check the surface periodically during the product's working time and pass heat over it again. Once the epoxy starts to gel, stop; disturbing it can leave marks.
3. Pop stubborn bubbles manually
A toothpick or pin can lift a bubble that won't pop, especially around embedded objects and edges.
4. For deep pours, be patient
Many deep pour epoxies are thin and slow-curing, giving bubbles time to rise on their own. Manufacturers differ on whether to apply heat to deep pours, because extra heat can affect a thick cure. Follow the product instructions.
Fixing bubbles after the epoxy has cured
Once the epoxy is hard, heat won't help. You'll need to open the bubbles and fill them.
Surface bubbles in a coating
- Let it cure fully per the data sheet, so the surface sands cleanly.
- Sand the surface until the bubbles are opened and the surface is uniformly dull. Many people work through progressively finer grits. The goal is to remove bumps and give the next coat something to grip.
- Clean thoroughly. Remove dust with a vacuum and wipe with a cleaner compatible with your epoxy (many manufacturers suggest isopropyl alcohol). Let it dry.
- Fill open craters. Dab a little mixed epoxy into each opened bubble so it doesn't trap air again under the next coat.
- Apply a fresh flood coat. A new 1/8 inch coat will level over the sanded surface and restore gloss. Use the tabletop calculator to know how much to mix.
Bubbles trapped deep inside a pour
If bubbles are buried deep in a casting or river, they're hard to reach. Options include drilling a small hole into the void and injecting epoxy, routing out the area and refilling it, or accepting them as part of the piece. For a river table, small deep bubbles are often hidden once the table is flattened and coated, but large voids that open during flattening should be filled with epoxy before the final finish.
Bubbles in castings from molds
Surface pits on castings can be filled with a small amount of epoxy and then sanded and polished, or coated with a thin layer of epoxy to restore the shine.
Preventing bubbles next time
Prepare the materials
- Warm the resin and hardener to room temperature before mixing. Some people place sealed bottles in a warm water bath; keep water out of the resin.
- Work within the recommended temperature range for the room and surface.
Mix carefully
- Stir slowly and steadily for the full time the manufacturer specifies, scraping the sides and bottom of the cup.
- Avoid whipping. If you use a drill mixer, keep it at low speed and the paddle below the surface.
- Let the mixed epoxy rest briefly before pouring to allow bubbles to rise — but don't exceed the pot life, especially with large batches, which heat up faster in the cup.
Seal porous surfaces
For wood, a thin seal coat brushed into the surface lets air escape before the main pour. Once it has set to the point the manufacturer recommends, the flood coat or deep pour is much less likely to fill with bubbles. Live edges and end grain benefit most.
Pour smart
- Pour low and slowly, in one spot, letting the epoxy spread.
- For molds, pour a thin first layer, brush it into details, then fill the rest.
- Pre-coat embedded objects with a little epoxy to release trapped air before placing them.
Use the right epoxy for the thickness
Thick pours should use a product rated for that depth, in as many layers as needed. The deep pour calculator works out the number of layers.
Consider pressure or vacuum (advanced)
Some resin casters use a vacuum chamber to degas mixed resin, or a pressure pot to shrink bubbles during cure. These methods require proper equipment rated for the purpose and careful reading of both the equipment and resin instructions. They're usually more relevant for small castings than for tabletops.
Quick troubleshooting
| Symptom | Likely cause | Try |
|---|---|---|
| Many tiny bubbles throughout | Cold resin or vigorous mixing | Warm parts first, mix slowly |
| Bubbles keep appearing on wood | Outgassing from the wood | Seal coat first; pass heat during working time |
| Bubbles around embedded items | Air trapped in the object | Pre-coat items; use a toothpick |
| Bubbles with cracks or yellowing in a thick pour | Too much heat — pour exceeded product's depth | Use deep pour epoxy and thinner layers |
| Craters after cure | Popped bubbles that didn't level | Sand, fill, recoat |
Summary
Most epoxy bubbles come from mixing, cold resin or air escaping from porous surfaces. While wet, use gentle, moving heat and patience; once cured, sand, fill and recoat. To prevent them, warm the parts, mix slowly, seal wood, pour low and choose the right product for the thickness. And mix the right amount the first time with the epoxy resin calculator — rushing to mix a second batch mid-pour is a classic source of bubbles.