How to Remove Bubbles from Resin

Heat gun vs butane torch: which should you use?

Both tools work by temporarily lowering resin viscosity at the surface, allowing trapped air to rise and escape. The right choice depends on your project size and the type of bubbles you're dealing with.

⚠️ Never use a hair dryer — it blows dust and debris onto your wet surface. Never use a regular candle flame — soot contamination ruins the pour. Only use tools designed for resin work.

The 6 root causes of bubbles in resin

Bubbles in resin almost always have a specific, preventable cause. Knowing the source tells you whether to fix it during mixing, pouring, surface preparation, or environment control. The heat gun is the last resort — not the solution.

1. Cold resin (most common)

Below 65°F, epoxy resin becomes thick and viscous — closer to honey than water. Thick resin traps air during mixing and holds it stubbornly in suspension rather than letting bubbles rise. If your workspace or storage area is cool (garages, basements in winter), this is likely the cause even if the bottles don't feel obviously cold to the touch.

Fix: Warm resin bottles in a bowl of warm (not hot) water at 90–100°F for 15–20 minutes before mixing. Dry bottles completely before opening. Bring your workspace to 70–75°F with a space heater at least one hour before mixing. Use a thermometer to verify both room and resin bottle temperature before starting. See our Resin Temperature Guide for working time adjustments by temperature.

2. Fast or incorrect mixing technique

Vigorous stirring whips air into resin the same way a whisk aerates cream. Circular stirring creates a vortex that draws air down from the surface into the mix. Using a drill mixer at high speed — common with large batches — is one of the fastest ways to introduce thousands of micro-bubbles that are nearly impossible to remove after pouring.

Fix: Stir slowly using a figure-8 or side-to-side motion for 3–4 minutes. Scrape the sides and bottom of the cup frequently — unmixed resin at the edges causes ratio errors, not just streaks. After mixing, let resin sit for 3–5 minutes before pouring. This rest period allows larger bubbles to rise and pop on their own. Transfer to a second clean cup and stir briefly — this breaks up residual mixing air near the cup walls.

3. Outgassing from wood or porous surfaces

Raw, unsealed wood contains trapped air in its grain structure. When liquid resin contacts the wood surface, it wicks into the grain and forces air out ahead of it — creating a steady stream of bubbles rising through your pour for anywhere from 10 to 60 minutes. This is particularly severe with oak, ash, cedar, and other open-grain species. Even with a torch, you cannot remove bubbles faster than the wood produces them.

Fix: Always apply a thin seal coat (brush coat of epoxy, not a full pour) over all wood surfaces 4–8 hours before your main pour. Let the seal coat reach the tacky stage. This fills the grain and seals the air inside before your main pour touches the wood. For river tables, seal the entire wood slab — edges and undersides too — not just the river channel area. See our Large Pour Calculator for river table material planning.

4. Pouring height and speed

Pouring resin from high above the mold (more than 6–8 inches) creates a falling stream that whips air into the surface on impact. Pouring too quickly creates turbulence that folds air into the upper layer of resin before it can escape. Both issues show up as a dense cluster of bubbles at the surface immediately after pouring.

Fix: Pour in a slow, thin stream from just above the mold surface — 1–2 inches if possible. Tilt the mold slightly and pour against one side, letting resin flow down and spread rather than falling straight into the center. For large flat pours, pour in a Z or S pattern across the surface rather than one central point.

5. Trapped air between layers

When pouring a second layer over cured resin, air can become trapped between the two layers if the previous layer has cured completely hard (more than 12–24 hours in most cases). Full cure creates a smooth surface that the new layer bonds to only chemically, not mechanically — and any small air pockets between the layers get compressed and forced upward as bubbles.

Fix: Pour the second layer during the tacky window — when the first layer is solid to the touch but still slightly flexible (usually 6–12 hours after pouring, depending on temperature). This creates a chemical bond that eliminates inter-layer air. If your first layer has already fully cured, lightly sand it with 220-grit before pouring the next layer. Use our Multi-Layer Pour Calculator to plan layer timing precisely.

6. Too much colorant or additives

Pigments, mica powder, alcohol ink, and glitter all introduce air into resin during mixing. More additives means more mixing time, which means more air incorporation. Exceeding 10–12% colorant by weight also interferes with the chemical cure, causing soft spots that may develop surface cratering that looks like cured bubbles. Alcohol ink is particularly prone to causing surface bubbling because it contains solvents that interact with the resin surface.

Fix: Add colorant to Part A before mixing with Part B, stir slowly, and stay within recommended percentages. For alcohol ink, add just 1–3 drops per 100ml and stir gently — don't over-mix after adding. Use our Resin Color Mixing Calculator for exact safe amounts by batch size.

Step-by-step: how to remove bubbles from resin after pouring

Once you've poured, you have a window of about 20–45 minutes (depending on temperature and resin brand) to remove surface bubbles before resin starts gelling. Here's the exact process:

Step 1: Wait 5 minutes after pouring

Don't reach for the heat gun the moment you finish pouring. Let resin settle for 5 minutes — most large bubbles will rise to the surface and pop on their own. Premature heating on a pour that's still being self-leveling can disturb the surface and push air into areas where it wasn't before.

Step 2: Apply heat with steady passes

Hold your heat gun or torch 2–4 inches above the surface. Move in slow, steady passes — left to right, then front to back. Don't hover over any single spot for more than 1 second. The goal is brief, even heat exposure across the whole surface. You should see bubbles popping (small craters that immediately fill in) as you pass over them.

Step 3: Repeat every 10–15 minutes for the first hour

With outgassing surfaces or certain resin formulas, bubbles continue rising for the first 45–60 minutes. Make passes every 10–15 minutes during this window. After the first hour, resin will be viscous enough that new bubbles can't easily rise, and heat passes become less effective.

Step 4: Cover loosely and leave to cure

After your last heat pass, cover the piece loosely with a cardboard box or similar tent to keep out dust. Don't seal it airtight — air circulation is needed for proper curing. Do not cover with plastic wrap directly on the surface.

What to do if bubbles are still present after curing

If bubbles have cured into the surface, they can often be fixed cosmetically. Sand the surface with 220-grit wet/dry sandpaper until the bubbles are leveled out. Clean thoroughly to remove all dust. Apply a thin flood coat of fresh resin — just enough to fill and cover the sanded area. This self-levels over the sanded surface for a clear finish. Large internal bubbles (more than 2–3mm deep) require more aggressive sanding and may not be fully salvageable without starting over.

Bubble prevention checklist: before every pour

The most effective bubble strategy is prevention — eliminating the conditions that create bubbles before you mix. Running through this checklist takes 5 minutes and prevents 90% of bubble problems.

Bubble removal by project type

Jewelry and small molds

Small molds (earrings, pendants, keychains) often have deep cavities relative to their surface area, which traps air easily. Use a heat gun on the lowest setting — the small surface area means high-intensity torch heat can overcure or yellow the edges before center bubbles pop. For very small pieces (under 10ml), a pressure pot is the most effective solution — it compresses bubbles to invisibility under 40–60 PSI without any risk of surface distortion from heat.

For embedded items like pressed flowers or glitter, heat can shift embeddings before they're fully set. Use minimal heat passes and focus on the perimeter rather than directly over any embedded elements.

Coasters and flat pours

Standard coasters (8mm deep) have enough surface area for a torch to work efficiently. Pour the base layer, wait 5 minutes, torch in smooth passes. For layered designs with pressed flowers or foil, pour a 1mm base layer first, let it reach tack (30–60 minutes), then add embeddings and top coat. This method prevents embeddings from floating and reduces the total bubble surface area per layer. See our Resin Coaster Calculator for exact amounts by size.

River tables and large pours

Large pours have two distinct bubble problems: outgassing wood and mixing air in large batches. The seal coat step is critical — apply seal coat to all wood surfaces 4–8 hours before the main pour and check that it has fully soaked in and tacked before proceeding. For large batches (over 2 liters), use a low-speed drill mixer but only for 60–90 seconds maximum — just enough to combine, not to fully aerate. A torch works better than a heat gun for river table surfaces due to the coverage area. Work systematically from one end to the other rather than back and forth.

Tumblers and vertical surfaces

Tumblers require rotation during curing to prevent resin from pooling. Bubbles on a tumbler often show up as long streaks rather than individual circles because the cup is rotating while bubbles try to rise. Use a heat gun (not torch) while the tumbler is rotating on the turner — hold it 3–4 inches away as the cup rotates past. Make multiple passes over 15–20 minutes. The rotation also helps bubbles migrate to the surface naturally.

Second and subsequent layers

Pouring over a fully cured layer creates inter-layer bubbles if the surface is too smooth for the new layer to grip. Sand lightly with 220-grit before pouring any layer more than 24 hours after the previous one. Wipe clean with a dry cloth — no water or solvent. Pour in the tacky window (6–12 hours after the previous layer) whenever possible to avoid this issue entirely.

Pressure pots: the professional solution

For jewelry makers and anyone producing high-volume batches of small castings, a pressure pot is the most reliable bubble elimination method available. Rather than popping bubbles, a pressure pot compresses them to a size below the threshold of visibility — typically under 0.05mm, completely invisible to the naked eye.

How it works: After pouring, place the mold inside a sealed pressure pot. Apply 40–60 PSI of compressed air. Maintain pressure for the full cure time (24–48 hours). At 60 PSI, gas bubbles compress to roughly 1/5 of their original diameter — a 1mm bubble becomes a 0.2mm bubble, invisible in finished resin. When pressure is released after full cure, the bubbles are too small to re-expand to visible size.

When to use a pressure pot: Jewelry at any price point above $15 per piece. Optical clarity pieces (marbles, spheres, decorative objects meant to be looked through). Any piece where customers will inspect closely and bubbles would cause returns. Pieces with deeply embedded objects where heat passes would be ineffective.

When not to use a pressure pot: Large flat pours (river tables, coasters over 200ml) — the mold volume exceeds most pot capacity. Layered pours with designs that need to be checked between layers. Any project where the artistic result depends on organic surface variation.

💡 A pressure pot requires an air compressor, regulator, and a properly rated pot. Starter pressure pot kits ($80–150) include everything needed. This is one of the highest-ROI equipment purchases for serious resin crafters — it eliminates the most common quality defect entirely.