Nothing ruins a beautiful epoxy project faster than bubbles. I've been there, spending hours perfecting a custom wood and resin table, only to spot tiny air pockets frozen in the glossy surface as it cures. That specific flavour of frustration? Not fun.
But removing bubbles in epoxy casting is entirely manageable once you understand where they come from and when to intervene. In this updated 2026 guide, I've tightened the advice, added angles I glossed over before, and expanded the vacuum degassing section properly - because that's where most people are still leaving results on the table.
My own bubble issue where I skipped the wood sealing step
Table of Contents
What Causes Bubbles in Epoxy Casting?
Before you can remove bubbles from epoxy resin reliably, you need to know where they're entering in the first place. Most makers focus on the pour - but the majority of bubbles are created before the resin ever hits the mold. The main culprits:
Air trapped during mixing. Mix too fast and you're essentially whipping the resin like egg whites - that's not what we're going for. Slow and deliberate wins here.
Pouring technique. Pouring from too high or too quickly invites air pockets right into the mold. Think honey, not a waterfall.
Wood pores releasing air. Unsealed wood is the silent saboteur. When warm epoxy hits porous wood, trapped air escapes upward, leaving a constellation of small bubbles you didn't cause during mixing. Sealing the wood first is the fix.
Temperature and viscosity. Cold resin is thick resin. Thick resin traps air more stubbornly and releases it more slowly. Working in a cold workshop - or skipping the warm-up step - makes every other bubble removal technique harder.
Humidity. Moisture reacts with certain hardeners and can contribute to surface fogging and microbubbles. I haven't had major issues personally, but in humid climates or wet seasons it's worth tracking.
The epoxy itself. This one doesn't get said enough: a low-quality or wrong-spec resin makes every other step harder. Cheap formulas tend to be thicker, have harsher mixing ratios, and shorter working times - all of which trap air more aggressively and give you less time to deal with it. Choosing the right epoxy for your project depth and pour size is the foundation everything else builds on. If you haven't sorted that yet, start with the RCG epoxy preparation guide before worrying about technique.
Understanding where bubbles enter tells you exactly where to intervene.
Tools for Epoxy Bubble Removal
Having the right tools isn't optional - it's the difference between a project you're proud of and one you're embarrassed to photograph. Here's what earns its place in my workshop for getting bubbles out of epoxy resin:
Heat Gun
My first line of defence for surface bubbles after pouring. A slow, steady sweep of warm air at 15–20 cm (6–8 inches) pops bubbles without scorching the resin. I reach for this before anything else.Butane Torch
Better for denser bubbles or thicker pours where the heat gun doesn't quite reach. Keep it moving - hold it still for even a second too long and you'll scorch or yellow the surface. I've done it. Learn from my impatience.Vacuum Chamber
The single most effective tool for epoxy bubble removal. Pulls dissolved and trapped air out of the mixed resin before it enters the mold. See the expanded section below.Pressure Pot
A different approach: instead of removing bubbles, it compresses them until they're invisible. Excellent for a flawless, glass-like finish on decorative castings.Silicone Mixing Tools
Lower turbulence than wooden sticks, easier to scrape clean, and they don't introduce fibres into your mix. A small upgrade that genuinely helps reduce bubbles from the start.
Step-by-Step: How to Get Bubbles Out of Resin
Before the Pour
This is where most bubble problems are either prevented or baked in. Preparation is everything - and most tutorials skip straight past it.
Seal your wooden surfaces first. The single most impactful step on any wood project. A thin seal coat of epoxy, brushed into the surface and allowed to tack up, closes off the pores before the main pour goes in. Skip this and the wood off-gases bubbles straight through your casting. I learned this the painful way on my first river table.
Warm the resin before mixing. Cold resin is more viscous and traps air more easily. Sit your components in a warm water bath (not hot - around 30–35°C / 86–95°F) for 10–15 minutes before mixing. The resin flows better, mixes more smoothly, and releases bubbles faster during degassing. If you do this regularly, a dedicated resin bottle warmer is a cleaner and more controlled approach than a water bath — more on that in the equipment section below.
Mix slowly and thoroughly. Scrape the sides and bottom of the container as you go. Most mixing mistakes happen in the bottom corners where resin and hardener sit unmixed. Set a timer for the full recommended mixing time and don't rush it.
Add pigments after mixing, not before. Stir pigments in gently after the resin and hardener are fully combined. You've already done the hard work - don't undo it by aggressively stirring in colour powder.
Rest the mixture for 5–10 minutes. After mixing, let it sit. Bubbles introduced during mixing will rise and pop on their own. Small pause, big payoff.
Degas with a vacuum chamber. See the full section below, this step alone can transform your results on any epoxy casting project.
No vacuum chamber? See the alternatives section below for the full fallback hierarchy.
💡 Pro tip: Gently warming the mixed resin in a warm water bath (30–35°C / 86–95°F) reduces viscosity and helps bubbles escape on their own. Not as thorough as vacuum degassing, but significantly better than doing nothing - and it costs you nothing extra.
During the Pour
Once you're pouring, the focus shifts to not introducing new air into the epoxy.
Pour a thin seal layer first. A thin base coat over the bottom of the mold, especially on wood projects, seals any remaining pores and gives you a foundation to build on.
Pour slowly and close to the surface. The higher you pour from, the more air you entrain. Pour as close to the mold surface as practical and let the resin flow rather than drop.
Use your heat gun promptly. Within a few minutes of each layer going in, make a slow pass. Surface tension drops with heat, and bubbles clinging to the surface pop readily. I keep the gun on low and do 2–3 passes in the first hour as the resin begins to thicken.
Watch the pot life clock. As epoxy approaches gel time, it thickens fast. Chasing bubbles in near-gelled resin just makes tracks in the surface. Know your working time and finish bubble removal well before it.
Vacuum Degassing Epoxy: The Deep Dive
Vacuum degassing is the step that separates consistent, bubble-free castings from hit-or-miss results. I mentioned it briefly in the 2025 edition. Here's the full picture.
How Vacuum Degassing Works
A vacuum chamber is connected to a vacuum pump, which removes air from the sealed container. As pressure drops, dissolved and trapped air expands and escapes from the mixed resin. The resin foams up dramatically, which looks alarming the first time, then settles back down, now substantially degassed.
The whole process takes 5–15 minutes per batch. When done right, you'll see the foam rise, peak, then collapse. That collapse is your signal it's working.
What to Look For in a Vacuum Chamber for Epoxy
Not all vacuum chambers deliver the same results. The spec that matters most isn't the brand - it's the achievable vacuum level. For epoxy degassing you're aiming for -0.9 to -0.98 bar (around 27–29 inHg), which represents 90–98% vacuum - as close to full vacuum as hobby and semi-pro equipment reliably gets.
Key things to check before buying:
Chamber volume. You need room for the resin to foam up - typically 3–4× the liquid volume. A 3-litre (1 gallon) chamber suits most hobbyist pours. Go bigger (5–6L / 1.3–1.6 gal) for larger batches.
Pump quality. The chamber is just a container - the pump does the work. A two-stage rotary vane pump reaches deeper vacuum faster. Single-stage pumps plateau around -0.85 bar - adequate for most work, but less effective on thick or slow-curing resins.
Lid seal and gauge. A quality acrylic or metal lid with a good gasket holds vacuum without flex. The gauge should ideally be calibrated in both bar and inHg.
Valve control. A bleed valve that releases vacuum gradually is far more useful than a simple on/off setup.
Recommended Epoxy Bubble Removal Equipment
There are two distinct categories: traditional chamber + pump kits, and the newer self-contained bubble removal machines from Resiners. They suit different situations.
Traditional Vacuum Chamber Kits
The classic setup: a stainless steel or acrylic chamber paired with a dedicated vacuum pump. More bulk and setup time, but more capacity for large pours.
Entry-level kit: 2 gal (7.5L) chamber + single-stage pump
⭐ My current setup: What I use for the vast majority of my projects. I'm running this with a 3 CFM pump, which hits target vacuum quickly without being overkill. Enough headroom for foam without overflow and handles everything up to medium pours comfortably. Best balance of size and cost to start with.Mid-range kit: 5 gal (19L) chamber + single-stage pump
The step up for larger pours and river table batches. More volume means you can degas bigger mixes in one go without splitting into batches. Worth it once your projects regularly push past the 2 gal limit.Premium kit: 9+ gal (34L) stainless chamber + single/two-stage pump
Built for serious volume. All-metal construction, handles the largest river table batches without breaking a sweat. Worth it if you're casting every week or at production scale.
Resiners AirLess Series - Self-Contained Epoxy Bubble Removers
Resiners built a compact, self-contained machine where you place your mixing cup directly inside. No pump to connect, no oil to maintain, no large steel chamber eating bench space. Three models in the lineup (Lite, AirLess, Pro) - if you're buying one, go straight to the Pro: -99kPa vacuum, 20L/min extraction, 3.2L (108 fl oz) capacity, and around 3 minutes per cycle. It handles all resin types including high-viscosity, and won the 2024 Red Dot Design Award. For smaller batch work the Lite is the budget entry point, but the Pro is where the real results are.
Check yourself: Resiners AirLess Pro
code ResinCraftGuild15 applies sitewide for 15% off.
Traditional kit or Resiners machine. Which should you get?
For batches under 500–600ml (17–20 fl oz), the Resiners machines are more convenient, faster to set up, quieter, and take up less space than a traditional chamber kit. For large river table pours mixing litres at a time, you still want a traditional chamber with sufficient volume. Some makers end up with both.
Epoxy Heating: Resiners Smart Resin Warmer
If you're regularly warming resin before mixing - and you should be - the Resiners Smart Resin Warmer is a cleaner solution than a water bath. It's a compact upright unit with a digital touchscreen, adjustable 30–70°C (86–158°F), and fits up to four 16oz (475ml) bottles at once. Warms to target temperature in around 10 minutes with auto shut-off built in. Pairs naturally with any AirLess machine: warm first, degas second, pour third.
Resiners also makes a few other tools worth knowing about if you're building out a full setup: the Cure Air is a hot-air circulation curing station that cuts cure time from 24 hours to around 2 hours and helps prevent surface bubbles forming during the cure; and the Mini Heat Gun is a compact, resin-specific heat gun - lighter and easier to manoeuvre than a full workshop gun for smaller pours and detail work.
Practical Vacuum Degassing Tips
Don't fill the cup more than 40–50%. The foam can triple the resin volume during degassing. Overfill and you'll have a mess inside the chamber. Line the base with plastic wrap for insurance.
Watch the foam, not the clock. Keep degassing until the foam rises, peaks, and visibly collapses - that's when the air is gone.
Release pressure gradually. Releasing vacuum too fast can suck air back into the resin. Use the bleed valve slowly.
Degas each batch separately. If your project needs multiple mixed batches, degas each one individually.
Thick-pour epoxy benefits most. High-viscosity resins hold air stubbornly. Deep pours with slow-cure formula - degassing is non-negotiable.
Warm before you degas. Cold resin is harder to degas. Warmer resin releases air faster and more completely.
Vacuum Chamber vs. Pressure Pot. What's the Difference?
Both fight bubbles in epoxy resin, but they work on opposite ends of the process.
A vacuum chamber is used before pouring. You degas the mixed resin while it's still liquid - bubbles have somewhere to go, up and out.
A pressure pot is used after pouring, during the cure. The sealed pot pressurises the air around the casting (typically to 2–4 bar / 30–60 psi), compressing any remaining bubbles until they're too small to see. The resin cures around them in that compressed state - and since cured epoxy is rigid, the bubbles stay permanently invisible.
The key distinction: vacuum removes bubbles; pressure hides them. Both give you a bubble-free result, but the mechanism is completely different.
Which do you need?
For most woodworking and epoxy casting projects, a vacuum chamber is the better primary investment. Removing air before the pour gives you more control across a wider range of project sizes.
For small decorative castings, jewellery, and inclusions, a pressure pot often delivers the clearest results - and many crafters in that space use it as their only bubble removal tool.
When You Don't Have a Vacuum Chamber
Not ready to invest yet? The honest hierarchy of alternatives:
Warm water bath to reduce viscosity before mixing (best free option)
Slow, deliberate mixing with a silicone tool
Extended rest time, 10–15 minutes instead of 5
Heat gun immediately after pouring
These combined get you most of the way there on shallow pours with low-viscosity epoxy. For deep pours or high-detail castings, there's no real substitute. Entry-level kits are under $100 and pay for themselves after one saved project.
Heat Gun vs. Torch for Epoxy Bubble Removal
Both tools apply heat to drop surface tension and pop surface bubbles. Knowing which to grab saves you from scorched surfaces and ruined pours.
A heat gun blows a wide, diffuse stream of warm air across the surface. That spread is the main advantage - you're warming a large area evenly rather than concentrating heat in one spot.
Best for:
Surface epoxy bubbles right after pouring
Large pours where you need to cover a lot of ground quickly
Beginners - the wider heat zone makes scorching much harder to do accidentally
Situations where you want slow, controlled, repeatable results
Technique: Hold it 15–20 cm (6–8 inches) from the surface. Move in slow, sweeping passes. Two or three passes over the first 30–60 minutes as the resin thickens is usually enough. Don't hover - holding still creates a heat-distorted crater.
Limitations: Won't reach bubbles more than a few millimetres below the surface. Deeper pockets need a torch or vacuum degassing.
My honest take:
This is what I reach for 90% of the time. Forgiving, consistent, less drama.
A torch delivers concentrated, intense heat to a small area. That intensity is both its strength and its risk.
Best for:
Stubborn epoxy bubbles the heat gun couldn't pop
Slightly deeper surface bubbles in medium-pour projects
Small pours where precision matters more than coverage
Getting into corners or edges a heat gun can't angle into
Technique: Keep the flame moving constantly. Short, controlled bursts at 10–15 cm (4–6 inches) from the surface. Never hold still over one spot, 2–3 seconds maximum before moving on. The flame should kiss the surface, not cook it.
Limitations: Smaller margin for error. A moment's inattention and you'll scorch the resin, introduce yellowing, or leave a heat-distorted patch. Coloured pours are especially unforgiving.
My honest take:
Useful, but I treat it as a second-pass tool, after the heat gun has done most of the work. Every burn mark I've made came from moving too fast and too confidently.
Heat Gun | Butane Torch | |
|---|---|---|
Heat spread | Wide, diffuse | Narrow, concentrated |
Surface bubble removal | ✅ Excellent | ✅ Excellent |
Deeper bubble reach | ❌ Limited | ✅ Better |
Beginner-friendly | ✅ More forgiving | ⚠️ Needs practice |
Risk of scorching | Low | Higher |
Best use case | General-purpose, large pours | Stubborn spots, precision work |
Speed | Slower, methodical | Faster (but riskier) |
The short answer:
Start with the heat gun. Reach for the torch only when it isn't enough and when you do, slow down more than you think you need to.
Tips and Tricks for Bubble-Free Epoxy
Heat gun technique recap. Hold it 15–20 cm (6–8 inches) from the surface. Slow, sweeping passes. Don't hover. The goal is to lower surface tension, not cook the resin.
Torch technique recap. Short bursts, constant movement. Too much heat scorches and yellows - I've earned that lesson more than once.
Don't overfill the vacuum chamber cup. Already covered above, but it trips up beginners every single time.
Bubbles in cured epoxy? Sand and recoat. For surface microbubbles after curing, fine-grit sanding (220–320 grit) followed by a fresh thin coat can restore a clean surface. Works well on most cases.
Microbubbles vs. large air pockets. Microbubbles respond to sanding. Large trapped pockets need to be drilled out, filled with fresh epoxy resin, and sanded flush. Tedious, but there's no shortcut.
Prevention over repair. Repairs on transparent or multicoloured epoxy castings rarely land 100%. There's always a visible seam or a reflection that betrays the fix. Double your prep time and you'll halve your repair time.
Advanced Epoxy Projects
Still figuring out where to start, or not quite sure your project is set up right before you pour? Don't skip the fundamentals - the guides below cover everything from calculating how much epoxy you need and building a leak-proof mold, to sanding and finishing your casting once it's cured. If any part of your prep feels uncertain, check those first. Bubbles are often just a symptom of a setup problem upstream.
Ready to push further into more creative territory? A few resources from the RCG archive worth bookmarking:
FAQ: Bubbles in Epoxy Resin
Why does my epoxy resin have bubbles after curing?
Bubbles in cured epoxy usually come from one of four sources: air introduced during mixing, air released from unsealed wood pores, resin that was too cold and viscous to release air naturally, or surface bubbles that weren't caught in time with a heat gun. The fix depends on the cause - see the step-by-step section above.
What is the best way to remove bubbles from epoxy resin?
Vacuum degassing the mixed resin before pouring is the most reliable method - it removes air before it can get trapped. For surface bubbles after pouring, a heat gun on a slow sweep is the most controlled approach. A pressure pot during the cure is best for small decorative castings where zero visible imperfections matter.
Does a heat gun remove bubbles from epoxy?
Yes, for surface bubbles. Hold the heat gun 15–20 cm (6–8 inches) above the surface and move it in slow, sweeping passes. The heat lowers surface tension and the bubbles pop. It won't reach bubbles more than a few millimetres below the surface - for those you need vacuum degassing or a torch.
How do you use a vacuum chamber for epoxy resin?
Pour your mixed resin into a mixing cup (no more than 40–50% full), place it inside the vacuum chamber, seal the lid, and run the pump until you reach -0.9 to -1 bar (27–29 inHg). The resin will foam up dramatically - keep running until the foam peaks and collapses. Release pressure gradually using the bleed valve, then pour. The whole process takes 5–10 minutes.
Vacuum chamber vs. pressure pot for epoxy. Which is better?
They solve different problems. A vacuum chamber removes air from the mixed resin before the pour. A pressure pot compresses any remaining bubbles during the cure so they become invisible. For most woodworking and casting projects, a vacuum chamber is the better primary investment. For small decorative castings where you want flawless clarity, a pressure pot is often preferred. For the most demanding work, use both.
How do I prevent bubbles in a thick epoxy pour?
Seal the wood first, warm the resin to 30–35°C (86–95°F) before mixing to reduce viscosity, mix slowly, vacuum degas each batch, and pour in layers. Use a slow-cure deep-pour formula - never a thin-layer epoxy in a thick application.
Why does epoxy bubble when poured on wood?
Wood pores trap air that gets released when warm epoxy flows over the surface. The fix is to seal the wood with a thin brush coat of epoxy first, let it tack up, and then pour your main layer. This closes off the pores and stops the off-gassing.
Conclusion
Bubbles will always be the first thing people notice in an epoxy project - and the first thing you notice when it's yours. But with the right prep, the right tools, and a proper degassing step, removing bubbles from epoxy casting is entirely within your control.
Seal your wood. Warm your resin. Mix slowly. Degas properly. Pour with patience. The process isn't complicated - it just requires respect for each step.
Have questions, hard-won lessons, or a project you're proud of?
Reply via email - I'd love to hear what you're working on.
Affiliate disclosure: This post contains affiliate links. If you purchase through them, RCG earns a small commission at no extra cost to you. Some products I've purchased, used and tested personally; others I've selected based on specs, community feedback, and research. I only recommend what I'd genuinely consider for my own workshop.