There’s a surprising amount to learn about how to remove bubbles from resin. That's why we have three blogs on bubbles in resin alone.  Whether you’re a woodworker making epoxy river tables, epoxy charcuterie boards, or an artist casting deep pour epoxies, most people try to avoid trapped bubbles in epoxy! Bubbles in resin are usually seen as imperfections.

           

“Spin the Bottle! One of the simplest, semi-automated, “low tech” mixing approaches to minimize bubbles in epoxy involves rotating the mixing container while holding a spatula next to the edge, as shown below. This simple setup can mix up to 2 L or ½ gallon of resin at a time. Rotation speed is variable, up to 110 rpm. You can achieve relatively bubble free epoxy resin automatically if you control the spinning speed. The cost is $70 on Amazon (Weishan store):

• Slow hand mixing to avoid resin bubbles.
  
  
• How you mix Part A and Part B of your epoxy resin is important to minimize epoxy bubbles. After adding epoxy resin and hardener together, stir them SLOWLY to avoid creating most of the resin bubbles in the first place. It’s true: it takes more time than stirring with a mixer on a drill, but it can be done.
  
  
• We recommend using a long silicone spatula because you can more easily scrape the sides and bottom of the mixing containers, than with a wooden tongue depressor. The silicone spatulas are also easily wiped clean with 91% IPA and can be used indefinitely – good for sustainability. The four spatulas shown can be purchased at Amazon for $8 total, or less in a store.
  
  
• Scraping the sides and bottom of the mixing container completely must be done several times, to ensure complete mixing. If you can see any striations at all in the mix, or if it’s not 100% clear, then it’s not yet fully mixed. Plan on mixing for at least 5 minutes if doing so by hand.
  
  
• When you think you’re done mixing, it’s best to transfer the mix to a clean container. This is because even with the above precautions, it’s difficult to mix the resin 100%, for example where the sides meet the bottom. Mix it a little more after transferring. This way you will not have any tacky spots after full cure. You’ve also just partially answered the question of, “How to get air bubbles out of epoxy?” which is by not whipping them in.
  
  
• Apply a seal coat to avoid bubbles in epoxy arising from air trapped in wood.
  
• Brushing on a thin epoxy seal coat applied to whatever wood will be contacted by the final pour, will minimize air bubbles. Otherwise, air bubbles in epoxy will arise from holes and pores in the wood surface after the final resin pour.
  
  
• Before applying the seal coat, it’s always a good idea to heat the wood first. We do not recommend using a propane torch unless you intentionally want to char the wood edge. (That can be a good look!) Open flames are a fire hazard. Instead, we recommend a good-quality hot air gun (see recommendations further below). These too can cause a fire if overdone, but it’s far less likely.
  
  
• Warming the wood causes air in the wood to expand, and exit the surface pores. Just warm it up. Don’t get the wood too HOT to touch, or you’ll accelerate the epoxy cure.
  
  
• Next: immediately apply a high-quality epoxy topcoat resin kit to the warm wood. You can select from the ”Top 4” out of over 50 candidates in the USA by going to the “2023 Epoxy Resin Online Buyers Guide for Woodworkers.” You may have to apply the seal coat twice, depending on the porosity of your wood, and the viscosity of the coating epoxy. Experience will guide you.
  
  
• A word of caution: 90% of the topcoat epoxy kits in the USA today still contain 25% nonylphenol in the final mix, or 250,000 ppm (parts per million)! Nonylphenol in epoxy is BAD. It’s a severe endocrine disruptor known to cause testicular atrophy and dramatically reduced sperm counts. It’s a liquid plasticizer, that does NOT react with epoxy. It just sits there in the solid cured resin, slowly migrating out. Nonylphenol is already banned in Europe. It will probably be banned in the USA soon. It should be. AVOID these choices! The issue of nonylphenol in epoxy is discussed in far greater detail in the “2023 Epoxy Resin Online Buyers Guide for Woodworkers.” The coating formulations with nonylphenol in epoxy are easy to spot, because they are DQ’d!
  
  
• As air in the still-warm wood pores cools and contracts,it'll “suck in” the topcoat you brush on, better sealing the pores. Let it cure to the point of being tacky, but not hard, and then make the final pour.
  
  
• If you want to make your final epoxy resin pour within a couple of hours after applying the seal coat, then choose a Topcoat resin kit from the “Top 4” in the  “Buyer’s Guide” with a 30-45 minute working time. These choices will cure to the point of being tacky in a couple of hours.
  
  
• Oops! You allowed the epoxy seal coat on the wood to get rock-hard before the final epoxy pour. As a result, the final epoxy pour will not adhere well to the epoxy-sealed wood. River Tables have even been known to fall apart because of this. If the seal coat is hard, you will need to roughen it up GREATLY with coarse sandpaper before the final epoxy resin pour. 
  
  
• Slightly heating the surfaces of the tacky seal-coated wood with a hot air gun is also a good idea, right before the final pour, for the reasons stated above. This will also help minimize air bubbles in epoxy arising from any unsealed areas in the wood, after the final cure.

• Pour mixed resins from the “bottom-up” to avoid trapping epoxy bubbles
  
  
• You want to fill from the bottom up, minimizing entrapped air as you pour. A simple way to do this is to pour the resin down a stick or rod to the bottom of what you’re filling. The resin will follow down the rod or stick.  
  
  
• A lot depends on the geometry of what you’re filling, but always consider how to best fill it from the bottom while minimizing trapped air. 

 

 

 

• How to totally AVOID resin bubbles? 100%? Use Static Mixers!

• Static mixers are like “Magic.” When this author first learned about static mixers years ago, they seemed like “magic.” Static mixing occurs just with two streams of flowing resin.  There are no moving parts.
  
  
• Two fluids pumped together, divide “at the leading edge of each element of the mixer, and follow the channels created by the element shape. At each succeeding element, the two channels are further divided by two, resulting in an exponential increase in stratification. The number of striations produced is 2ⁿ where 'n' is the number of elements in the mixer.”
  

• With enough mixing elements, the striations become as small as the molecules!  It’s the ultimate mixing. When the starting resins are fully degassed, then mixed statically, the final mix will also have ZERO bubbles. Absolute bubble-free perfection.
  
  
• Commercial static mixers are typically made of polyethylene and are cleanable with 91% IPA. They are also disposable, costing around $3 each.
  
  
• Sticky Stuff Dispenser: A very handy, shop-sized, hand-pumped static mixer is described below. This is the Sticky Stuff Dispenser, a hand-pumped static mixer, from Michael Engineering, in Mt. Pleasant, MI.
  
  
• Michael Engineering’s “Model A, Sticky Stuff Dispenser”:
  The model shown with the line attached is Michael Engineering’s “Model A” Sticky Stuff Dispenser, with flexible line and Static Mixer attached.  The model without the flexible line (resold by Total Boat) simply pumps out the correct ratios of “A-Side” and “B-Side” resin, unmixed.
  
  
• As priced here, it has valves to manage thin fluids, like amine hardeners, as well as a hand-held dispenser with the static mixer attached, & line. “Model A” tanks hold one gallon in one container, and half a gallon in the other. As shown, including ten of the 30-element plastic static mixers (#8-30), the set-up sells for $817 (2/23).
  
  
• “Pump and Dump.“ (Not the official name!) Michael Engineering’s Model A on the right (as resold by Total Boat) shows the same unit, but without the hand-held static mixer. It meters the “A-Side” and “B-side” accurately with every hand-pumping action. When priced with the same valves for handling low-viscosity amines, it costs ~$466 (without the static mixer manifold and line).
  
  
• The Sticky-Stuff Dispenser comes in several different configurations, depending on the volumetric mix ratios of A-Side to B-Side resin. For example, one configuration allows adjustable volumetric mix ratios of between 6:1 and 2:1, while another configuration allows 2:1 to 1:1 mix ratios.
  
  
• Depending on the mix ratios, output per manual stroke of the aluminum lever shown above varies between 10 and 18 cc/stroke.  In practical terms, Model A hand-pumps up to 1 quart/minute of perfectly mixed resins.
  
  
• They also have a larger model: “Model B, Sticky Stuff Dispenser.” It pumps between 41-76 cc/stroke or up to 4 quarts (one gallon)/minute! This model costs $313 more than Model A and also has larger tanks (two 2-gallon tanks, OR two 5-gallon tanks optionally). It handles higher viscosities as well. This would be the model to get when making large river tables repeatedly, if so inclined.
  
  
• The perfect conditions for these static mixers to operate within is having the viscosity of both the A-side and  B-Side being around 1000 cps and equal.
  
  
• They’re not inexpensive mixers. However, if you have even a semi-production situation, it would quickly make your life simpler, while also probably saving you money.
  
  
• Consider the typical static-mixing scenario: Both tanks of the hand-pumped Sticky Stuff dispenser are filled with the A-Side and B-side resin of your choice (vacuum degassed as needed). If pigmented, these tanks could slowly be stirred, but you’d have to add that option. There’s a manifold with a static mixer at the end of a hand-held line. It leads straight to your river table mold, filling it from the bottom to the top, with zero bubbles in the mix! (Static mixers are the ultimate answer to: “How to get bubbles out of resin!”)
  
  
• Further, you probably will save a LOT on resin costs. When pouring a 10-gallon table, it’s difficult to accurately estimate how much resin you’ll need. People always mix a little extra. On average, you’d probably save ~ 1 gallon of “Just-in-case” epoxy resin on a large table. The average price of deep-pour epoxy resins purchased in 3-4 gallon quantities across over 40 formulators is $107/gallon, delivered.  
  
  
• If making repeated epoxy-wood river tables, It wouldn’t take long to pay off the cost of a Sticky Stuff dispenser and static mixer. We’ve all watched videos of very large river table pours, where a misjudgment caused the workers to have 6-8 gallons of extra resin. Ka-ching!  Wasted resin costs can be totally avoided with a static mixer.
  
  
• Limitations:  The “Sticky Stuff Dispenser” manual indicates not to exceed 5,000 cps for either the A or B-sides, but they say it’s best to stay below 2,500 cps.  Also, if the viscosity of the two materials was too different, they say they mix less well.  For example, mixing one material that’s 20 cps, with another that’s over 100 times higher, say 2,500 cps, may not work.
  
  

The end, #1 Bubble Blog: Avoid Bubbles When Mixing Resins

#1 Bubble Blog: Avoid Bubbles When Mixing Resins.

Discusses how to mix and dispense epoxy resins while minimizing or 100% avoiding all micro bubbles in the first place.

#2 Bubble Blog: Use Low Viscosity, Long Gel-time Resins.

Discusses the importance of low viscosity resin and long gel times for how to get bubbles out of epoxy.

#3 Bubble Blog: How to Get Rid of Bubbles IN Resin.

This blog on “How to get bubbles out of resin,” discusses the resin degassing chamber, as well as how to get rid of bubbles in resin SURFACES.