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Effective Epoxy Resin Venting: Removing 100% Air Bubbles, Mixing, Heating, Vacuum Pumps & Chambers

Mgorski102 25710 14
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  • #1 16986818
    Mgorski102
    Level 8  
    Hello
    I would like to ask how to effectively vent epoxy resin so that it is 100% free of air bubbles. I manage to get rid of 90% of the same method of mixing, heating the resin to about 40'C, and firing at the end with a burner. But the remaining 10% are really tiny bubbles often visible only in cold light. I tried to vacuum it, but I have problems with it. Temporarily as a vacuum container I wanted to use a jar with a valve, I used a milking machine CTA MILK GPV 200 to make a vacuum
    Effective Epoxy Resin Venting: Removing 100% Air Bubbles, Mixing, Heating, Vacuum Pumps & Chambers
    But it is not able to create the necessary vacuum because nothing happens, the pressure it produces is too weak?
    Which vacuum pump should I use? Will I buy enough for 300 PLN?
    In the future I would like to buy such a vacuum chamber
    / Chamber-VACUUM-4-2l-to-degassing resin / link I will add that I use epidian 652 resin.
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  • #2 16986941
    czareqpl
    Level 33  
    Or maybe it is worth trying a vibrating table? Works well when compacting / de-aerating concrete.
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  • #3 16987690
    Mgorski102
    Level 8  
    Yes, but I mean really small bubbles.

    I have read that the milking machine's correct value is 50Kpa, which gives 500mbar, while 50mbar is needed for venting the resin.

    So I do not understand, maybe I'm doing something wrong.
  • #4 16991283
    ladamaniac
    Level 40  
    These 50mbar, it's probably from zero, or absolute pressure, that is, your pump should make 950mbar of underpressure.
  • #5 17012499
    saskia
    Level 39  
    It may be mediated, for example, by a small cyclone or a centrifugal filter.
  • #6 17012876
    DecoDominik
    Level 14  
    Effective Epoxy Resin Venting: Removing 100% Air Bubbles, Mixing, Heating, Vacuum Pumps & Chambers

    One of the methods is the pressure chamber in which the casts become heavy.
    The pot has two advantages.
    You can use it as a vacuum chamber for pre-venting resins.
    And then after connecting to the compressor as a pressure chamber.
    Which will help get rid of small bubbles that were formed during potting the mold.

    Vacuum pumps are ok for hobbyists.
  • #7 17012968
    Anonymous
    Level 1  
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  • #8 17013034
    DecoDominik
    Level 14  
    With a freezer, it can be useful, but different resins bind differently.
  • #9 17013560
    buczkog
    Level 16  
    There remains also the question of mixing the resin itself. First of all, it should not be "blown" at the mixing stage. I use for this purpose an agitator that does not protrude above the surface of the resin. In this case, the bladders are trace by the formation of the vortex during mixing.
  • #10 17037519
    Mgorski102
    Level 8  
    I'm stubborn with the problem by simply buying a casting resins that are self-venting.

    Thank you for your help
  • #11 17081054
    StachCzarnecki
    Level 9  
    Hello !!!

    Which resin did you buy? a lot of this on the market, and Epidian 652 actually gasses inside while bonding ... And a layer of 1.5 cm is too much for him ...


    greetings
    Stach
  • #12 17605010
    Pawel16146
    Level 2  
    I have used a spray bleeder agent. I bought it on one of the auction portals.
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  • #13 17751190
    Szacun 56
    Level 7  
    Good morning, Mr. Pawel, 16146, could you give the name of this agent for venting the resin and on what portal you bought it too I am looking for something (I found a paraffin concealer but I do not know if it works) I play with EPIDIAN 652 resin and IDA hardener THANK YOU VERY
  • #15 17876743
    satcom666
    Level 12  
    Welcome gentlemen. I know that the subject is from last year but it warms up because it is still visible in search engines. I use the vacuum chamber of my own production for degassing Epidian 652. First, I try to mix with the hardener (and possibly with the pigment) so that the resin does not aerate then "zilc" I close in the vacuum chamber for about 10 minutes, evacuating to a value of about 0.9 - -1 Atm. Then I slowly equalize the pressure and reduce the surface tension of the resin with a burner and again for about 3 minutes to -1 Atm. If the resin is not damp or old - these operations are 90% sufficient. Once at the auction I bought such a resin, which at the first negative pressure boiled like a beer poured into a beer mug at the end of the barrel and after repeatedly venting it was still bubbling - I did not buy anything from this master ...

    As for the vacuum chamber - I use a thick garage made of stainless steel and sealed with a self-adhesive gasket for the window cover with fittings made of plexiglass 10 mm thick for fittings I have finished the vacuum gauge to see what happens to the air suction I use the compressor from the refrigerator, which at the same time in the "other side" (together with a regulator bottle with a pressure reducer and a separator / dehydrator kit I am using as a handy compressor for the airbrush and home work - the compressor itself is a different topic - but to flatter it, just enter the "DIY fridge" and then do it

    There is also a method to bind binding resins in the pressure chamber and this is a very good method, but for me it has major disadvantages
    1. Making a DIY pressure chamber is much more difficult than a vacum
    2. Maintaining pressure in it (which is necessary for proper operation) is much more difficult than vacuum in vacum
    3. The resin must be under constant pressure to fully bond - which takes a long time - see item 2.

Topic summary

✨ Effective venting of epoxy resin, specifically Epidian 652, is crucial for eliminating air bubbles during the mixing and curing process. Users have reported achieving up to 90% bubble removal through methods such as heating the resin to approximately 40°C and using a burner. However, tiny bubbles remain problematic, often visible under cold light. Suggestions for improvement include using a vacuum pump capable of achieving at least 50 mbar of underpressure, with recommendations for specific vacuum pumps and chambers. Alternative methods discussed include utilizing a vibrating table, a pressure chamber for post-casting, and cooling the resin in a refrigerator to reduce bubble formation. Proper mixing techniques, such as using a submerged agitator to minimize vortex formation, are also emphasized. Some users have explored self-venting resins and venting agents available on auction sites.
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FAQ

TL;DR: For near-100% bubble removal, target ~50 mbar absolute (~0.95 bar vacuum); “your pump should make 950 mbar of underpressure.” [Elektroda, ladamaniac, post #16991283]

Why it matters: This FAQ helps makers and small shops choose gear and steps that reliably clear micro-bubbles in epoxy pours.

Quick Facts

What vacuum level do I actually need for epoxy degassing?

Aim for ~50 mbar absolute pressure, which equals about −0.95 bar on a gauge. That level expands and extracts micro-bubbles effectively. As one expert put it, “your pump should make 950 mbar of underpressure.” Verify your gauge reads near −0.95 bar and holds steady during the foaming phase. Poor seals or weak pumps stall bubble rise. [Elektroda, ladamaniac, post #16991283]

Why won’t a milking-machine pump work for resin?

A milking pump around 50 kPa creates ~500 mbar absolute pressure. Effective degassing needs ~50 mbar absolute. That’s a 10× deeper vacuum than the milker delivers. The mismatch means bubbles won’t fully expand or escape. Choose a pump rated for deep vacuum, not just moderate suction. [Elektroda, Mgorski102, post #16987690]

How should I mix epoxy to avoid adding air?

Keep the mixer head below the liquid surface and avoid a vortex. Use slow, steady strokes or a low-speed paddle that never breaks the surface. This minimizes entrained air at the source, making later degassing faster and cleaner. Scrape cup walls gently to blend without whipping. [Elektroda, buczkog, post #17013560]

What’s a simple DIY vacuum setup that actually works?

Use a thick steel pot as the chamber, a 10 mm plexiglass lid with a gasket, and a refrigerator compressor as the pump. Add a vacuum gauge to monitor drawdown. This low-cost rig can pull to about −1 atm on the gauge and supports repeat cycles. Ensure all fittings are airtight. [Elektroda, satcom666, post #17876743]

How long should I keep epoxy under vacuum?

Run about 10 minutes to full drawdown, then slowly vent. Briefly flame the surface to lower surface tension. Pull vacuum again for roughly 3 minutes to finish. Watch the foam rise and collapse before venting fully. Time varies with viscosity and batch size. [Elektroda, satcom666, post #17876743]

Should I heat epoxy before or after degassing?

Warm the resin to about 40°C before mixing to lower viscosity, then degas. After pouring, sweep a small torch over the surface to pop residual bubbles. Keep the flame moving to avoid scorching. Heating helps, but excessive heat can speed cure too much. [Elektroda, Mgorski102, post #16986818]

Can a pressure pot help with micro-bubbles after pouring?

Yes. A converted pressure pot can first act as a vacuum chamber, then as a pressure chamber with a compressor. Pressurizing collapses remaining micro-bubbles to invisibility. Many hobbyists use this two-mode approach for clearer casts and smoother surfaces. [Elektroda, DecoDominik, post #17012876]

Is cooling the mold a valid trick to reduce bubbles?

Yes. Chilling the filled mold a few degrees Celsius suppresses bubble formation and rise. Cure time becomes much longer, often around 24 hours before demolding. This helps when equipment is limited but demands patience and dimensional stability. [Elektroda, Anonymous, post #17012968]

Why does my resin ‘boil’ the moment I pull vacuum?

Some batches gas aggressively and foam like beer, even under repeat cycles. This can signal old or moisture-laden resin, or unsuitable formulation. In one case, the material kept bubbling after multiple degassing attempts and was rejected. Replace bad stock early. [Elektroda, satcom666, post #17876743]

What if I just buy a self-degassing casting resin?

That’s a practical workaround. Switching to a casting resin marketed as self-venting can eliminate persistent micro-bubbles when process changes fail. Users report better clarity without extensive equipment. Always verify layer limits and cure schedules before large pours. [Elektroda, Mgorski102, post #17037519]

Is a vibrating table worth trying for epoxy casting?

A vibrating table helps consolidate and de-aerate thick materials like concrete. For epoxy, gentle vibration can nudge bubbles upward after pouring. Use low amplitude to avoid frothing the mix. Combine with vacuum or pressure for best results. [Elektroda, czareqpl, post #16986941]

Can I pour Epidian 652 in thick layers?

Epidian 652 struggles in thicker sections. Reports show a 1.5 cm layer is too much for clear, bubble-free results. Use thinner pours or choose a resin designed for deep casting. Adjust catalyst ratio only per manufacturer guidance. [Elektroda, StachCzarnecki, post #17081054]

What’s a ‘bleeder’ or anti-foam spray, and where to get it?

Anti-foam sprays reduce surface tension and help bubbles release. Hobbyists source them from marketplaces by searching for resin venting or anti-foam products. Apply sparingly per label. Test with your specific resin system before critical parts. [Elektroda, Pawel16146, post #17771114]

What is a cyclone/centrifugal filter here, and does it help?

A small cyclone or centrifugal filter can mediate entrained air or aerosols before or during processing. It’s an accessory idea to improve clarity and keep the system cleaner. Integrate only if your setup benefits from pre-separation. [Elektroda, saskia, post #17012499]

Give me a quick 3-step degassing workflow I can copy today.

  1. Mix carefully to avoid aeration, then place the cup in the chamber.
  2. Pull vacuum for ~10 minutes; vent slowly; briefly flame the surface.
  3. Pull vacuum again for ~3 minutes; then pour or proceed. Monitor foam rise and collapse. [Elektroda, satcom666, post #17876743]

What gauge reading equals ~50 mbar absolute on my setup?

On a standard gauge that reads relative to atmosphere, ~50 mbar absolute corresponds to about −0.95 bar. If your gauge shows near −0.95 bar and holds, you’re in the right window for epoxy degassing. Seal quality matters as much as pump rating. [Elektroda, ladamaniac, post #16991283]
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