I'm thinking of cold crashing my current brew, but I am not comfortable with the idea of allowing sanitizer to be sucked in, and I'm not happy with foil

I have heard that maybe there are micro foam bungs or some sort of filter, but struggling to find such a thing on the googles.

Does anyone use these things? Know what they are called so I can find them?

3 Answers 3


What's the problem with foil? When I cold crash, I seal the fermenter either with a solid stopper or foil. Since fermentation is done there's no need to do anything else. AAMOF, you want to stop air from getting into the fermenter, whether it has microbes or not. I would not recommend using anything porous.

  • Foil is still going to let air in, right? I thought is that some filtration is better than none.
    – Mild Fuzz
    Commented Jun 24, 2015 at 10:07
  • If you crimp the foil and put a rubber band on it, no air will get in. There is no need for filtration at all. You want to avoid any air getting into it.
    – Denny Conn
    Commented Jun 24, 2015 at 15:29
  • Okay, so the pressure drop's effect on my PET carboy would be my concern, although if man of your experience isn't concerned, maybe I shouldn't be either...
    – Mild Fuzz
    Commented Jun 24, 2015 at 19:10

Northern brewer has them in starter supplies. That said star san becomes yeast nutrient in contact with wort or beer. This from Charlie Tally interview on BN in '07.

  • Hmm, struggling to see the product you mean in the starter supplies
    – Mild Fuzz
    Commented Jun 22, 2015 at 7:43

Alcohol bubbling

Letting the air pass through a strong alcoholic solution, as vodka or absynthe.
Alcohol is known to be hostile to a lot of organisms: keep in mind that surgeon sanitize their hands with products based on alcohol.
If you do set up a good turbolent flow without losing too much contact time, you should manage to reduce in great part the microbial count in your airstream.

Geometry of the apparatus, on a budget

The idea is getting plenty of curves, so air has to go through multiple alcoholic phases and optimally a final washing water phase. Getting one more washing water phase in the middle would be ideal.
Stainless steel piping fittings or traps (also called siphons) would be the ideal choice: coupling multiple U fittings will give you this solution for less than 25$, and it will hold to sanitation standards higher than the food industry has.

Water Absorption

In technical terms, it'd be called "absorption airstream contamination": ditching sanitizers in favour of strong alcoholic solutions will already make the air more-than-FDA safe, but if you really have an issue with air containing a small part of alcohol, you can place another fitting or trap where clean water will rest.
This process is used in the pharmaceutical industry, for a safety regulation framework of reference. Using distilled water in this curve would be ideal: it tends to have a very low starting microbial count, and the alcohol it will absorb (thus removing it from the air stream).

If you do choose this solution, I can estimate the amount of water and\or the maximum air flow to get a fixed concentration of alcohol, or if you choose the bubbling solution I can relate the number of curves.

Even when they tell you otherwise, traces of chemicals always linger by the very nature of chemical reactions: the smaller the concentration, the slower the reaction. After a while, it slows so much it practically stops.

Live easy, very small traces can be safely neglected both by taste and health, and I don't mean figuratively: under a certain concentration, there is no evidence that a substance can alter the equilibrium of your body. How low that certain concentration is, however, varies by substance, hence my offer.


Only a few alcohol resistant strands would pass, and they'd have to be more easily dispersed in air than water or liquid phases: competitive growth should hold them back, however.

  • not going to stop being sucked in, which is the problem during cold crashing
    – Mild Fuzz
    Commented Jun 24, 2015 at 19:08
  • I may have poorly expressed myself: updated the answer: is it any clearer? Commented Jun 25, 2015 at 14:01
  • When the force is sucking, the liquid will not stay in the traps as it does during fermentation, it will be sucked into the beer. Short term, fine, but will the traps are clear, the beer is exposed.
    – Mild Fuzz
    Commented Jun 25, 2015 at 14:25

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