I fermented my first batch of extract in a plastic 'ale pail' using an airlock with the following mixture in it:

  • 50% tap water; and
  • 50% whiskey

It never bubbled. Not even once. In 3 days. And while I can't prove scientifically that the lid was on tight, it was on as tight was I could make it!

But, when I cracked open the lid and took the SG, it was obvious that fermentation was occurring). I was told by someone recently that airlocks consisting of either distilled water or alcohol usually don't bubble:

"Usually won't get bubbles if just using distilled water or alcohol, not enough surface tension."

I'm curious as to what this means (exactly), because to me (an uninitiated rookie), if CO2 is trying to escape, it shouldn't matter whether you're using alcohol, distilled water, tap water or crude oil: gas has to escape!

So what's so special about both distilled water and alcohol that causes it not to bubble when used inside an airlock?!? I guess I'm hung up on the meaning of "not enough surface tension".

2 Answers 2


To elaborate on my comment more.

Some airlocks won't show tale tale signs of c02 that has already escaped if using a solution in them that won't form bubbles on their surface like pure water or alcohol.

When using starsan (a foaming sanitizer) you will see bubbles or foam in the air lock long after fermentation has slowed. Giving you the assurance that fermentaion is active, with out opening the fermentor.

During vigorous fermentation it is impossible to miss bubbles regardless of the solution as long as the c02 is going through the airlock and not leaking out elsewhere.

Many beers, ciders and meads especially can hit terminal gravity in a matter of hours and leave little visible signs it did anything. Taking an actual gravity reading is best, but sometimes it's not practical just for diagnosis (1 gallon batch of mead) this is where a foaming airlock solution is helpful.


Since you mentionned you were fermenting in an Ale Pail, I'd add to Evil's answer that they are notorious for not having an airtight seal, so CO2 can leak through the side of the lid (the easiest path).

From a simple Google search, you'll see that it is a pretty common "problem" (quoted because it really shouldn't affect your brew during primary fermentation since no air can enter as CO2 is produced in the bucket).


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