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Old 01-23-2013, 04:26 PM   #1
Dec 2012
Youngstown, Ohio
Posts: 1

I have home brewed dozens of the same batch. Why is sometimes my air lock bubbles like crazy and sometime no bubbles? Same 5 gallon bucket, same temp when yeast is pitched and 24 hrs later sometimes bubbles and sometime no bubbles? Beer tastes the same. Any ideas? Thanks.

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Old 01-23-2013, 04:37 PM   #2
Post Hoc Ergo Propter Hoc
Revvy's Avatar
Dec 2007
"Detroitish" Michigan
Posts: 40,939
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An airlock is just a vent, a valve to release EXCESS co2, to keep the lid from the fermenter from flying off. That's IT. That's it's only purpose. Some fermentations produce a lot more EXCESS co2 that need to go out the airlock, others don't. Some seals on buckets or stoppers ALSO let co2 out..either way it's the same. You want EXCESS co2 to get out of the fermenter by some means. The amount or how much an airlock does or doesn't bubble, doesn't matter.

"x bubbles/ minute or whatever" does NOT equate to "y gravity points." It's NOT a gauge.

Airlocks are one of the most superfluous things out there, yet new brewers tend to attribute near mystical importance as to how it behaves, or if it behaves at all.

Remember gas expands and contracts due just as much from environmental reasons such as a change in temp or barometric pressure as from anything being wrong. It often stops or starts because the dog tried to hump the fermenter, or the vacuum is running OR a truck drives by and disturbs any trapped co2 in the trub at the bottom....If you look at an airlock for what it is, a vent, then you realize that all an airlock bubbling means......

Is that an airlock is bubbling. Or isn't......*shrug*

For example a couple weekends ago if you lived in most of the United Sates, you experienced an unseasonable WARM UP over the weekend which could very easily result in gas expansion in your fermenter or secondary...In other parts of the states you had storms, which meant a change in barometric pressure...It was an active weekend weather wise. We had a TON of new brewers starting panic threads because suddenly beers that they had in secondary from their Christmas presents, that were doing nothing for weeks (like they should do in secondary,) suddenly their airlocks started bubbling. So they, having equated an airlock as a fermentation gauge and NOT a vent, suddenly started assuming that fermentation was happening (and in their nervous noobishness were just SO SURE that their beer was infected).....NOT for once even thinking in terms of airlocks merely being vents, and that gas expands when it is heated, and contracts when it is cooled. And that's going to cause airlock to bubble or stop....Just as much as fermentation.

That's why I tell folks to ignore what the airlock does or doesn't do. It really means little to the yeast.
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Old 01-23-2013, 05:15 PM   #3
Oct 2008
Denver, CO
Posts: 561
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I would agree with most of what Revvy just posted, except that I would suggest that if you're literally seeing no bubbles at all on a normal-ish gravity beer (e.g. ~1.050) in a 5 gallon bucket that has ~1/4 to 1/3 volume headspace - you should recognize that you have a sealing issue.

Your yeast definitely don't care if your bucket doesn't seal, but you should, especially if you plan on leaving the beer in that bucket for more than a week or so. If your bucket doesn't seal well, after vigorous fermentation is complete, you have oxygen getting in your bucket and that can affect the flavor of your beer (in a bad way).

As a point of comparison, I've only fermented in glass carboys, never in plastic buckets. I've never had one fermentation, out of 100 batches, where I didn't see vigorous airlock activity. This means there is a good seal, and this is a good thing. I don't want to worry about a bunch of oxygen getting into my fermentations and degrading the flavor of my beer that I worked so hard on.

Yes, recognize that it is a vent and not a gauge, but I would not suggest that you ignore what it does or doesn't do. It is still telling you something, and if you learn how to interpret what it is telling you, you can understand your fermentations better and make better beer.

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