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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