While the airlock is releasing CO2, it is also keeping things like bugs and bacteria out of your beer or wine. But what’s going on if the airlock is still? There are many things it can mean and we’ll go over them.
An airlock is a small widget that goes on top of a fermenter and plugs the hole in your stopper. The airlock is filled with a small amount of water, neutral spirit, or sanitizer (preferably star san if you use a sanitizer, in case reverse pressure sucks it in). If you know how yeast work, you know they convert sugar into alcohol and carbon dioxide. When that is happening there is usually some “activity in the airlock”. The pressure of the newly added CO2 builds and pushes the water in the airlock outwards in order to escape. Without it, the pressure would be too great, and your stopper would shoot off with a bunch of foam like a vinegar baking soda volcano; or your fermenter’s structure may fail causing a massive mess, or even injury in rare cases.
Throughout this article, it is important to note that airlock activity is not a good measurement of active fermentation between batches. Things like the amount of liquid in the airlock can affect how vigorous the bubbling is, or it could just be gas escaping the liquid from agitation and not actual fermentation. However, if you do have airlock activity, you can gauge when that specific batch is slowing. Gravity measurements are a sure fire way to read if fermentation is active.
If you’ve pitched your yeast and it’s been over 24 hours, but don’t see any airlock activity, you may be thinking that fermentation isn't happening. However there could be a different problem.
No Seal / Bad Seal: This typically happens in buckets where the lid isn’t secured tightly on the bucket. Gas will take the path of least resistance out of your vessel. A crack or poor seal on your lid will let gas out easier than it having to push a few milliliters of water up a tube. Alternatively, if you didn’t fill your airlock enough, it may be escaping through a gap there.
Large Amount of Headspace: While a large amount of headspace won’t stop a fully sealed fermenter from bubbling forever, it will however take longer to show any visual airlock activity. The more empty space the resides in your fermenter, the longer it may take to show airlock activity.
Lag Phase: Depending on the size of your yeast pitch, you may notice that there is no activity after a full day or two, this could be due to an under pitch of yeast. If this is the case, they are working on multiplying before they convert sugar into alcohol and CO2.
Killed Your Yeast: Your yeast may have lost its viability by either shipping it in hot weather without an ice pack, pitching too hot, storing your yeast improperly, or being much too far past date. If you can plan ahead and have a concern about yeast viability, you can make a starter.
Sometimes after heavy aeration you can get slow airlock activity that then stops a few hours later. This can cause alarm before fermentation actually begins as it looks like a stall. This is just excess air leaving the solution and going up through the airlock.
The bulk of fermentation in beer can be done in four or five days. This can be confusing to newer brewers who read that you wait 2-3 weeks before bottling. This is true, and your should wait, but not all of that time is dedicated to fermentation. The yeast also takes time to drop out and clean up certain off flavors.
When in doubt, always take a hydrometer reading. This will be the best way to determine the status of your fermentation. You can tell if you’re fermentation is in the beginning middle or end stages, or if it has stalled by this method.
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