Airlock activity after I thought fermentation was done

[Cliff Morris]

I’ve had my brew in the carboy for almost 3 weeks. Fermentation started hard on the 2 day and went for ~3 days and has died off since. I haven’t seen much activity and planned on bottling this coming weekend but I checked it today and I’m getting an air bubble about every 10 secs. What’s going on and should I be worried for the quality?

 

[MaxStout]

Could just be dissolved CO2 coming out of solution. Or fermentation still going. Take a hydrometer reading, and another one a day or two later. If they are the same, beer is done fermenting.

 

[histo320]

Airlock activity bus just one indicator of fermentation. Only a hydrometer sample will tell you if it is 100% finished.

I've thought I had beers that were finished and came back a few days later and it was active again. Not sure if it was a change in temp or what but started bubbling again.

Take a hydro sample, it is is at your FG then you are good to bottle or keg. If it's a few points off wait a few more days then take another sample.

Another help is if you can see there beer and if you don't see any visible activity.

 

[Qhrumphf]

All an airlock bubble means is that the pressure inside the fermenter is higher than the pressure outside (plus partial pressure of the airlock itself).

It doesn't inherently tell you why.

It could be fermenting, or it could be a temperature change, or a small vibration (walking by it) knocking some CO2 out of solution increasing the headspace pressure.

There's a few other possibilities. An inhibited STA1 yeast strain (diastaticus) can attenuate to very high levels but take quite a long time to do it.

Related, could be a contamination issue from some wild yeast or diastaticus (including above if a diastaticus strain wasn't intentional).

If this was dry hopped, hop creep could be a very likely explanation.

 

[LittleRiver]

I’ve had my brew in the carboy for almost 3 weeks. Fermentation started hard on the 2 day and went for ~3 days and has died off since. I haven’t seen much activity and planned on bottling this coming weekend but I checked it today and I’m getting an air bubble about every 10 secs. What’s going on and should I be worried for the quality?

Changes in temperature or weather (barometric pressure) can cause bubbling, so that's not necessarily an indicator of fermentation activity.

If primary fermentation was evident for 3 days (I'm assuming the krausen fell after that) and you've given it 3 weeks total, I personally would feel quite comfortable bottling it this weekend.

As others have mentioned, you can know for sure that fermentation is done by taking readings on successive days, but in my experience I would say that it's done, and OK to bottle.

 

[Cliff Morris]

Awesome! Thanks for all of your help, I don’t have a hydrometer but I’ll get one tomorrow and see where I’m at