Co2 After Fermentation Has Finished....

[Pandreas]

I'm curious as to why the airlock on my fermenter continues to bubble, even a few days after the hydrometer readings indicate that fermentation is complete...

I currently have a stout brewing, has been in the fermenter now for 8 days. SG at 1018 and stabilised. airlock ticking over every few minutes. I dry hopped with fuggles yesterday and the airlock began working REALLY fast for a few hours....

I am guessing there is C02 remaining in the beer after the fermentation process that continues to escape until the beer goes flat.... is this right?

 

[Insight]

Yep, you're mostly right. You are seeing the co2 come out of solution, which happens more rapidly when the beer gets warmer. Your beer will never quite go "flat" - it will always retain some co2. When you dry hop, the motion of the hops and the dissolving of the hop oils disturbs the co2. You'd probably see the same thing if you threw a bar of soap in the fermenter :blink:

 

[Wasabi]

I don't mean to add a negative spin to your beer but if you have an infection or a wild yeast strain they can also produce CO2 or other gasses as they munch away on nutrients in the beer.

Though you'd hopefully notice this in our beer.

 

[tangent]

don't forget that a low pressure cell of weather will make your airlock bloop. it's not a measuring device, it's there to stop goobers, trust your hydrometer, not your airlock.

 

[The King of Spain]

Also if you are using a fridge and there is fair temperature differential between the ambient & your fridge, what happens when you open the fridge door you create a pressure diffential between the cold air in your your fermenter and the now not so cold air in your fridge. This can result in bubbles that have nothing to do with CO2 production.


See here

 

[Tony M]

and the yeast will have a bit of a munch on the trub