Science of bubbling

uberlad · Jan 10, 2012

Hey folks,

I'm a relative newbie... Got 8-9 brews under my belt so far. I just brewed a caramel amber ale on Saturday and the bubbling stopped yesterday (Monday). I know the advice traditionally given is to shut up and let it do it's thing. My question however is this: Why does it stop bubbling at all? Isn't the yeast still generating gas? I don't understand the science I guess. What is the yeast doing when it stops bubbling?

Thanks in advance!

BrewKnurd · Jan 10, 2012

Once the yeast is done eating, it stops producing any significant amount of CO2. It goes to sleep.

uberlad · Jan 10, 2012

So the yeast is done/asleep once the bubbling stops? A lot of other threads say the bubbling stops once the yeast eats the "easy sugars" but it is still converting other sugars. Shouldnt I be bubbling for more than a day and a half?

Tinga · Jan 10, 2012

bubbling has nothing to do with yeast activity. bubbling only has to do with an excess of pressure in the carboy. this pressure can be cause by yeast eating sugar and making CO2 or it can be caused by temperature swing or a combination of both. There is more to fermentation than yeast eating sugars though. during the vigorous first couple days when the yeast are eating a majority of the sugar they create the most CO2 which is when the majority of the bubbling happens but again bubbling is not a direct measure of yeast activity. after the yeast eat most of the sugars up they go back and clean up some of their by products and don't generate as much CO2 during this phase.