How long should Stout actively ferment? Mine just halted fermentation.

Hello there,

I brewed an Irish Stout this weekend from brewers best. I was curious if it's normal for fermentation to start quickly (within the first 12 hours) and then halted almost completly (bubbles about once per minute or a little longer) after just about 72 hours?

Just curious whats typically for Irish Stout.

Thanks,
Lorne

It's typical for any beer. Each fermentation is unique and different. An assertive strain of yeast can rip through wort in less than 72 hours depending on the gravity of the beer, available nutrients and initial oxygen level. The only way to know if the primary fermentation is done is to take SG readings and have them remain the same for 2-3 days.

Each fermentation is different. Bubbles really do not mean anything more than the pressure inside the fermenter is higher than outside. During the first,very active part of fermentation CO2 can build up, but seeing no bubbles does not mean that fermentation is over.

Which yeast did you use? and what temperature is it at? The bulk of fermentation can be over pretty quick sometimes.

Here is a short video that shows bubbles really mean nothing....

Your bubbles stopping only means that it's stopping bubbling, NOT necessarily that fermentation has halted. More than likely it's just slowing down, like all fermentation does.

You have fermentation. IGNORE what your airlock is or isn't doing. And trust those of us who've been doing it longer than you?

Bubbling doesn't really mean anything other than the airlock is bubbling. And airlock is not a fermentation gauge, it's a vent to bleed off EXCESS gas, be it oxygen or EXCESS co2. It shouldn't be looked at as anything else, because an airlock can bubble or stop bubbling for whatever reasons, including a change in temperature (gas expands and contracts depending on ambient temps) changes in barometric pressure (You can have bubbling or suckback in the airlock, depending on pressure on the fermenter) whether or not a truck is going by on the street, the vacuum cleaner is running, or your dog is trying to have sex with the fermenter. Or co2 can get out around the lid of the bucket or the bung...it doesn't matter how the co2 gets out, just that it is.

And bubbles don't coordinate with anything concrete within the fermenter either, "x bubbles/y minute" does NOT TRANSLATE to any numerical change in gravity....if an instruction says do something when bubbles do something per something, throw the instructions out.

Fermentation is not always dynamic, just because you can't see what's going on, doesn't mean nothing is going on. And just because your airlock starts up, and then slows down or stops in a few days, doesn't mean fermentation is over YET, it just means the excess co2 is not coming out of the airlock...not that the yeast is done.

The only way to know how your beer is doing is to take a hydrometer reading, if you're worried. But not until 72 hours have gone by. Then if you're still concerned, take one...then you'll know.

Counting bubbles does not equate to anything usable in fermentation. It's not like "x bubbles/minute= y gravity points." It just means that co2 is being released....but it could also NOT be bubbling, and still fermenting away.

Relax, leave your beer alone and let it do it's thing for a couple more weeks, and most importantly, IGNORE what your airlock does or doesn't do.

In fact you might find this discussion on the superfluousness of airlocks something that will help you get a handle on this. It was started by a newer brewing who just grasped this concept.

The way to determine if fermentation is complete, is to take 2 grav readings over a three day period. Not by counting bubbles.

lorne17 said:

I was curious if it's normal for fermentation to start quickly (within the first 12 hours) and then halted almost completly (bubbles about once per minute or a little longer) after just about 72 hours?

Click to expand...

Yes, that's normal for Irish stout. I remember brewing one on a Monday and drinking it with dinner on Wednesday (it wasn't too mellow but it was OK). But you need to be sure that fermentation is complete because I brewed on last year that stopped fermenting after about 72 hrs because of a cold spell when it was only half attenuated. That was pretty bad beer. So if the apparent attenuation is in the 70's you are OK. If not you have a problem.

Thanks all! I wasn't too worried, but just thought I'd ask.

Also I used a dry yeast (first time I used it) and rehydrated it prior to pitching it. I don't know what kind it was as I threw out the packet and this recipe: http://brewersbestkits.com/pdf/1023 2013 Irish Stout Recipe.pdf doesn't list it. But that's my recipe I followed.

Thanks again for all the pointers! These forums rock...