how do you know your beers done fermenting?

I understand the importance of the hydrometer and of course I use mine as its a great tool. I usually follow the rule to take three consecuitive hydrometer readings before bottiling but is it fool proof? Like if the fermentation is almost done and its going very slowly then it may take more than 3 days to ferment out right?

Currently i have a beer thats fermenting at 65 F and has slowed down to a crawl and iv been taking hydro readings that are a week or more apart but still getting the same hydro reading. I dont think its done though because if i look in my glass carboy with a flashlight i can see some little bubbles rising up. these bubbles are yeast still working and fermenting right?

Sounds like it is either done or stuck. Is the krausen gone? What was the OG? What is the gravity now? What kind of beer is it.

Can you give us the OG and target FG?

Not necessarilly. Co2 gets dissolved in solution as a natural product of fermentation. It doesn't all go straight to the head space & out the airlock. How much co2 stays in solution depends on the wort temp during fermentation. You can see a lot of airlock bubbling during initial fermentation if the FV is sealed well,& it's a healthy yeast pitch making a vigorous ferment. Once bubbling in this instance slows or stops,it just means that initial fermentation is done. It'll then slowly,uneventfully creep down to FG. Then give it 3-7 days to clean up fermentation by products & settle out clear or slightly misty before priming & bottling.

unionrdr said:

Not necessarilly. Co2 gets dissolved in solution as a natural product of fermentation. It doesn't all go straight to the head space & out the airlock. How much co2 stays in solution depends on the wort temp during fermentation. You can see a lot of airlock bubbling during initial fermentation if the FV is sealed well,& it's a healthy yeast pitch making a vigorous ferment. Once bubbling in this instance slows or stops,it just means that initial fermentation is done. It'll then slowly,uneventfully creep down to FG. Then give it 3-7 days to clean up fermentation by products & settle out clear or slightly misty before priming & bottling.

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This. Those little bubbles you see are called off gassing. If gravity has been stable week to week it's done (provided that gravity is around where it was supposed to finish).

Taking gravity readings is foolproof. If your gravity is stable, the beer is done fermenting.

As others have said, CO2 gets dissolved in the beer and yeast cake. The bubbles you're seeing is just off-gassing.

When I have reached my predicted FG I take a reading every other day on the ole hydrometer. Once I get three consistent readings that are the same, I rack it into bottles or into a keg to age and carb. If you dont have a hydrometer, get one ASAP and learn to interpret the readings that you get. It will tell you everything you will need to know to make certain decisions while brewing.

Wheelchair Bob

mrrshotshot said:

This. Those little bubbles you see are called off gassing. If gravity has been stable week to week it's done (provided that gravity is around where it was supposed to finish).

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Thanks for clearly pointing that out. I wondered if it was just off gasing... I guess even at a cooler temperature of 65F you can still see a steady stream of co2 being released. because thst is what i was seeing, a small amount of tiny bubbles steadily rising up from bottom to top.

shanek17 said:

Thanks for clearly pointing that out. I wondered if it was just off gasing... But then i thought the bubbles could be yeast still fermenting and didnt want to bottle to soon.

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The hydrometer is pretty foolproof- but instead of three days, having two gravity readings a week apart is even safer if you're worried.

There are other signs that fermentation is finishing that you can see before breaking out the hydrometer. One is that the beer will start to clear, from the top down. It'll get darker at the top first, and then the whole batch will get darker looking as the yeast drops out. I'd look for that before taking a hydrometer reading- because then it's most likely to be finished.

I only package clear beer. First, because there is far less crud in the bottles then. Also, it's just more aesthetically pleasing.