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How to know when fermentation is finished

Hey everyone, first time brewer here with a question about fermentation. How am I supposed to know when my brew is done fermenting and when I should bottle it? I know the recommended time frame is 1 to 2 weeks. Tomorrow will be one week of fermenting. The layer of foam has subsided and bubbles are coming out of the airlock very slowly, but there is still a really thin layer of really tiny bubbles and spots that look like yeast that haven’t gone to the bottom of the fermenter yet. I’m not sure if I should bottle it tomorrow after a week or let it go for another week to let the little bit that is left to ferment completely. Anyone have any advice or insight? It would be very appreciated!!!

Do you have a hydrometer? Do you know what your O.G. was and what your F.G. is supposed to be?

If not, let it Primary for two weeks, then transfer to Secondary or Bottle.

No, I don’t have a hydrometer. I probably should invest in one. I don’t know what the OG or FG is supposed to be either. It didn’t mention anything about it in my kit or anything like that. How would I know what they are supposed to be? Thanks for the advice. I was leaning towards letting it sit one more week just to finish everything up completely since I don’t really have time to bottle it tomorrow anyway lol. Thank you!

If you purchased a kit it should tell you what the O.G. and F.G. should be.
I never base a complete fermentation by airlock activity. Also, I have only had one bottle bomb, but I believe it was due to a defective bottle. The more I started inspecting bottles, the more small cracks I found.

Ive had beer in Primary for 2 weeks and still had bubbles due to CO2 being released from the beer or yeast cake, but fermentation was complete.
I highly recommend a hydrometer.

If your beer came out bad or didn’t ferment correctly and you posted a question about it everyone would ask for your O.G. and F.G. so its worth buying.

You don’t necessary need a hydrometer. You can figure out when fermentation is complete just by looking like you have been doing.

Any time estimates for when a batch should be done are not reliable. Yeast is a living being and it works at its own pace, not ours. If you try to rush things, and bottle while fermentation is still active, you can get dangerous bottle bombs, so be careful! When in doubt, it is always best to wait a little longer.

You will be able to tell when fermentation is complete when the airlock stops bubbling and the surface clears and the yeast begins to sink to the bottom. At that stage, when you are 99% sure that fermentation is complete, I would still recommend waiting at least another 3-4 days before bottling just to be safe. Warming the beer up near the end of fermentation is also a good idea. You should conduct most ale fermentations in the low to mid 60s Fahrenheit, but at the end of fermentation you can safely bring this up to 70-75 F for the last few days. This helps keep the yeast awake and ensures they can finish the job. You can do this for lagers as well, although in that case temperatures in the 60s are good enough, assuming you fermented in the 40s or 50s.

Don’t believe anyone who says all beers are done fermenting in a week or two. It is baloney. Usually this is the case, but not always. I have seen fermentations completed in as little as 2-3 days, and as long as 3-4 months. It depends on many many factors, including the health and amount of yeast, the yeast strain used, temperatures, nutrients… the list goes on and on. No one can accurately predict for every single batch when the yeast will be finished. Let the yeast tell you when they’re done, not the other way around. Be careful. When in doubt… just wait a few more days, or an entire week, and then bottle. If you don’t, you could be sorry.

Here’s a picture of what the surface of the beer is looking like after two weeks. Still looks like yeast floating on the top with hardly any bubbles at all. Am I supposed to wait for the surface to completely clear up or is this ready to be bottled? Please let me know, thank you everyone!

To me it looks like fermentation is done. What is floating there are bits of trub and rafts of yeast that have clumped on to them. While those would eventually drop to the bottom, it can take a long time for that to happen. If you put the beer someplace cold, it will all drop down in a day or two, and will clear the beer some as well. I would say it is safe to bottle.

I would also say that the beer will improve if you let it sit longer. It will be clearer and have a cleaner flavor if given extra time. Like Dave said above, when in doubt it is always safer to wait a bit more, but as this is your first batch you must be anxious to taste it, so go ahead and start the next one.

Thanks for the advice. I think I’ll put it in my fridge the rest of today and over night and bottle it tomorrow afternoon. I won’t be at my house all week so I’d rather get it bottled while I’m here and yeah I’m ready to try it!!! Also, is it going to be alright if some of that floating stuff gets into the bottles? Sorry for all the questions, I’m just trying to get the hang of everything.

If you syphon the beer into another container to mix with the priming sugar immediately before bottling, most of the floaters will stay behind. And if some does get into the bottles, they will likely settle out to the bottom along with the yeast before you drink it.


how’d it turn out for you?

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