Outgassing vs. Fermentation - Home Brew Forums

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Old 04-08-2009, 08:03 PM   #1
Schnitzengiggle's Avatar
Feb 2009
Tucson, AZ
Posts: 2,560
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I have a primary that has had airlock activity for over 3 weeks. What is the difference between outgassing and fermentation, and how long can outgassing occur after fermentation is finished?
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Old 04-08-2009, 08:06 PM   #2
bradsul's Avatar
Sep 2006
Ontario, Canada
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Only your hydrometer knows the difference. Once the reading is the same for 3 days in a row it's finished fermentation and just outgassing. At three weeks I'd guess fermentation is most likely finished.
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Old 04-08-2009, 09:16 PM   #3
ArcaneXor's Avatar
Nov 2007
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If you have a carboy or Better Bottle, it's easy to tell - shine a flashlight in there and see where the bubbles originate. If they all come from the yeast bed, you've got fermentation (or, at least, organic activity - anaerobic breakdown of organic matter can also release gases unrelated to fermentation). If the bubbles originate from the walls of the carboy well above the yeast bed, you've got outgassing.

As long as your expected final gravity has been reached and has remained stable for a week or so, you can convince those last, persistent yeast to quit by cold crashing.

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