General Category > Yeast and Fermentation

Thought It Was Finished

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I made an Oktoberfest last month and the recipe called for Wyeast 2112 | California Lager.  Based on some feedback I received on another post, I decided to do a semi-lagering phase and chilled it down to 40°F.  Before dropping the temperature, I checked the S.G. a few days in a row and it was holding steady at 1.016, which was a little above the estimated F.G. of 1.013.  No big deal I figured.  So, I've had it in my freezer for two weeks and decided that I would bottle it today.  I was brewing another beer this morning so I took the carboy out of the freezer to let the Oktoberfest warm up a little before bottling.  As it warmed, I noticed signs of fermentation - a lot of bubbles on top of the beer (that weren't there when I took it out) and the air lock was bubbling every five seconds or so.  I took another reading at the S.G. was at 1.013. Should I let the beer ferment at 65°F for a few more days and check the S.G. again?  I'm afraid if I try to bottle it now, I might get too much carbonation in the bottles.  This is my first attempt at a lager so I've never experienced this situation before.  Thanks!

Jeff M:
Bubbles dont necessarily mean fermentation. As i understand it as CO2 warms up it expands, so all you could be seeing is the remains of fermentation co2 coming out of suspension in the beer.


Going by airlock activity is far from reliable as far as tracking fermentation progress goes. As mentioned before, the solubility of CO2 in beer decreases as the temperature rises. When the beer warms up you will have CO2 leaving solution for a while. As long as the gravity reading stays the same, it's done. Monitoring gravity is really the only accurate way to track fermentation progress.

If you didn't warm up your previous samples you are also seeing how temp affects the density of liquid.  Colder liquid is more dense so the gravity will read a bit higher.


What the others have said. Most likely it is finished. Bubbling airlocks are a poor way to determine fermentation, as all it means is co2 is coming out of so,union, which can happen weeks after fermentation has finished and especially as the beer warms up.


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