# How long to leave in the fermenter



## megasuke (16/7/13)

Have two questions about my Ginger Brew.

The starting OG was 1.040 and now about 2wks later it has dropped to 1.011. Around about what OG does the brew stop doing its stuff? I tasted it and there's still a strong taste of brown sugar to it so I'm thinking a while off yet?

I have to be away for the next two to three weeks. If the brew stops fermenting while I'm away is that a bad thing? Do I need to bottle it straight away after it stops?


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## Truman42 (16/7/13)

Check your gravity for 2-3 days and if it hasn't changed its done. It wont matter if you leave it although you could probably chill it down to 3C while your gone for a cold crash to clear it up a bit.


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## megasuke (16/7/13)

Leave tomorrow morning so won't be able to check it till I get back. It's still bubbling gently through the airlock though so it might be a while of yet. This is all guess work on my part though.
It's getting to be 14C and 16C here will that slow or stop the fermenting at all? What do you mean by a "cold crash"?


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## Dan Pratt (16/7/13)

If you have a temp controlled fridge for the FV then chill it down to suggested low temp, when you get back ramp up the temp on a heat pad and fermentation will finish itself. Consider it a lagered GB.


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## jammer (17/7/13)

Be aware if you cold crash in the f.v you are gonna get suck back from the air lock as the liquid cools. 
Guess its ok if you got vodka or stars an in it.


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## JDW81 (17/7/13)

There is an easy solution for that. Don't use an airlock.


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## yum beer (17/7/13)

jammer said:


> Be aware if you cold crash in the f.v you are gonna get suck back from the air lock as the liquid cools.
> Guess its ok if you got vodka or stars an in it.


not likely.
the air around the fermenter will cool quicker than the air inside so there is no 'suck back'.
the air lock will hold almost dead level the whole time.


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## MCHammo (18/7/13)

yum beer said:


> not likely.
> the air around the fermenter will cool quicker than the air inside so there is no 'suck back'.
> the air lock will hold almost dead level the whole time.


It doesn't matter which cools first/faster. The fact that the volume inside the fermenter is reducing means that it will tend to suck air in. That said, depending on the temperature difference between chilled/non chilled, how long fermentation continues once in the fridge, and reduced solubility of gasses at lower temps, suck back may actually be reduced or prevented.


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## Judanero (18/7/13)

I thought gas was more soluble at lower temps?


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## MCHammo (18/7/13)

Damn, you're right. At higher temps, anyway. Not sure what happens close to freezing, though.It may not change much in a narrow temperature band anyway (and without stirring, the wort would take a very long time to reach saturation anyway. But that is another mechanism for facilitating suck back through the airlock.


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## yum beer (18/7/13)

Go back to your oldschool Cadbury ads......'atmospheric pressure does the work'
As long as the temp inside the fermenter is higher than the air outside it will not suck air in, even as it reduces in volume, the warmer air/co2 inside will expand and hold the space.
By the time the temps are levelled out the pressure diference is too small to have an effect.
If you need proof, cold crash your fermenter and watch the air lock...diddly squat, nothing, zip, zilch.....bring some beer to kill some time.


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