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Old 07-05-2012, 02:00 AM   #11
emjay
 
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Quote:
Originally Posted by BetterSense
Well, looking through the stir plate thread, there were several people with massive stir plates that can handle a carboy. I can totally see dropping a stir bar in the carboy and setting it on a stir plate just in case you want to rouse the yeast some during fermentation. It sounds like some people do it.
I got one like that as a test product of a commercial unit. I'm not sure it can be done with a computer fan, though.

 
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Old 07-05-2012, 02:07 AM   #12
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I guess in theory it can be done in the first 24-36 hours of fermentation, but if you have to do this to make good beer I'd say you have other problems.... IMO!
I don't have problems with attenuation, so I'd never do it.

 
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Old 07-05-2012, 03:17 AM   #13
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Quote:
Originally Posted by Budzu View Post
Hmm what aeration? If fermentation has already started, is not co2 being produced and haven't other gases been pushed out of the fermenter? how is the stir plate is going to actively pull oxygen into the beer if its not in the fermenter? I call bunk on the above replies.
Seems like it would be an excellent idea for the first 24 hours.
What's going on here?I've never considered this angle before.

 
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Old 07-05-2012, 03:26 AM   #14
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I'm pretty sure the same goes for erlenmeyer starters on stir plates.. there's not much if any oxygenation going on after fermentation starts.

I've done stirred 6 gallon carboys, but the best vessel for this is the sankey keg. 1/6 bbl or 1/2 bbl, they work great with a 2.5" stir bar in the perfect bottom center of the keg. I use them for starters for 2 barrel batches. It is a large dc computer fan that I use, with 7-9 volts.
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Old 07-05-2012, 02:51 PM   #15
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There is stirring and then there is aeration. Not all stirring is aeration. Once you put the airlock on to prevent any more oxygen from coming in, you are just stirring, not aerating.

The yeast themselves do a pretty good job of keeping things roused up so a stir plat isn't really necessary. However, if you want to go for it, it won't cause any harm to the beer.

There are a few yeast that are notorious for dropping out early, and if using one of these yeast, then there might be some benefit (although the occasional swirl would probably be enough)
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Old 07-05-2012, 05:15 PM   #16
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Stirring a carboy that has an airlock will not oxidize anything.
One thing not mentioned here is the effect of CO2 on ester production. I will guess you may get more esters by driving off CO2, but the esters may go with it.
Try a side by side that would be fun.

 
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Old 07-06-2012, 06:30 AM   #17
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It could certainly be a good idea once reproduction is over... more yeast exposed to the wort for 'mellowing.' Artificial bechwood aging. If the fermenter is sealed you don't have to worry about O2. Stirring would also eliminate thermal stratification, which, if you've played around with immersion chillers and multiple thermometers, is very significant.

 
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Old 07-25-2012, 12:25 AM   #18
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I'm very interested in stirring to eliminate thermal stratification. My one concern is whether it would increase fermentation of proteins and other undesirables that have settled at the bottom of the vessel. I recall that John Palmer advises against leaving beer in primary for that reason. It would also eliminate the ability of the brewer to transfer to secondary and with that transfer leave behind the same proteins and other undesirables. Thoughts?
Truly temperature controlled fermentation in home brew is something of a dream of mine. Ideas I have, barring a solution to this issue:
- Really wide fermentation vessels
- Immersing the fermentation vessel in a well circulated liquid e.g., water to keep it well temperature controlled throughout by convection

I'm leaning toward option 2 above once I have a big enough place to put it together.

 
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Old 07-25-2012, 12:40 AM   #19
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To address the transfer issue you mentioned, from my experience doing this it should not create a problem, as long as you can stop the stirring.

The reason is, it will speed your fermentation, causing the yeast to flocculate earlier. If you can see the ferment, you may notice when the yeast tries to cling together to drop out. At this point (or a day before you desire to transfer), you can stop the stir, chill a bit if possible, and everything will settle out very quickly after, allowing you to cleanly transfer. Its similar to what you'd expect decanting a starter. So it also depends on the yeast strain.
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Old 07-25-2012, 12:48 AM   #20
andrewskibrewski
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Another good thought to home brew fermentation - buy a refrigerator big enough to stick your fermenter into. I brew in fl and its hot! Indoor temps of 78 degrees sometimes still fermenter my beer strong! However the refrigerator can be controlled with an on off switch, but it on low and control the beer fridge. A solution to heat ferment refrigerator

 
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