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Old 10-30-2009, 08:37 PM   #31
springer's Avatar
Feb 2008
Wappingers falls NY
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I have to say the quality of his products is top notch. If it works out for me I will have to buy a few more . I have two 1/2 barrels and three 1/4 that I want to use as fermenters . I already used the 1/2 a few times but with a stopper and airstop
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Old 10-30-2009, 08:37 PM   #32
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Jun 2007
Greenville, SC
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Originally Posted by springer View Post
wasn't walking the barrel used towards the end of fermentation? Just like when I swirl the carboy a few days after active fermentation is complete just to rouse the yeast a little .

And conditioning is done after the active fermentation is completed.

I asked why do it during an active fermentation . Because the yeast are doing a pretty good job of it on their own.
Oh, I thought you were talking about rousing at the end of fermentation. I don't claim to be an expert, but it seems to me if you pitch enough yeast, using a stir plate for a whole batch is probably useless. That is unless you are trying to achieve a very specific goal, like a really dry beer with no adjuncts.

I also know we can't compare everything we do to commercial brewers, but you don't see them mixing up thier fermenting wort. I guess I'm trying to say that I don't fully understand the point of this. Why would I want to constantly stir my fermenting wort when I can get desired attenuation through proper aeration and pitch rates?

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Old 10-30-2009, 08:41 PM   #33
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Oct 2005
Oak Grove, Oregon, USA
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Even if the top of a flask is left completely open (rarely the case) how is the oxygen getting in there once it is full of co2?
Two reasons: 1. air-entrainment due to friction 2. yeast give off very little CO2 during their growth.
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Old 10-30-2009, 08:56 PM   #34
Aug 2009
Reading, Pennsylvania
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Originally Posted by Revvy View Post
I'd like to see it done both on a closed setup like yours, but also done in a typical carboy/airlock setup that most folks have. I have a feeling the results would be quite different. That perhaps in a closed environment, purged of o2 it would work great, and their would be no oxydation worries...but in a "real world" or typical hb'ers situation it would be a setup for disaster.
Your statement shows a lack of understanding of physical chemistry. Check out references to Henry's Law. In any fermenter situation, carboy or otherwise, gases exist in equilibrium between two phases, gaseous (headspace) and dissolved gas in solution. the rate of transfer in this equilibrium is a surface area limited function.

For example, when you use an oxygen stone or fish tank bubbler to pump o2 through your wort, the wort picks us a high level of o2 quickly due to surface area to volume ratios of tiny bubbles and the high partial pressure of o2. Similarly, boiled, degased starter wort picks up oxygen because whirlpool agitation increases surface area exposure, but still the wort will only dissolve enough o2 gas to be in equilibrium with the partial pressure of o2 in the headspace. So relative to the gas/liquid interface stirring merely hastens the balance of equilibrium.

BUT in a fermenter yeast use o2 and "fart out" co2 into solution So the partial pressure of dissolved o2 decreases over time and the partial pressure of co2 increases over time. Additionally, the total pressure in the headspace is regulated by the airlock/blow off. So as the co2 builds up in solution it increases the partial pressure of gaseous co2 (equilibrium). But since the total pressure is fixed, gas is driven off through the airlock. That gas is a mixture of co2 and o2. Over time the faction o2 in the headspace limits toward zero through being driven off through airlock and being used by the yeast.

My understanding is that "oxidation flavors" are caused by excess dissolved o2. From this it would seem prudent to drive off excess dissolved oxygen as quickly as possible, prehaps through agitation in an oxygen defficient environment.

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Old 10-30-2009, 09:18 PM   #35
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Aug 2008
Austin, TX
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Originally Posted by Edcculus View Post
Why would I want to constantly stir my fermenting wort when I can get desired attenuation through proper aeration and pitch rates?
The objective is maximize the movement of the yeast throughout the wort. A stir plate is an effective means to achieve constant yeast movement. The secondary objective is to speed the conditioning process.

For example, studies have shown leaving cold break in the fermenter increases the nucleation sites for CO2 during active fermentation, which allows the CO2 to be released more readily from solution. This induces stronger currents (swirling) within the wort, a "natural" method for yeast movement. We're just talking about augmenting that process with mechanical motion.
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Old 10-30-2009, 09:21 PM   #36
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Dec 2007
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Originally Posted by Bonysplicer View Post
Ah! It's not a matter of disliking your explanation! I certainly did not mean to offend. I was just looking for a bit more of a scientific explanation than "Oxidized beer is not yummy" I was merely conjecturing and offering my thoughts on the situation
Then go talk to a scientist, this board is to give advice, not provide you with "scientific" explanations of everything. I've brewed enough beer to know you don't want to put your carboy on a stir plate.

But please, feel free to do so and report back with the results.

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Old 10-30-2009, 10:20 PM   #37
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Aug 2009
southern IN
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Originally Posted by JVD_X View Post
A fermenter is not a closed system, it out-gases.

Also, O2 CAN come back the other way if the pressure on the outside exceeds the pressure on the inside. This happens most often when you put an airlock on while the wort is still warm.
Maybe slightly..but not for long. The wort will start to outgas and form a CO2 blanket over the beer since it is heavier than the O2. I respect the Rev's opinions but sometimes i wish someone would say "I'm not sure, I have not tried that sort of thing. You should try it and educate all of us." I once posted a thread basically saying that, "here is what i did, these are my results" and almost everyone told me that i had to be wrong.

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Old 10-30-2009, 11:42 PM   #38
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Dec 2007
"Detroitish" Michigan
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Originally Posted by oldschool View Post
I respect the Rev's opinions but sometimes i wish someone would say "I'm not sure, I have not tried that sort of thing. You should try it and educate all of us."
Uh, I think I said that, TWICE in this thread....

Originally Posted by Revvy
If you don't like our explanation, and have your own theory then why don't you try it and prove us wrong? Me personally, I don't want to risk 5 gallons of beer to know if I am wrong or not.
Originally Posted by Revvy
Then YOU do it...make up a 10 gallon batch of beer....split it into two fermenters, pitch EXACTLY one packet of dry yeast into each batch....Spin one with a stirbar, leave the other alone. Bottle and come back in 6 weeks and see if half the batch tastes like cardboard.

Actually THREE times, I also discussed Larmarguy's experiment and offer some ideas as to that as well.
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Old 10-31-2009, 01:33 AM   #39
Jul 2009
Chelmsford, MA
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I've been thinking of adding agitation to my next fermenter. I don't see any reason that it would have anything other than a positive affect on the fermentation. The agitation doesn't need to be terribly vigorous and probably not even continuous to get maximum attenuation out of the yeast. You'd likely have to adjust your brewing process a bit for slightly higher attenuation, but in the long run it's probably an extremely consistent fermentation method.

Oxidation shouldn't be a concern at all. I'm not sure why it would be, there's no oxygen in there.

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Old 10-31-2009, 02:05 AM   #40
Nov 2008
Kansas City
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Originally Posted by wildwest450 View Post
I've brewed enough beer to know you don't want to put your carboy on a stir plate.
How can you know something when you lack anecdotal observation or even a rudimentary understanding of why it would be true?

Bonysplicer has a point in that the oxidation argument, that is stated as a matter of fact, is laughable. It blows me away that somebody can think that agitating the beer would change the composition, apparently via magic, of the gas that is in contact with the surface. It certain would change the surface area exposed to gas, but that doesn't matter if all of the gas is inert (as it was right before the magic happened).

Also laughable, that two HBT posters with more street cred than Bonysplicer are doing the same damn thing and nobody is calling them stupid.

My 2 cents, I think recirculating the beer with a pump is a more promising approach (and one practiced by a number of commercial breweries).

My other 2 cents, this is the wrong message board to use the word "why" on.

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