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Old 10-30-2009, 07:38 PM   #21
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Originally Posted by Bonysplicer View Post
But a fermenter is (usually) a closed system with a one-way airlock, so the quantity of oxygen in the system is finite. As the yeast utilize the dissolved oxygen in growth, doesn't more O2 dissolve into the solution in equilibrium with the O2 partial pressure?
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.


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Old 10-30-2009, 07:43 PM   #22
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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.

My fermentations work fine without needing to do it. I pitch enough healthy yeast, and aerate my wort with an o2 stone, so I have never had any issues with fermentation. The yeasties seem to swim around eating sugar and peeing alcohol and farting co2 good enough on their own without needing an amusement park ride to do so.
...and finally I find a quote that is signature worthy!!!


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Old 10-30-2009, 07:45 PM   #23
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I need to invest in an Airstone for pre-fermentation aeration of the wort. I think once your yeast is pitched( at a high rate of coarse), the only time you have to worry about O2 level in your fermentation vessel is the the lag time phase; the shorter the less chance you have of o2 being able to exist. once the fermentation starts, I think the yeast create enough co2 to shove out what ever o2 exists in the car boy. I have yet to make any serious OG beers, so I dont think I will need to agitate mid fermentation any time soon. plus I like the set it and forget it method- I just come take gravity readings once I noticed the airlock has settled out a little bit, but I always rely on gravity readings.

the question I have related to this subject is- how much does a airstone/pump help fermentation? I assume it would help with lag time , and maybe the yeast replicate faster due to higher levels of O2? once their going their going, but how will 02 help with aeration of wort?

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Old 10-30-2009, 07:46 PM   #24
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Originally Posted by lamarguy View Post
Assuming a closed fermentation (no exposure to O2 after fermentation begins), I can think of a couple of reasons:
  1. For high OG beers, to avoid having to "rouse" the yeast (e.g., walk the barrel).
  2. To hasten conditioning. Keeping the yeast in suspension would expose more by-products to a larger quantity of yeast in a shorter time, this reducing the conditioning period. Budweiser does this with beechwood chips (increases yeast exposure surface area).

Some of us plan to experiment with a "stir plate" approach for larger batches (5 - 10 gallon). The theory is sound and the equipment cost to test the idea is negligible.
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.
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Old 10-30-2009, 07:50 PM   #25
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the question I have related to this subject is- how much does a airstone/pump help fermentation? I assume it would help with lag time , and maybe the yeast replicate faster due to higher levels of O2? once their going their going, but how will 02 help with aeration of wort?
If you pitch the proper amount of yeast aeration/oxygenation isn't that important the yeast will go right to work on the sugar. O2 is important during reproduction not fermentation.
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Old 10-30-2009, 07:51 PM   #26
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I'd like to see Lamarguy's experiment..but I will only believe it if it is done similar to how I mentioned...
The original large scale stir bar idea was discussed here.

I plan to use a closed, positive pressure vessel to conduct the fermentation test. I'll likely split a 5.5 gallon batch and ferment at the same temperature.



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But I am wondering.....in doing it with a 5 gallon batchdoes anyone think the stirbar and stirplate needs to be sacled up proportionately, of will the little 1" baby on the satndard plate be enough.
Yes, the size of the stir bar and centrifugal force is certainly a design concern. The goal is to achieve minimal agitation at the bottom of the fermenter, not a vigorous whirlpool. I believe that can be achieved with a 3" - 4" stir bar and a large 6" computer fan.

Only real world testing will tell. Once I get my repaired sanke fermentation kit back next week, I should have an opportunity to test the idea.
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Old 10-30-2009, 07:54 PM   #27
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Originally Posted by lamarguy View Post
The original large scale stir bar idea was discussed here.

I plan to use a closed, positive pressure vessel to conduct the fermentation test. I'll likely split a 5.5 gallon batch and ferment at the same temperature.





Yes, the size of the stir bar and centrifugal force is certainly a design concern. The goal is to achieve minimal agitation at the bottom of the fermenter, not a vigorous whirlpool. I believe that can be achieved with a 3" - 4" stir bar and a large 6" computer fan.

Only real world testing will tell. Once I get my repaired sanke fermentation kit back next week, I should have an opportunity to test the idea.
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.
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Old 10-30-2009, 07:58 PM   #28
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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.
I suppose it depends on your definition of active fermentation. I consider the fermentation "active" until terminal gravity is reached, the beer is removed from the yeast, or the yeast are inhibited in some way (cold, sodium metabisulphite, etc.).

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I asked why do it during an active fermentation. Because the yeast are doing a pretty good job of it on their own.
Agreed, I just elaborated on the potential benefits for having a stir bar in a fermenter post active fermentation.
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Old 10-30-2009, 08:22 PM   #29
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I most likely should have worded it as during vigorous fermentation not active

I would like to see your results also.. How is the conversion unit that Derrin sells working with the closed system ? I have yet to use the one I bought.

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Old 10-30-2009, 08:30 PM   #30
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How is the conversion unit that Derrin sells working with the closed system ? I have yet to use the one I bought.
With the pressure relief valve and MFL fittings, it integrates well into my setup. That is until I realized it wouldn't hold more than ~1 psi after a few minutes. Turns out the unit was damaged during shipping and I didn't realize it until I went to use it (gas out port weld had a hairline crack).

Derrin repaired it quickly and I should have it back early next week. Put it this way, I like it so much I ordered a second unit from him.


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