Can you bottle half a 5 gal batch(carboy size?) - Home Brew Forums
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Old 05-15-2012, 11:02 PM   #1
suzanneb
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Apr 2012
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Can you bottle half a 5 gallon batch and put the other half into secondary if the secondary container is a 5 gallon carboy.
in other words will i run into any trouble with oxidation or anything by having my secondary fermentor being half full with beer and half full with air?

i want to add some flavors to the second half so i can taste the differences between two exact batches



 
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Old 05-15-2012, 11:04 PM   #2
H-ost
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Totally fine.

Just remember to account for less priming sugar. If it is truly half then you can cut what you normally use in half. There are also priming calculators out there.


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Old 05-15-2012, 11:04 PM   #3
mxpx5678
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you should be fine. just make sure you put an airlock or blowoff on it.

 
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Old 05-16-2012, 03:40 PM   #4
HomebrewMTB
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If you want to do this frequently, you should get a 3 gallon carboy. It's the right tool for the job.

 
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Old 05-16-2012, 04:25 PM   #5
spearko520
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if you are worried about oxygen, i think it's the diameter of the side of the beer exposed to atmosphere, not the height of the container interior. if you have a six inch cylinder four foot long, filled to the top, you have the same exposure as one filled halfway. if you were full up to the neck, then you will have more o2 exposure now that your diameter has increased as your level has dropped, but my experience has been that it's okay. i use oversized carboys and even large diameter glass jars with no issues. if you are really worried purge w co2 or argon or pour a little seltzer onto the top...
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Old 05-16-2012, 05:11 PM   #6
zeg
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Quote:
Originally Posted by spearko520 View Post
i think it's the diameter of the side of the beer exposed to atmosphere, not the height of the container interior. if you have a six inch cylinder four foot long, filled to the top, you have the same exposure as one filled halfway.
The diameter (or, really, the surface area) exposed will affect the rate of oxidation. The volume of head space (so surface area times empty height) will affect the total amount of oxidation that can occur, since there will be more oxygen available for reaction. This is assuming that there is no flow of fresh air in through the airlock.

 
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Old 05-16-2012, 06:15 PM   #7
suzanneb
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so what you guys are saying is the surface area of the liquid(based on the diameter of the vessel) will affect the rate of oxidation. the height will affect how much oxygen is available. but since the beer is usually filling the headspace with co2 and no new air is getting in. and since fermentation is pretty much done and there is much more oxygen available to invade the beer won't this cause a problem?

 
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Old 05-16-2012, 06:31 PM   #8
mxpx5678
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Quote:
Originally Posted by suzanneb View Post
so what you guys are saying is the surface area of the liquid(based on the diameter of the vessel) will affect the rate of oxidation. the height will affect how much oxygen is available. but since the beer is usually filling the headspace with co2 and no new air is getting in. and since fermentation is pretty much done and there is much more oxygen available to invade the beer won't this cause a problem?
you could always purge it with CO2 first if you have that available.

 
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Old 05-16-2012, 06:42 PM   #9
zeg
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Quote:
Originally Posted by suzanneb View Post
so what you guys are saying is the surface area of the liquid(based on the diameter of the vessel) will affect the rate of oxidation. the height will affect how much oxygen is available. but since the beer is usually filling the headspace with co2 and no new air is getting in. and since fermentation is pretty much done and there is much more oxygen available to invade the beer won't this cause a problem?
During active fermentation, CO2 will be produced and will displace O2, so it's really not an issue. You'll have some protection after fermentation is mostly done because there's still CO2 in solution that will outgas, but eventually you run out of protection. So once fermentation is done, if you're worried about oxidation, you need to take steps to prevent it---the beer can no longer protect itself. The easiest way is to fill the carboy all the way up to minimize both exposed area and reduce the head space volume to a negligible amount. If you can't do that, then adding a neutral blanket (CO2 or N2, or I've heard reports of food grade mineral oil being used, but I really wouldn't go there) is an alternative.

Note that, for all the talk of a CO2 blanket forming, that's not really quite how it works. Unless the beer produces/releases enough CO2 to displace all the air in the headspace, the CO2 it does produce will mix quite thoroughly in there, so you'll get oxygen exposure. When it produces a huge amount of CO2 at the beginning, it mixes as well, but it's continually pushing the mixed air out, so the concentration quickly tends toward pure CO2. If you put a blanket in, you've then got to put your airlock on to keep it in place.

Finally, let me just say that I'm a n00b, so I'm not necessarily saying you will or won't have a problem with oxidation. So you may be fine just letting it ride, my advice is aimed at taking the best action if you decide that you're worried about oxidation in the first place.

 
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Old 05-16-2012, 07:24 PM   #10
bobbrews
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I will say that it is not fine and that you will most likely run into oxygenation issues.

Putting 2.5 gallons of wort in a 5 or 6 gallon carboy to ferment is fine; it will actually create a richer, denser C02 blanket than 5 gallons in a 6 gallon carboy... which is a good thing.

However, putting 2.5 gallons of beer in a 5 or 6 gallon carboy to condition is not fine. That C02 blanket you worked so hard to achieve is gone and replaced with 2.5-3.5 gallons of empty air space.

Take HomebrewMTB's advice and get yourself a 3 gallon secondary.



 
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