Air volume in carboys

carrisr · Post by **carrisr** » Tue Mar 30, 2010 12:13 pm

OK, so as you can see from my pics over in the "Who's Brewing" section, I'm trying to do 2.5 gallon batches in 3 gallon carboys. Should I be concerned about oxidation with all that airspace, especially in secondary?

My plan was to transfer to a secondary c'boy of the same size in about another week or once the fermentation looks mostly complete. Then another two weeks or so in secondary before bottling. Or would I be better off leaving it in the primary since, in theory, most of the oxygen should have been driven off my all that CO2?

BrewHound · Post by **BrewHound** » Tue Mar 30, 2010 12:59 pm

You do not have to worry about the primary. The onset of fermentation will take care of this for you as the byproduct of fermentation is CO2. This will drive off all oxygen and air. The air lock will prevent it from reentering the carboy.

As for the secondary. Yes that is a small concern. However, what you could do is take a CO2 tank and put a hose in the carboy (above the liquid) and give it a little juice to drive off the air then recap.

jjbuck · Post by **jjbuck** » Tue Mar 30, 2010 3:52 pm

BrewHound wrote:You do not have to worry about the primary. The onset of fermentation will take care of this for you as the byproduct of fermentation is CO2. This will drive off all oxygen and air. The air lock will prevent it from reentering the carboy.

As for the secondary. Yes that is a small concern. However, what you could do is take a CO2 tank and put a house in the carboy (above the liquid) and give it a little juice to drive off the air then recap.

If you can't get the house to fit you might try a hose.

carrisr · Post by **carrisr** » Tue Mar 30, 2010 6:00 pm

Is there a cheap way to do that? I figure the tank and regulator would set me back around $100, which I can't afford right now.

Matt F · Post by **Matt F** » Tue Mar 30, 2010 9:27 pm

I wouldn't worry about it. I ferment 5 gallons in a 6.5 gallon glass carboy. I do not do a secondary based on recommendations from Jamil Z and Mr. Wizard in BYO. I only do a secondary when dry hopping or for long fermentations. Most healthy primary fermantations are done in 7-10 days. Take a gravity reading when you think it is done. Skip the secondary, rack to your bottling bucket, bottle, wait a couple weeks and enjoy.

brownbeard · Post by **brownbeard** » Wed Mar 31, 2010 7:33 am

I do a secondary, but I never purge the secondary with CO2. For all the little problems that arise in the brewery, oxidation is not something I have had a problem with.

carrisr · Post by **carrisr** » Wed Mar 31, 2010 6:21 pm

Thanks for the input guys. It looks like the main fermentation is basically done. I think I'm going to go ahead and do a secondary with this one because I'm worried it might be cloudy. I think I was a little hot on the boil, and I transfered all of the trub into the fermenter. When I do the other half of this kit I'll try doing primary only and see how that compares. I think I can probably skip secondaries on darker beers.

It's amazing how much controversy there is on secondaries. I've read a lot of forums and articles and there seems to be no agreement. Even the "experts" admit to skipping secondaries frequently.

Another hot topic seems to be aeration methods and whether to aerate the starter or wort. Since I'll probably rarely do starters I guess I'll stick with shaking the fermenter.

Post by **JimPotts** » Wed Mar 31, 2010 10:14 pm

I wouldn't worry about it, either. But there was an article a year or two ago in BYO (I think) about capturing CO2 from the primary. Basically, you can take an uninflated mylar balloon, and hook it up to your primary airlock. It will fill with CO2. Later, you can use that CO2 to purge oxygen from your secondary if you want.

Personally, I wouldn't worry about it.

-Jim

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BrewHound · Post by **BrewHound** » Thu Apr 01, 2010 9:57 am

JimPotts wrote:I wouldn't worry about it, either. But there was an article a year or two ago in BYO (I think) about capturing CO2 from the primary. Basically, you can take an uninflated mylar balloon, and hook it up to your primary airlock. It will fill with CO2. Later, you can use that CO2 to purge oxygen from your secondary if you want.

Personally, I wouldn't worry about it.

-Jim

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Damn, thats a cool idea Pottsy, Guess the only problem would be when do you put it on the primary so that you capture enough CO2 but don't cause the balloon to explode.

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