How Much is Too Much Air

Discussion in 'General Brewing Discussions' started by Tom McLean, Feb 20, 2014.

  1. Tom McLean

    Tom McLean New Member

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    How much space should I leave in a carboy used as a secondary fermentor? Volumes never turn out just right to exactly fill a 5 or 6 gallon carboy. Do you just leave some space (2 or 3 quarts) or do you go out of your way to get it full to the neck. My beer stays in the secondary for 6 to 8 weeks before bottling, while it finishes fermenting and gets conditioned etc.
     
  2. Ozarks Mountain Brew

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    when you ferment all the dead space on top gets filled up with co2, the air you see coming out of the air lock, so as long as your fermenter is sealed and not opened after fermentation stops it doesn't matter, if you open it and seal it back after fermentation your adding air back in on top of the beer and under a very small percentage could bond with the beer but its unlikely unless it sits there for months or more
     
  3. chessking

    chessking New Member

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    Common practice has been that in the secondary you should leave as little air space as possible to prevent oxygen exposure. Back when I used to secondary, I primary fermented in a 6.5 gal. carboy, and transferred into a 6 gal secondary to limit head space. Now I just leave it in the primary for 3 to 4 weeks, then keg/bottle. This limits O2 exposure, saves extra equipment cleanup, and leaves the beer on the yeast cake longer, ensuring that the yeast complete the fermentation and diacetyl cleanup. But if you plan to secondary. limit the head space, or flush out with CO2.
    Or you could just drink it sooner before oxidation sets in.
     
  4. ebstauffer

    ebstauffer New Member

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    +1
     
  5. MrBIP

    MrBIP Active Member

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    Ya, that... :D

    I've been doing primary and secondary in the two 6.5 gallon glass carboys when I got started. Have had some beers around for several months and not noted any oxidation. (I did recently by a 6 gallon plastic specifically for secondary, but not for any reason other than just needing more carboy space).
     
  6. Tom McLean

    Tom McLean New Member

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    We brew in an open fermentor, and transfer to a carboy after the major fermenting activity has finished, this takes from 4 to 7 days. Usually there is still some activity. The beer is then kept in the carboy for another 3 weeks to finish fermenting before we lower the temperature and condition it for another 4 to 6 weeks. Tat is a total of 7 to 9 weeks. The problem is we have not been accurately measuring fermentor volume, and end up with a half gallon or more short of a full carboy. What do the brewers here do to solve this problem? I found some good beer and filled the carboy up into the neck.
     
  7. Ozarks Mountain Brew

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    we don't fill the secondary head space is fine, we keep it chilled and just like putting something in the fridge, that slows any bad things from happening. If you want to keep something stored for long periods of time just keep it chilled or put it in a keg and add C02 to it
     
  8. The Brew Mentor

    The Brew Mentor Well-Known Member

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    I get the " Longer time in the fermentor thing" , but why so long?
     

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