Amount of air left in carboy

[GoCardinals09]

I have 2, 5 gallon carboys and was wondering what the standard was for amount of air / no beer area at the top of the carboy during primary and secondary fermentation is. Does it matter how empty or full the carboy is? If its too full will it pop the airlock off right?

Thanks

 

[ChshreCat]

For a primary fermenter, you probably don't want to use one of those since they'd be a little small. They'd be good for a secondary/brite tank though. I'd pick up a 6.5 gallon better bottle or bucket for primary.

 

[zac]

I wouldnt use a 5 gal carboy for a primary, you're sure to pop the airlock. But for secondary, a 5 gal is where its at.

Primary= 6 gal minimum, 6.5 is better, (a 7.9 gal bucket is best)
Secondary= 5 gal is best, everything else is ok.

 

[homebrewer_99]

Air/head space is really nothing to worry about since the yeast gives off CO2 and displaces any air in the carboy.