Dear Friends, could you please help me to understand why a bottle 33 cl of beer correctly primed (6 grams/liter of corn sugar, 2.4 volumes CO2, FG 1.002) and no infected, but not completely filled up (let’s say, half filled) is quite exploded when I opened it after 2 weeks of conditioning at 25°C degrees roughly? The other bottles (correctly filled up) have absolutely no problems. Thanks so much! Ciao! Carlo from Italy
Hi Carlo,
I’m not exactly sure of the science at work here, but your experience matches what I have observed in many years of judging homebrew competitions. Low filled bottles tend to overcarbonate, while high filled bottles tend to undercarbonate. Approximately 1 inch (2.5 cm) of head space in the bottle works well.
At one point I read that this has to do with the amount of CO2 that’s in the bottle but not dissolved in the beer. When there is only a little bit of free space, there is only a little bit of compressed CO2 that rushes out when you open the bottle. But when there is a lot of open space, there is a lot of CO2 that is compressed but doesn’t need to dissolve in the beer. So when you open the bottle, all of this compressed gas rushes out. Which in turn agitates the beer and causes it to foam.
Beer holds more CO2 (~2.5 v/v depending on beer style) than the headspace (1 v/v).
Thank you very much to all of you!
joe_meadmaker’s opinion coincides with the one a friend of mine (Paolo Lerda, master brewer at his own italian craft brewery Trunasse in Cuneo, producing since long time wonderful Ales) gave to me some minutes ago! Next time I’ll avoid to collect all last drops of beer from bottling tun, filling a bottle only half volume! It was really a bomb!
Thanks again! Cheers!