Volumes CO2 in bottling, and PSI in kegging - Home Brew Forums

 Home Brew Forums > Volumes CO2 in bottling, and PSI in kegging

10-09-2013, 11:34 PM   #1
passedpawn
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When we bottle beer, we shoot for "Volumes CO2". The typical beer is 2.4 volumes of CO2.

What is a "Volume of CO2"? If any amount CO2 were given free reign, it would expand to the size of the universe.

Also, why is "Volumes of CO2" used in bottling, but PSI is used in kegging? They are both trying to get to the same thing. Why don't we talk about PSI in bottling?
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10-09-2013, 11:40 PM   #2
Black
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From what I understand, you apply pressure (psi) to dissolve co2 in the beer, to reach the desired volumes of CO2. It is probably a volume of CO2 per milliliter, liter, etc.. That I don't know.

I never stopped to think about it but now i'll have to do some research.

Cheers!

10-09-2013, 11:41 PM   #3
Black
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10-10-2013, 12:10 AM   #4
GotPushrods

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Quote:
 Originally Posted by passedpawn When we bottle beer, we shoot for "Volumes CO2". The typical beer is 2.4 volumes of CO2. What is a "Volume of CO2"? If any amount CO2 were given free reign, it would expand to the size of the universe. Also, why is "Volumes of CO2" used in bottling, but PSI is used in kegging? They are both trying to get to the same thing. Why don't we talk about PSI in bottling?
Volumes are dependent on pressure and temperature. We talk about pressure in the keg, but the temperature is implied. Changing the temperature will change the carbonation at that pressure.

We don't talk about pressure in the bottle since we can't directly apply pressure to the bottle. But it's there, for sure. It also changes with the temperature of the bottle, which is why you want to put it in the fridge before opening. It will cool and absorb more carbonation.

10-10-2013, 12:35 AM   #5
passedpawn
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Quote:
 Originally Posted by Black
Quote:
 The amount of CO2 dissolved in beer is most often referred to in terms of volumes. Volumes of CO2 are defined as the volume the CO2 gas would occupy if it were removed from the beer at atmospheric pressure and 0o C
OK, so what volume does a thimble of CO2 occupy if removed from beer?

A gas will expand to fill its container. So a thimble of CO2 would expand to fill the universe. What volume is that?
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10-10-2013, 02:37 AM   #6
ajdelange
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When we say that a beer contains 2.4 volumes of CO2 we mean that if all the CO2 were removed from the beer and dried that it would, at STP, occupy 2.4 times the volume of the beer. IOW 1 liter of beer carbonated to 2.4 volumes contains 2.4L of CO2 at STP.

Volumes are used in kegging too. One consults the ASBC or Zahm and Nagle table which tells him the pressure he must apply at a given temperature in order to obtain x Volumes carbonation.

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