I typically carbonate my beers by bringing it down super cold and blasting it with 30psi, shaking it, and repeating a couple times. Is there anyway to calculate the volume of dissolved CO2 when using this method? Say, after 3 shakes at 30psi the CO2 volume is 2.1... To be more clear I'm using "method 2" on page 4 of this PDF http://www.morebeer.com/themes/morewinepro/kegging.pdf
Measuring volume of CO2 in beer using force carbonation
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The volumes at equilibrium for various temperatures are available from tables and formulas which are widely published. But that's at equilibrium. There would be no way to tell what they would be after 3 shakes at a given pressure.
After you get the shaking finished and you set it to the serving pressure that maintains your preferred carbonation level use this chart to figure out your volumes of CO2. For example, if you use 12 psi at 40°F then you are at about 2.5 volumes of CO2.
This, assumed that you have reached equilibrium.
zachattack
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Agreed. A "shake" is something that's rather subjective and not really quantifiable. You can measure the pressure in the headspace following the shake, read the pressure once the system equilibrates, and use a carbonation chart or calculator to calculate the volumes.
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This will not work. It does not reflect the dissolved volume, only headspace pressure.
zachattack
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It will (and does) work, but I should have specified that you need to wait for the system to equilibrate.
At equilibrium the dissolved volume is very easily calculated from the headspace pressure using Henry's law. Given a large volume of beer and a small headspace it would likely reach equilibrium relatively quickly, or almost immediately after another quick shake (with no gas entering the keg). With a full keg you can neglect any losses in the headspace. Some people on here have a pressure gauge mounted on a gas QD that they use for this purpose.
PlinyTheMiddleAged
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Is there any such thing as a flow meter that can measure the volume of CO2 going into the keg? If you knew you had 5 gallons of beer in your keg and your flow meters registered 12.5 gallons of CO2 flowing past the (theoretical) meter, then you'd know that your force carbing yielded a beer carbed at 2.5 volumes.
Obviously, this is not a calculation and I've assumed the headspace is zero but one could theoretically measure carbonation levels (if such a flow meter were available).
Obviously, this is not a calculation and I've assumed the headspace is zero but one could theoretically measure carbonation levels (if such a flow meter were available).
It will (and does) work, but I should have specified that you need to wait for the system to equilibrate.
At equilibrium the dissolved volume is very easily calculated from the headspace pressure using Henry's law. Given a large volume of beer and a small headspace it would likely reach equilibrium relatively quickly, or almost immediately after another quick shake (with no gas entering the keg). With a full keg you can neglect any losses in the headspace. Some people on here have a pressure gauge mounted on a gas QD that they use for this purpose.
There ya go..:rockin:
That was the missing part!!
With respects to reaching equilibrium quickly due to small headspace, that is
not actually correct. Shaking the keg will not allow you to achieve equilibrium, instead it will assist with forcing the co2 to dissolve. If wanting to quickly carb.. Certainly roll, shake, purge, pour..
Then let it settle for a few days with the proper pressure/temperature..
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Zahm makes a guage/meter that would allow you to measure, however you can do the same by measuring temperature, and pressure, then refer to the chart (example: http://www.kegerators.com/carbonation-table.php)
zachattack
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PlinyTheMiddleAged
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Yes, you could use temp and pressure if the system is in equilibrium. But I was picturing the OP sitting with the chilled keg hooked up to CO2 set at (something like) 30 psi and shaking it until it was properly carbed. If the regulator was at 30 psi on a 40°F keg, you wouldn't be at equilibrium for a properly carbed keg - if you were at equilibrium at those conditions, you'd be at over 4 volumes.
If you used a flow meter, then you can do this under non equilibrium conditions - set a pressure above the required equilibrium pressure for the temp/carb level required and shake until you force the needed volume of gas into the keg. Once you see that 12.5 gallons of CO2 have gone into the 5 gallons of 40°F beer in your keg, burp the pressure relief valve and turn the regulator down to 12 psi.
But there are problems with what I'm proposing - cost for one, and I'm neglecting head space effects.
Jsprinceiii is right - go ahead a force carb and then check equilibrium conditions after letting the keg sit for a bit. Look up on the chart your temp and pressure and adjust as needed to hit your desired number of volumes.
