Carbonation calculations at 12C - not sure I understand

[DaleO]

I have a best bitter that has reached FG fermenting at 18C. I want to cask it and condition it at 12C adding some sugar for priming. The CO2 in the beer is around 0.8-0.9 volumes after primary. When I put 12C as the new beer temperature the calculator then says the beer doesn't need sugar and the new CO2 volume is 1.12 volumes? Does the CO2 volume increase with the temperature drop? I know beer holds more CO2 when cold but surely the beer needs to create the additional CO2 to up the volume from 0.8 to 1.12

Please show me how to work out how much priming sugar to add at 12C to get 1.2 volumes of CO2. Thanks

 

[VikeMan]

The reason for the calculator asking you the temperature is so that it can estimate the residual CO2. Dropping the temperature, in a closed cask, won't increase the residual CO2. So the temperature at the end of fermentation is the one you'll want to use in the calculator.

 

[DaleO]

The reason for the calculator asking you the temperature is so that it can estimate the residual CO2. Dropping the temperature, in a closed cask, won't increase the residual CO2. So the temperature at the end of fermentation is the one you'll want to use in the calculator.

thanks Vikeman. That clears it up

 

[ncbrewer]

I'm curious. How did you figure the current CO2 volumes to be 0.8 - 0.9?

 

[VikeMan]

I'm curious. How did you figure the current CO2 volumes to be 0.8 - 0.9?

I don't know how @DaleO did it, but that's about right for a room temperature beer at equilibrium with the atmosphere.

 

[doug293cz]

I don't know how @DaleO did it, but that's about right for a room temperature beer at equilibrium with the atmosphere.

Almost. ~0.8 volumes is about right for a room temp beer at equilibrium with a fermenter headspace that is 100% CO2 at atmospheric pressure (CO2 partial pressure of 14.7 psi.)

Brew on

 

[DaleO]

I'm curious. How did you figure the current CO2 volumes to be 0.8 - 0.9?

It’s what the brewing app gives as the figure. I brewed at between a low of 18C and high of 20C.

 

[DaleO]

Almost. ~0.8 volumes is about right for a room temp beer at equilibrium with a fermenter headspace that is 100% CO2 at atmospheric pressure (CO2 partial pressure of 14.7 psi.)

Brew on

That’s interesting. I open fermented the first 3 days and then closed the lid for the last 4 days. So perhaps the open ferment will result in a lower CO2 volume?

 

[doug293cz]

That’s interesting. I open fermented the first 3 days and then closed the lid for the last 4 days. So perhaps the open ferment will result in a lower CO2 volume?

Depends on how much CO2 came off during the last 4 days. It's possible that the fermenter headspace got close enough to 100% CO2 for there to be a negligible difference (w.r.t. carbonation.) If the ferment was mostly done after 3 days, then your starting carb level is likely lower, but impossible to estimate.

Brew on