Gas and fizziness?

[ssashton]

Hi everyone,

I used to use a pure CO2 gas bottle with my corny kegs, but I now have a 'beer gas' bottle which is 60% CO2 and 40% Nitrogen.

I'm just not getting the fizz, despite having the keg at 3.5C and pressure at 30PSI which this chart says should give me 2.6 volumes CO2.

https://jollygoodbeer.co.uk/2015/08/23/under-pressure-keg-beer-pressure-in-the-uk/
I've read that the pressure in the keg should go down as the gas is absorbed, but I don't see more than a couple PSI change over a week. That also leads me to think there is little point leaving the gas bottle connected (which I didn't).

Does the head space make a difference? I guess only the surface area exposed to the beer and the pressure matter (assuming gas will be replenished to maintain PSI). I know some people shake the keg, but I thought a week would be enough time to absorb the gas anyway.

 

[smcc]

when you are carbing your beer you want to have the bottle on, basically the pressure in the headspace is forcing gas into the liquid so as its absorbed you want more gas to fill the space and maintain pressure. This can take (depending on PSI setting) anywhere from 3-10 days. I prefer lower PSI and longer carbonation period as for me it gives better head retention.

You always want some head space in the keg to help this process in a 19l corny keg you would want to leave about 0.5 to 1 litre for gas to keep the pressure on your beer.

Some people who want beer quick can connect the gas at 30psi and turn the keg on its side and gently rock it back and forth for about 30min or so to force this but I dont recommend this process I would only do this in an emergency where beer is needed that evening.

A week at something like 15psi should have your beer carb'd. One final thing and I am sure you havent but make sure you have connected at the gas connect and not the liquid

 

[Hoppyland]

I've never used nitrogen, but I suspect that you won't get the same "fizziness" as with pure CO₂ if you're putting in a significant proportion of nitrogen. Think of a can of Draught Guinness as opposed to Guinness Original.

 

[ssashton]

Thanks for the replies!

I think I answered my own question. It was just taking a lot longer to naturally absorb the CO2 than I expected.

Over about 1 week with the keg sitting in the fridge at 30PSI and disconnected from the gas bottle, I barely saw 2PSI of pressure drop. I gassed it back up to 30psi and then shook it around a for a few minutes. I immediately saw about 4psi of pressure drop. So it absorbed more in a few minutes of shaking than it did sitting still over a week.

Yes a mixed gas will give less fizz than pure CO2 for the same pressure and absorption time, but that's why I have it at 30psi rather than about 10psi for pure CO2 to get the same volume of CO2.

I'm told most larger and pale ale in pubs uses 60% CO2 / 40% nitrogen. While stout like Guinness draft will be 50% CO2 / 50% nitrogen or even more to the nitrogen side and presumably even higher pressure.