Kpa for Nitrogen

[chriscapetrib]

Hi All
Right here we go again.....

Can anyone help with some pressures for gassing with nitrogen.

I have checked out BOC and they have a 75 - 75% Co2 + N mix and a 55 - 55% Co2 + Nitrogen mix.

If anyone can tell me how long to gas with each they will receive a nice dark ale with a delicious creamy head or their money back.

cheers all

[rwh]

I think with nitrogen what you do is you divide the pressure by the proportion of CO2 in the mix.

so, for 75%: (pressure you would normally carb at) / 0.75
for 55%: (pressure you would normally carb at) / 0.55

i.e. you want the pressure to be higher than what you would normally use.

The reason for this is that you want the same amount of carbonation, and the beer only cares about the partial pressure of CO2 to achieve this. Also, the solubility of nitrogen in beer is significantly less than the solubility of CO2.

I think guinness and kilkenny use a 15% CO2 mix.

[chriscapetrib]

so, for 75%: (pressure you would normally carb at) / 0.75
for 55%: (pressure you would normally carb at) / 0.55

i.e. you want the pressure to be higher than what you would normally use.


That makes sense!! so it would be as if the N2 is not really there? - I think.

In my case 300kpa/.75 = 400kpa = 300kpa Co2 & 100Kpa N2

Is that right?

BOC guy said 55% Co2 was for Guinness & Kilkenny?

[rwh]

Yep you're right on most points. According to wikipedia, Guinness requires 25% CO2 and 75% Nitrogen. I also looked at the grain and grape website to see what they offered. They have Air Liqide stuff, aligal 2 and 13. Aligal 2 is 99.5% CO2. Aligal 13 is 60-85% Nitrogen, and 15-40% CO2.

[chriscapetrib]

Cheers rwh - thanks for the info!