another attempt at nitro

[odie]

so...it's once again time to tap a stout. I've not had success getting a nice nitro pour since I always seem to be over carbed. I just don't have the volumes dialed in.

Well this time I've got my RIS fermented in the keg, I cranked up the pressure a couple days room temps and then burped down to about 2-3psi to do 18 bottles for conditioning.

With the remaining beer in the keg and increased head space expanded it seems to gassed off to be stable around 10psi at 80'F. so like 1.1 vol?

So just drop it in the keezer and hook up my nitro at around 25-30psi?

 

[mac_1103]

Won't it lose carbonation if you keep it on pure nitro? Do you have (or can you get) beer gas?

 

[odie]

when I say "nitro" I mean "beer gas". 70/30 or 75/25 mix depending on supplier.

wanting that elusive cascade effect and creamy head...

 

[day_trippr]

The Brewers Friend carbonation calculator indicates 80°F and 10 psi would equalize at roughly 1.1 volumes, so you're definitely in the right ball park...

https://www.brewersfriend.com/keg-carbonation-calculator/

Cheers!

 

[camonick]

I assume you’re dispensing with a stout faucet? If so, putting it on about 30 psi of beer gas should get you in the ballpark. I don’t know why it is, or what happens, but it usually takes a couple weeks of my beer sitting on gas before I get the cascade effect through my faucet. Also, liquid line length is irrelevant with a nitro set up. When I’m running a stout faucet, I use just enough line to get from the back of my shank to my keg.

 

[crazyjake19]

Nitro beers should have enough residual carbonation from fermentation that no further carbonation is needed. I usually keg my Irish stout, plop it in the keezer, and I'm serving the next day at 30-35psi with a great cascade.

 

[day_trippr]

Well...I suppose under the right conditions one could get close to going straight from fermentor to tap, but I've been brewing the same double imperial chocolate stout for 15 years and the pour quality always benefits from some exogenous CO2 first...

Cheers!

 

[odie]

well...the volume of CO2 target is so low that it seems mostly just naturally occurring or absorbed without any additional PSI. The charts seem to indicate basically zero PSI at serving temps to achieve desired CO2 volume.

The charts seem to indicate 1.1 volumes (10psi at 80f) will become basically become significantly more volumes once it chills to serving temps.

My keg is about half empty since I bottled some beer at a higher CO2 volume. It's sinced gassed off into the head space.

Am I right to assume that I should bleed all the CO2 PSI out right before I hook up the nitro? Otherwise, the CO2 in the head space will get forced back into the beer when the nitro pressure is cranked up?

 

[day_trippr]

The charts seem to indicate 1.1 volumes (10psi at 80f) will become basically become significantly more volumes once it chills to serving temps.

That would be wrong. A specific volume of CO2 value doesn't change with temperature. 1.1 volumes at 36°F will be 1.1 volumes if the beer is warmed to 80°F, and vice versa.

I never bother venting the head space CO2 when hooking up a keg to my stout faucet setup. Also, only the CO2 partial pressure in the beer gas matters wrt affecting the existing CO2 - the nitrogen component doesn't have any effect on CO2...

Cheers!

 

[odie]

well...i'm thinking if the keg starts half empty...there is 1.1 volumes in the beer and 1.1 volumes in the head space. going from low to no PSI to suddenly 30 PSI...won't that cause the CO2 to migrate into the beer until a new equilibrium is reached?

The Nitrogen will not migrate, but the CO2 will?

Starting with a full keg, there is almost no head space.

 

[mac_1103]

well...i'm thinking if the keg starts half empty...there is 1.1 volumes in the beer and 1.1 volumes in the head space. going from low to no PSI to suddenly 30 PSI...won't that cause the CO2 to migrate into the beer until a new equilibrium is reached?

The partial pressure of CO2 in the headspace of a keg on 75/25 beer gas at 30 PSI is about 11 PSI. How much difference is the 10 PSI of CO2 in the headspace before you hook it up going to matter? Too many maths for me. But I can't imagine that pulling the PRV one more time before you hook the keg up to the beer gas will hurt anything.