Using a mixed gas to dispense

[timtoos]

Hi all,

I have a Brown Porter that I want to serve using a 70/30 mixed gas (N2/C02).

I have the gas, new regulator and serving tap but I don't know what I should do. Do I carbonate as normal then serve using the mixed gas, but serve at a much higher pressure (say 30psi).

What is the general advice? Do you even need to carbonate at all? I have never used a mixed gas. What sort of pressures, temperatures etc are the norm?

The beer at the moment is in keg and not carbonated.

Thanks

[PeeBee]

I've pondered using mixed gas to retain CO2 levels well below 1.0 volumes. It's what "mixed gas" is all about. Using high gas pressures but limiting the amount of dissolved CO2 and the acid it creates (hence "smooth-flow", etc.). It is possible to dissolve the nitrogen and get very creamy heads (yeuch in my opinion!) but for that you need frigid temperatures and possibly mechanical means to coax the nitrogen to dissolve in any meaningful quantity (as championed by Guinness - my opinion is double yeu...; err, like above).

You could probably have got away with pure CO2, but as you've got the kit and intend to carbonate at 30psi:

(... first a bit of easy maths which you might skip: 30PSI(G) plus atmospheric pressure, say 15PSI, gives 45PSI - absolute, i.e. no "G" - divide by 0.3 - 30%, this is "partial pressure" calculations - is 13.5PSI, less atmospheric pressure, is minus 1.5PSIG ...):

Carbonation levels well in "Real Ale" cask territory! You may want to bump the pressure up to 35PSI(G) and even chill the porter a bit and hope to dissolve more nitrogen (like in Guinness - yeu... yeah I've done that already).

Maybe not the reply you expected? But then I am puzzled why home-brewers fart about with mixed gas. Perhaps someone can point out my "errors"?

[FUBAR]

My approach with Porter or Stout is to carb the beer up with C02 to 15psi at 10c for 24 hrs and then serve with 70/30 at 30psi , works OK for me and gives that nice smooth creamy mouthfeel and thick dense lacing head . I even serve my pales with 70/30 but force carb with C02 to 30psi for 24 hrs , perfect for my taste as I do not like the carbonic bite & mouthfeel of highly carbonated drinks .

[f00b4r]

My approach with Porter or Stout is to carb the beer up with C02 to 15psi at 10c for 24 hrs and then serve with 70/30 at 30psi , works OK for me and gives that nice smooth creamy mouthfeel and thick dense lacing head . I even serve my pales with 70/30 but force carb with C02 to 30psi for 24 hrs , perfect for my taste as I do not like the carbonic bite & mouthfeel of highly carbonated drinks .

Do you ever bottle from the keg with these beers and if so do you change anything, eg letting them carb a bit higher as mixed gas isn’t being used to serve?

[FUBAR]

My approach with Porter or Stout is to carb the beer up with C02 to 15psi at 10c for 24 hrs and then serve with 70/30 at 30psi , works OK for me and gives that nice smooth creamy mouthfeel and thick dense lacing head . I even serve my pales with 70/30 but force carb with C02 to 30psi for 24 hrs , perfect for my taste as I do not like the carbonic bite & mouthfeel of highly carbonated drinks .

Do you ever bottle from the keg with these beers and if so do you change anything, eg letting them carb a bit higher as mixed gas isn’t being used to serve?

No I have not tried to bottle from a keg , must give it a try with the keg of stout I'm drinking now . Although the only method I have to do it is a carbonation cap , which has only been used so far for tap flushing with cleaner .

[PeeBee]

My approach with Porter or Stout is to carb the beer up with C02 to 15psi at 10c for 24 hrs and then serve with 70/30 at 30psi , works OK for me and gives that nice smooth creamy mouthfeel and thick dense lacing head . I even serve my pales with 70/30 but force carb with C02 to 30psi for 24 hrs , perfect for my taste as I do not like the carbonic bite & mouthfeel of highly carbonated drinks .

I love this! Human ingenuity is just great. I've tried to explain mixed gas use from a "geek" perspective, issues and all. "FUBAR" side-steps all that waffle, carbs things up as he wants it with pure CO2, then serves with 30/70 mixed gas (at a higher pressure) ... "Issues? What issues?".

"Partial pressure" still applies (it's one of them laws of physics). But the nitrogen is only slowly displacing the CO2, and initially the proportion of CO2 increases (pure CO2 at 15psi being dilute with 30/70 mixed gas - there is some sort of loose pub "convention" to put CO2 % first - at 30psi, so at first the space above the beer is filled with - grind, spark, grate - 65% CO2 and 35% nitrogen at 30psi, which is the same as pure CO2 at - more mental grinding - about 75% of 30psi ... 22psi(g) - cor, that were hard; and possibly wrong!). It takes time before the CO2 drops to noticeable levels (if ever in the lifetime of a keg) and during that time nitrogen is dissolving (it does dissolve, just not as quick as CO2, or in the quantities of CO2).

Sorry about all that. I just didn't want people to think there are two ideas being suggested. Same idea, just "FUBAR" has twisted it into a more practical solution. (I need a coffee now - too early for a beer!).


[EDIT: Some of my maths might be baffling? "Partial Pressure" really needs to be considered in absolute pressure readings i.e. in relation to a vacuum. Or about 15psi higher than "what the gauge tells you"; hence that little "g" after "psi". 14.7psi is nearer to sea-level pressure, but I was rounding up.]

[MashBag]

I use mixed gas for wine dispense. Very good for red @ 5psi.

[timtoos]

Thanks all