Originally Posted by BierMuncher
You can't carbonate with beer gas. Nitrogen doesn't abosrb into the beer. Beer gas is used for pushing the beer.
In a lot of older pubs, the distance the beer has to travel from casks to the taps is quite a long distance and requires substantial pressure. To apply that much pressure using CO2 only would over carbonate the beer...hence...beer gas mix. It can be set at a higher pressure to push beer over long distance, without absorbing, and over carbing the beer.
I have had success force carbonating with both popular beer gas mixes (all beer gas is a mix unless you specify pure nitrogen-- which i use to push wine on tap
Either the 75% nitogen/25% CO2 beer gas mix (typically this mix has a female regulator attachment), or the 70% nitrogen/30% CO2 (typically or at sometimes has the male regulator attachment-- just like any CO2 tank) work fine.
No priming of the keg is necessary. Just hook the kegs with flat bright beer in them to the beer gas and set the regulator between 35 and 40 PSI for a few days. As the beer cools in the kegerator and absorbs the gases pour a pint every day-- out of a stout faucet of course-- until you get your desired carbonation/head. Then dial the regulator back to 30 to 35PSI. This is the serving pressure and can be adjusted within that range or there abouts to control the head of your beer.
If you over carbonate by accident just turn off the gas and bleed the relief valve and leave the keg for a day. Pour a beer-- if still over carbonated repeat... This of course is based on the beer being 38F and using 5 to 6 ft of 3/16" beer line. Your regulator pressure will need to be increased if you serve the beer warmer.
As a side note-- the beer gas tanks-- at least the one with a female regulator attachment are different then CO2 tanks. They have stem mechanism that helps mix the gases properly when released.
However IME the gases do settle and probably stratify (layer). IME as the tanks empty the force carbonating takes longer-- sometimes I shoot some straight CO2 in the keg to speed the process up. I assume this is because most of CO2 has been push out already (CO2 is heavier then nitrogen and the tanks draw at least partially from the bottom of the tank)
What i have found helps a great deal is-- if can remember to--- carefully pickup, flip up side down, and shake the beer gas tank periodically... I do it very time i clean the beer lines and it has really helped when carbonating a nitro beer when the tank gets low.
Getting both the nitro and C02 to absorb into the beer is important in getting the right head out of your faucet. The nitrogen does dissolve into the beer-- it just takes 30 PSI to do it-- and it is whats responsible for that beautiful cascading effect of gas leisurely leaving the pint and forming a beautiful head. The CO2 is important as well as it gives the beer mild carbonation that lasts as you drink--- b/c as soon as that cascading effect is over after the pour-- all the nitrogen has left the beer-- and without the CO2 dissolved in the beer -- the beer would taste extremely flat.
Nitrogen is wonderful because it creates the fine, frothy, silky, and goddess like bubbles, in the head of a guinness or proper guinness clone as the case may be... Unlike CO2 ---which is 4 molecules in 10,000 in our atmosphere, and explodes from the beer like on frantic jail break looking for freedom and creating large frothy bubbles and escape holes (great for standard pint but not for an irish stout)--- Nitrogen is 70% of our atmosphere and is in no rush to join its fellow friends outside the beer-- so it leisurely floats up and leaves the beer ever so gently, leaving behind barely noticeable and petite little bubbles-- which are just the perfect compliment to a well crafted pint of irish stout!
P.S. The 10% roasted barley, 25% flaked barley, and the rest pale malt is the great recipe for a guinness clone... A great variation is to substitute some roasted barley for chocolate malt or darker carafa. The hops don't matter-- 25 to 40 IBUS to taste. You only needed a boiling addition (60-90 minutes). I often just rinse the yeast off and reuse dry hops from a previous IPA. Works great and saves cash. My favorite yeasts are either the irish or american. The british is does not compliment a dry stout and often the final gravity remains high enough so that floating the stout on pales or lagers doesn't work. the american clears much more quickly is good, and avoid me from having to have multiple strains on hand. The irish adds diacetyl flavor that actually balances the harshness of the roasted barley nicely. If you plan on black and tans make sure to keep you OG below 1.045 so that the final gravity will be lower then anything you plan to float the beer on. If it ain't it won't float!