« on: January 22, 2014, 08:54:11 PM »
This is from a different site. I dont have any experience with nitro mixes.
I generally force carbonate my beer straight after a period of cold crashing - so it will be pretty clse to 0 deg C.
The process for force carbonating a beer in preparation for serving for nitrogen is just a shortened version of how I normally force carbonate as described below:
1. Set your Co2 pressure to about 40-45psi and connect to the keg.
2. Force air out by bleeding keg through release valve.
3. Invert the keg and shake/roll to encourage the dissolution of co2 into the beer.
4. After a while (more on this below), turn the keg the right way up, close the tap on the co2 tank then roll/agitate the keg on it's base to allow the pressure in the headspace to disperse into the beer and to equalize.
5. By watching where the pressure gauge finally settles as you agitate the keg, you will be ale to see how much pressure you have forced into the beer thus far.
6. Repeat from step 3. until the equalized pressure is at or just below the target carbonation for your beer.
Non nitrogen beers still benefit from 4 - 5 days conditioning as the carbonation becomes finer and less soda-like. Nitrogen served beers seem to be fine right there and then as the nitrogen has a much finer mouthfeel than Co2 to start with. As I mentioned earlier, the nitrogen masks a lot of flavour too (seems to be the defining characteristic of 'smooth-pour' beers), meaning that it's drinkable sooner.
Regarding how long to agitate for: It takes a bit of experience to know how long to 'force' it for before measuring it but it's generally a couple of minutes for a higher carbonated beer or for the aforementioned stout, about 30 seconds. In any case, dropping the pressure is a matter of letting the beer sit for a day or 2 with the release valve twisted open.
I use a nitrogen mix of 20% Co2/80% N - here in NZ its called Cellamix 12. There are other versions with higher Co2 and they are also used for serving stouts and other smooth pour beers - but it was explained to me that one of the main uses for the higher Co2 mixes was to maintain the pressure of beers in kegs for a long time without the risk of overcarbonation, which seems to happen with partially full kegs left at servig Co2 pressure.
[EDIT] Forgot to mention that you will need to hold the keg pressure at much higher levels with nitrogen mixes - basically, the less Co2, the higher the pressure. I leave my 20/80 mix at around 30-35psi. Guinness recommend 20/80 mix at 40psi but I find this results in with too much head on the beer after a week or so in the keg.