thecebruery
Active Member
Just wanted to share a method I've been working on over the past few weeks to quickly (30 minutes) and accurately (to w/in 0.5psi) burst carbonate a keg.
I'm sure some folks have figured this out technique out or think that it's a little too much work if they're having success w/ the "set to three times serving pressure and shake for five minutes" or "100 back and forth rolls" or whatever technique works for you. But as a small commercial establishment, I occasionally need not only rapid but also highly accurate carbonation in a keg, and can't afford to wait too long or potentially overcarbonate a keg.
I use sankes, but there's no reason this method wouldn't work with cornies.
The method, in essence, uses your regulator as an indirect manometer for your keg pressure.
1) Chill your beer down to 37F/3C. Sometimes that's right after I cold crash, but if I don't have time/the need to rapidly carbonate, this means an overnight trip from where the kegs have been hanging out in my cold storage room (kept at 18C) to the freezer.
2) Hook up your regulator to your keg coupler. Make sure you have a super long gas line. If you're using cornies, that's all you need. Since I'm using a sanke, I have a special coupler that has a 1/2" stainless steel cap and a few teflon discs and o-rings inside to ensure a tight seal covering the beer out connection. I guess you could also have a tap or something hooked up to it, but that will complicate matters when you're rolling your keg around.
Also, make sure everything is super tight. You want to be reading the keg pressure as your regulator reading drops, not atmospheric pressure.
3) Give the keg 35psi and roll it around for a while - say, 100 rolls, or 3 minutes.
4) Crank the regulator all the way down to zero. Continue to roll the keg around. As the CO2 in the headspace achieves equilibrium w/ the partial pressure of CO2 in the beer, CO2 will continue to flow from your gas line/regulator in to the keg, and the pressure reading will drop.
After 100 or so rolls/5minutes, you'll probably see your pressure drop below your ideal serving pressure at 40F (note: I use this temperature because I assume once you take your keg out of the freezer at 37F, it's going to gain a few degrees F over the thirty minutes or so it takes you to perform this, so I use 40F to account for this). After a while longer, the regulator reading will level off at the point where the pressure in the regulator is equal to the pressure in the keg - for me, this is usually around 4 or 5 psi.
5) Jack the pressure back up to 35psi, and give it another 50 shakes/3 minutes of rocking.
6) Repeat step 4, dropping the regulator all the way down to zero and watching as everything comes to equilibrium. This time, your pressure should be a little higher - say 6 or 7 psi.
7) Repeat steps 4 and 5 until the pressure drops to and holds steady at your ideal serving pressure (or a little below it). With each iteration, you're adding a tenth or two tenths of a volume of CO2 as the reading goes up by 1 or 2 psi, but you're never shaking for so long or at such a pressure that you run the risk of overcarbonating, and as each iteration only takes 6 or 7 minutes, the whole process only takes about half an hour. I find that four or five iterations takes me up to 10psi, and then I'll let the beer sit at 11psi and calm down in my keezer for 6 hours or so and it pours perfectly.
Like I said, it's a lot more involved than the set-it-and-forget-it method, more involved than the "set it at three times the serving pressure and leave it 24 hours" method, and even more involved than the "three times the serving pressure and roll it around for five minutes" method. But it has the benefit of using a larger number of smaller, more discrete steps to take out all the assumptions and simplifications that the last two of those above methods make about headspace area and diffusion rates based on SG and whatnot.
I'm sure some folks have figured this out technique out or think that it's a little too much work if they're having success w/ the "set to three times serving pressure and shake for five minutes" or "100 back and forth rolls" or whatever technique works for you. But as a small commercial establishment, I occasionally need not only rapid but also highly accurate carbonation in a keg, and can't afford to wait too long or potentially overcarbonate a keg.
I use sankes, but there's no reason this method wouldn't work with cornies.
The method, in essence, uses your regulator as an indirect manometer for your keg pressure.
1) Chill your beer down to 37F/3C. Sometimes that's right after I cold crash, but if I don't have time/the need to rapidly carbonate, this means an overnight trip from where the kegs have been hanging out in my cold storage room (kept at 18C) to the freezer.
2) Hook up your regulator to your keg coupler. Make sure you have a super long gas line. If you're using cornies, that's all you need. Since I'm using a sanke, I have a special coupler that has a 1/2" stainless steel cap and a few teflon discs and o-rings inside to ensure a tight seal covering the beer out connection. I guess you could also have a tap or something hooked up to it, but that will complicate matters when you're rolling your keg around.
Also, make sure everything is super tight. You want to be reading the keg pressure as your regulator reading drops, not atmospheric pressure.
3) Give the keg 35psi and roll it around for a while - say, 100 rolls, or 3 minutes.
4) Crank the regulator all the way down to zero. Continue to roll the keg around. As the CO2 in the headspace achieves equilibrium w/ the partial pressure of CO2 in the beer, CO2 will continue to flow from your gas line/regulator in to the keg, and the pressure reading will drop.
After 100 or so rolls/5minutes, you'll probably see your pressure drop below your ideal serving pressure at 40F (note: I use this temperature because I assume once you take your keg out of the freezer at 37F, it's going to gain a few degrees F over the thirty minutes or so it takes you to perform this, so I use 40F to account for this). After a while longer, the regulator reading will level off at the point where the pressure in the regulator is equal to the pressure in the keg - for me, this is usually around 4 or 5 psi.
5) Jack the pressure back up to 35psi, and give it another 50 shakes/3 minutes of rocking.
6) Repeat step 4, dropping the regulator all the way down to zero and watching as everything comes to equilibrium. This time, your pressure should be a little higher - say 6 or 7 psi.
7) Repeat steps 4 and 5 until the pressure drops to and holds steady at your ideal serving pressure (or a little below it). With each iteration, you're adding a tenth or two tenths of a volume of CO2 as the reading goes up by 1 or 2 psi, but you're never shaking for so long or at such a pressure that you run the risk of overcarbonating, and as each iteration only takes 6 or 7 minutes, the whole process only takes about half an hour. I find that four or five iterations takes me up to 10psi, and then I'll let the beer sit at 11psi and calm down in my keezer for 6 hours or so and it pours perfectly.
Like I said, it's a lot more involved than the set-it-and-forget-it method, more involved than the "set it at three times the serving pressure and leave it 24 hours" method, and even more involved than the "three times the serving pressure and roll it around for five minutes" method. But it has the benefit of using a larger number of smaller, more discrete steps to take out all the assumptions and simplifications that the last two of those above methods make about headspace area and diffusion rates based on SG and whatnot.
