New to Kegging—Carbonation Questions

[BrewbieVet3]

Hello all. I just started kegging last weekend. I kegged 10 gallons of ale in 2 corny kegs, using 20 psi. I’m really pleased with the product and kind of disappointed I didn’t start kegging sooner. That said, I have some questions about carbonation/psi I’m hoping someone out there can answer.

1) First, once you’ve kegged and force carbonated, do you have to maintain force carbonation pressure in perpetuity? Or can you reduce to serving pressure? Right now I’ve been switching from 20 to 10-12 psi, then back to 20 psi.

2) Second, when bottling from a keg, do I need to worry about temperatureand vapor pressure? If I bottle my ale, being kept at 35F and force carbonated at 20 psi, will the bottles become bottle “bombs” if the temperature rises to 55F or higher?

Any pointers would be helpful. Thanks!

 

[grampamark]

Once the beer is carbonated you leave it at the pressure which is appropriate for your storage temp and the desired level of carbonation. You determine the temp and pressure by consulting a carbonation chart.

Say your kegerator is set to 38° F and you want around 2.5 volumes of carbonation. Find 38° on the far left column and follow that row to the right until you’re in the 2.4-2.5 vol. range and follow that column up to the top row. On the chart above that would put the pressure in the 10-12 psi range. There are several ways to get the beer carbonated to the desired chart pressure. Some work better than others.

You stated that you carbonated the beer at 20 psi and are serving it at 10-12 psi and are apparently satisfied with the carb level. In that case just leave the beer at 10-12 psi. Increasing pressure between servings will slowly increase the carb level until it’s too high and you will start getting more foam than beer when pouring. If you bottle some of your brew it’s going to stay at the same level of carb at the same temp. If you look at the chart you will see that 2.5. vols. of carb @38° will drop to less that 2 vols. @55°.

You can carbonate the beer by picking the desired pressure for your temperature and setting the pressure to the chart pressure which gives that volume of carb at that temp. That’s called chart pressure. Leave the beer alone for 2 weeks and it will be perfectly carbed. If you want to speed the process up, set the pressure to 30 psi and leave it for 24 hours, perhaps a bit longer. Then, turn the gas off and leave it of for 24 hours, during which time the beer will absorb the excess pressure on the headspace. After that, turn the gas back on and leave at your chart pressure. The carb level will increase a bit over the next couple of days until it reaches equilibrium and your beer is at your desired carb level in a few days instead of a couple of weeks.

You can carb beer in a matter of minutes by force carbing, but you can significantly over carb it if you continue the process just a few minutes too long. Force carbing involves setting the pressure quite high, say, 50-60 psi and laying the keg on its side, with the gas connected and the posts on top, and then rolling and shaking the keg quite vigorously for 10 minutes, or so. This exposes more of the beer to the gas and speeds up the absorption of the gas significantly. The drawback is that the margin between well carbed and way over carbed is pretty narrow and it takes a lot more time to get the excess carb vented off than it‘s usually worth.

Good luck with your continued, excellent, adventures in kegging. Learning, and enjoying, the process is well worth it.

 

[bracconiere]

If you bottle some of your brew it’s going to stay at the same level of carb at the same temp. If you look at the chart you will see that 2.5. vols. of carb @38° will drop to less that 2 vols. @55°.

but acording to the chart that would only result in ~2psi increase, so no bottle bombs. and on chilling back down the co2 will go back into solution? i think that's a true observation anyway....

10 minutes, or so.

OH DAMN! if you burst carb which i do. you'll learn cold crash FIRST! and do it by weight! trying to get warm beer to take co2 is a serious pain! i had to shake, take a smoke break, shake it more, drink a beer. finish it off....now that i throw it in a fridge till it's 38-40f, takes it quick..

 

[BrewbieVet3]

Once the beer is carbonated you leave it at the pressure which is appropriate for your storage temp and the desired level of carbonation. You determine the temp and pressure by consulting a carbonation chart.
View attachment 726783
Say your kegerator is set to 38° F and you want around 2.5 volumes of carbonation. Find 38° on the far left column and follow that row to the right until you’re in the 2.4-2.5 vol. range and follow that column up to the top row. On the chart above that would put the pressure in the 10-12 psi range. There are several ways to get the beer carbonated to the desired chart pressure. Some work better than others.

You stated that you carbonated the beer at 20 psi and are serving it at 10-12 psi and are apparently satisfied with the carb level. In that case just leave the beer at 10-12 psi. Increasing pressure between servings will slowly increase the carb level until it’s too high and you will start getting more foam than beer when pouring. If you bottle some of your brew it’s going to stay at the same level of carb at the same temp. If you look at the chart you will see that 2.5. vols. of carb @38° will drop to less that 2 vols. @55°.

You can carbonate the beer by picking the desired pressure for your temperature and setting the pressure to the chart pressure which gives that volume of carb at that temp. That’s called chart pressure. Leave the beer alone for 2 weeks and it will be perfectly carbed. If you want to speed the process up, set the pressure to 30 psi and leave it for 24 hours, perhaps a bit longer. Then, turn the gas off and leave it of for 24 hours, during which time the beer will absorb the excess pressure on the headspace. After that, turn the gas back on and leave at your chart pressure. The carb level will increase a bit over the next couple of days until it reaches equilibrium and your beer is at your desired carb level in a few days instead of a couple of weeks.

You can carb beer in a matter of minutes by force carbing, but you can significantly over carb it if you continue the process just a few minutes too long. Force carbing involves setting the pressure quite high, say, 50-60 psi and laying the keg on its side, with the gas connected and the posts on top, and then rolling and shaking the keg quite vigorously for 10 minutes, or so. This exposes more of the beer to the gas and speeds up the absorption of the gas significantly. The drawback is that the margin between well carbed and way over carbed is pretty narrow and it takes a lot more time to get the excess carb vented off than it‘s usually worth.

Good luck with your continued, excellent, adventures in kegging. Learning, and enjoying, the process is well worth it.

GrandMark, thank you for the excellent post! You explained everything I had questions about. Cheers!