Question About Keg Carbing

gresc · 10-26-2007, 01:59 AM

Folks, when I carb a keg I force carb with CO2 but I keep the CO2 hooked up for the duration of the carb cylce.

But... Does the gas really need to stay connected. For example, if I pressurize the keg @ 30 PSI at 40F and then disconnect once it reaches pressure can I just let it sit for a week ?

**Bobby_M** · 10-26-2007, 02:12 AM

As the CO2 is absorbed into the beer, the pressure of the headspace will drop. Whether or not an initial 40 psi charge will eventually equalize to your desired carbonation level is beyond me.

If I had to guess at the math, you'd have to figure out how much headspace there was as a percentage of the total keg volume. Take that ratio and apply it to the initial pressure. So, if the headspace is .5 gallons, it's one tenth of the keg volume. Therefore, if at a given temperature it takes 10psi to reach 2 volumes, it would take an inital charge of about 100psi in that small headspace. I might be totally wrong. The easy answer is to just leave the gas connected so the pressure is what you set it at.

WhatToBrew · 10-26-2007, 02:17 AM

You are forcing CO2 into the beer. When you bring it to pressure right off, the CO2 hasn't yet dissolved into the beer, as it sits the CO2 dissolves into the beer and more CO2 dispenses from the tank to the keg to maintain the pressure until you've reached the desired carbonation level.

Here's a good pdf from Northern Brewer on kegging:

http://www.northernbrewer.com/docs/pdf/corny-keg.pdf

gresc · 10-26-2007, 02:35 AM

I guess my question was along the lines of what Bobby M describes. I'm more curious than anything. It would seem to me if you could compute what Bobby M describes you can almost assure youself perfect carbonation. Of course, the initial charge may not be practical and may have to be require some trial and error but I wonder if anyone has ever done this. It seems like many of the variables are known, Temp, Beer Vol, Beer Type Carb Volume. Once this was known, set the pressure and wait for equilibrium ?

Professor Frink · 10-26-2007, 03:07 AM

I'd say put on the CO2, get the pressure up to where you want, take it off, then wait 4 days or so and test it. You should be at equilibrium by then, if it's not carbed enough, you can always put more CO2 on it.

**david_42** · 10-26-2007, 01:43 PM

Once a keg is fully carbonated, it will hold the pressure. It will change only if the temperature changes.

**BierMuncher** · 10-26-2007, 01:59 PM

Quote:

Originally Posted by gresc

...if I pressurize the keg...then disconnect once it reaches pressure can I just let it sit for a week ?

A keg is really nothing more than a large beer bottle.

FWIW, I charge at 30PSI at 37 degrees for 48 hours...shut off the manifold, then set back down to 10-12PSI for the duration.

THis gets me to pretty consistent carbonation within 5 days.

Important to note that I use check valves in my gas lines to prevent the higher (new keg) pressure from pushing back to the lower pressured kegs or even the regulator. If I didn't have those, I'd close the manifild, bleed excess off the keg...then set down to 10-12 PSI.

gresc · 10-26-2007, 08:00 PM

Thanks Munch; I just wish this was more formulaic.
But just curious how often do you shake the keg (or do you) and for how long (2 minutes) ?

**Bobby_M** · 10-26-2007, 08:32 PM

What is your situation that causes you to want to remove the gas? I assume you only have like two gas connections on your kegger but you want to hit a new keg with high pressure and more it to another fridge somewhere until you need it?

**BierMuncher** · 10-26-2007, 08:50 PM

Quote:

Originally Posted by gresc

Thanks Munch; I just wish this was more formulaic.
But just curious how often do you shake the keg (or do you) and for how long (2 minutes) ?

Don't shake it. Results are too sporadic.

In a "perfect world" we would set the PSI to 10 and give it 10-14 days.

I have one vacant tap upstairs, so I charged my new Centennial Ale at 30PSI on Wednesday night. I'll drop it down to 12PSI tonight when I get home an by Sunday evening, I'll be ready to hook up and serve.

PS - This centennial ale recipe is finally dialed in and perfect.