Quick Carb Method To Avoid Overcarbing Keg

In my brewing opinion, the only redeeming quality of the old crank and shake method of beer carbonation is that it may properly “carbonate” beer to a desired level when correctly executed. That’s on a good day. On a bad day? I really cannot imagine a day much worse than the one you describe. You over-carbonated your beer by rushing the carbonation process. Then you attempted to quickly reduce the carbonation, and in the process lost about a third of your beer, likely destroyed any semblance of decent beer foam, risked getting beer in your gas lines, and generally made yourself sick with the failed effort. No, I am not going to sugarcoat this bitter pill. This was a total bomb! You know all of this, and hopefully see some humor in a painful experience. I am just hoping that others can learn from your question.

It is clear that homebrewers will continue to crank and shake, despite all of the warnings and admonitions to the contrary. So, against my better judgement, I will explain how I would go about quickly carbonating a keg using a brute-force method.

So here is the set-up:
1. 5-gallon (19 L) Cornelius “Corny” keg containing cold beer at some known temperature. It is important that the keg have some gas space above the liquid. For the sake of discussion, I am assuming a beer temperature of 38 °F (3 °C).
2.Target carbonation level of 2.5 volumes of carbon dioxide. This is “normal” carbonation for flavorful beers.
3. Carbon dioxide tank, regulator, check valve between the regulator and hose, a 6-foot gas hose equipped with a flare end, one “beer-out” fitting, and one “gas-in” fitting.
4. Gas pressure gauge with 0-25 psi range (such as a spunding valve) connected to “gas-in” fitting, sothat the internal Corny keg gas pres-sure can be measured.

I prefer ball-lock Corny keg fittings, and like those that can be attached to swivel, flare fittings. This allows for easy disassembly of hoses after use so that everything can be cleaned, sanitized, and allowed to dry before storing. Since the crank and shake method usually involves a bit of foaming and spraying, it is important to use brewing tools that are designed for this. That’s why the check valve on the gas regulator is important; beer may move into your gas line and you do not want beer being pushed into your gas regulator.

OK, now that my kit is defined, the only thing required to begin is a target pressure. Referring to the table on above, I am choosing a target head pressure after carbonation is deemed complete of 11.5 psi. My approach is tiered; the first tier is rapid and I want to jam as much gas into my beer without over-carbonation. The second tier requires more finesse because the crank and shake method is, as you know, prone to overdoing things.

So here is the technique:
1. Attach “gas-in” fitting to the gas line.
2. Adjust the gas regulator to 11.5 psi, and pressurize the keg headspace.
3. Turn off the gas from the regulator, remove the “gas-in” fitting from the keg, remove the “gas-in” fitting from the gas hose, attach the “beer-out” fitting, and turn the gas on (a valve after the regulator is handy to have).
4. Attach the pressure gauge assembly to the “gas-in” fitting of the keg; this will be handy to observe during the carbonation process.
5. Tier 1 Carbonation:
a. Connect the “beer-out” fitting to the keg so that gas can flow into the keg through the dip tube. Shake the keg for about a minute, making sure to listen to your regulator during this shaking period. As gas is dissolved in the beer, the headspace pressure is reduced, and gas flow into the keg can be heard as carbon dioxide rushes through the pressure regulator. After a minute you probably need to take a short break. With rested arms, give your keg another minute shake, again listening to the flow of gas through the regulator. Repeat until no gas is heard flowing through the regulator during the shake cycle.
b. Disconnect the gas line, move the keg back to your keg refrigerator, and close the door on the fridge. Allow the keg to rest for at least 30 minutes. This gives time for beer and gas to equilibrate, foam to settle, and a bit of cooling to occur.
c. Repeat steps a-b until very little gas flow into the beer is heard. Note that during these steps it is impossible to dissolve more carbon dioxide into the beer than what is permitted by the pressure/temperature solubility.
6. Tier 2 Carbonation:
a. Increase the carbon dioxide pressure to 3.5 psi higher than the pressure used in Tier 1 Carbonation. In this example, this means increasing the pressure to 15 psi. This is where there is a risk of potentially over-carbonating the beer.
b. Connect the “beer out” fitting to the keg so that gas can flow into the keg through the dip tube. Shake thekeg for a minute, making sure to listen to your regulator during this shaking period. As gas is dissolved in the beer, the headspace pressure is reduced, and gas flow into the keg can be heard as carbon dioxide rushes through the pressure regulator.
c. Disconnect the gas line, move the keg back to your keg refrigerator, and close the door on the fridge. Allow the keg to rest for 30 minutes.
d. If the pressure reading from the pressure gauge on the keg is less than 11.5 psi, repeat steps a-d until thekeg pressure is pretty close to 11.5 psi.
e. Allow the beer to rest at least 1 hour before serving.

I can hear the jeers already about how slow and conservative this method is, but it is controlled and will not result in grossly over-carbonated beer. One important tip about force carbonation by any method is to clean, sanitize, and purge gas hoses prior to use. A hose that is simply connected to a carbon dioxide source and equipped with a ball lock fitting is full of air, and will very effectively inject oxygen into beer if not purged prior to use. This is extremely important because an air-filled line will quickly oxidize your beer.

On a related, but entirely separate topic, foamy beer can come from a keg even when the beer carbonation is perfect. Based on your description of things, I think it is reasonable to conclude that your beer carbonation was wonky, at best. Wonky or not, draft system balance is critical to achieve a well poured beer. A simple balancing rule when using 3⁄16” beer line is to add 0.5 to your carbonation pressure, 11.5 psi in this example, and divide this number by 2.2. This gives you the length of draft line required to balance the keg pressure with line restriction. So in this example we have serving line length = (11.5 + 0.5)/2.2 = 5 1⁄2 feet.

The best way to prevent having to resort to this method is proper carbonation from the onset and it is best to exercise patience. Forced de-carbonation is a recipe for trouble. To reduce carbonation, simply vent the head space pressure of your keg and allow the beer to rest for a few hours (this time depends on degree of over-carbonation). After this venting period, boost the keg pressure back to your equilibrium pressure (11.5 psi for the above) and taste. This may take a couple of cycles to dial in.

Response by Ashton Lewis.