Using pressurized CO2 to condition homebrewed beer

beer still

Your beer's carbonation level, known as the condition, is determined by both the temperature and the pressure of the beverage.

Most gases are more soluble in cold liquids than in warm and higher pressures keep that gas from escaping into the atmosphere. The amount of gas dissolved in beer (its carbonation level) is measured in volumes. To say the carbonation level is "2 volumes" means that every cubic inch of beer has 2 cubic inches (at standard temperature and pressure) of CO2 dissolved into it.

As with all other aspects of beer, tradition and personal taste determine how much the beer is conditioned. Un-pressurized finished beer has between 1.2 and 1.7 volumes of CO2 per volume of beer. Most beer is packaged with 2.3-2.8 volumes of CO2 (compare this to sodas, which contain 3.5 volumes). Each beer style, however, has a traditional carbonation level, just as it has traditional hop bitterness. Belgian ales and German Weiss for example, are usually carbonated to 3-3.2 volumes but are sometimes found with as much as 5.1 volumes. In the case of cask-conditioned real ale, the desired level has to do with physics. At typical cellar temperatures (50-55°F [10-13°C]) and ambient pressure, an open cask of ale can hold only about 1 volume of CO2. That defines "true-to-style" carbonation for British real ale.

To obtain a given level of carbonation; choose the desired serving temperature and the desired carbonation level (in volumes). The chart will indicate the conditioning pressure needed. After your keg of beer has had a day or so to condition at the selected pressure, you may need to reduce the pressure for serving (usually to about 10-15 psi). The carbonation level will eventually drop to this lower setting, but the process is very slow. You'll probably find that once carbonated, the beer can be kept at dispensing pressure until consumed.

For ale served at about 50°F (10°C), a good starting point is to carbonate the beer for several hours maintaining 10 psi. The 3/16-in. diameter vinyl beer line tubing drops about 3 lbs. of pressure per foot of length with an additional ½ lb. pressure drop for every vertical foot that the keg is above the source. If you're dispensing with a 3-ft., 3/16-inch ID dispense hose and picnic tap, a 10 psi pressure should give you a very nice serve. At pressures of 15 psi and above you'll probably see a little excess foam.

Now you're ready to carbonate the beer: With the tank set at the pressure required for the desired carbonation level, allow the keg to pressurize until you no longer hear any gas flow. Then agitate the keg by rocking it gently on its side. This agitation exposes more surface area of the beer to the CO2 and allows the gas to dissolve faster.

If you can refrigerate the keg with the gas supply attached, simply leave the regulator set to the desired pressure and agitate occasionally. When the beer is at serving temperature and no more gas flows into the keg when you agitate it, the beer is conditioned. The time needed to get perfectly conditioned beer depends only on how quickly you can cool the beer to serving temperature and how much time you spend agitating it to dissolve the CO2.

If you can't refrigerate the keg while connected to the CO2 tank setup, you'll have to repeatedly connect the gas, agitate the keg, disconnect, and continue to cool. With the regulator set to the desired final keg pressure, each charge of gas is fairly small. To speed the process you can over pressurize on the first few charges. This puts more gas into the keg. With each successive charge reduce the regulator pressure downward toward the desired final pressure. With practice you can gauge this process so that on the last attempt to add gas at the final pressure and temperature, only a small amount of gas will flow into the keg and conditioning is complete. Regardless of the technique you use, fully conditioned beer can be yours in a matter of days.

Dispense: Whether or not you force-carbonate your beer, you will find yeast sediment at the bottom of your keg. Cutting 3/4-in. from the end of the long dip tube will prevent sediment pick-up during dispense.

A cold draft: Instead of using a simple picnic tap to dispense their beer, many brewers choose to install a beer faucet right in the fridge.

Accessories: With the convenience of CO2 pressure, an entire world of opportunity opens up to the inventive home brewer. CO2 can be used to pump beer anywhere you want. You can easily set up a closed transfer system for moving beer from one keg to another by using quick-disconnects with threaded fitting outlets and lengths of tubing terminated with female swivel fittings.

A draft system also makes filtering easier. Replaceable cartridge filters can be installed in the transfer line to provide crystal clear beer in the dispense keg. Other optional equipment includes counter pressure bottle fillers, insulation jackets, and adjustable pressure relief valves. Corny keg fittings and repair parts are available almost everywhere soda is sold. The 5-gallon soda canisters offer an endless variety of other uses.

If you choose to modify your keg, limiting your experiments to the keg lid will ensure that mistakes can be easily fixed without destroying the keg itself.

Kegs that are just too ugly to use for beer, or are missing valve parts and aren't worth reconditioning, make excellent storage containers for grain and hops. And don't overlook the container's original purpose; many homebrew supply shops also sell soda-making kits. Making your own root beer or ginger ale can be lot of fun.

homebrewed beer with malted grains and hop flowers

Home Beer Brewing

Brewing beer is an American Tradition.