Beer Fact Friday: Volumes of CO2
Carbon dioxide—the gas that gives beer its bubbly texture—dissolves readily in beer. Certain factors can affect how easily CO2 dissolves: The colder the beer, the more gas that will be absorbed into the liquid. The warmer it is, the less gas that will be dissolved. Pressure is also a factor: Higher pressure, more dissolved CO2; lower pressure, less dissolved CO2. Even altitude can affect how readily a beer absorbs carbon dioxide.
The amount of carbon dioxide dissolved into a beer is measured in units called “volumes of CO2.” This gets a little technical, but a “volume” is the space that the CO2 would take up at a standard temperature (32° F) and pressure (one atmosphere) if removed from the beer. In other words, if one gallon of beer contained two volumes of CO2, the CO2 by itself would occupy twice the space the beer takes up, or two gallons. Make sense?
Most beers you’ll find in bottles or kegs range between 2-2.5 volumes of CO2, but the level of dissolved gas can vary by style and method of service. Cask-conditioned beers—beers fermented in and served from the same cask, with no added gas whatsoever—typically have CO2 levels of around 1.2 volumes. Beer styles meant to be lively on the palate and served with a large, dense foam head, such as Belgian ales and Hefeweizen, can even get up to 4 or 5 volumes of CO2.
Beer Fact Friday is our weekly exploration of the topics that make beer the world’s most interesting beverage. Check back here next week—or follow us on Facebook, Instagram, or Twitter—for more fascinating beer trivia.