is the pressure used to overcome the tendency of carbonated beer to foam, especially during packaging. Usually, beer is seen without counterpressure; for example, beer that is poured into a glass or that is inside of an open bottle or can. In this case, the carbon dioxide dissolved in the beer tends to form bubbles and rise to the top. This is precisely what counterpressure prevents. When filling a bottle, keg, or other package under counterpressure, the pressure of the CO2 in the head space of the package is greater than the pressure required to prevent these bubbles from forming. The goal is a “quiet fill” where the package is filled quickly and efficiently with minimal foaming. Typically, a counterpressure of 0.5 to 1 bar (7 to 14 psi) above the equilibrium pressure of the beer is sufficient to prevent excessive foam.

See also carbon dioxide, carbonation, and foam.