Principles of Carbonation
The time required to reach a desired carbon dioxide concentration depends on a number of physical factors. Temperature and pressure play an important role in determining the equilibrium concentration of carbon dioxide in solution. Increasing the pressure leads to a linear increase in carbon dioxide solubility in beer. Decreasing the temperature gives a nonlinear increase in carbon dioxide solubility in beer. Consequently, the equilibrium concentration cannot be attained without either increasing the pressure or decreasing the temperature. Thus, the closer the carbonating temperature is to 0°C and the higher the pressure, the greater the carbon dioxide absorption. The amount of carbon dioxide that dissolves is a function of time, with the rate decreasing exponentially as equilibrium is approached.
Carbon dioxide levels are stated as volumes of gas at standard temperature and pressure per volume of beer. Fixing the temperature and pressure at appropriate settings will bring about the desired carbon dioxide concentration. This relationship between pressure, temperature, and carbon dioxide volumes is given shown in the Carbon Dioxide Volume Table in Appendix B. To use this carbonation chart, look up the volume of CO2 that you wish to dissolve in the beer, cross reference it to the temperature your beer is at, and this will tell you the gas pressure needed. For example, if you want 2.1 volumes of carbon dioxide in your beer and the temperature of your beer is at 0°C you need to adjust the psi to 8.0.
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