Accurately Calculating Sugar Additions for Carbonation
Accurately calculating the carbonation is a great exercise for working with apparent and actual attenuations as well as working with the extract % or Plato scale. The latter is not essential, but makes things more intuitive.
The final carbonation of bottle conditioned beer depends on the CO2 currently present in the beer and the CO2 that will be generated during bottle conditioning.
The amount of CO2 already in the beer depends on the CO2 pressure and the temperature of the beer. It can be determined by using a Carbonation Table. These tables show the equilibrium of CO2 content that exists for a given CO2 pressure and beer temperature.
The amount of CO>sub>2</sub> created by bottle conditioning is based on the amount of sugar that is fermented. Each gram of fermentable extract is fermented into equal parts (by weight) of alcohol and CO2 (this is not exactly true, but close enough for this calculation).
The easiest way to add fermentable extract to beer is through the addition of pure sugar. This can be dextrose (corn sugar) or succrose (table sugar).