How is specific gravity related to beer?
Specific gravity is a measure of the density of a liquid. Distilled water has a specific gravity of 1.000 at 60F(15C) and is used as a baseline. The specific gravity of beer measured before fermentation is called its Original Gravity or OG and sometimes its Starting Gravity (SG). This gives an idea of how much sugar is dissolved in the wort (unfermented beer) on which the yeast can work. The range of values goes from approximately 1.020 to 1.160 meaning the wort can be from 1.02 to 1.16 times as dense as water (in British brewing the decimal point is usually omitted). When measured after fermentation it is called the Final Gravity (FG) or Terminal Gravity (TG). The difference between these two values is a good gauge of the amount of alcohol produced during fermentation. The OG will always be higher than the FG for two reasons. First, the yeast will have processed much of the sugar that was present, thus, reducing the gravity. And, second, the alcohol produced by fermentation is less de
