Density

The measurement of the weight of a solution, as compared with the weight of an equal volume of water. Density can either be expressed as degrees Plato or as specific gravity. Degrees Plato is most commonly used by professional brewers in the United States and Continental Europe whereas specific gravity is more than likely to be used by homebrewers. Specific gravity (sp gr) is the density (weight per unit volume) of substance (fermentable and unfermentable sugars) divided by the density of pure water, which has a specific gravity of 1.000 at 4 degrees C. Rather than expressing specific gravity in its usual form it is often abbreviated. Brewers refer to specific gravity as “gravity” (SG) ignoring the decimal (e.g., 1050 for 1.050) or simply stating gravity as “50” which is common among British brewers.