Theory: Specific Gravity

Specific gravity is an expression of the weight of a substance compared to the weight of water. The unit of measure for specific gravity is weight divided by volume—grams per milliliter, for example—but is commonly expressed as a number without units. Water has a specific gravity of 1.000. (At 4°C/40°F, water weighs 1.000 g/mL. For confectionery purposes, however, temperature need not be considered when measuring specific gravity.) Substances heavier than water have a specific gravity greater than 1.000; those lighter than water have a specific gravity of less than 1.000. Marshmallow with a specific gravity of 0.40 weighs 40 percent as much as an equal volume of water. When aerated confections are being made, it is desirable to produce consistent results rather than a denser product one time and a lighter product the next. To this end, formulas for aerated products often provide the specific gravity to which the mixture should be whipped. If each batch has the same specific gravity, the finished candy always has the same density and texture.