Cream for whipping must be sufficiently rich in fat to form a continuous skeleton of globules. The minimum fat concentration is 30%, the equivalent of “single” or “light whipping” cream. “Heavy” cream, at 38 to 40% fat, will whip faster than light cream, and forms a stiffer, denser, less voluminous foam. It also leaks less fluid, and so is valued for use in pastries and baked goods, and for piping into decorative shapes. For other purposes, heavy cream is usually diluted with a quarter of its volume of milk to make 30% cream and a lighter, softer foam.