Cream with 30% or more fat can be turne into whipped cream by mixing it with air. The resulting colloid is roughly double the volume of the original cream as air bubbles are captured in a network of fat droplets. If, however, the whipping is continued, the fat droplets will stick together destroying the colloid and forming butter; the remaining liquid is buttermilk. Confectioner's sugar (also known as icing sugar) is sometimes added to the colloid in order to stiffen the mixture and to reduce the risk of over whipping.