Icing Sugar

Icing sugar, is granulated white sugar that has been crushed into a fine powder and cornstarch is added to prevent caking. It is ideal for icings or as a sprinkle-on dessert topping. Different grain sizes are available, 6X, 10X and 12X icing sugars.
The “X” designations are derived from the mesh sizes of the screens used to separate powdered sugar into various sizes. Thus, 6X would have a larger particle size, whereas 10X would have a smaller particle size. 12 x gives smoothest possible icings and fondants
Store icing sugar in a cool, dry location (not the refrigerator). When it gets moist, it develops lumps. And because of its physical properties, it may absorb strong odors if left unsealed.