Do you have to powdered sugar in icing?

Yes, powdered sugar is one of the essential ingredients in icing (also known as frosting).

Powdered sugar, also called confectioners' sugar, icing sugar, or 10X sugar, is a finely ground sugar mixed with a small amount of cornstarch to prevent caking. The cornstarch content typically ranges from 3% to 5%. Powdered sugar is used to make icings, frostings, glazes, and other desserts because it dissolves easily and quickly when combined with liquids.

Other types of sugar, such as granulated sugar, brown sugar, or turbinado sugar, cannot be used as a direct substitute for powdered sugar in icing. Granulated sugar, for example, does not dissolve well and will create a gritty texture in the icing.