Question: what is the difference between royal icing sugar and icing sugar?
Answer: Icing sugar is also called “10x”, “powdered” or “confectioner's” sugar. It's a very finely ground sugar mixed with about 3% corn starch by weight. Royal icing is made by mixing icing sugar with egg white. Generally a 3:4 ratio of egg whites to cups of icing sugar (3 egg whites to 4 cups icing sugar).