Royal icing is a hard white icing, made from softly beaten egg whites, icing sugar (powdered sugar), and sometimes lemon juice. It is used on Christmas cake, wedding cakes, gingerbread houses and many other cakes and biscuits, either as a smooth covering like marzipan, or in sharp peaks. Glycerine is occasionally added to prevent the icing from setting too hard.
As well as coating cakes and biscuits, royal icing is usually considered a decorative icing since it can be used to create many decorative effects, such as flowers and figures. Royal icing is often piped into shapes which are allowed to harden on a non-stick surface. These can then be arranged to create edible decorative effects on a variety of sweet foods.