Cookie icing does not harden and will not dry hard like royal icing will. ... However, cookie icing can be used to decorate cookies and gingerbread houses – just keep in mind that the icing will remain soft. It will take about 45 minutes to 1 hour for cookie icing to set.

Can decorating icing dry?

Since icing does not dry hard, stacking iced cookies is not recommended. Individual cookies can be packaged in a treat bag once the icing has set. For best results, store cookies at room temperature in a single layer in a cookie or cake box.

How do you stiffen icing for decorating?

By bringing down the temperature, the frosting should tighten up immediately. This is a great trick for buttercream frosting that may have been overmixed or made in a warm kitchen. If this doesn't seem to do the trick, try adding sifted powdered sugar, a few tablespoons at a time.