Royal icing looks much the same as buttercream frosting when wet, but it dries rock hard so you can make cake decorations that won't crumble or soften. While it's often used to cover sugar cookies, you can also use royal icing to make individual decorations to use on cakes. Made from a mixture of powdered sugar, meringue powder and water, the decorations must dry completely before storage and will last for up to a year. You can make flowers, letters, animal designs or decorations for gingerbread houses.
Line baking trays with parchment paper and pipe the royal icing decorations onto the paper. Alternatively, cut a small square of parchment paper and place it on top of a flower nail. Pipe the flower onto the small paper square and transfer it to the parchment-lined baking trays.
Set the trays on a flat work surface in a well-ventilated room. Place them on a counter or table where they won't be in the way. If possible, set the trays on the work surface first before piping the decorations.
Turn on an oscillating fan in the room to circulate air and speed drying. This is optional. If some trays are closer to the fan than others, rotate the trays every few hours so the decorations dry evenly.
Leave the royal icing decorations out to dry for eight to 24 hours or until completely dry and hard. How long it takes depends on the thickness of the decorations. Thin decorations that look like lace or spiderwebs, for example, dry much faster than large, thick, three-dimensional flower decorations. It helps to make a spare decoration you can attempt to break as a test for dryness.