While both luster dust and petal dust are types of edible powders used for cake decorating, they have slightly different characteristics and purposes. Luster dust is primarily used for adding shimmer or shine to cakes by giving them a metallic or pearlescent effect. It is often applied dry by sprinkling or with the help of a brush. On the other hand, petal dust is typically used for creating realistic color variations on flower petals or other delicate details on cakes. Petal dust has matte finishes without any metallic sheen and works best when mixed with liquid such as alcohol or lemon extract before applying it onto the cake surface using brushes or airbrushes.