Fine metal flakes that are mixed with a varnish and used as a pigment in some types of printing inks to impart silver, gold, or other types of metallic luster to the printed image. Metallic powders used in inks are produced in different grades and with varying degrees of fineness, depending on the desired end-use characteristics. Despite such names as Silver or Gold, less precious metals are typically used. "Silver" is actually made from aluminum, and "Gold" is made from brass, copper or other metals, depending on the shade desired (from Pale Gold to Rich Gold). Specially-made vehicles are needed to carry these pigments to ensure proper binding to the substrate and to impart the desired level of brightness. Metallic powder-based inks, especially bronze powders used in "gold" inks, need to be mixed just prior to using, as they tarnish rapidly. The vehicle is designed to dry rapidly, so as to prevent a minimum of post-impression tarnishing. (See Pigment.) Often, metallic powders are added to the substrate following the printing of a highly-tacky, non-drying ink, a process called bronze dusting.