Metallic inks are made of particulates, several compounds working together to form what ends up on the page. As a result, metallic inks are opaque (not transparent) and have specific particle size requirements (no larger than 25 micrometers [microns]) in order to function with an offset press, a traditional form of the printing press where images are moved from the plate to a rubber blanket, and finally to the printed surface.
Metallic particles float to the surface of the ink in a process that is referred to as "leafing." This process gives the ink its reputable shine and luster. The longer a metallic ink is allowed to dry, the greater its shine quality. Metallic inks that incorporate ultraviolet hardeners lose a significant portion of their shine in favor of faster drying time.
As metallic inks leaf, the particles resting on the surface are highly susceptible to rubbing and smudging. Metallic inks are often coated with varnish or other aqueous coating to preserve the line quality of the ink, though at some sacrifice to luster. When a metallic ink loses some luster to coating, it is referred to as "softening." This characteristic of metallic inks may be mitigated by allowing proper drying time for the ink and applying any coating solution sparingly.