Metallic paint, as opposed to regular or “solid” paint, is also known as polychromatic or “metal flake” paint. It is very popular in the automotive industry because the metal flakes in the paint give the car a sparkling look and highlight the contours of the car's body. A metallic paint has a relatively larger pigment than solid paint. Metallic paint generally needs a base coat and a clear top coat of lacquer to protect it and give it an extra gloss. Variations of metallic paint are “pearlescent” paint which appears as different colors depending upon the angle of light, “flip” paint where the colors change more radically and “flamboyant” paint which uses a metallic silver base coat and is topped with a translucent colored lacquer. Flamboyant paint is a favorite for motorcycle and bicycle paint jobs. It creates an extraordinary effect of depth. Unfortunately, if it gets scratched or damaged, it is almost impossible to retouch. Aside from the look, metallic paint does not fight rust or last longer than solid paint.
Because the proper flow of paint in an airbrush is critical in order to create the right paint pattern, the question has been raised about which airbrush is best for metallic paint. Some wonder whether a Gravity Feed airbrush is better than a Siphon Feed unit for metallic paint. Others debate about the need to swirl the cup frequently to prevent the metallic pigments from settling at the bottom of the paint, hence the advantage of a Siphon Feed airbrush.
The critical element in airbrushing with metallic paint is the pigment size. When the airbrush needle is pulled back to allow paint to flow, the tiny space between the needle and the nozzle will usually not be large enough for the pigments in metallic paint to pass through. Even if the paint is diluted, the small aperture will still block the large pigments. There are two common solutions to this problem.
The first solution is to spray at a lower pressure. At an air pressure of about 8 psi, the needle can be pulled back farther, widening the aperture so the large metallic paint pigments can pass through. Another solution is to use an airbrush with a larger needle/nozzle configuration. An airbrush with several head assemblies to choose from would be ideal. The debate isn't done, however. Some artists insist that tip size is irrelevant and that the right air pressure is the answer.
This makes the question of a Gravity Feed or Siphon Feed airbrush moot, as far as metallic paint is concerned. A Gravity Feed unit would only be preferred if the work involves fine detail. Either type with a 0.3 mm opening should work well with metallic paint.
Metallic paint does not cost more than solid paint but cars painted with metallic paint command a premium at the showroom and at re-sale time. For this reason, many car buyers opt for cars with metallic paint.