While silver is considered an achromatic color, many shades and appearances can be generated. From soft, smooth gray appearances to very bright, sparkling, almost jewel-like tones, the palette is almost endless. The wide variety of shades is based on the very large number of aluminum pigment grades available on the market today. All are based on the same highly reflective metal, but differences in particle shape, size and particle size distribution contribute to the metallic effect we are familiar with. Probably the most unique aluminum pigment feature is that it is actually a flake, unlike most other organic and inorganic pigments. This morphology generates and supports the reflective nature of the pigment. Larger flakes will typically provide brighter, more sparkling appearances, while smaller flakes offer greater opacity, grayer appearances and smoother, less sparkling colors.
Aluminum pigments share many, if not all, of the properties of the metal itself and, when formulated into a coating, can enhance the performance in addition to supporting the aesthetic function. They have been widely used for their performance features in many applications, ranging from roof coatings to auto-body putty, anti-corrosive coatings and reflective (heat, UV, IR) coatings. Some of the important performance properties shared between metal and pigment are excellent opacity; high reflectivity to UV, IR and visible light; barrier property performance; and heat reflectivity. While most of the properties shared between metal and pigment are positive, there are several that present challenges when formulating into coatings.