The ductile nature of the metal sused means that milling or crushing of spherical aluminum powder in the ball mill creates flakes with shape factors (flake thickness: flake diameter ) of 1:50 to 1:200.        Silver Dollar Shape: Using fine-grained spherical aluminum powder with extremely narrow particle size, after slow grinding process, we can get aluminum sheets with smooth surface, moderate diameter-thickness ratio, narrow particle size distribution, high sparkle and strong hiding power.         Snowflake and Scale Shape: They are made by grinding aluminum powder with coarser particle size. Statistical particle thickness can vary depending on the product and the milling technology used, i.e. the various pigments are not monodisperse particles but heterodisperse systems with a more or less statistical distribution of particle sizes and thicknesses.         Particle size distribution in metallic pigments has a decisive influence on the optical properties of the applications. It is essential, therefore, to measure particle size distribution for quality control and in order to classify the pigments, the anisotropy of the flakes makes this in difficulty

  Lubricants must be added at all stages of the production process to prevent from clumping, which has a unique effect on the wetting properties of metallic pigments. There are obvious differences in wetting properties between between leafing type and non-leafing type.   Leafing pigments       Due to their high surface tension leafing pigments are not wetted by the binder and therefore float on the wet film. This effect is achieved by the use of e.g. stearic acid as lubricant .       In paint systems with strongly polar solvents or binders there is always a danger that the leafing pigments will "drown" through wetting and turn into non-leafing pigments. This possibility must betaken into account       when drawing up the formula of paints. If necessary special leafing stabilized pigments should be used.   Non-leafing pigments       Non-leafing pigments are created either by the addition of strongly polar substances or wetting agents to leafing pigments or by the use of special lubricants (e.g. oleic acid) directly in the milling process.       Non-leafing pigments are completely wetted and thus spread evenly throughout the entire paint film.