Color, appearance inconsistency in metallic powders.(Powder Coating)

We recently tested some metallic powders on our large metal cabinets. The surface is all splotchy with some dark areas and some very shiny areas. We use manual, corona charging spray guns. Why is the surface so inconsistent in color and appearance?

Metallic powders available on the market can be divided into two broad categories: "bonded" and "dry-blended." In a bonded powder, the metallic flakes are attached (bonded) to conventional powder particles (those combined of resin, pigment, various additives, etc.) to form a rather homogenous mixture--a mixture in which all particles have similar specific gravity, size, dielectric properties, shape, etc. For the most part, …