basically four stages of blends controlled by three grayscale textures-
trace: black creates a lightly bumped leafed metal with hard edges on the bump
glaze: ceramic glaze with it's own surface texture apart from the raw surface at black.
pitting: uses the ceramic's bump map to assign a 'grime' from wear to the top surface
grease: can be used to locate 'grime' in areas of wear, like the rim of a bowl