Anodizing is an art as much as it is science. Finding the balance of chemistry and process to give the desired outcome of surface appearance and finish. Anodizing can be both functional as well as decorative. Increasing the natural oxide layer of aluminum improves wear properties and corrosion resistance, while also changing reflectance and allowing dyes to be absorbed form improved cosmetics.
Starting with a clean surface, and then modifying etch rates, etch type, and surface finish prior to anodize, many profiles and appearances can be created.