Correlation between optical appearance and orientation of aluminium

► The optical appearance of aluminium corresponds to the roughness of the surface. ► The roughness corresponds to the etching time and the orientation of aluminium. ► The roughness increases in the sequence: (111) - (100) - (110) - higher index surfaces. ► The gloss decreases and the lightness increases in the same sequence. ► Inhomogeneity of the optical appearance of aluminium can be attributed to corresponding orientation inhomogeneity.