A process for manufacturing a strip of aluminum alloy having high surface homogeneity with an upper side showing after a 1 m thick sulphur anodic treatment, an optical roughness value S_N measured on three 5 cm longitudinal sections and three 5 cm transverse sections, such that its mean variation on each section, defined by the ratio: (Maximum S_N-minimum S_N)/Mean S_N is less than 20%, and the difference S_N=S_N max -S_N min is less than 20. The strip is manufactured by continuous casting between two cooled rolls from a casting tank containing the liquid metal connected to an injector, and feeding the liquid metal into the gap between the two rolls. The injector has an upper lip recessed by at least 2 mm with reference to a lower lip of the injector.