2. Examples and data

2.1 Copper alloys

Copper alloys are numerous, and their natural color ranges from red (pure or low-alloy copper) to gold (Cu-Zn brass, the "orichalcum" of the ancients), through various shades of yellow (Cu-Sn bronzes) and pink (low-alloy bronzes).

These are certainly the metal alloys for which the notion of patina, whether natural or intentional, has been the most widespread and appreciated. This is due to their widespread use in artistic creation since antiquity [13] , [46] . This historic antiquity of "art bronzes" (a term which, in everyday language, refers to most copper alloys in addition to binary Cu-Sn alloys) no doubt...