2. Examples and data

2.1 Copper alloys

There are many different copper alloys, and their natural colors range from red (pure copper or low-alloy copper) to gold (Cu-Zn brass, known as "orichalcum" in ancient times), including several shades of yellow, varying in lightness (Cu-Sn bronzes), and pink (low-alloy bronzes).

These are undoubtedly the metal alloys for which the concept of patina, whether natural or intentional, has been most widely used and appreciated. The reason for this is their extensive use in artistic creation since ancient times [13] , [46] . This historical character of "art bronzes" (a term which, in everyday language, refers to...