Do you know what “patina” is? Patination is the process by which a metal object develops a thin layer of oxidized metal on its surface. This thin layer is called “patina” and it can be formed unintentionally (by exposure to oxygen) or intentionally (with a chemical treatment).
See below this statue in Commerce Square, Lisbon with a surface layer of green patina caused by oxidation. The same statue is shown in the second photo after the removal of the patina and with the original finish from 1775 now exposed again. The dark color of the statue made English sailors call the square “Black Horse Square”. (sources https://en.wikipedia.org/wiki/Patina and Philadelphia Museum of Art) #history #lisbon #patina #bronze #statue