I was surprised how patination is both art and chemistry; regulated oxidation, acids

https://wiki-canyon.win/index.php/Dormer_Style_for_100_Years:_Copper_That_Doesn%27t_Lie_to_Architects_or_Proprietors

I marvelled how patination is both art and chemistry; managed oxidation, acids, and waxes produce living coatings that develop with weather yet continue to be protectively sealed.