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

https://wiki-global.win/index.php/Salvo_Metal_Works:_The_Designer%27s_Partner_for_100-Year_Copper_Chimney_Shrouds

I was surprised just how patination is both art and chemistry; controlled oxidation, acids, and waxes develop living coatings that evolve with climate yet continue to be protectively sealed.