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

https://wiki-wire.win/index.php/Dormers_You_Can_Count_On:_The_Honest_Aging_of_Hand-Fabricated_Copper

I was surprised how patination is both art and chemistry; managed oxidation, acids, and waxes produce living finishes that progress with weather yet stay protectively sealed.