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

https://www.scribd.com/document/1058364989/Why-the-Most-Requiring-Designers-Specify-Custom-made-Copper-Finials-And-What-They-Become-in-100-Years-150365

I marvelled how patination is both art and chemistry; regulated oxidation, acids, and waxes develop living surfaces that progress with weather yet remain protectively sealed.