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

https://garrettpdrt345.cavandoragh.org/snow-guards-not-a-surprise-the-century-scale-case-for-customized-copper

I was surprised exactly how patination is both art and chemistry; regulated oxidation, acids, and waxes create living coatings that evolve with weather condition yet stay protectively sealed.