I marvelled just how patination is both art and chemistry; managed oxidation, acids

https://juliussxgk239.yousher.com/what-occurs-after-100-winters-copper-smokeshaft-shadows-by-salvo-metal-works

I was surprised how patination is both art and chemistry; managed oxidation, acids, and waxes develop living coatings that advance with weather condition yet remain protectively sealed.