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

https://codynucp768.theglensecret.com/snow-guard-truths-copper-s-unequaled-long-life-in-alpine-and-coastal-projects

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