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

https://travisptln953.raidersfanteamshop.com/copper-does-not-lie-why-architects-pick-salvo-metal-works-for-custom-smokeshaft-shrouds-that-last-a-century

I marvelled how patination is both art and chemistry; managed oxidation, acids, and waxes produce living surfaces that evolve with weather yet stay protectively sealed.