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

https://tysonzymk871.yousher.com/what-occurs-after-100-winters-copper-smokeshaft-shadows-by-salvo-metal-works

I was surprised exactly how patination is both art and chemistry; controlled oxidation, acids, and waxes produce living finishes that develop with climate yet continue to be protectively secured.