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

https://www.scribd.com/document/1041906801/Dormers-That-Don-t-Trick-The-100-Year-Efficiency-of-Custom-made-Copper-by-Salvo-Metal-Works-150522

I was surprised just how patination is both art and chemistry; regulated oxidation, acids, and waxes develop living surfaces that progress with weather yet continue to be protectively secured.