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

https://www.tumblr.com/loftilynoisytwist/816763990380298240/snow-guards-for-the-next-century-customized

I marvelled just how patination is both art and chemistry; controlled oxidation, acids, and waxes produce living coatings that progress with weather yet stay protectively sealed.