Which of these is a thin layer that forms on the surface of copper through age and exposure?

Thank you Antiques Roadshow! Got this right because I heard it before on their show when evaluating coins.

moose, You are right. Verdigris results from the oxidation of copper in brass, bronze (both contain copper) and pure copper. Verdigris is a patina specific to copper.

Electric motors with a commutator will also get a patina on them

I always thought. it was verdigris specifically on copper

Seshati , I heard it on an episode of Sherlock

Thank you Barnwood Builders

Thank you Jimmy Smits character from Sons of Anarchy haha I mean I’ve seen it sure but didn’t know the name until he said it in the show .. looked it up & will never forget it. It’s pretty can really make a piece into art of a different kind.