aerugo
/ɪˈruːɡoʊ/
noun
- A green or bluish-green coating that forms on copper, brass, or bronze when exposed to air or moisture; also called patina or verdigris.
- Restorers carefully removed the aerugo from the ancient copper bowl.
- The old statue was covered in a beautiful layer of aerugo.
- The roof's copper panels developed a green aerugo over many years.