patination

Patination is a surface finish, often seen on metals like bronze, that is created by the chemical action of the environment or by the artificial application of chemicals. This process results in an attractive layer, typically in shades of green, brown, blue, or black, which can preserve and decorate the metal.1

The term "patina" originated from the Latin word for a shallow dish, and in the 17th century, Italians used it to describe the green film forming on copper. By the mid-18th century, English speakers adopted the term for this phenomenon. Over time, the meaning expanded to include any surface appearance that has become more beautiful with age or use, such as on old wood or tarnished silver.2