Copper VerdigrisIt is a green or blue-green patina that forms on the surface of copper when it is exposed to oxygen and moisture. It is created by the oxidation of copper in the presence of salt, sulfur compounds, and water.
The verdigris is created by the reaction of copper with acetic acid, which produces a greenish color. The color can range from bright blue-green to dull green or even black, depending on the concentration of copper, the presence of other chemicals, and the amount of time the copper is exposed to the air. Copper verdigris is often used to give an aged or antique look to metal objects, and it is also used as a decorative effect in buildings and artwork.