Verdigris

Definition - What does Verdigris mean?

Verdigris is the green pigment extracted to copper plates via acetic acid application. In short, it is the thin corrosion layer that exists on bronze, copper and similar materials caused by aging or environmental exposure.

Verdigris is usually composed of carbonates or oxides. It is slightly transparent and and characterized by low stability. It also can be produced from the action of seawater, air and other environmental elements on the material over a period of time. It is copper carbonate, but when close to the sea, it may be copper chloride. If acetic acid is present during weathering, it may have copper acetate.

Verdigris is also known as patina.

Corrosionpedia explains Verdigris

Today, verdigris is primarily used in industrial settings as a fungicide or a catalyst that supports organic reactions. It also is widely used in dyeing and medicine production.

Historically, verdigris was a vital tool for Greek artists and was utilized as pigments in art objects and paintings. The bright green shade of copper acetate made verdigris the most used pigment in painting until the 19th century.

Verdigris can be produced by using a variety of methods, including:
  • Hanging plates of copper in hot vinegar inside a sealed container
  • Putting copper strips in contact with wood blocks brushed with acetic acid and then sealed and buried in dung
  • Interaction of copper and wine resulting from oxidation
  • Reaction of copper sulfate solutions with barium or lead solutions

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