Why is the Statue Green?
The answer is in the air.
The Statue’s skin is made of copper, and when copper is exposed to oxygen in the air, it undergoes a chemical reaction called oxidation. The reaction causes a fine crust or film to develop that is usually green in color. This layer protects the original metal underneath. In copper and bronze, this natural protective process is called Patination. It took nearly thirty years for the Statue to turn from her original copper color to the green you see today. The palination process can also be observed on buildings where copper or bronze are used for roofing and ornamentation such as the ferry dock on Liberty Island and on the roof and domes of the Immigration Station at Ellis Island.
Courtesy hmdb.org
