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Why is the Statue of Liberty green?
It was originally a shiny copper color, and the green layer protects the metal.
The statue's skin is made of thin copper sheets, about 3/32 of an inch thick according to the National Park Service, which is roughly the thickness of two pennies stacked. The sheets were hammered over wooden forms in France and then riveted to an internal iron framework designed with the help of Gustave Eiffel. When the statue was dedicated in 1886, the metal looked like a bright, reddish-brown new penny.
Copper reacts slowly with oxygen, moisture and airborne compounds. First it darkens as a layer of copper oxide forms. Over years, further reactions with carbonates, sulfates and chlorides in the air, including salt from the harbor, produce blue-green copper minerals that make up the patina. The color change in New York is generally described as taking place over a few decades, with the statue appearing largely green by around the early twentieth century, though the exact timing is not precisely documented here.
The patina is not rust or decay in the usual sense. It forms a stable, tightly bound film that slows further corrosion of the copper beneath, which is why the thin skin has lasted well over a century. A common misconception is that the green is paint. Efforts at the time of the 1980s restoration focused on repairing the iron framework, where corrosion between iron and copper was the real structural problem, rather than removing the green surface. The original torch was replaced in 1986 by a new one covered in gold leaf, which shows that not everything on the statue is copper-colored or green.