The Statue of Liberty has not always been its iconic green. When it was first unveiled in 1886, it was a classic copper. But when copper reacts with oxygen and the right mix of pollutants, it takes on a green-blue hue.
The key pollutant in this mix was sulfur. When the Statue of Liberty was built – and in the decades that followed – New York’s air was thick with sulfur from coal burning, which reacts with copper to form copper sulfide and sulfate, changing its color.
The government should have expected this change in shade. The patina that forms on copper is ‘verdigris’, a green–blue pigment. Humans have known about verdigris for centuries, if not longer. It was widely used as a green pigment in paintings.
But if they did expect a color change, their reaction suggested otherwise. By 1906, Congress was concerned that this was not a patina but corrosion. It wanted to paint the Statue of Liberty to protect it. When The New York Times revealed the plans in a piece titled ‘To Paint Miss Liberty!’ there was a public outcry.
A week later the Times reporter spoke to artists and architects to get their feedback on the plan and published the findings in a follow-up. Artists couldn’t believe the plan. As one put it: ‘I think my attention has never been called to a greater bit of proposed vandalism than this.’ He went on to explain that the patina wasn’t a threat to the sculpture, but a protective layer for the copper underneath.