New York’s iconic, blue-green statue of liberty wasn’t always green. When the statue was gifted to the US from France in 1885, she was actually a shiny copper color. A new video reveals the chemical reactions involving oxygen and even air pollution that led to her color change from copper to liberty green.
The statue of liberty was a gift from France to the US as a way of commemorating the US’s fight for independence, as well as their own aspiration for democracy.
A video, published by the American Chemical Society, explains that the 305-foot (93 meter) statue was built over nine years in sections of copper skin on top of an iron skeleton.
According to the National Park Service, the statue is made of thirty tons of copper – enough to make 435 million pennies.
‘In her first few decades in the Big Apple, the state slowly turned from that shiny copper color to a dull brown and the, finally, to the blue-green, or as they’d say back in France, ‘verdigris’ we see today,’ said the video’s narrator.
When it changed color, some officials suggested restoring her back to her original color, but after the public protested against this decision, she was left the way she is.
The statue’s color change was as a result of oxidation reactions between copper and the air.
But it was more than one reaction – the color change is due to about 30 years worth of different reactions leading to a mixture of greenish minerals.
Oxidation reactions happen when an atom loses an electron to another atom.
In the case of the statue of liberty, her color change was bound to happen due to oxygen in the atmosphere that is ‘hungry’ for electrons.
On top of this, elements of New York City’s polluted air added to the color change too.
The first chemical reaction of the color change involved copper giving up electrons to electron-hungry oxygen in the atmosphere.
This led to a mineral called culprite – which is pinkish red.
Then, culprite loses even more electrons to oxygen, forming a new mineral called tenorite, which is blackish in color.
The black color of tenorite explains why the statue got darker over time, forming a dark brown color.
Then, further chemical reactions occurred when sulfur in the atmosphere reacts with water.
Sulfur comes from natural processes such as volcanic eruptions, but also from man-made emissions from boats, cars, airplanes and factories.
When sulfur dioxide in the atmosphere reacts with water, it produces sulfuric acid.
Sulfuric acid forms green minerals with copper oxides, so the sulfuric acid in the atmosphere made the state green over time.
Added to that, chloride from the sea spray surrounding Ellis Island where the statue is located made the statue even greener.
The statue stayed this way for over 100 years because the exposed copper is now oxidized and stable, but the statue wouldn’t be the same anywhere else.
The Daily Monitor