Copper naturally turns green over time as it reacts with oxygen in the air – a chemical reaction known as oxidation. The green colour is simply the natural shade of the patina that forms over the copper surface; the patina protects the copper from deterioration and creates a light bluish-green facade which can be seen on many copper rooftops and copper structures.
HOW LONG DOES IT TAKE COPPER TO TURN GREEN?
Copper doesn’t turn green overnight, it transitions through a number of stages over the years, moving from its initial orange shade into a dull brown colour, before finally settling into the familiar green tint.
Why is the Statue of Liberty Green?
Over time, copper reacts with oxygen in the air, and this causes the original shiny orange colour to turn green. The Statue of Liberty is exposed to the rough sea air from the North Atlantic Ocean, brought into the Upper Bay.
Has the Statue of Liberty always been Green?
No. As we show below, the Statue of Liberty started as the classic copper colour – shiny orange, and over changed to brown, then to green. This colour change process has taken around 30 years.
To demonstrate the timescale of this transition, we’ve used the most famous and iconic example of this process on Earth: the Statue of Liberty. The animation below tracks its changing colour pallette over the months and years since it was first installed on what is now known as Liberty Island:
COPPER PATINA COLOUR CHART
The patina which forms over copper works to protect and preserve the underlying copper material. This is different to what happens to iron during oxidation, where rust forms over the surface, deteriorating the material over time.
From the Statue of Liberty to a commercial copper roof, the green patina prevents further oxidation, making copper one of the most long-lasting roofing materials you can find.
STATUE OF LIBERTY HISTORY
The Statue of Liberty’s full name is the ‘Statue of Liberty Enlightening the World‘, and was a gift of friendship from France to the United States.
It is recognised as a universal symbol of freedom and democracy. The Statue of Liberty was dedicated on 28th October 1886. It was then designated as a United States National Monument in 1924.
Learn more about the Statue of Liberty.