Ah.
The Statue of Liberty.
The symbol of freedom, liberty and America and everything that’s great about this country.
There she is.
Lady Liberty standing there in all her blue/green glory.
But did you know she wasn’t always that blue green hue?
You probably do know that she was a gift from France in 1885, as a way of commemorating
our fight for independence and their own aspirations for democracy.
This 305 foot statue was built over 9 years in sections of copper skin on top of an iron
skeleton.
According to the National Park Service, the statue has about thirty tons of copper, which
is enough to make 435 million pennies.
Yes bright reddish-gold pennies.
But the statue of Liberty isn’t the same color as well, any penny I’ve seen.
So how to explain Lady Liberty’s color change?
Simple.
You’d change colors too if you stayed outside in that NYC polluted air for almost 150 years!
We’re kidding...mostly.
It all comes down to chemistry.
In her first few decades in the Big Apple, the statue slowly turned from that shiny copper
color to a dull brown and then, finally, to the blue-green, or as they’d say back in
France, “verdigris” ; on screen - green of Greece] we see today.
Officials suggested trying to restore her to the original color, or painting her.
But after public outcry, they decided to just leave it the way it is.
And it’ll keep looking like that until Dr. Zaius shows up.
Anyway, her color change happened because of oxidation reactions between copper and
the air.
Now I know some of you smartypants might be saying “Duh!”.
But copper’s patina is more complicated than just one reaction.
It’s due to about 30 years worth of oxidation reactions creating a mixture of minerals.
So let’s get into it.
Now, when an atom loses electrons in a chemical reaction it’s called oxidation.
This process was first observed in reactions that involved oxygen, hence the name, but
it can happen with other elements too.
Lady Liberty’s transformation from coppery red to blue-green was inevitable as soon as
they parked her in New York Harbor.
And here’s why.
First there’s all the oxygen in our atmosphere, hungry for electrons.
Then you add all the elements in New York’s polluted air to the mix, et voila!
In the first reaction, copper gives up electrons to oxygen.
That creates this mineral, cuprite, which you can see is a pinkish-red.
Next, cuprite loses more electrons to more oxygen, forming blackish tenorite.
The black color of this tenorite explains why the statue slowly got darker over the
years, forming a dark brown.
Now let’s pivot to sulfur reactions.
Sulfur finds its way into the atmosphere as sulfur dioxide through natural processes,
including volcanic eruptions.
But humans have also put a lot of it there too with their boats, and cars, and pesky
airplanes and factories.
So when sulfur dioxide gets together with water, it forms sulfuric acid, which can form
green stuff with copper oxides.
Throw in the sea spray around the statue’s Ellis Island home, and it’s inevitable.
Now back to our color change.
Lady Liberty gets painted with this sulfuric acid and her green color gets forming.
Throw in some chloride from the sea spray around the statue’s Ellis Island home, and
well, you can see what happened.
Here’s the chemistry breakdown: tenorite, that black stuff, reacted with sulfuric acid
and water to make blue-green brochantite.
And thanks New Yorkers there was even more sulfuric acid in the air so the brochantite
became green antlerite in some places on the statue.
Wherever the seaspray hit the statue of Liberty and didn’t get washed away by rain, brochantite’s
sulfate got swapped for chloride and made olive-green atacamite.
So there it is!
That beautiful and well known blue/green hue.
The Statue of Liberty has stayed this color for over a hundred years because all the exposed
copper is now oxidized: she’s stable at this point of her life.
At least until she decides to take a walk.
She wouldn’t be the same if she’d lived somewhere else.
If nothing else, she has a New Yorker’s thick skin, and it’s helped protect her
over all these years.
So what do you think?
Should Lady Liberty stay the blue-green color of freedom?
Or return to her glorious brown?
Let us know in the comments and one just more thing.
We have a message for you from our friend Vanessa
at BrainCraft.