Egyptian Blue: How an Ancient Pigment Could Save Lives

[♩INTRO ]
The tale of the world’s first artificial pigment has all the elements of a good thriller:
an ancient mystery, a dramatic rediscovery, and some cutting-edge future technology.
Today, this age-old chemical compound may help scientists prevent forgery and even save
lives.
But before it was doing any of that, it was adding color to the tombs of Egyptian pharaohs.
The color blue was a big deal to the ancient Egyptians.
It was the color of the sky and the Nile, and people came to associate it with creation
and fertility.
But the earliest pigments were made from things like different minerals or charcoal, which
means lots of browns, reds, and yellows.
One of the only natural sources of blue pigment was a rare, valuable mineral called lapis
lazuli.
It was ground up and turned into a deep blue pigment known as ultramarine.
And instead of paying big bucks for that blue, the ancient Egyptians got creative with some
chemistry and invented the world’s first artificial pigment.
Egyptian blue first appeared around 2600 BCE and eventually spread throughout Mesopotamia
and the Roman empire.
The only information we have about how it was made in ancient times comes from a Roman
writer named Vitruvius.
The ingredients were sand, which we now know was probably made of quartz, copper-containing
minerals, and natron, which is a salty mix of different sodium compounds that Egyptians
used for embalming, too.
You had to mix this stuff together, shape it into balls, stick those in a clay jar,
and heat them in an oven.
Then, you could grind them up to get some blue pigment!
This pigment was used in paint for wall art or mummy coffins, or in glazes for pottery.
But as other colors like red and yellow became all the rage in Roman art, Egyptian blue lost
popularity.
By around the fourth century, it began to fall out of use.
And, eventually, the formula for making it was lost.
The story picks up in 1814, when archaeologists found Egyptian blue while excavating the ruins
of Pompeii.
They sent samples to London for analysis, where chemists tried to figure out what it
was made of by mixing it with and dissolving it in other substances and seeing what happened.
After a lot of experimentation, we now know that the chemical name of Egyptian blue is
calcium copper tetrasilicate.
This could have been made by heating the ingredients Vitruvius mentioned — quartz sand, a copper
compound, and natron — along with calcium-containing lime, which may have been hanging out in the
sand the ancient Egyptians used.
This mixture needs to be kept at around 900 or 1000 degrees Celsius for a couple hours
to make the magic happen.
We still don’t know how the ancient Egyptians originally figured this recipe out, but the
chemical reaction would have required careful control of this super hot temperature and
the flow of oxygen into a furnace.
Not only that, but the consistency of their results was also incredible — Egyptian blue
pigment is almost exactly the same chemical in tombs built across nearly 3000 years.
And, today, the pigment is still surprising us.
Scientists discovered in 2009 that, when visible light is shined on them, Egyptian blue molecules
emit infrared radiation — the long-wavelength light that our eyes can’t detect, but can
be felt as heat or be picked up by certain cameras.
This makes the pigment easy to identify in ancient artwork.
Scientists can even determine if a worn-away sculpture or other piece of art was once painted
blue from traces of the chemical.
But this property of Egyptian blue means it has a bunch of other potential uses as well.
Infrared can pass through human tissue more easily than some other wavelengths of light,
like the visible spectrum or UV.
So it could be incorporated into a dye for new medical imaging techniques.
It could also be used in new types of security ink to prevent counterfeiting and forgery.
Or it could be made into a dusting powder for fingerprint detection on shiny or patterned
surfaces, where normal fingerprint powder is hard to see.
Ancient chemists trying to paint a blue sky on the walls of tombs could never have imagined
the ways their work would be used today.
But the story of Egyptian blue, it seems, is just beginning — again.
Thanks for watching this episode of SciShow!
For more on the science of color, check out our video where Stefan talks about 3 colors
that scientists discovered!
And if you want to keep getting smarter with us, you can always go to youtube.com/scishow and subscribe.
[♩OUTRO ]
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Egyptian Blue: How an Ancient Pigment Could Save Lives

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