Thursday, March 13, 2008

The Colour Purple or is it?

So how do you mix Purple?

Anyone who has even had an art class will answer by mixing Blue and Red together.
Sounds simple enough doesn't it? However some research reveals a story about purple that spans back into the history of ancient china and involves a buried Terracotta army.

In 1974, a province in China was suffering a drought, so farmers began digging an irrigation well, the fact is that they didn't find water, but what is now widely considered the Eight Wonder of the World. What they discovered below the earth were more than 8,000 life sized warriors, horses and other figures made to accompany and protect Qin Hi Huang, the very first Emperor of China on his journey into the afterlife.

Many of us have seen pics of the warriors in their natural Terracotta colour, but they weren't always this colour apparently. Two thousand years ago, the warriors were actually brightly coloured, no two the same.

One of the colours found on these model warriors, supposedly the highest ranking of the officers, was known as Han Purple. It seems this presented an interesting conundrum to archaeologists, in that Purple pigment was rarely found on ancient artefact's.

Han Purple has since been found scientifically to fade in acid, so colorless particles found in pigments containing Han Blue and Han Purple may be particles which were originally purple but which faded after burial in acidic conditions.

Blue and Purple are not colours found in surface soils and would therefore not have been created using earth. Blue pigments only began to appear in history when mining began and even then they were extremely rare, as was the case with Lapis Lazuli. A blue stone which was once powdered and mixed with oil to create the pigment named Ultramarine meaning "Beyond the sea" and which is often seen in the beautiful blue Renaissance paintings of the 1600's.

The original source for Lapis lies in the valley of the Kokcha River, at Sar-e-sang meaning "Place of Stones" which is in the province of Badakshan in north-eastern Afghanistan. Marco Polo mentioned these mines in 1271 and he noted that the stones were processed to make colour, although Ultramarine has been made synthetically since 1828. Lapis came to Europe via Venice, which was the main trading port between Europe and the East. Today it is still mined by hand and when the stones are brought to the mine surface, they are sorted into three general categories being "Rang-i-ob" meaning "Colour of Water", "Rang-i-sabz" meaning "Green" and "Surpar" meaning "Red Feather". Surpar is considered the highest quality of Lapis, because it has a deep blue-violet tone.

Good Lapis is very rare and very expensive although a new source in Chile has provided a good alternative to the that found in Afghanistan and at a slightly cheaper price. The Egyptians held Lapis in high esteem, it was as precious as gold and as a consequence they were often used together in jewellery and still are today.
Purple has always been associated with royalty, power and wealth.

So how did Ancient China mix up the colour purple?
A bit of detective work reveals that it was indeed synthetic. This means that Chinese artisans were performing synthetic inorganic chemistry more than 2700 years ago.

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