Detail of a mural from an Eastern Han tomb with artificial pigment

Han Purple: A 2,800-year-old artificial pigment that quantum physicists are trying to understand

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Han purple is an artificial pigment created by the Chinese over 2,500 years ago, which was used in wall paintings and to decorate the famous terracotta warriors, as well as ceramics, metal ware, and jewelry. The pigment is a technological wonder, made through a complex process of grinding up raw materials in precise proportions and heating to incredible temperatures. So intricate was the process, that it was not reconstructed again until 1992, when chemists were finally able to identify its composition. But this was just the beginning. According to a news report on io9.com, research since then has discovered amazing properties of Han purple, including the ability to emit powerful rays of light in the near-infrared range, as well as being able to collapse three dimensions down to two under the right conditions.

The production of Han purple, otherwise known as Chinese purple, dates back as far as 800 BC, however it appears that it was not used in art until the Qin and Han dynasties (221 BC – 220 AD), when it was applied to the world famous terracotta warriors , as well as ceramics and other items. 

“Prior to the nineteenth century, when modern production methods made synthetic pigments common, there were only hugely expensive purple dyes, a couple of uncommon purplish minerals, and mixtures of red and blue, but no true purple pigment – except during a few hundred years in ancient China,” writes Samir S. Patel in ‘ Purple Reign: How ancient Chinese chemists added color to the Emperor’s army ’.

For an unknown reason, Han purple disappeared entirely from use after 220 AD, and was never seen again until its rediscovery by modern chemists in the 1990s.

Traces of Han purple can still be seen on many of the terracotta warriors

Traces of Han purple can still be seen on many of the terracotta warriors ( realhistoryww.com)

The Synthesis of Han Purple

Unlike natural dyes, such as Tyrian purple (from c. 1500 BC), which are organic compounds and typically made from plants or animals, like the murex snail, Han purple was a synthetic pigment made from inorganic materials.

Only two other man-made blue or purple pigments are known to have existed in the ancient world – Maya blue (from c. 800 AD), made from a heated mixture of indigo and white clay, and Egyptian blue, which was used throughout the Mediterranean and the Near and Middle East from 3,600 BC to the end of the Roman Empire. [Read similar: Egyptian Blue – The Oldest Known Artificial Pigment ].

Scientist Elisabeth FitzHugh, a conservator at the Smithsonian, was the first to identify the complex synthetic compound that makes up Han purple – barium copper silicate, a compound that differs from Egyptian blue only through its use of barium instead of calcium.

"Egyptian blue" tripodic beaker

"Egyptian blue" tripodic beaker ( Wikimedia). The composition of Han purple differs from Egyptian blue only in the use of barium instead of calcium.

The similarities between Han purple and Egyptian blue led some early researchers to conclude that the Chinese may have learned to make the pigment from the Egyptians. However, this theory has been largely discounted as Egyptian blue was not found further East than Persia.

“There is no clear reason why the Chinese, if they had learned the Egyptian formula, would have replaced calcium with barium, which necessitates increasing the firing temperature by 100 degrees or more,” writes Patel.

So how exactly did the Chinese stumble upon the intricate formula to make Han purple, which involved combining silica (sand) with copper and barium in precise proportions and heating to about 850-1000 °C? A team of Stanford physicists published a paper in the Journal of Archaeological Science ( summary here ), which proposes that Han purple was a by-product of the glass-making process, as both glass and the purple pigment contain silica and barium.  Io9.com writes that barium makes glass shinier and cloudy, which means this pigment could be the work of early alchemists trying to synthesize white jade.

Fluorescent properties

Since its composition was first discovered, scientists have continued to investigate this unique pigment. Researchers at the British Museum discovered that, when exposed to a simple LED flashlight, Han purple emits powerful rays of light in the near-infrared range. According to their study, published in the journal Analytical and Bioanalytical Chemistry , the Han purple pigments show up with startling clarity under the right conditions, meaning that even faint traces of the color, which are invisible to the naked eye, can be seen with infrared sensors.

A Western Han ceramic bowl from Hebei or Hanan province

A Western Han ceramic bowl from Hebei or Hanan province (Avery Brundage Collection, asianart.org), which contains traces of Han purple. The purple pigment becomes strongly fluorescent under infrared sensors (right).

Comments

love this stuff.

Tsurugi's picture

So....I take it these properties of the pigment are assumed to be accidental?

As in, someone in ancient China accidentally made high-efficiency infrared-reflecting dimension-collapsing quantumpaint?

Well, no. They just made some purple dye. We spotted the bonus features. Which don't really have any functional uses, they're just really interesting. 

Tsurugi's picture

In other words, yes. They accidentally made high-efficiency infrared-reflecting dimension-collapsing quantumpaint.

"It has no functional uses," hah. Quantum physicists are still trying to understand it and you're in here claiming it has no functional uses. I love your habit of making definitive statements on things you know absolutely nothing about.

Quantum effects aside, if you can't think of any functional uses for a paint that is highly reflective in the near infrared, your imagination must be horribly atrophied.

Bite me. These are just comments, old bean. They didn't accidentally find anything other than what they wanted: a nice purple colour. You have to do modern stuff to it for the effects. And if I need some IR reflective paint, I'd have to think twice about the cost of a pot of something made in blast furnace conditions as opposed to something synthetic and (poetically) mass produced in China. I really can't see it being daubed on aircraft carriers anytime soon as a camouflage or used in insulation as the main properties seem to be with light. And I'm not going to be that fussed if someone who thinks "rock" might transport you to another dimension, wants to throw me a condescending "hah". Stop being so serious. No one from Stanford is going to contact any of us for suggestions about what to do to it next.

Tsurugi's picture

Hmm. I was a bit snarky in my reply. I apologize.

I think this stuff qualifies as "synthetic and mass-produced in China". It is definitely a synthesized material, made in China, and in copious amounts.
Furnaces are not that unusual in modern mass-production of synthetic materials. The cost is mitigated by economies of scale(i.e., really big pots in really large furnaces).

The fact that it is so highly reflective in the infrared is useful visually, but it also means it is an excellent heat insulator.

The legend is that rock is sometimes a barrier between worlds or dimensions. Whoever this person is that thinks it's a transport has poor attention to detail. I wouldn't be much fussed over what they said either.

It is true that I take the subject of archaeology and ancient mysteries pretty seriously, and I figured anyone who took the time to read and then comment on these articles must also take it seriously in some way, or they wouldn't be here. Are you telling me not to take you seriously?

I don't need to be affiliated with an institute or organization. My fascination with the subject is what drives me to read the articles and to comment or converse about the content. Who cares if Stanford isn't going to contact us for suggestions?

Besides, I already told Los Alamos everything when they called yesterday.

Brilliant! Just keep hold of the patents: that's where the real power is!

I like your style. Let's take this to the next level as in, "other worldly".

Tsurugi's picture

I’m in. You got a ship? Where we goin’? Can we make a stop at Saturn? I heard it has a moon covered in hydrocarbons that aren’t made of fossils. Fossil-free fossil fuels! With that and the superquantum superpaint, we’d be set to save the world. Or conquer the universe. Whichever is easiest.

Are you inately crass, or have you just merely wasted the time you have spent gaining your education so you can be that way to people. I bet your wife and children look forward to you coming home at night.

Tsurugi's picture

*looks up the definition of "crass"*

Hmmm...crass, adjective: without refinement, delicacy, or sensitivity; gross; obtuse; stupid.

I'd say it's innate. So it’s good thing for my wife and kids that I don't have a wife and kids.

Cheers!

P.S. education wha?

I bet Just after china was united as one country by first emperor, the silk road then provided better trade for china and egypt for element trade. Do both china and egypt use blue and purple ? or as i see, they may have decided one use the other, thus each had their own uniqueness.. Anyone want to object my story, provide proof i am wrong, would like to read it :) i am not assuming i am right. But i bet i am right.

Conspiracys abound. Next anciens aliens episode?

Everyone knows that Annunaki spaceships were powered by super flat purple paint!!

Tsurugi's picture

Where's the conspiracy in this?

It was a joke....... Sorry?

Tsurugi's picture

No! You can't fool me.

YOU'RE PART OF THE CONSPIRACY DX

Tsurugi's picture

Another question just occurred to me. Why, exactly, are quantum phycisists looking at this paint in the first place?

Because it contains Barium and Copper

Yttrium barium copper oxide is a well know superconductor…..

Measurements in some experiments looked at the superconducting characteristic of YBaCuO films when it was supported on barium silicate...this is a different structure so the scientists (having the equipment already at hand) just decided to have a look to see if it had any special properties.

Dr. Derek Cunningham
Author The Long Journey (400,000 Years of Stone Age Science)

Do you want me to ask Stanford?

Dr. Derek Cunningham
Author The Long Journey (400,000 Years of Stone Age Science)

His theory is very sound and rational....But I think the Clovis technology chased the sun rather than run from it. For me to think that Early Man did not make note of Arial and Sea Born Species "Going somewhere" to the South and returning again every year over several thousand years would be highly unintelligent of us. If the same Fauna lived on the tip of every Continent at the time so could the Men depending on these species for survival. Man Followed these food sources for sure...Without a doubt...

Question is...did they go Counterclockwise or Clockwise? I venture to say Counterclockwise first. Clockwise second or third time around.

Tsurugi's picture

Thanks for the link! All very interesting.

But it doesn't explain why phycisists decided they should start doing superconducting experimentation on an ancient pigment... :)

Maybe the Chinese just thought it was pretty?

rbflooringinstall's picture

They probably know something about quantum physics that we now are only beginning to understand.

Peace and Love,

Ricky.

of the elements of the periodic table.  Flourescencent molecule absorbs UV light and emit as lower visible light.  S Kean The Disappearing Spoon which I am reading again and undoubtably will reread. 

Easily understandable and a fun read.  I have wondered if our past cyclic conditions on Earth would act to amass or accumulate or even transmute elements via a particularly stong emission from the sun .  If these cycles actually left easily accessible surface deposits of pure elements it would not be long before one of our curious selves began investigating.  Our discovery of the periodic table of elements required a lot of hit and miss and tedious purifying to obtain an elemental sample. 

I enjoyed this article, but you guys lost me on 3D to 2D and quantum physics is way over my head. Can someone please explain collapsing dimension in little people talk. I read it because I was interested in ancient coloring technique and was absolutely memorized with the brilliance of the color. Science lesson anyone?

Tsurugi's picture

I had a similar reaction to the whole "dimensional" aspect of this. It sounds very interesting but the descriptions were sort of vague. So, I followed the links to relevant articles and papers and read those too. I think I have a bit more understanding of what they're on about, now.

The stuff about "collapsing a dimension" is basically saying that we expect 3D objects to always have 3D effects or interactions--so for example, when a magnetic field is being emitted from an object that has length, width, and depth; we expect the field to have length, width, and depth as well--but this is not the case with this material when it is cooled to near-absolute zero. The magnetic field it emits is collapsed in one of its dimensions.

They are theorizing that this happens because of layering. The paint crystallizes into a bunch of very thin sheets or layers, and all the atoms in a given layer are in alignment with each other, but not necessarily in alignment with the atoms in the layers above and below. Since magnetic fields are a product of atomic alignment, the magnetic field emitted by a given layer does not combine with the fields emitted by the layers above and below it. So the field has length and width, but no depth.
Since every layer is emitting a magnetic field like this, the overall effect is described not as a two dimensional magnetic field--there is depth, because the fields are stacked just like the layers of paint are--but a field that has been collapsed in one of its dimensions.

Not sure if that makes it more clear what they are talking about, lol. Describing three dimensional and two dimensional things in a one-dimensional medium(text is linear, only one dimension) is not easy.

What it is saying is the effect isgenerated from only the surface….so it becomes “two dimensions”

Graphene, which forms atomic sheets, is a two dimensional system. The nanomaterial here is three dimensional but under the correct conditions the effect being studied is apparently limited to just the material’s surface. There is however some question over the definition being used here is truly limited to just the surface or perhaps is also employing the layer of atoms underneath the surface.

 

Dr. Derek Cunningham
Author The Long Journey (400,000 Years of Stone Age Science)

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