Science reveals secrets of a mummy’s portrait

How much information can you get from a speck of purple pigment, no bigger than the diameter of a hair, plucked from an Egyptian portrait that’s nearly 2,000 years old? Plenty, according to a new study. Analysis of that speck can teach us about how the pigment was made, what it’s made of — and maybe even a little about the people who made it. The study is published in the International Journal of Ceramic Engineering and Science.

“We’re very interested in understanding the meaning and origin of the portraits, and finding ways to connect them and come up with a cultural understanding of why they were even painted in the first place,” says materials scientist Darryl Butt, co-author of the study and dean of the College of Mines and Earth Sciences.

Faiyum mummies

The portrait that contained the purple pigment came from an Egyptian mummy, but it doesn’t look the same as what you might initially think of as a mummy — not like the golden sarcophagus of Tutankhamen, nor like the sideways-facing paintings on murals and papyri. Not like Boris Karloff, either.

The portrait, called “Portrait of a Bearded Man,” comes from the second century when Egypt was a Roman province, hence the portraits are more lifelike and less hieroglyphic-like than Egyptian art of previous eras. Most of these portraits come from a region called Faiyum, and around 1,100 are known to exist. They’re painted on wood and were wrapped into the linens that held the mummified body. The portraits were meant to express the likeness of the person, but also their status — either actual or aspirational.

That idea of status is actually very important in this case because the man in the portrait we’re focusing on is wearing purple marks called clavi on his toga. “Since the purple pigment occurred in the clavi — the purple mark on the toga that in Ancient Rome indicated senatorial or equestrian rank- it was thought that perhaps we were seeing an augmentation of the sitter’s importance in the afterlife,” says Glenn Gates of the Walters Art Museum in Baltimore, where the portrait resides.

The color purple, Butt says, is viewed as a symbol of death in some cultures and a symbol of life in others. It was associated with royalty in ancient times, and still is today. Paraphrasing the author Victoria Finlay, Butt says that purple, located at the end of the visible color spectrum, can suggest the end of the known and the beginning of the unknown.

“So the presence of purple on this particular portrait made us wonder what it was made of and what it meant,” Butt says. “The color purple stimulates many questions.”

Lake pigments

Through a microscope, Gates saw that the pigment looked like crushed gems, containing particles ten to a hundred times larger than typical paint particles. To answer the question of how it was made, Gates sent a particle of the pigment to Butt and his team for analysis. The particle was only 50 microns in diameter, about the same as a human hair, which made keeping track of it challenging.

“The particle was shipped to me from Baltimore, sandwiched between two glass slides,” Butt says, “and because it had moved approximately a millimeter during transit, it took us two days to find it.” In order to move the particle to a specimen holder, the team used an eyelash with a tiny quantity of adhesive at its tip to make the transfer. “The process of analyzing something like this is a bit like doing surgery on a flea.”

With that particle, as small as it was, the researchers could machine even smaller samples using a focused ion beam and analyze those samples for their elemental composition.

What did they find? To put the results in context, you’ll need to know how dyes and pigments are made.

Pigments and dyes are not the same things. Dyes are the pure coloring agents, and pigments are the combination of dyes, minerals, binders and other components that make up what we might recognize as paint.

Initially, purple dyes came from a gland of a genus of sea snails called Murex. Butt and his colleagues hypothesize that the purple used in this mummy painting is something else — a synthetic purple.

The researchers also hypothesize that the synthetic purple could have originally been discovered by accident when red dye and blue indigo dye mixed together. The final color may also be due to the introduction of chromium into the mix.

From there, the mineralogy of the pigment sample suggests that the dye was mixed with clay or a silica material to form a pigment. According to Butt, an accomplished painter himself, pigments made in this way are called lake pigments (derived from the same root word as lacquer). Further, the pigment was mixed with a beeswax binder before finally being painted on linden wood.

The pigment showed evidence suggesting a crystal structure in the pigment. “Lake pigments were thought to be without crystallinity prior to this work,” Gates says. “We now know crystalline domains exist in lake pigments, and these can function to ‘trap’ evidence of the environment during pigment creation.”

Bottom of the barrel, er, vat

One other detail added a bit more depth to the story of how this portrait was made. The researchers found significant amounts of lead in the pigment as well and connected that finding with observations from a late 1800s British explorer who reported that the vats of dye in Egyptian dyers’ workshops were made of lead.

“Over time, a story or hypothesis emerged,” Butt says, “suggesting that the Egyptian dyers produced red dye in these lead vats.” And when they were done dyeing at the end of the day, he says, there may have been a sludge that developed inside the vat that was a purplish color. “Or, they were very smart and they may have found a way to take their red dye, shift the color toward purple by adding a salt with transition metals and a mordant [a substance that fixes a dye] to intentionally synthesize a purple pigment. We don’t know.”

Broader impacts

This isn’t Butt’s first time using scientific methods to learn about ancient artwork. He’s been involved with previous similar investigations and has drawn on both his research and artistic backgrounds to develop a class called “The Science of Art” that included studies and discussions on topics that involved dating, understanding and reverse engineering a variety of historical artifacts ranging from pioneer newspapers to ancient art.

“Mixing science and art together is just fun,” he says. “It’s a great way to make learning science more accessible.”

And the work has broader impacts as well. Relatively little is known about the mummy portraits, including whether the same artist painted multiple portraits. Analyzing pigments on an atomic level might provide the chemical fingerprint needed to link portraits to each other.

“Our results suggest one tool for documenting similarities regarding time and place of production of mummy portraits since most were grave-robbed and lack archaeological context,” Gates says.

“So we might be able to connect families,” Butt adds. “We might be able to connect artists to one another.”

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3D Printing Industry

Interview: AMT and DTI on how they created new 3D printing food-contact applications

“Food-contact applications are definitely a place where 3D printing will take a bigger piece of the cake, it’s only the tip of the iceberg for us with surface treatment. It’s a market that will grow a lot in the coming years, so there’s a big potential there.” That’s how Mads Østergaard, Team Manager at The […]

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Author: Paul Hanaphy


Reaction microscope ‘X-rays’ individual molecules

“The smaller the particle, the bigger the hammer.” This rule from particle physics, which looks inside the interior of atomic nuclei using gigantic accelerators, also applies to this research. In order to “X-ray” a two-atom molecule such as oxygen, an extremely powerful and ultra-short X-ray pulse is required. This was provided by the European XFEL which started operations in 2017 and is one of the the strongest X-ray source in the world

In order to expose individual molecules, a new X-ray technique is also needed: with the aid of the extremely powerful laser pulse the molecule is quickly robbed of two firmly bound electrons. This leads to the creation of two positively charged ions that fly apart from each other abruptly due to the electrical repulsion. Simultaneously, the fact that electrons also behave like waves is used to advantage. “You can think of it like a sonar,” explains project manager Professor Till Jahnke from the Institute for Nuclear Physics. “The electron wave is scattered by the molecular structure during the explosion, and we recorded the resulting diffraction pattern. We were therefore able to essentially X-ray the molecule from within, and observe it in several steps during its break-up.”

For this technique, known as “electron diffraction imaging,” physicists at the Institute for Nuclear Physics spent several years further developing the COLTRIMS technique, which was conceived there (and is often referred to as a “reaction microscope”). Under the supervision of Dr Markus Schöffler, a corresponding apparatus was modified for the requirements of the European XFEL in advance, and designed and realised in the course of a doctoral thesis by Gregor Kastirke. No simple task, as Till Jahnke observes: “If I had to design a spaceship in order to safely fly to the moon and back, I would definitely want Gregor in my team. I am very impressed by what he accomplished here.”

The result, which was published in the current issue of the journal Physical Review X, provides the first evidence that this experimental method works. In the future, photochemical reactions of individual molecules can be studied using these images with their high temporal resolution. For example, it should be possible to observe the reaction of a medium-sized molecule to UV rays in real time. In addition, these are the first measurement results to be published since the start of operations of the Small Quantum Systems (SQS) experiment station at the European XFEL at the end of 2018.

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IEEE Spectrum

CES 2020: The Best—and Wildest—Gadgets

At CES, among the bigger, brighter TVs, mock smart homes that seem to know more about you than you do, and all the Alexa- and Google-Assistant-enabled devices eager to talk to you, are a few products that defy categorization. Some of these new products grabbed my attention because they involve truly innovative technology. Some are just clever and cheap enough to catch on, and some are a little too wild to find a big market—but it’s still impressive when a developer realizes an extreme dream.

So, as CES 2020 retreats into history, here is my top 10 list of CES gadgets that at least got my attention, if not a spot on my shopping list. There is no way to rank these in order of importance, so I’ll list them roughly by size, from small to big. (The largest products demonstrated at CES, like John Deere’s AI-powered crop sprayer, Brunswick’s futuristic speedboat, or Hyundai’s flying taxi developed in partnership with Uber Elevate can’t be called gadgets, so didn’t make this roundup.)


2D antimony holds promise for post-silicon electronics

Not everything is bigger in Texas — some things are really, really small. A group of engineers at The University of Texas at Austin may have found a new material for manufacturing even smaller computer chips that could replace silicon and help overcome one of the biggest challenges facing the tech industry in decades: the inevitable end of Moore’s Law.

In 1965, Gordon Moore, founder of Intel, predicted the number of transistors that could fit on a computer chip would double every two years, while the cost of computers would be cut in half. Almost a quarter century later and Moore’s Law continues to be surprisingly accurate. Except for one glitch.

Silicon has been used in most electronic devices because of its wide availability and ideal semiconductor properties. But chips have shrunk so much that silicon is no longer capable of carrying more transistors. So, engineers believe the era of Moore’s Law may be coming to an end, for silicon at least. There simply isn’t enough room on existing chips to keep doubling the number of transistors.

Researchers in the Cockrell School of Engineering are searching for other materials with semiconducting properties that could form the basis for an alternative chip. Yuanyue Liu, an assistant professor in the Walker Department of Mechanical Engineering and a member of UT’s Texas Materials Institute, may have found that material.

In a paper published in the Journal of the American Chemical Society, Liu and his team, postdoctoral fellow Long Cheng and graduate student Chenmu Zhang, outline their discovery that, in its 2D form, the chemical element antimony may serve as a suitable alternative to silicon.

Antimony is a semi-metal that is already used in electronics for some semiconductor devices, such as infrared detectors. As a material, it is only a couple of atomic layers thick and has a high charge mobility — the speed a charge moves through a material when being pulled by an electric field. Antimony’s charge mobility is much higher than other semiconductors with similar size, including silicon. This property makes it promising as the building block for post-silicon electronics.

Liu has only demonstrated its potential through theoretical computational methods but is confident it can exhibit the same properties when tested with physical antimony samples, which is the team’s next step. But the findings have even broader significance than simply identifying a potential replacement for silicon in the race to maintain Moore’s Law into the future.

“More importantly, we have uncovered the physical origins of why antimony has a high mobility,” Liu said. “These findings could be used to potentially discover even better materials.”

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What gives a 3-meter-long Amazonian fish some of the toughest scales on Earth

Arapaima gigas is a big fish in a bigger river full of piranhas, but that doesn’t mean it’s an easy meal. The freshwater giant has evolved armor-like scales that can deform, but do not tear or crack, when a piranha — which has one of the animal kingdom’s most powerful bites — attacks. Researchers from UC San Diego and UC Berkeley describe the unique properties of the Amazonian Arapaima skin and its potential for human-made materials October 16 in the journal Matter.

Arapaima‘s adaptation naturally solves a problem that engineers face when attempting to develop synthetic armors. Arapaima‘s scales have a tough, yet flexible, inner layer bound by collagen to its mineralized outer layer of scales. Similarly, bullet-proof vests are made of several layers of flexible webbing sandwiched between layers of hard plastic. But human-made materials are bound using a third adhesive material, whereas the fish’s scales are bound on an atomistic level; they grow together, weaving into one solid piece.

“A window may appear strong and solid, but it has no give. If something attempted to puncture it, the glass would shatter,” says senior author Robert Ritchie, a materials scientist at UC Berkeley. “When nature binds a hard material to a soft material, it grades it, preventing this shattering effect. And in this case, the binding structure is mineralized collagen.”

Other fish use collagen like Arapaima does, but the collagen layers in Arapaima scales are thicker than in any other fish species. The scales alone are each as thick as a grain of rice. Co-authors Yang, Quan, Meyers, and Ritchie hypothesize that this thickness is the secret to the fishes’ defense.

They tested this by soaking cracked Arapaima scales in water for 48 hours, then slowly pulling the edges apart while adding pressure to a central point. As they added pressure, they observed that the part of the mineralized, hard outer layer expanded, cracked, then gradually peeled off. The scales then localized the crack, containing it and preventing damage from spreading in the twisting structural collagen layer. If the pressure did break through to the collagen, it deformed the layer instead of breaking it.

If humans can develop a flexible hierarchical structure that behaves like the collagen layer in the fish scales, Ritchie says that better, potentially impermeable, synthetic armors can be made. But he also acknowledges that this reality may be a number of years down the line.

Until then, Ritchie’s team will investigate how Arapaima‘s scales have adapted to prevent penetration from piranha bites as well as how nature behaves this way in other species.

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Catapult Inspired By Leonardo da Vinci

I have changed the “bucket” to be wider for bigger “projectiles” and added a thumb wheel of easy range adjustment.

But the bigger redesign is the fulcrum. I split it into two parts to be printed easier.
Now the hole for the axle goes now through all the way, so a longer threaded is needed

EDIT 4/30/2019

As mentioned below I managed to break/wear out the spring rather quickly.
Hence I added a beefed up version. This might not be the engineering approach of Leonardo as he had presumably no access to rubber bands. I use my catapult as an office toy and am therefore not too concerned with historical accuracy.

P.S. I will need to redesign the spring and strengthen it. It suffered material fatigue due to tightening the rubber bands to much, because I wanted to increase range and power. Stay tuned!

P.P.S: Here is the original:

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