Registan, Samarkand, Uzbekistan. Courtesy Wikimedia Commons

My apologies for a few weeks hiatus over here at Artful Science.

Last summer I got married and we are finally off on our honeymoon to Uzbekistan (aka the honeystan) where we will explore some awesome Silk Road architecture.

Given that we’ll be looking at a lot of mosaics, I thought I’d point you to this post on the conservation of tile art and the 2011 Nobel Prize in chemistry.

See you at the end of April…

This gold gilding at the Reales Alcazares of Sevilla was added in the 19th century.

There’s beautiful gold gilding at Reales Alcazares royal palace in Seville, Spain.

Yet it turns out that the pretty gold gilding you see in the image on the left is not precisely original.

The World Heritage Site was originally built in 914 AD, and then expanded from the 14th to the 16th century.

Recently, Spanish researchers found a layer of paint lying below the gold gilding that contains lead chromate, a pigment that wasn’t used until the 19th century. So the gold lying above must have been added afterwards.

Yellow lead chromate pigment is responsible for the bright color of many old school buses, and it was even used as a colorant for yellow candy before falling out of favor because both lead and chromate are extremely toxic.

Cross section showing gold gilding on top and yellow lead chromate paint below.

Spanish researchers report that the lead chromate layer was added sometime after 1818 above a deteriorated layer gold gilding, probably as part of a 19th century restoration project.

The lead chromate may have been painted on as false gold to keep up appearances before new gold gilding could be applied.

Or it’s possible that the lead chromate was painted on just before the new gold gilding: The paint may have acted as a foundation layer to help the new gold gilding adhere.

This conundrum is reported in the inaugural issue of Heritage Science, the first peer-reviewed journal to focus entirely on cultural heritage science. (Welcome!!)

This 7th century BC amber found in an Italian tomb originally came from the Baltic area even though Italy had its own sources of amber.

There’s a variety of interesting topics reported in the journal’s first edition, including a way to determine the geographical origin of amber which provides clues about early trading roots of the fossilized tree resin.

There’s also an analysis of medieval Hungarian silver coins, and several papers on the effects of pollution and humidity on cultural heritage objects, from ancient architecture to antique books.

The issue also contains a cool paper about a sculpture accidentally discovered behind a wall of St Petersburg’s Winter Palace in 2010.

The sculpture, called Fugitive Slave and made by the Russian artist Vladimir Beklemishev, was inspired by the anti-slavery novel Uncle Tom’s Cabin. It was initially exhibited at the World’s Fair in Chicago in 1893, and then sent to Russia before being hidden in the palace wall after the sculpture suffered heavy damage during World War Two.

The sculpture was made to look like bronze, even though it is definitely not bronze.

That’s why the scientists are keen to study its make-up: The pseudo bronze involves creative use of gypsum, iron, copper and arsenic.

But perhaps the most interesting read in the inaugural issue of Heritage Science is the very pointed essay by journal editor Richard Brereton.

Brereton does not mince words about the devastating effect of 20th century progress on cultural heritage. He begins with his hometown of Bristol, where “post-war planners destroyed more of Bristol than [World War 2] bombs” and goes on to decry lost heritage in other parts of Europe, Asia and the Americas.

“Capitalists, aristocrats, democrats and communists were all at it in the twentieth century, destroying a heritage that had evolved very slowly for centuries. In the past there had been waves of localized destruction, for example in Rome, the Popes raided marble from the Coliseum in order to construct new churches, and in Latin America, the Spanish conquistadors organised a mass destruction of Inca, Aztec and many other cultural artefacts – for example there are only fragments of Aztec written texts available due to the enthusiastic destruction of material by priests. But the twentieth century appears unique for a mass international desecration of our global historic heritage. Most governments were dependent on some sort of political support, even tyrants have to feed their armies, and people wanted hot water in the homes and good food on the table and washing machines and televisions rather than fine paintings and important buildings.”

Here’s to reading more in Heritage Science about how 21st century science can inform efforts to conserve what’s not been destroyed in the 20th century.

The tomb of Richard I’s heart in Notre Dame of Rouen, France. Credit: walwyn—professor-moriarty.com

A French-based research team recently had a rare opportunity to get to the heart—quite literally—of some 12th century European history.

Using a battery of scientific equipment, they took a closer look at how the heart of English king Richard I was preserved for posterity.

Also known as Richard the Lionheart because of his military prowess, Richard I was king of England from 1189 to 1199.

He led a Crusade to the Holy Land in 1190, but the mission failed to take Jerusalem, its main objective.

On the way back home he was imprisoned by an Austrian duke and the German emperor and then only released after payment of what was literally a king’s ransom.

The remains of the heart were found in this lead box. Credit: Yohann Deslandes/ Musée départemental des Antiquités/ Département de Seine-Maritime

He died in 1199 when he was shot with a crossbow while besieging a castle in Chalûs, France.

According to a then-common practice, his body was divided up for burial in multiple graves.

His internal organs were buried in Chalûs, his heart was embalmed and placed in a tomb at Notre Dame de Rouen cathedral, and the rest of his body was buried at an abbey in southern France.

In 1838, a lead box containing the remains of Richard’s heart was found at the cathedral.

The box is engraved “HIC IACET COR RICARDI REGIS ANGLORUM”—“Here is the heart of Richard, King of England.”

To learn more about how the seat of the king’s soul was preserved for posterity in medieval times, forensic medical investigator and pathologist Philippe Charlier of University Hospital Raymond Poincaré, in Garches, France, and coworkers analyzed Richard I’s mummified heart.

The powdery remains of Richard I’s mummified heart as they appear today. Credit: Philippe Charlier

The wide variety of techniques they used to get to the heart of the matter included everything from scanning electron microscopy to mass spectrometry.

In their paper on the study, the team writes that the heart “was deposed in linen [and] associated with myrtle, daisy, mint, frankincense, creosote, mercury, and, possibly lime.”

They conclude that the goal of using these materials was both to preserve the heart and keep it smelling good, insofar as possible.

“This embalming method is of great importance, as we do not have any procedure or surgical treatise known for this period (end of the 12th century A.D.) describing the methodology and/or composition of the embalming material,” the researchers note.

Ansel Adams took The Tetons and the Snake River in 1942. Credit: National Archives

In the 1990s the market for photos exploded. As snapshots started selling for millions of dollars, sham photos also slipped into the fray before the art world had any way to authenticate originals.

And so cultural heritage researchers had to play some serious catch-up, and quickly.

That’s the gist of my recent cover story on photo conservation. It explores how two fraud cases helped turn the field from a niche research area to a mature science.

And as always happens when reporting, many cool tidbits didn’t fit in to the final piece… In this case, the pivotal role eBay played to help researchers develop ways to catch fakes.

But first, a bit of background on photo fraud:

In the photo market, people will pay more money for an image when it was actually printed on paper by the photographer himself or herself. The price can also increase when the print is older.

So, for example, the Getty Conservation Institute’s Art Kaplan told me that an Ansel Adams photograph printed in the 1920s can sell for hundreds of thousands of dollars, while the exact same photograph printed a few decades later (say, the 1970s) can sell for just tens of thousands of dollars.

It turns out that researchers wanting to authenticate a photo spend a lot of time scrutinizing the paper on which it has been printed, because photo paper generally provides the best dating and provenance clues.

For example, researchers look for chemicals called optical brighteners which were added to all photo paper to brighten images starting in the 1950s. If a photo is purported to have been made earlier than the 1950s, then it can’t have any optical brighteners in the photo paper.

Likewise, in the 1880s, companies started adding a so-called baryta layer to the top of photo paper as a physical barrier between image and paper, so trace impurities in the paper wouldn’t leach into the image layer and wreck the picture.

Each company used a different ratio of barium and strontium in the baryta layer, and companies also changed these ratios over time. Since most photographers were loyal to a particular photo paper brand, authenticators check to see whether a suspect photo has barium and strontium ratios that correspond to the photographer’s preferred company during the era when the photograph was supposedly printed.

Of course to make these comparisons, you need an enormous database of reference photo paper, says Paul Messier, a photograph conservator who helped develop ways to authenticate Lewis Hine prints in one of the world’s first million-dollar photo fraud cases.

“A switch flipped on when I was working on the Hine project,” Messier says. “I realized that there needs to be a reference collection and that it didn’t exist. So I very aggressively began collecting papers.”

But where the heck do you get examples of Kodak or Agfa paper from the 1930s or 40s or 70s? Many companies specializing in traditional photo printing paper have gone out of business as people have turned to digital photography. And many photo paper companies don’t have archives of every batch of paper they produced over the past century.

The answer, of course, is eBay.

The online market helped Messier create an archive of over 5000 different samples of photo paper from the 20th century. The folks at the Getty Conservation Institute also told me they buy old photo supplies on eBay. (Public donations have also beefed up reference collections.)

The surface texture of different photo paper. Credit: Paul Messier

After examining innumerable samples of photo paper from his collection under a microscope, Messier came up with yet another promising way to authenticate photo paper: By analyzing surface patterns.

Messier began noticing subtle differences in textures of photograph paper from one manufacturer to another, and within manufacturers, over time.

Now he’s now working with researchers at the Museum of Modern Art in New York, and a team of signaling processing experts to come up with a way to identify a paper’s source from its surface texture alone.

The idea, Messier says, is to “show the system an unknown texture. It would go through its database of identified textures, and it would say, that’s a Kodak F surface from the 1950s.” Then researchers could check whether a photographer used Kodak F surfaces on other prints.

It’s another authentication tool made possible through eBay.

Incidentally, eBay is a boon to other areas of cultural heritage science too. The online market has enabled everything from Picasso paint analysis to modern plastic artifact research.

These are perfect plastic replicas of 20-foot-long, two million-year-old whale fossils found in Chile.

These may look like real fossils, but they are actually perfect plastic replicas of 2 million-year-old whale skeletons made using a 3D printer.

This printing technology, which can create 3D versions of objects as diverse as a guns or the brain of a man with no memory, was hyped last week by President Obama when he said that 3D printing “has the potential to revolutionize the way we make almost everything.”

The technology certainly saved the day for Smithsonian paleobiologist Nick Pyenson.

Pyenson had been finishing up a research trip in Chile in 2011 when he decided to check out a local highway construction site in the Atacama Desert where workers had supposedly uncovered dozens and dozens of whale skeletons.

“I didn’t really believe the rumors at first,” Pyenson says. But when he arrived, “It was unlike anything I’d ever seen.” Pyenson described the experience at the American Association for the Advancement of Science meeting in Boston.

Local museum officials were racing to dig out the skeletons before highway workers paved over the area, Pyenson says. Although the skeletons clearly needed to be removed, a problem with removal is that spatial information about different constellations of fossilized bones is then lost.

This information is essential for answering all sorts of interesting research questions, such as why so many whales died and were buried together two million years ago. For example, the whales could have swum into a bloom of toxic algae and died or they might have fallen victim to a landslide.

Pyenson went home to DC and immediately recruited the Smithsonian’s in-house 3D imaging and printing team (aka the Laser Cowboys), who came back with him to Chile and spent a week imaging the whale fossils with a high resolution laser scanner. The team then went home and began analyzing the fossil images.

They also also began printing out awesome replicas like the one you see above, which is many times smaller that the original. (The whale fossils span between 20-30 feet in real life.) Pyenson says the Smithsonian has industrial partners who will soon print out a full sized version pro bono, which would have otherwise cost the museum $1 million.

It seems Pyenson’s team has already figured out why all these whales died but he’s staying mum about it, while the scientific paper winds its way through the peer-review process—so stay tuned. Once the discovery is published, Pyenson says they’ll put the data online so others around the globe can access and analyze it.

Although this laser scanning and 3D printing could give researchers around the world the ability to study skeletons without physically handling them, old-school fossil analysis is in no danger of going extinct.

That’s because you need to have physical access to fossilized bones to identify whale species, Pyenson says, or to extract DNA–but probably not from these fossils because they are likely too old to bequeath intact samples.

For more on the cool whale graveyard discovery, check out this article in the Smithsonian from last year.

Laser cowboy Vince Rossi hard at work.
Credit: Nick Pyenson

The two Mona Lisas: Left: the putative young upstart. Right: The Louvre Classic. Credit: Mona Lisa Foundation

“The Mona Lisa Foundation’s mission is to make Leonardo’s ‘Earlier Mona Lisa’ known and loved in its own right, as much as the version that hangs in the Louvre Museum.”

This quote comes from the website of a Swiss organization that sent out a press release yesterday announcing it had new scientific proof that a painting of a younger looking Mona Lisa is the first portrait da Vinci made of the famous muse.

And a maelstrom of news followed.

But let’s just be clear about this new scientific proof: It’s the radiocarbon dating of a piece of cloth canvas.

New tests at the Swiss Institute for Technology in Zurich (ETH) suggest the canvas cloth was made between 1410 and 1455. Previous dating experiments at Oxford pointed toward the 17th century, which implied the painting was not made by da Vinci, who lived between 1452 and 1519.

Since the canvas cloth date just needs to fall before the production of the painting, the new carbon dating does lend credence to the claims that the artwork could have also been made by da Vinci.

But it’s JUST the dating of the cloth, folks: There’s no proof in the current study that da Vinci actually made the painting.

I found it a bit odd that the Mona Lisa Foundation didn’t name the scientist involved in the carbon dating or include him or her in the press material.

So I called ETH’s media relations folks and was told that Hans-Arno Synal from the Laboratory of Ion Beam Physics had done the work based on an “unattributed sample without information of the origin of the material or the object where this sample came from.” The institute has now emailed reporters a statement that notes: “Conclusions on origin or authenticity on the object from which this sample may originate cannot be drawn from this result only.”

Of course, the Swiss Mona Lisa Foundation claims that there is other scientific evidence to support the idea that the young version of the portrait was made by da Vinci.

For example, in a press release they note: “Previously, four tests undertaken by Prof. John Asmus, nuclear physicist, who digitised the brushstrokes of both paintings, established scientifically that both the ‘Earlier Version’ and the ‘Mona Lisa’ in the Louvre would have been executed by the same artist. This brushstroke analysis identifies conclusively an artist in the same way that DNA or fingerprints identify criminals.”

This is a rather breathless claim too. I mean, the brush stroke research certainly suggests that the artwork is consistent with being da Vinci’s–or somebody who used his brushes, and liked his style so much that they copied it.

In fact it’s actually really hard to prove a piece of artwork is authentic because doubters always want more evidence. It’s much easier to prove something is a fake because the presence of modern or geographically incongruous materials is pretty damning.

So the new carbon dating is very interesting, but it’s not a smoking gun. Let’s all take a deep breath.

A fake crystal Aztec skull

There’s a great report out about how the British Museum and the Smithsonian teamed up to prove that two crystal skulls, one at each museum, are actually fakes.

Both skulls were purportedly made by Aztecs in Mexico prior to Columbus’ arrival. The British Museum bought its skull from Tiffany and Co. in 1897 while the Smithsonian received its skull in 1960 from an anonymous donor.

Although skulls are common motifs in Aztec art, museum curators at both institutions were suspicious of the skulls for a couple of reasons.

For one, neither skull comes from well-documented official archaeological excavations.

Also something was weird with the teeth.

To quote the report:  “The rigid linearity of features representing teeth contrasts with the more precise execution of teeth on pre-Columbian artefacts.”

It sounds like whoever faked the crystal skulls was a little too fond of idealized, modern dentistry.

To prove the two skulls were fakes, the researchers assembled some legitimate crystal Aztec artifacts. Then they used scanning electron microscopy to study the surface of both real and suspect crystal objects.

Surface of the crystal objects: Irregular in legitimate artifacts (left) and rotary wheel made fakes (right).

Turns out that the surface of the real artifacts have irregular etch marks, a sign that the pieces were carved with hand-held tools. The suspect skulls have a patterned surface, a sign they were made with rotary wheel tools and hard abrasives.

“Rotary cutting wheels were not introduced to stone workshops in Mexico until after the Spanish conquest of Mexico in 1521. The skulls therefore cannot be of Aztec manufacture.”

Awesomely, the museum researchers noticed a small deposit of something unknown in the Smithsonian’s skull. Using x-ray diffraction they discovered that the deposit was silicon carbide, a synthetic abrasive only used in stone carving workshops starting from the mid 20^th century onward. The Smithsonian artifact had probably been made shortly before it was sent anonymously to the museum.

The researchers also had a closer look at the British Museum’s fake skull and discovered  green, worm-like inclusions in the rock.

“Using Raman spectroscopy, the green inclusions were shown to be an iron-rich chlorite. These minerals are found in mesothermal metamorphic greenstone environments. Sources of this type are not found in Mexico or within the ancient Mexican trade network.” In fact, they are typical in rock crystal from Brazil or Madagascar.

Wham bam.

Interestingly, the report alludes to the fact that there are other crystal skulls around: “An increasing number of large and small quartz skulls have become known, particularly in recent decades.” Perhaps the owners should take a closer look at the surface etching of these skulls…

Top: The original. Middle: The mock-up. Bottom: Mock-up & portrait below. © J. Paul Getty Trust

So you’d think that making a replica of a Rembrandt might be frowned upon by the art world, but this copy of “An old man in military costume” has full approval of its owners.

In fact, the folks at the Paul Getty Museum in LA, asked their own intern to replicate the masterpiece as well as the hidden painting beneath it.

It seems that there’s a pretty good reason for making the copy, or “mock-up” as the researchers call it.

For years, museum researchers have known that there’s another painting beneath the military portrait. But they’ve had a tough time getting more than just a faint whiff of the image hidden below using standard analytical methods.

Over the past few years, a new technique called scanning macro X-ray fluorescence (MA-XRF) has proven itself useful for uncovering hidden paintings on canvases by Van Gogh, Goya and others.

The question is whether MA-XRF would work for Rembrandt’s military portrait. And specifically, whether a portable X-ray device was powerful enough to do the trick or whether the painting should travel to a more a powerful synchrotron X-ray source, such as in Hamburg (DESY) or at Brookhaven National Labs in New York.

It comes down to the fact that museums don’t like shipping valuable and fragile art around the world unless it’s absolutely necessary.

Enter intern Andrea Sartorius (who I momentarily hoped was a descendent of the 17^th century Croatian weight-loss fanatic & innovator, Sanctorius Sanctorius. Sadly the names are not quite the same.)

Anyway, Sartorius painted a copy of the original Rembrandt using the same kind of pigments and binder that he would have used, and she included another portrait below the military one.

Then the copy was shipped around the world to be analyzed using X-rays from the various synchrotron sources and from the portable device. Turns out it’s worth the trip to more snazzy X-ray sources if you want to see the hidden painting below. The team argues in this paper that transporting the Rembrandt to a synchrotron facility is actually “useful and relevant.”

The paper’s lead researcher, Matthias Alfred, praised the mock-up: “It is the first time that a painting was reproduced in such an elaborate way for these tests.” It seems that experiments on mock-ups help museum staff decide whether sending expensive art to outside labs for analysis is worth the risk and effort.

And that, my friends, is how a fake Rembrandt can sometimes be a good thing.

Roman skin cream from the 2nd century A.D. found in a temple below London Southwark. Credit: Nature

Last week, while working on an article about the chemical make-up of 2000-year-old medicine tablets from a Roman shipwreck, I read that back in 2003 archeologists had unearthed a full canister of cosmetic skin cream, hidden in a Roman temple drain in Southwark, London.

When a Museum of London curator opened up the 2nd century A.D. canister, she found it full of white ointment, awesomely reminiscent of modern-day Nivea cream.

This rare find was then chemically analyzed by University of Bristol’s Richard Evershed, who has a quirky research niche: Figuring out the composition of ancient medical, food and cosmetic concoctions, usually by studying residues leftover on old pottery. (He made news last December by reporting that the fatty deposits on pieces of ancient Polish pottery are Northern Europe’s oldest evidence of cheese-making.)

So what precisely was in the creamy white ointment?

In a 2004 Nature paper, Evershed’s team announced that “the Londinium cream” was primarily made up of animal fat, probably from cattle or sheep. They also detected starch, which was likely isolated by boiling roots and grains in water. In addition, the cream contained a tin dioxide mineral called cassiterite with the chemical formula SnO2.

Then came some reverse engineering. Evershed’s team mixed together a new cream based on the proportions of animal fat, starch and tin dioxide that they had measured in the ancient ointment. Here’s how they describe its aesthetic appeal:

“This cream had a pleasant texture when rubbed into the skin. Although it felt greasy initially, owing to the fat melting as a result of body heat, this was quickly overtaken by the smooth, powdery texture created by the starch. Remarkably, starch is still used for this purpose in modern cosmetics. The addition of SnO₂ to the starch/fat base confers a white opacity, which is consistent with the cream being a cosmetic. Fashionable Roman women aspired to a fair complexion, and the Londinium cream may have served as a foundation layer.”

Recreated cream. Credit: Nature.

The researchers go on to say that employing tin to color the ointment white would have been safer than using toxic lead-based pigments, which was common in that era. “White Roman face paint typically comprised lead acetate, prepared by dissolving lead shavings in vinegar.”

They write that it’s not clear whether the cream’s maker intentionally opted for tin because it is non-toxic compared to lead. During the 2nd century A.D., Roman society was slowly becoming aware of lead poisoning… But then again, the chemists of that era weren’t very adept at distinguishing lead from tin, note the authors.

Another possibility is that the cosmetic-maker used tin out of convenience, because nearby Cornish mines had abundant deposits of tin dioxide. Or perhaps our cosmetic-maker was an early pioneer of the buy-local scene.

Tablet holder. Courtesy: Erika Ribechini

When researchers want to learn about the cosmetics, culinary dishes, elixirs and other concoctions created and consumed by long-lost cultures, they typically try to recreate recipes found in ancient documents and then analyze the products in a lab.

Or researchers go spelunking in museum vessels, hoping to find a residue at the bottom of a pot or on a pottery sherd that can be chemically identified with increasingly sophisticated analyzed technology. Unfortunately, tell-tale residues on dirty dishes have often been destroyed by time, weather and/or hungry microbes.

That’s why the six intact medicinal tablets found in a 2000-year-old shipwreck off the coast of Tuscany is an extraordinary find.  “It has been very exciting to be in contact with a rare, original, ancient therapeutic product,” says Erika Ribechini, a scientist at the University of Pisa, who just published a paper in PNAS announcing its chemical constituents.

Ancient pill from the 1st century BC. Courtesy: Erika Ribechini.

Here’s an article I wrote (and some others) about her team’s analysis of the 1^st century BC tablets, which revealed that the ancient Roman pill was heavily laden with zinc, a metal that Ribechini believes was used to cure eye disease, possibly infection or inflammation. (Zinc is present in Neosporin, the topical antibiotic.) Also found in the pill was beeswax, plant pollen and all sorts of plant and animal fats.

One of my favorite parts of the paper was the tangential reference to other medical objects found near the pills amid the Pozzino shipwreck, including an iron probe (oh my) and a bronze cupping vessel.

“The cupping vessel had a peculiar shape that was typical of a medical tool used for bloodletting or as an instrument to apply hot air to soothe aches.” The authors think that a traveling physician was probably on board with his wares.

Given the option of an iron probe, bloodletting or a zinc tablet to cure my ailments, I think I’d pop the pill, thank you very much.