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The two Mona Lisas debate – Everybody take a breath now.

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

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. Continue reading →


Fake crystal Aztec skulls

A fake crystal Aztec skull

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. Continue reading →


When a Rembrandt copy is not a forgery

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

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 17th 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.


Ancient Roman cosmetics: Skin cream from the 2nd century A.D.

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.


Ancient Roman remedies: Popping pills for 2000 years

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 1st 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.


Dirty Dishes: Fatty residues on pottery fragments point to 6000 B.C. cheese-making

This pottery sherd was part of an ancient strainer used by prehistoric humans to separate cheese curds from whey. Credit: Nature.

Nearly eight thousand years ago in an area that is now called Poland, a prehistoric person skipped dish-duty.

Thanks to this delinquency, researchers in Poland and the UK led by Richard Evershed have been able to analyze the dirty residues on these dishes.

Today the scientists report in Nature that the fatty acid leftovers are Northern Europe’s earliest evidence for cheese-making.

And tomorrow, teenagers everywhere will begin arguing that dirty dishes buried under beds are a gift to future archeologists.

But seriously, archeologists are interested in the onset of cheese-making for several reasons. Continue reading →


Star Trek Replicators, Dystopian Futures, And The #foodchem Carnival

Over here at C&ENtral Science, we’re celebrating Thanksgiving with a food chemistry blogging carnival. Artful Science will return to regularly scheduled programming after we manage to digest all the turkey…

Jean Luc drinking his signature tea

“Tea. Earl grey. Hot.”

I never gave much thought to Jean-Luc Picard’s quintessential beverage request from the Star Trek The Next Generation replicator machine until last week.

I was talking with some friends about an article I had just filed with my editor about note-by-note cuisine. It’s the new passion of Hervé This, one of the co-founders of molecular gastronomy.

As I was describing This’ idea of creating food from chemical scratch, one molecule at a time, I suddenly realized that this is pretty much what Picard’s replicator machine had been doing all along on the Enterprise. Continue reading →


A Fun Video About Photo Conservation And The History of Photo-making

Earlier this year, I had the opportunity to visit the Getty Conservation Institute with videographer Kirk Zamieroski.

This is a cool video he made about the photo conservation research that takes place in the GCI’s Los Angeles laboratories.

It features the GCI’s Art Kaplan talking about a few of the 100+ different photo-making processes (wowsers!) used since the dawn of photography.

Enjoy!

PS:  ….And if you want to know why some old photos have a brownish “sepia” look, check out this piece about the research of GCI’s Dusan Stulik and Tram Vo.


The military borrows from cultural heritage science.

This illuminated manuscript has helped out the US army’s remote sensing. ©Lorenzo Monaco, Praying Prophet, National Gallery of Art, Washington, Rosenwald Collection

Civilian society constantly makes use of aerospace and military inventions:

Can anyone say the Internet? Or transparent braces? (These nearly invisible dental devices are made from a material called polycrystalline alumina, which was initially developed by NASA “to protect the infrared antennae of heat-seeking missile trackers,” notes Discovery.com)

Cultural heritage also borrows from NASA: Portable X-ray fluorescence spectroscopy (XRF) was developed for MARS missions, so that roaming rovers could assess the chemical make-up of rocks on that planet.

Now XRF is a must-have tool for conservation scientists, who want to analyze the chemical composition of art that cannot be transported into a lab, such as a cave painting or Renaissance fresco.

But what about reversing the direction of technology export, so that cultural heritage scientists return the favor by developing new analytical tools for art research that then get delivered to the greater world of science?

This has not happened—until now*. Continue reading →


Weeping Paintings

Otto Piene’s Harvest began to shed white tears in 2000, seven years after it was completed. Credit: ICOM-CC publications.

You don’t really expect a seemingly dry painting to suddenly start oozing streaks of wet paint, seven years after its completion.

So when Otto Piene’s Harvest, which was finished in 1993, began to weep white paint in 2000, owners, conservators and the artist were all rather surprised.

Although Harvest is Piene’s only work to start weeping, the strange liquefying process has happened to dozens of other artworks from contemporary artists as varied as Jonathan Meese and Frank von Hemert, explains Jenny Schulz, a conservator in Cologne, Germany, who’s made it her business to figure out why. “It’s quite a common thing,” she says.

Taking a closer look at several of these paintings, Schulz figured out something that all the weeping paintings had in common: The tears occurred in places on the canvas where the artist has laid down a thick layer of oil paint.

A close-up of the tears from the thick, white base layer on Harvest by Otto Piene. Credit: ICOM-CC publications.

Although the thickly-laid paint seems to dry, it turns out to be unstable and capable of liquefying. But why? It’s not as if applying thick layers of oil paint is a new thing among artists… Yet the weeping painting issue is relatively new, having emerged in the last two decades or so.

What’s changed, Schulz says, is formulation of oil paints. Until recently oil paint was made using linseed oil. But the problem with linseed, she says, is that it has a tendency to yellow over time.

So paint formulators began exchanging linseed oil for sunflower oil, because sunflower oil doesn’t yellow.

The problem is that sunflower oil doesn’t dry as well. That’s because the oil contains fewer reactive double bonds, which are required to form a permanently dried paint complex, Schulz says.

Thick layers of the sunflower oil paint may seem to dry, but they are unstable. Subjected to changes in temperature and humidity or even the jostling that occurs during transport, these layers can collapse, releasing component parts as a gooey tear running as fast as 2 centimeters per month. Continue reading →



From The CENtral Science Blogs