Art conservation that does more harm than good

Hindsight is 20-20, as they say. This week Art Daily* reported that a widespread preservation treatment, developed to help canvases survive humid environments, actually makes paintings more vulnerable when humidity levels soar.** “The wax-resin treatment was enormously popular in Europe and the U.S. during the 1950s and 1960s,” says Cecil Krarup Andersen at the Royal Danish Academy of Fine Arts, who made the discovery. “Many masterpieces, such as Rembrandts and Van Goghs were preventatively treated with wax-resin linings to help protect the artwork from humidity degradation. The treatment does exactly the opposite.” Anderson has just wrapped up her PhD work on the topic, a research project that began because museum staff at Statens Museum for Kunst were trying to figure out why Danish Golden Age paintings treated with wax-resin were not resisting the insults of time as well as they should. I needed a little background on wax-resin treatment which Andersen kindly provided: It was popularized in the 1800s by a Dutch restorer named Nicolaas Hopman. One of the first masterpieces to be treated was Rembrandt’s Night Watch in 1851. The overall motivation was logical: Hopman thought that coating the back of a canvas with beeswax and an extra layer of canvas would act as a protective support for the painting. Later on, he and others began mixing tree resin in with the wax because it added stiffness. Throughout the 20th century, the treatment gained popularity. Until the 1970s. That’s when conservators started talking about the importance of reversibility, the idea that any conservation treatment on artwork should ideally have an undo button, just in case a treatment turned out to have unforeseen, negative, long-term impacts or in case a better treatment came along sometime in the future. At a conference in Greenwich, England, in 1974, a group of high profile conservators decided that wax-resin treatments were not reversible and should be discontinued, Andersen says. Wax-resin treatments were gradually phased out, but it was too late for thousands of masterpieces that had already faced the hot iron. Initially conservators used irons to melt the wax-resin on to the back of paintings, upon which they adhered the extra canvas layer. Then in the 1950s, specialized heating tables were invented. These tables could uniformly heat the wax-resin and seal the back lining to the painting “in no time,” Andersen says. They made it easy for conservators to overdo it, she says. (As an aside, Andersen says the treatment additionally flattened out the texture in some paintings.) Another reason 1970s conservators became nonplussed with wax-resin was that the treatment actually changed the color of paintings. Sometimes the hot wax and resin would...

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Figuring out what killed crazy Caravaggio

“Caravaggio’s life was even darker than his paintings.” This is how Italian microbiologist Giuseppe Cornaglia began an account of his uphill battle to figure out what microbial pathogen may have killed the famous and violent 16th and 17th century Italian painter, who died under rather curious circumstances in 1610. Cornaglia is part of a growing number of researchers who look into the dental pulp of skulls found in graves, in search of DNA from ancient pandemics. The field is called paleomicrobiology, and it’s been used to figure out what microbes caused the Plague of Athens, which indirectly helped Sparta topple Athens in the Peloponnesian War, and which in turn instigated the decline of classical Greece. Paleomicrobiology has also been used to show that tuberculosis was already in the New World before Columbus showed up carrying a host of other deadly pathogens on board. So, given that Caravaggio died under strange circumstances (more on that in a second), Cornaglia wanted to look at Caravaggio’s remains and see if he could detect the presence of a deadly pathogen in the artist’s dental pulp. Dental pulp harbors the DNA of microbes present in the person at death. The pulp tissue is covered by protective enamel so that contamination from other microbes can’t occur during the intervening centuries, before forensic researchers dig up the skeleton and crack open the tooth. The first problem Cornaglia faced was that he didn’t know where Caravaggio’s remains could be found. This is not entirely surprising when you learn more about the painter. Caravaggio was an angry guy and quick to pull out his sword. During a fight in 1606, at age 35, he tried to castrate his opponent during a street brawl in Rome, Cornaglia said. The castration was successful. But it also killed Caravaggio’s foe, leaving Caravaggio with a murder charge and a life on the run. The experience didn’t reign in Caravaggio’s predilection for violent fights. According to Cornaglia: “The artist’s last years were spent desperately running from one city to another. After stopping by Naples, he travelled to Malta, only to get into trouble after yet another brawl. Caravaggio was imprisoned by the Knights in August 1608 and later expelled from the Order “as a foul and rotten member.”… After some time spent in Sicily, unknown assailants attempted to murder Caravaggio in Naples, succeeding in disfiguring his face… Contemporaries described the artist as a madman during this time, exhibiting increasingly strange behavior and exploding into a violent rage at the slightest provocation.” Digression: some researchers have wondered if Caravaggio’s inherent aggression was being exacerbated by lead poisoning, as the dude actually ATE off of...

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

“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...

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When a Rembrandt copy is not a forgery

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...

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The military borrows from cultural heritage science.

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*. (*Or so I think, after asking folks in the know… If I’ve missed an example, I trust the Internet’s dilligent fact-checkers to clarify.) Anyway: As far as I know, the first case of analytical technology export from a museum lab to the outside world of science comes courtesy of John Delaney, who works at the National Gallery of Art in Washington. Delaney has long been working in the field of near infrared imaging spectroscopy (NIRS), sometimes with the army’s Night Vision Lab. NIRS is versatile analytical tool that can be installed on satellites for remote sensing of ground soil chemistry. Or it can be put in a medical device to measure a patient’s blood oxygen and hemoglobin levels through their skin, non-invasively. One of the coolest applications of NIRS in cultural heritage science is to visualize paintings made below other paintings, such as the hidden portrait of a beautiful woman below Picasso’s Le Gourmet, which is a still-life of a child eating. Delaney’s project to uncover another hidden Picasso painting was very recently profiled in the New York Times. Earlier this year, Delaney published an article in Angewandte Chemie wherein he used NIRS imaging equipment from the US military’s Night Vision lab to study binders and pigments in a 15th century illuminated manuscript by Lorenzo Monaco, called Praying Prophet. Too much incident light can hurt the ancient, fragile document, so Delaney had to use the lowest possible light power settings, filter that light, and effectively work at the sensitivity limits of the NIRS instruments. As part of the project his team improved the sensitivity of two cameras used to analyze the manuscript. Delaney says that the new cameras which operate at low light levels have now also been used on paintings and tapestries to map wool and...

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Weeping Paintings

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. 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. Other paint components can help or hinder the instability, Schulz says. For example, formulators have been increasingly replacing lead-based pigments for titanium- or zinc-based ones in white paint. Unfortunately, lead seems to help paintings stay stable, while replacements are not as effective. Additional ingredients in oil paints such as bees wax  (used to stabilize pigments) and aluminum stearate (used to improve viscosity) may also play a role in the ability of sunflower-oil paint to dry completely, Schulz adds. She’s currently developing recommendations for formulators and artists on ways to avoid the weeping painting problem—and she’s also working on strategies for conservators tasked with stopping the flow. As an aside, paintings aren’t the only cultural artifact to shed tears: Plastic...

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