Authenticating Pieces Of The Berlin Wall

Fifty one years ago today, communist officials in East Germany erected the Berlin Wall to stop the exodus of their citizens to capitalist West Berlin. The 155-km barricade came down 28 years later in 1989, and since then, every self-respecting tourist shop in town sells chunks of spray-painted concrete to anyone seeking a piece of 20th century history. Today’s price for a chunk of the Wall, as determined during my lunch-time walk to the local tourist shop from my office at the East-West border in Berlin: €4.95 or about $6.10. You can get a better deal if you buy these cellophane-wrapped mementos from street vendors. A few years ago, the rather ample supply of German history for sale got Ralf Milke, a geochemist at Berlin’s Free University, wondering whether he could find a way to authenticate pieces of the Wall. Since then he’s developed a technique that uses X-ray diffraction to confirm whether a supposed chunk of the Berlin Wall is indeed genuine. Milke did a series of X-ray diffraction experiments with definitely authentic pieces of the wall to get fingerprint spectra of several elements found in the Berlin Wall concrete, such as silicon from the quartz or calcium from the calcite used to make concrete. He also found that all the fingerprint spectra of Berlin Wall samples have an unusual mark. It’s probably a trace mineral found in the quarry in Rüdersdorf, near Berlin, where the calcite used in the Wall was mined, Milke explains. Exactly what that trace mineral or metal is remains a mystery, but if the unusual mark doesn’t show up in the x-ray diffraction experiment, then the chunk of concrete isn’t a piece of the Berlin Wall, Milke asserts. “It’s an easy yes or no answer,” he says. Milke has tried to get a little Berlin Wall authentication business going, but so far only a handful of people have been willing to pay the €5 he charges to verify samples. That hasn’t stopped him from testing the wares of Berlin Wall vendors around town, he says. Some of the more fraudulent vendors don’t even use concrete when they create Berlin Wall fakes. Of course if these petty crooks want to evolve into criminal masterminds, they could find a way to use calcite from the Rüdersdorf quarry to mix their own concrete, and thus produce a fake that cannot be identified by Milke’s method. But pieces of the wall—fake or real—are still pretty inexpensive. So I’d wager that it may be a while yet before it’s financially worthwhile for that level of criminal conspiracy to seep into Berlin’s tourist keepsake...

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Figuring Out Copper Corrosion To Fight Artifact Forgery

The green corrosion on copper artifacts, sculptures and buildings is so aesthetically pleasing that countless recipes exist in books and online so that do-it-yourselfers can create the same look on anything made from the metal. But depending on the recipe or the environmental conditions, that pretty green color could be any one of a handful of different corroded copper chemicals, such as nantokite (CuCl) or paratacamite (Cu2(OH)3Cl). Or, in the case of the Statue of Liberty, the green patina is a copper sulfate. Copper can also corrode into other colors besides green, such as browny-red cuprite or black tenorite. Scientists don’t actually know precisely which conditions produce the different corrosion chemicals—but they should, especially when the authenticity of an artifact is in question. For example, museum researchers need to know if the corrosion chemicals on a possibly fake copper artifact came from natural aging processes or are the result of a quick-aging forged process. To help solve this problem, Mark Graeme Dowsett, a physicist at the University of Warwick teamed up with an analytical chemist at Ghent University called Annemie Adriaens. First they started reading do-it-yourself patina manuals, such as, The Colouring, Bronzing and Patination of Metals. Then the scientists used intense X-rays to spy on the formation of one of copper’s green corrosion products, nantokite, as they made the patina according to different recipes. Among their discoveries, the team found that some steps in the recipe, such as rinsing the newly produced patina in water, produced side-products such as browny red cuprite. “Most protocols for producing the green copper patina were not developed in a systematic way,” Dowsett says. We want to figure out what’s actually going on in these different processes, he adds. Next the team is working out the conditions for making other green copper patinas, beyond nantokite. Watch out copper artifact...

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Bringing A Controversial Mural in LA Back To Life

In 1932, David Alfaro Siqueiros got kicked out of Mexico for his political leanings so the artist spent six months in Los Angeles, California, where he produced a controversial mural called América Tropical. Siqueiros may not be as well-known as his teacher and contemporary Diego Rivera, but these two, along with José Orozco, formed “Los Tres Grandes,” the big three Mexican muralists of the early 20th century. During his stint in LA, Siqueiros was asked to paint a mural on a second story wall that overlooked Olvera Street, which was–and still is–a romanticized, somewhat kitschy Mexican market set up for tourists. The idea was for Siqueiros to produce something that celebrated tropical America. The expectation was probably that it might be a romanticized vision of Mexico—just like the street below. Instead Siqueiros, who was a die-hard Communist, produced a profoundly political piece of art: A crucified indigenous Mexican is at the forefront of the mural, with an American Eagle flying ominously above. A sharp shooter approaches from the right with his gun aimed at the Eagle. To say the piece made a splash is a pretty major understatement. Some praised the artwork for the potency of its political and social statement. But city officials were not impressed and they pushed successfully for the mural to be whitewashed, explains Leslie Rainer, a senior project officer at the Getty Conservation Institute who is leading the mural’s conservation, and who gave me and a few others a tour of the mural’s site in downtown LA. Since the site is under construction, the mural was covered for protection, as you can see in the photo below. The site will hopefully be reopened for public viewing in the next year or two—fingers crossed. (The $8.95 million project, which is being paid for jointly by the Getty and the City of LA, has faced many delays). Many decades of outdoor exposure as well as the whitewashing took a serious toll on the artwork, Rainer says. The mural has lost all of its color, leaving just a shadow of the original piece. Conservation efforts won’t reintroduce color.  This is because there’s no color documentation of the artwork, so any addition of pigment would be a misrepresentation, explains Susan MacDonald, head of GCI Field Projects. Instead, Rainer and the GCI team have carefully cleaned off the whitewashing and reattached parts of the crumbled plaster. They’ve also been doing non-invasive analyses of the artwork, which is an unusual marriage of traditional fresco painting and cement (instead of lime plaster), Rainer says. Siqueiros was really enamored with the (new-to-him) cement and concrete materials that he encountered during his stint...

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Christians Artists Embellished Spain’s Muslim Paintings

For nearly 800 years, the Islamic Moors occupied Spain, building extraordinary buildings that still draw hordes of tourists today. Case in point: the Alhambra. Less well known is the Madrasah Yusufiyya of Granada, the only Islamic university from the Moorish era left standing in Spain. It was built in 1349 and operated for about 150 years, until the Christians conquered the region in the late 1400s. The lovely Madrasah Yusufiyya was then used extensively by the Christians, most likely as administration buildings, says Carolina Cardell a conservation scientist at the University of Granada. In fact the Christians liked the building so much, Cardell says, that in the last 500 years they have done a lot of touching up, repainting, restoring and embellishing of paintings covering the stucco and wooden interior walls of the Madrasah Yusufiyya. Yet art historians haven’t really known the extent of these interventions. So over the past few years, while the Madrasah Yusufiyya has been under restoration, Cardell and her team of scientists took a closer look at the paintings with a suite of analytical technology. She’s just published a paper in Analytical Chemistry about the interventions to the Madrasah Yusufiyya over the past 500 years. (As an aside, Cardell was also involved in the discovery of ancient ovens that were used to bake bones in order to create a patina added to Granada’s medieval walls as a strengthening agent.) But back to the Islamic paintings. Cardell’s team used a technique called micro-X-ray diffraction to distinguish between lapis lazuli, a blue pigment used by the original Islamic artists, and ultramarine, a synthetic version of lapis lazuli, which has been made industrially from 1828 onwards. Although the blue pigments in lapis lazuli and ultramarine share the same complex chemical formula, the scientists could distinguish between the two by looking at the texture of the paint. The lapis lazuli originated in Afghani mines, and thus has a potpourri of grain sizes as well as some impurities. Conversely, the ultramarine was made industrially and thus has really tiny, similarly-sized grains. Cardell’s team also saw evidence of some other blue pigments in Madrasah Yusufiyya’s paintings, including azurite (copper carbonate) which hails from the Islamic era and another called blue smalt, which originated in the 19th century and is made from finely ground potassium cobalt glass. Besides touching up the Madrasah Yusufiyya paintings using the same colors of the original Islamic artists, Cardell’s team also discovered that the Christians did a little souping up. For example, they found that Christian artists added gold gilding on top of certain sections that were originally blue. Although Moorish artists did paint with gold (there is some in the Alhambra),...

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Conserving Mosaics: A Nod To The Chemistry Nobel Prize

In honor of today’s Nobel Prize in chemistry to Dan Shechtman for the discovery of quasicrystals, I thought I’d write a little post on the world of mosaic art conservation. Bear with me–there is a connection. (This is precisely what I said when Paula Artal-Isbrand, a mosaics conservator at the Worcester Art Museum, answered the phone. Luckily, she didn’t deem me a random freak and then hang up.) OK. So back to the Nobel Prize. Quasicrystals are regular patterns of atoms that never repeat themselves, much “like the fascinating mosaics of the Arabic world,” noted the prize’s press release. This got me thinking–and blogger David Bradley too—because moments later he tweeted the perfect Moorish mosaic example you see here. And I knew I had to learn a bit more about mosaic art conservation and restoration. So here it goes: Tiles in mosaic art can be made of a serious potpourri of materials, such as glazed terracotta (in the case of many Moorish mosaics), as well as stone, glass, porcelain, marble, metal and wood. Compared to paintings, paper and textiles, mosaics are relatively sturdy, and not particularly susceptible to problems like light degradation, Artal-Isbrand told me. But that doesn’t make them immune to the elements, particularly because many pieces are stored outside as part of buildings. For example, freeze-thaw cycles can lead to tile and mortar cracking. Bacteria and fungi growing on the surface of these artworks can deposit ugly stains from their excretions that stay behind even after the microbes are wiped away. Worse is when there’s a crack in a tile which permits water to seep in, and thus creates a cozy home for microbes below the glaze—entirely out of reach for conservators. If the mosaic’s tiles or mortar have calcium carbonate as an ingredient (and many do), roots of plants and trees will try to extract the mineral, which is also problematic, Artal-Isbrand explained. But one of the major problems faced by mosaic conservators is the fact that there are often lose chunks at the edges of the artwork, which museum or archeological-site visitors are tempted to take home as a souvenirs. “They really need to be guarded,” she said. I asked Artal-Isbrand if conservators ever add protective coatings to mosaics. It turns out she had recently finished a project to remove unnecessary protective coatings—added decades ago—from a large Roman floor mosaic originally from Antioch which is currently housed at the Worcester Art Museum. (Roman floor mosaics are mostly made of stone, although they also used glass on occasion, Artal-Isbrand explained. That is until the Romans realized glass dissolved with time.) Back in the day (I’d guess the 1960s)...

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A Visit To The Opificio, Italy’s Primary Restoration Lab

Italy has no shortage of art, and when that art needs a face-lift, it takes a trip to the Opificio delle Pietre Dure e Laboratori di Restauro, the country’s national restoration laboratory. Located in an elegant old stable in Florence, the Opificio is like a spa for cultural heritage artifacts, where paintings, frescoes and sculptures go for age-extending treatments. When I visited, Cecilia Frosinini, an art historian and the Opificio’s director of mural paintings, was kind enough to give me a tour. As we wandered through the extensive labs, dozens of restorers were working on a wide variety of pieces including Renaissance paintings sent from Budapest for anti-aging therapy, ceramic sculptures, water-damaged frescoes and a wooden statue of Christ that had been painted to look like bronze during an era when bronze was popular but too expensive for some budgets. The Opificio has also been recently involved in everything from using ultraviolet light to bring out cool, hidden details in Giotto paintings to the restoration of Santa Croce Basilica’s famous frescoes. Like many great things in Florence, the Opificio has its root with the city’s famous Medici family. The first half the Opificio’s Italian name translates to “workshop of semi precious stones.” And as the name suggests, the Medicis founded the Opificio in 1580s to produce furniture decorated with semi precious stones, Frosinini told me. Time passed and the workshop began restoring their own pieces. By the 19th century, art made from other materials such ceramic, marble and jewelry, was also being restored, she added. The second half of the Opificio’s name, Laboratori di Restauro, refers to the restoration laboratory founded in 1932 by Ugo Procacci, who was a very important Italian art historian at the beginning of the 20th century. Around the same time that Procacci was starting a restoration lab in Florence, other museums around the world were also doing the same, such as the Fogg Art Museum in Boston and the National Gallery in London. These early restoration labs were making use of X-ray imaging–which was becoming more widespread in many fields outside medicine–to see into panel paintings and reveal what they were composed of (such as wood, metal etc). X-rays were also being used to see if there were previous paintings lying below what could be seen with the naked eye. In 1975, Italy’s newly established a Ministry for Cultural heritage decided to merge the 1932 restoration science lab and Medici’s restoration facility together and move everything into a former military horse stable. One of the major projects currently keeping Opificio restorers busy is a major restoration project of five panel paintings by Giorgio Vasari...

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