Issue Date: September 20, 2010
The late afternoon sun is streaming through the windows of the seaside Picasso Museum on the Mediterranean coast of Antibes, France, where a handful of scientists are huddled around a computer. They are surrounded by Pablo Picasso’s paintings and a battery of lab equipment that they’ve transported during an 11-hour drive from Italy.
Antibes might be best known as a beach vacation hot spot, but for four days in late August, it’s the primary destination for a group of mobile conservation scientists who traverse Europe in a white Volkswagen van to study masterpieces of art. Europe is full of culturally important objects, many of which are too fragile to move or are simply the wrong shape and size to fit on a typical lab bench—think of Michelangelo’s enormous “David” sculpture or prehistoric artwork painted on a cave wall.
This mobile laboratory—known as MOLAB—is the brainchild of Bruno Brunetti and Antonio Sgamellotti, two chemists at Italy’s University of Perugia, but its day-to-day scientific and logistical operations are run by researcher Costanza Miliani of the Institute of Molecular Science & Technology, also in Perugia. MOLAB first hit the road in 2001 as a scientific service to Italian museums, but it expanded to roam all of Europe in 2004, with funding from the European Commission. The traveling scientists make about 30 trips per year to far-flung places such as mountain monasteries and archaeological sites as well as to high-traffic museums such as the Accademia Gallery, in Florence, and the Tate Modern Museum, in London. Just in the past four years, the van drove 72,000 km (45,000 miles), Miliani says.
Although scientists have long done fieldwork both in museums and in exotic places, two trends in conservation research inspired the creation of MOLAB back in 2001, Sgamellotti says. The first was the development of noninvasive techniques to study artwork in the late 1990s and early 2000s; the practice of nabbing pigment and other samples from masterpieces is now considered taboo. The second was the concurrent development of microelectronics that have made unwieldy analytical instruments—such as infrared spectrometers, atomic force microscopes, and even nuclear magnetic resonance spectrometers—smaller and more easily portable (Acc. Chem. Res. 2010, 43, 728).
A squad of 15 scientists with expertise in using a variety of such instruments is now based in Perugia. Depending on the conservation science task at hand, a subset of researchers with the required skills goes on MOLAB road trips; the projects are selected through an application process assessed by several experts from across Europe.
On this Sunday afternoon at the Picasso Museum in Antibes, five members of the MOLAB team have been mobilized to help solve an art history problem: Picasso had a predilection for using a brand of plain old house paint called Ripolin to create his masterpieces instead of sophisticated and more expensive artist paints—but not always. Curators want a way to noninvasively distinguish which paint Picasso used, and the museum in Antibes has one of the best collections of Picasso’s industrial-paint-based artwork, particularly from a sojourn he made in the city in 1946.
Picasso liked painting with Ripolin instead of a fine arts material to “shock and disgust” the art establishment, says Francesca Casadio, director of conservation science at the Art Institute of Chicago. Casadio crossed the Atlantic Ocean with her colleague, Gwénaëlle Gautier, to join the MOLAB group, which also includes Roland May of the Interregional Center for Conservation & Restoration of Cultural Heritage, in Marseille.
Picasso also used Ripolin for logistical reasons. In one case, Picasso had only three weeks before a gallery opening in which to paint a whole exhibit, Casadio explains. Oil paints simply weren’t expedient because they took months to years to dry.
Logistics and shock value aside, there were also plenty of aesthetic reasons to choose Ripolin: It dried into a bright, shiny layer, and you couldn’t see the brush strokes—characteristics that people still seek in wall paint. “Artist oil paints of the time had a buttery consistency, where you could see the brush strokes,” Casadio says. “Traditional oil paints also dried somewhat matte compared to Ripolin.” Picasso inspired other painters, such as Wassily Kandinsky and Joan Miró, to get on the Ripolin bandwagon.
Ripolin dried very quickly—but only when applied in thin strokes. Sometimes when artists would apply thicker layers of the industrial paint on a canvas, it created so-called canvas wrinkles, Casadio says. These features appear when the air-exposed side of a thick Ripolin layer dries much faster than the bulk paint, causing the outer layer to wrinkle.
Curators have long used the presence of these wrinkles, as well as Ripolin’s sheen, to diagnose use of the paint. But this method of analysis is not always accurate, partly because the wrinkling effect began to appear in paintings produced with artist paint. This is because artists began including additives, such as Harlem’s Siccative, to traditional oil paints to make them dry faster, which led to the same canvas wrinkles.
These additives sometimes make it difficult to distinguish fine paints from Ripolin, necessitating an analytical chemistry approach. Developing this technique “will be challenging because both artist paint and Ripolin were oil-based, and the type of pigments used were similar,” Gautier says.
Previous attempts to develop a scientific way to distinguish Ripolin were stymied by a lack of reference samples of the household paint from the 1940s. Then came eBay. Gautier and Casadio have managed to buy online about 25 old Ripolin paint cans and hundreds of old paint swatches, which they are using to develop standards.
Meanwhile, in Antibes, the MOLAB team—which also includes photochemistry expert Aldo Romani and postdocs Chiara Anselmi and Francesca Rosi—is using infrared spectroscopy and ultraviolet-visible spectroscopy to fingerprint Ripolin paint on actual canvases, without touching or harming the masterpieces.
The Picasso Museum in Antibes is a quintessential client for MOLAB, Miliani says. The museum has a small but solid collection of 23 paintings and 44 sketches by Picasso, as well as two floors for nonpermanent work. But its size and budget of approximately €1 million ($1.2 million) per year don’t accommodate a scientific staff. “It makes no sense for us to buy equipment,” says the museum’s director, Jean-Louis Andral, even though he’s interested in the answers to art history questions that science can provide. “But it’s perfect to be able to have a mobile lab come here, with all the equipment and with the people who are used to dealing with the science,” he adds.
Although MOLAB often works with museums that don’t otherwise have access to scientific instrumentation and expertise, bigger museums with in-house labs also sometimes request a MOLAB visit, often because they don’t yet have the budget to purchase a particular piece of portable noninvasive equipment. For example, the British Museum, in London, does own noninvasive equipment—but not all of it is fully portable. Miliani says that researchers there wanted to study a pre-Columbian codex that is so fragile it could not even be transported to the museum’s lab nearby. So MOLAB drove from Italy to London to do the research in the room where the codex is housed under controlled temperature and humidity, she says.
About one-third of the 30 annual trips MOLAB takes are outside Italy. The longest drive was to Oslo, Norway—a three-day trip in one direction—to study the pigment chemistry of Edvard Munch. But the team can also tell pothole-inspired war stories about a two-day, snail-speed haul on back roads to a Romanian monastery to examine illuminated manuscripts.
“When a potential grad student contacts me, the first question I ask is whether they have a driver’s license,” Sgamellotti quips. Although driving is their main form of transportation, the team members have also carried tens of thousands of dollars’ worth of equipment on a raftlike boat through the canals of Venice. It was the only way for the equipment to reach the city’s famous St. Mark’s Basilica, where the MOLAB team did some research on the church’s mosaic tiles. With so much aboard, the water level was only a few inches from the boat’s rim, making “that trip so stressful that we didn’t even take any photos,” Miliani says.
At other times, mobile-lab personnel have hiked to archaeological sites and delivered equipment with handheld pulleys and other contraptions while trying to prevent dirt from mucking up equipment “that already suffers enough from all the traveling,” Miliani says.
One of MOLAB’s best known early projects was to help conservationists at Accademia Gallery celebrate the 500th anniversary of Michelangelo’s “David” in 2004 by figuring out whether the famous sculpture needed “a birthday bath,” Sgamellotti says. The team first searched the entire body of the masterpiece to locate the dirtiest spots. The researchers found that “David” was covered with sulfates from top to bottom—mostly deposits from air pollution, as well as wax, probably from the days when candlelight was ubiquitous. They also found that the sculpture’s lower half, and in particular its foot, was contaminated with oxalates, which could have come from people touching it, Miliani says. In the end, restorers decided to clean “David” with deionized water because it was sufficient for dissolving the dirt.
The team has also helped museums clean more modern pieces, such as Andy Warhol’s portrait of actress and writer Brooke Hayward. Warhol created this piece in 1973 with acrylic paints, but by 2008, surfactants in the paint had oozed to the artwork’s surface, forming gray, dirt-attracting deposits. Luckily, the surfactants were water-soluble, and London’s Tate Museum, which owns the painting, was planning to swab the painting clean. They requested MOLAB’s participation because the team could provide its portable atomic force microscope, which was used to assess whether the surface was free of the surfactant or whether more cleaning was required, Sgamellotti says.
The MOLAB team has also solved degradation mysteries, such as why paintings found on the exterior casings of mummified Christian monks in Egypt are bleaching. When the MOLAB team trekked to Copenhagen’s Ny Carlsberg Glyptotek museum, its members figured out that the discoloration is not caused by pigment degradation—as was commonly thought—but instead by a dehydration reaction of the gypsum canvas on which the paintings were made.
In Antibes, the MOLAB scientists are taking infrared spectra of Picasso’s “Nu Couché au Lit Blanc” (“Nude Lying on a White Bed”) to see whether they can find a signal corresponding to Ripolin’s white zinc oxide pigment. They are hoping that the pigment’s semiconducting bandgap can be differentiated from that of other white pigments in paints of that era, such as white zinc sulfide. In one small section of the painting, the scientists have also seen a signal from an unidentifiable white pigment they haven’t previously found in Ripolin of that era. Picasso or an art restorer might have touched up the masterpiece with a different paint, or the artwork might have become altered in some unforeseen way. In either case, a typical museum visitor wouldn’t notice what the noninvasive instruments have revealed.
As the sun begins to set, the MOLAB researchers start joking around, punchy from a 12-hour workday that’s likely to stretch into the night. The team is discussing the incoming data while sitting on darkly stained wooden stools that Picasso himself used when painting in Antibes 60 years ago. The stools are not exactly comfortable or ergonomic, but it’s not hard to understand why the scientists—surrounded as they are by Picasso’s masterpieces and the Mediterranean Sea—are motivated to go the extra mile to solve the mystery of his paints.
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