Finding The Culprit For Van Gogh’s Darkening Yellows

The Sunflower still-life series is possibly Vincent van Gogh’s most famous work. Unfortunately the warm yellow hues that make the paintings memorable come from pigments that don’t have a long life-expectancy. During the 19th century, chrome yellow pigments came in to fashion among painters and then quickly went out again, as artists realized that the vibrant yellow color was unstable and would lose its vibrancy when exposed to light. For example, Claude Monet and Pierre-Auguste Renoir both steered clear of the chrome yellow pigments. But van Gogh threw caution to the wind and continued to use chrome yellow until his suicide in 1890—a tragic hint, perhaps, of his own instability and imminent breakdown. This week, conservation scientists at the Van Gogh Museum in Amsterdam have been taking a closer look at chrome yellow pigments in Vase with Sunflower, and a few other paintings, to learn more about the degradation problem. The museum’s staff has recruited a group of traveling conservation scientists from Perugia, Italy, called MOLAB to come help out. (MOLAB has a sophisticated collection of analytical equipment that can study artwork without harming it.) It’s not the first time MOLAB has worked on the chrome yellow issue. Last year, they worked with almost the same team of van Gogh experts to discover why chrome yellow turns from bright yellow to a dingy brown in the presence of sunlight. Here’s why: Chrome yellow pigment is primarily lead chromate (which, incidentally, is the pigment for yellow school buses and was also briefly used to color candy in the 1800s—yikes!). Different yellow hues can be made by mixing in lead chromate oxide and lead chromate sulfate. The darkening of the yellow paint occurs because the chromium in the pigment is reduced from a hexavalent (Cr6+) to a tetravalent (Cr3+) state. The team also reported that sulfur compounds in the paint seem to exacerbate the process. The sulfur is probably present from lead chromate sulfate added to modulate the yellow hue. MOLAB has been back in Amsterdam this week to study more van Gogh paintings, says Costanza Miliani, a lead researcher with MOLAB. The plan is to see if sulfur is indeed a culprit in chrome yellow degradation. Hopefully the team will eventually find a way to thwart and reverse this breakdown so that van Gogh’s vibrant yellows aren’t lost...

Read More

Stinky, Degrading Film And How To Stop It

Like humans, fungi have a taste for old movies. The problem is that they like to eat the film rather than watch it. Adding insult to injury, fungi produce copious amounts of stinky odors from their consumption of classic flicks. In fact, this fungi flatulence can cause headaches, nausea and irritated eyes in humans. (In particular, one airborne fungal molecule called 1-octen-3-ol.) For this reason film archive staff fear any sort of mold on film reels: It means their precious collections are being destroyed by fungi. Furthermore the fungal digestion produces smells that can make conservators sick. That’s why the UK’s North West Film Archive approached researchers at Manchester Metropolitan University (MMU) to ask if there was any way to build a machine to detect the problematic odors. Last week, MMU’s Craig Banks and his collaborator Gavin Bingley reported a handy new mold flatulence detection device. With such a machine, conservators can test film reels donated from attics and basements. Sometimes these donations are so thick with dust it is hard to distinguish from mold—unless conservators take a sample and try growing it in a lab, Banks says. (Which then means the conservators may be exposed to the stinky molecules they’d much rather avoid.) Another benefit of the device: If invasive fungi manage to sneak into storage areas, the detector can forewarn conservators about the moldy intruders before the growth gets out of hand—or is visible to the naked eye. It’s worth pointing out that even if mold is kept at bay, old degrading film produces its own special brand of harmful flatulence. The first kinds of film were made from cellulose nitrate and cellulose acetate. In addition to being flammable, these kinds of plastic degrade in the presence of light, heat and air to produce nitric acid and acetic acid. Both of these molecules can become airborne, where they float around and catalyze degradation in nearby, otherwise unsuspecting film. It’s what conservators call the “vinegar syndrome” – primarily because acetic acid is vinegar and degrading film smells like a salad freshly tossed in vinaigrette. Conservators try to delay film breakdown in two ways. First, by keeping film archive temperatures low, which slows down degradation reactions. Second, by keeping archives well aerated and/or by capturing acetic and nitric acid. Now it seems, conservators will have a third way to help keep old film by being destroyed. Here’s what amuses me: Film is a form of art that appeals to our eyes (and sometimes) ears, but it is our noses that are petitioned when film is under...

Read More

Drilling Holes In To One Painting To Look For Another. Hmm…

This blog devotes a lot of digital real-estate to cool experiments on art and artifacts that are non-invasive, or at least minimally so. So I’ve got to admit that I was not particularly overwhelmed by the breathless reports last week in a myriad of media about a project to drill 14 holes into a Vasari painting in order to search for a possibly hidden da Vinci below. The articles were subsequent to a press release by National Geographic on March 12, which was presumably trying to raise interest in a documentary about the project airing a few days later (March 18). Yesterday the well-respected Art-Info published an interesting take-down of the drilling project, entitled “The Search for the Lost Da Vinci Fresco: Serious Science or Irresponsible Hype?” The piece pointed to a protest-petition against the project signed by 530 members of the museum community, including high-profile curators at the Met and the Louvre. According to the Art-Info article, none of these critical folks got face-time in the National Geographic Channel documentary. This is how the writer Kate Deimling put it: “”Finding the Lost Da Vinci,” which aired on the National Geographic Channel on March 18, certainly looked like an infomercial for the project. The program’s narrator describes opposition to the drilling as a “media feeding frenzy” and an “attack from the press,” but none of the experts opposed to it is interviewed or even mentioned by name. Instead, scientists in lab coats decry the opposition to their work and are then seen boring holes into the painting while dramatic music plays.” The Art-Info piece also voices criticism from the conservation science community, namely that the pigments detected by the drilling project might be from brick instead of paint. Another criticism is that non-invasive analytical equipment (such as newer radar technologies) should be used instead of destructive...

Read More

Rare Aztec Document Gets A Check-Up

In 1521, the Aztec capital of Tenochtitlan fell to the Spanish invaders, who burned libraries and destroyed most of the manuscripts pertaining to Aztec history, religious rituals and economy. The Codex Fejérváry-Mayer is one of just two dozen or so Aztec texts to survive the Spanish invasion. It’s also just one of just six screenfold books that were penned before Cortez started his conquest of Mexico’s indigenous people. So suffice to say that it’s a pretty exceptional record of the pre-Spanish Mesoamerican world. This codex is called a screenfold book because Aztec scholars would literally twist and fold the 22-page, double-sided document to cross-reference a particular date to two calendar cycles: the yearly cycle of 365 days and the sacred cycle of 260 days (called tonalpohualli). Joanna Ostapkowicz, a curator at the World Museum in Liverpool, which hosts Codex Fejérváry-Mayer, explains it in this way: “In the hands of ritual practitioners and other high-ranking individuals, the codex became a guide for people’s actions. The screenfold’s internal reading structure is right to left and is determined by the number-and-sign sets of the calendar: how the images and symbols cross-referenced each other was then interpreted by the reader, who was well versed in the significance of the various icons. Although an object of great respect, the codex was also a tactile, malleable reference tool: a user could consult both sides simultaneously by folding parts of the codex onto itself. Reading it offered guidance on appropriate days to travel, to celebrate a deity’s beneficence with sacrifices, to plant crops or to name a child.” These days the codex is not twisted and folded as it once was. In fact, it doesn’t get handled much at all due to the animal-skin document’s fragility and worth. When Mesoamerican experts want to study the codex, they typically have to rely on photographs, Ostapkowicz notes. A very rare exception was made a few weeks ago when MOLAB, a nomadic team of conservation scientists from Italy, drove up to Liverpool to help museum staff study the pigments, dyes and binders used to make the codex. The MOLAB team has a battery of snazzy equipment that can study fragile artwork without taking a sample of it—in the same way that an X-ray, ultrasound or MRI can give doctors insight about what’s going on inside a patient without invasive surgery or removal of a blood sample. In the case of the codex, the analytical equipment used by the scientists relies on X-rays and infrared light to diagnose the document’s inner make-up. I’m really looking forward to what the researchers find, once all the data is analyzed. As Ostapkowicz puts it,...

Read More

Think You Can Identify A Van Eyck?

Many art historians have eyed Three Maries At The Tomb and agreed that it’s a Van Eyck. What’s debated is whether Jan painted the artwork or whether it was his older brother Hubert. Or more likely, whether the painting was a sibling collaboration. For example, the brothers both worked on the famous Ghent Altarpiece: An inscription on the back says it was started by Hubert and finished by Jan, six years after Hubert’s death. However, art historians debate which brother had a greater influence on the paintings in the Ghent Altarpiece. Did Jan humbly follow his older brother’s stylistic lead or did Jan turn the artwork into a masterpiece with his own artistic flair? These sorts of questions also arise with Three Maries At The Tomb. There’s a good chance it was also a brotherly collaboration: Art historians note that Three Maries At The Tomb is stylistically similar to a painting in the Ghent Altarpiece called Adoration of the Mystic Lamb. Furthermore, experiments to date Three Maries At The Tomb’s wood backing suggest the artwork was made sometime after 1419, which is before Hubert died in 1426. This week, science will weigh in further on the sibling teamwork. Conservators at the Museum Boijmans Van Beuningen in Rotterdam are currently preparing Three Maries At The Tomb for an exhibit later this year. During this process, they requested the services of MOLAB, the traveling group of conservation scientists from Perugia, Italy. (MOLAB is funded by the European Union to help museums do scientific research on art, with equipment they might not otherwise be able to afford. Before Rotterdam, MOLAB was just in Gdańsk, Poland, where they were working on some Memling paintings at the National Museum.) MOLAB scientists will use all sorts of snazzy, non-invasive equipment to image the artwork’s surface and interior in 3D. They will also use X-rays and infrared light to study the painting’s pigment chemistry. Museum researchers will then compare this data with previous results from experiments on the Ghent Altarpiece paintings. These investigations may help museum researchers eventually figure out who did what on the collaborative paintings—not just Jan or Hubert, but also other artists and conservators who retouched the painting over its several centuries of life. If you want to do your own (visual) examinations of Three Maries At The Tomb, check out the Road To Van Eyck exhibit in Rotterdam later this...

Read More

Mercury In Platinum Prints Makes Things Sepia–Or Does It?

Around 1889, Gertrude Käsebier, a 37-year-old, unhappily married mother of three, decided to go to art school. A decade later, around 1900, Käsebier’s photo studio in New York City was so successful that her platinum print portraits were “the thing to have,” in turn-of-the-century socialite circles, says Tram M. Vo, an independent conservator who has been collaborating with Dusan Stulik at the Getty Conservation Institute. “At the time, photographers charged about $12 for 12 prints,” Vo says. “Käsebier charged people $25 just to sit for a photograph and $5 for a single print.” There’s not a lot known about Käsebier’s techniques in the dark room because she didn’t leave many notes behind. So Vo is trying to learn about her methods using an analytical technique called X-ray fluorescence spectrometry (XRF). Conservation scientists use XRF to get a list of the chemical elements present in an artwork using X-rays—all without touching or destroying the artwork. In particular, Vo wants to learn more about the so-called sepia look in many of Käsebier’s prints. Sepia is the word used to describe when black and white photographs have a brownish tint that gives the shots a warm feeling. In today’s digital world, giving a photo a sepia look is just a Photoshop click away. But when Käsebier wanted to give her platinum prints the sepia look she had to use dark room chemistry. Photo history experts have long thought that if a photo from that era had a sepia look, it probably came by means of a few drops of a mercury bichloride, added during the development process. Vo is finding that this might not always be true. Vo used the XRF to look at the elements in Käsebier’s sepia-looking photographs. She found that some of Käsebier’s sepia prints had no mercury present, and thus the warm tones must have come from a different process—but what? It’s possible that Käsebier sometimes got the sepia look from iron found in development solutions, Vo says. Normally the iron would be rinsed off the print during the development process, but if the iron was left behind, it could break down cellulose in the paper over time, which would add a sepia tinge to the prints. Vo also used XRF to look at Käsebier photographs that didn’t have the sepia look, and was surprised to find mercury on non-sepia black and white prints. Käsebier must have used mercury in other dark room processes, but it’s not clear yet which ones. Obviously there’s more fun photo-forensic work left to be done to completely understand Käsebier’s techniques. Even though Käsebier used mercury regularly in the darkroom, which is not precisely the...

Read More