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Finding The Culprit For Van Gogh’s Darkening Yellows

Van Gogh's Vase with Sunflowers is getting a pigment check-up this week. Credit: Wikimedia Commons.

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.
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Rare Aztec Document Gets A Check-Up

The first page of the Codex Fejérváry-Mayer, a rare Aztec document painted on deer-skin prior to Cortez's conquest. Credit: Liverpool World Museum.

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.”

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Think You Can Identify A Van Eyck?

Three Maries At The Tomb by a Van Eyck brother, or possibly both.

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? Continue reading →

Vincent Van Gogh’s Last Months

Vase with Fifteen Sunflowers. Credit: Wikimedia commons.

In the last year of Vincent van Gogh’s life, as his mental illness escalated and before his suicide in 1890, the Dutch impressionist painter voluntarily committed himself in to two French hospitals.

The isolation didn’t thwart van Gogh’s productivity–he painted some 200 paintings during the 15 months he spent in treatment. Nor did the isolation prevent him from experimenting with trendy new pigments bequeathed by the industrial revolution, such as chrome yellow, which he used to paint his famous sunflower series. This pigment fell out of favor by the 1950s when its lead and chromate make-up was found to be toxic.

Unfortunately, chrome yellow and other then-trendy pigments degrade if they are exposed to light. For example, the degradation turns the bright yellow pigment into a rather sad looking green color. Earlier this year Koen Janssens, at the University of Antwerp, in Belgium, explained the chemistry behind this degradation, by using X-ray spectroscopy to show that when the chromium in the yellow paint was subjected to too much light, it went from a hexavalent state to a trivalent state. Many media outlets reported on the discovery, including C&EN and Newscientist.

The MOLAB van on the road in Greece. Credit: MOLAB.

Now Janssens has turned his attention to the so-called red lake pigments that van Gogh used in paintings during the 15 months of his life. Janssens recruited the help of MOLAB, a group of roaming scientists who travel around Europe with high tech, portable equipment. Their gear can help him study light degradation of the valuable art without harming it.

Last week, the MOLAB team, aka CHARISMA, drove 1500km from Perugia, Italy, to the Kröller-Müller Museum, in Otterlo, in the Netherlands. The Kröller-Müller has 22 paintings from van Gogh’s last months of life, and with the help of the mobile lab, the researchers can study the red pigment degradation without moving or harming the artwork.

Hopefully the new research will clarify the chemistry of the paint breakdown so that further degradation of van Gogh’s work can be avoided.

I can’t help thinking about the tragic irony of it all… that as van Gogh’s mental health was rapidly deteriorating, he was expressing himself using paint that was itself unstable.

Up Some Scaffolding, En Route To Heaven

At the top of the scaffolding in Capella Maggiore. ©Sarah Everts

During most of my visits to Italy, I end up with neck cramps after craning my head backward for hours to look at faraway ceiling frescoes in churches across the country. But last week, I found myself peering directly into the eyes of fresco angels at the top of the Capella Maggiore in Florence’s famous Santa Croce Basilica.

These frescoes have been under restoration since 2005 and for the next few months small groups of people can climb the scaffolding to view the artwork up close. The frescoes were painted in the 1380s by Agnolo Gaddi, a disciple of Giotto, one of the architects of the Italian Renaissance.

I climbed up the scaffolding with Mariarosa Lanfranchi, a restorer from the Opificio delle Pietre Dure, Italy’s foremost restoration laboratory. She’s been leading the fresco restoration project.

One of the first questions she asked me is whether I suffer from vertigo, because we would be going up about 30 meters to reach the very top of the cathedral. Assured that I wouldn’t suffer a panic attack, she began her awesome tour by telling me that the last restoration of part of the church’s frescoes was in the 1930 or 40s.

Angels up close. ©Sarah Everts

Since then, air pollution has coated the art with a layer of brownish grime. Meanwhile, construction around the city has covered the artwork with little chunks of gypsum dust. The frescoes are porous, and with the city’s high humidity, the gypsum penetrated into the frescoes, giving the artwork a rather speckled look, Lanfranchi explained.

To remove the grime and gypsum, the restorers used the “Florentine method,” a combination treatment of ammonium carbonate, followed by a treatment of barium hydroxide, Lanfranchi said. The first step of adding the ammonium carbonate dissolves the unwelcome dust and gypsum (calcium sulfate dihydrate) so that both can be removed from the surface and inside the fresco’s pores.
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