Category → pigments
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
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.
When cultural heritage scientists go on the road, one of the most useful tools they take with them is something developed for Mars exploration: a hand-held X-ray fluorescence spectrometer. The Art Institute of Chicago’s Francesca Casadio wrote a snappy little ode to the machine, which NPR awesomely calls a “science gun.”
When researchers point the admittedly weapon-like device at a painting or a sculpture, they are able to find out which elements are present in the artwork. So for example, Casadio has used the machine to discover that about 1000 years ago, Chinese artists used a red, mercury-based paint called vermillion to decorate the lips of a female sculpture.
She also discovered that sometime in the 1800s an over-enthusiastic restorer used a zinc-based paint to give the sculpture “a new coat of lipstick,” Casadio told NPR. Hear the whole NPR piece here.
I heart the space connection. Astrochemists needed rugged and portable equipment to analyze the elemental make-up of the Martian landscape. The X-ray device also doesn’t harm whatever it is analyzing because researchers don’t need to remove a piece of the sample to do the analysis.
Instead, X-rays are directed on to the artwork or Martian rock and they either get scattered or absorbed in a way that reveals which elements are in the sample.
All these characteristics fit the bill for cultural heritage science. These researchers need sturdy, portable, non-invasive devices to study priceless art in caves, at archeological sites or even at a private collector’s home. And that’s why Casadio calls X-ray fluorescence spectrometers “the most exciting high-tech tools you’ve never heard of.”
Microbes can be an ugly pain-in-the-butt for artifacts.
Even if the bacteria and fungi growing on heritage buildings, frescoes, space suits and archival documents can be killed, they often leave behind some rather unpleasant stains that are really hard to clean off the sensitive surfaces of artifacts. That’s the situation in King Tut’s tomb, for example, where fungi have left behind dark brown spots on the beautifully painted walls.
Today the Harvard Gazette wrote about this issue: At the request of Egyptian heritage officials, researchers at the Getty Conservation Institute swabbed the walls of King Tut’s tomb, and sent samples of the brown muck to Ralph Mitchell, a Harvard microbiologist who specializes in cultural heritage science. Getty chemists figured out that the dark spots are actually melanin–the same pigment that builds up in your skin when you get a tan–while Mitchell’s team figured out that the fungi are dead and probably won’t be producing any more browny spots. Mitchell thinks that the fungi initially grew because the tomb was sealed before the paintings inside were dry, suggesting that the teenage king was buried in a hurry. The still-wet surface thus provided tempting real-estate for melanin-producing fungi.
It turns out that melanin-producing fungi have also stained marble in Italian cathedrals after an ill-advised attempt to protect the marble using acrylic polymers. The acrylic on the marble attracted the staining microbes who found the plastic to be a tasty meal. But microbes will also grow on buildings, art and artifacts that haven’t received unwise “protection.” For example, orangey carotenoid pigments are often left behind by bacteria on stone buildings, Mitchell says, and frescoes have been stained rosy red due to the phycoerythrin pigments produced by cyanobacteria.
The question remains: How does one remove these unfortunate discolorations? Continue reading →
One major motivation was time: Industrial wall paint dries in a matter of hours, while oil paint can take months. Like the rest of us, these artists had moments of procrastination. Being able to produce work just days before the opening of a new exhibit was certainly a perk, says Francesca Casadio, an organizer of the conference From Can To Canvas, and the director of conservation science at the Art Institute of Chicago.
Artists had other motivations for using Ripolin, such as shocking the stodgy traditional art world by using an industrial product, Casadio says. Some motivations were probably purely aesthetic: Industrial paint was glossier than matte oil paint. And in addition, artists could achieve unusual textures on artwork surfaces with the quick drying paint.
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