Monday, January 29, 2007

Chemical Blends

Some ninth century Iraqi artists may have literally died for their art, suggests new analysis of Iraqi stucco fragments from this period. A fragment, taken from the ancient palace-city of Samarra, contains three arsenic-based pigments that are known to be poisonous and may cause cancer upon exposure.

Although the findings will not be published until May in the Journal of Archaeological Science, curators at London's Victoria and Albert Museum, where the fragments are housed, have already taken special handling precautions.

"The fragments are stored in a locked cabinet and only handled as little as possible by curators in the Museum’s Middle Eastern section who wear nitrile (special sturdy rubber) gloves," Mariam Rosser-Owen, curator of the Middle East collections at the museum, told Discovery News.

Lucia Burgio, a conservation scientist at the museum, added that researchers also might wear face masks and work in a "fume cupboard." If the object should go on display, it would be placed in a special case "to avoid any accidental contamination of members of the public."

For the study, Burgio, Rosser-Owen and colleague Robin Clark used a non-invasive, high tech process called Raman microscopy, which scanned a grid pattern over the surface of the fragments to construct maps of chemical information. These maps revealed that an otherwise innocuous-looking stucco fragment of colorful stripes contained the toxic pigments orpiment, pararealgar, and another related substance.

These orange-yellow minerals are toxic arsenic sulphides. Orpiment was even once used to coat the tips of poison arrows.

The ancient Iraqis, however, probably did not realize the minerals were poisonous, although some artists may have died for their craft.

"People died young until a couple of centuries ago, and I guess other illnesses were causing artists to die before they got poisoned to death by the materials they were using," explained Burgio. "What happened to their apprentices, who ground and prepared the pigments on a routine basis, I don’t know."

The fragments were once colorful wall paintings on a fine gypsum surface that decorated mosques and palaces at Samarra, which is just over 77 miles away from Baghdad.

Construction of this massive, ancient city created "an early golden age for architectural decoration," according to the researchers. While small, the fragments show beautifully rendered decorations based on plant forms, animals and courtly activities, such as people enjoying wine and dancing. The style is uniquely Arabic, but was possibly influenced by Central Asian artwork.

Clark, a professor in the Christopher Ingold Laboratories at University College London, said the toxic pigments were also "well known in Western Europe." Shades of green, including emerald green, are also sometimes poisonous elements of certain early European art, due to the presence of arsenic-containing copper arsenite and copper arsenoacetate.

Alastair Northedge, professor of art and Islamic archaeology at the University of Paris, is one of the world's leading western experts on Samarra. He recently authored the book, "Historical Topography of Samarra."

Northedge told Discovery News that he is "sure the conclusions are correct" in the recent study.

"It was interesting to see the painters were poisoning themselves with arsenic," he said.

Toxins aside, remains of Samarra, also known as the Abbasid Caliphate in Iraq, comprise a site of important archaeological relevance.

"The Abbasid Caliphate was one of the high points of world civilization," said Northedge, "but it has been more or less inaccessible because of Saddam, and now the war."

A new international project,, has been set up to better understand the site and what its art and architecture would have looked like during its golden age. – Discovery News 1/22/2007

I only occasionally mess with toxic paints, these days. My children are plagued with asthma and I feared worsening their condition via the introduction of chemical asthma; so a few years ago I began experimenting with creating my own acrylic-based formulas that utilize the minimal amount of solvents, but still retain wet flow and a multi-layered dried appearance. – DN

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