Nanoparticles Reveal Ancient Artwork

Aug. 13, 2009 -- Modern nanoparticles are revealing ancient artwork.

Scientists from the Metropolitan Museum of Art in New York City and elsewhere are treating microscopic artwork from as far back as ancient Egypt with silver nanoparticles to reveal the brilliant dyes used to color now-drab pieces of art.

"There is one big problem when investigating ancient materials or anything that is valuable; you can't take as much material as you would like," said Marco Leona, a scientist at the MET who co-authored a new article in the journal Proceedings of the National Academy of Sciences detailing the method.

"For a textile, that could have been three millimeters. Using this new technique we can get results from as little as 25 microns."

Silver nanoparticles work by absorbing tiny amounts of dye molecules and enhancing the reading of diluted dyes. The nanoparticles also prevent otherwise fluorescent substances from reflecting too much light when a laser is shined on them.

Using such a tiny sample is important when art historians and scientists study small fragments of 4,000-year-old Egyptian letters. Removing even a tiny sample often destroys important details about the available technology and materials available to ancient civilizations.

In the PNAS paper, Leona identified a brilliant and well known red dye, known as madder lake, by using the silver nanoparticles.

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Madder lake is derived from the madder plant.

"Just looking at the plant you would never know it contains this rich color," said Leona. "It takes some complex chemical reactions to obtain the product."

First, the madder plant, a small shrub with yellow leaves and no outward indication of a brilliant red dye, has to be dug up. The roots are then left in a dark, damp place to ferment and help release the dye.

A mild acid or base is then applied to the solution, creating a bright yellow or blue color. The solution is then neutralized, and the red dye drops to the bottom, ready to stain fabric red.

Egyptians used madder lake as early as 1400 B.C. Now that range has been extended to 1900 B.C. The ancient Egyptians, says Leona, were much savvier at biochemistry than we give them credit for.

The silver nanoparticles also helped Leona connect two 12th century French statues with each other, and with the Far East.

Both statues were painted using a red dye that comes from the ground up shells of an East Asian insect. For that dye to travel from Asia to France reveals a complex trade network of several civilizations spanning half the globe.

The PNAS paper details the Egyptian and French examples. Since Leona submitted the paper, he has used the silver nanoparticles on dozens of artworks to reveal the original color of now colorless statues and colored the sunsets of faded paintings.

Leona isn't the only one using silver nanoparticles.

Scientists from the Getty in California and the Art Institute of Chicago, among others, are also using the technique, and are very excited by their results. The Getty, with some help from Leona, has even created an exhibition that presents ancient artwork next to images of what the original artwork originally looked like.

"We can rewrite history because the object itself becomes our primary source of information," said Francesca Casadio, at the Art Institute of Chicago. "These pieces teach use about trade patterns, the exchange of materials and the artists who created them."

Related Links:

Discovery News blog: Archaeorama

HowStuffWorks.com: Ancient Egyptian Art

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