Werner Forman/Corbis; (inset) Mazel et al., Analytical Chemistry, online edition (2007)

Bloodhound.
New diagnostic techniques revealed traces of blood (inset, in blue) in microscopic samples from ancient African artifacts such as this one.

Crimson Clues From the Ancient Past

Chemists have confirmed something that archaeologists and art historians have long suspected: Ancient sculptures found in western Africa contain blood from ritual animal sacrifices in their patina. The study, which used new diagnostic techniques, should yield a greater understanding of the practices of artists from long ago, and it could open the way for more detailed analyses of the world's most precious artifacts.

Anthropologists and ethnologists have uncovered much cultural evidence, from oral histories and illustrations, that ancient African artists often used ritual animal blood in their creations, generally as attempts to please or appease their deities. In the empire of Mali, for example, which flourished from the early 13th century to the late 15th century C.E., the Dogon people decorated or painted their sculptures with various pigments thought to be composed partly of blood. But because of the age of the artifacts, the composition of the patina has eluded standard chemical analyses.

So a team from the Centre for Research and Restoration of the Museums of France in Paris and other institutions in France employed a quartet of new techniques. Working with mass-spectroscopy specialists at the French national research agency in Gif-sur-Yvette and with scientists at the European Synchrotron Radiation Facility in Grenoble, they used two types of mass spectroscopy and two methods of x-ray scanning. The techniques are so sensitive that they can detect even a few target molecules in a few micrograms of material, says physical chemist Pascale Richardin, a co-author of the study. They also offer the advantage that one technique can detect a desired molecule that the others might miss. In this instance, the measurements revealed the unmistakable presence in the patina of a form of iron associated only with blood, the team reports in an upcoming issue of Analytical Chemistry.

The research shows without doubt that the wooden figures were used in ceremonies involving animal sacrifice, says electroanalytical chemist Christian Amatore of the École Normale Supérieure in Paris, who calls the protocol "failure-free." Next up, says Richardin, is analyzing the painting materials used by the masters of the European Renaissance--not to look for blood, but to attempt to reveal the secrets of their colors and textures.

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