Feb. 28, 2007 — Clothes say a lot about a person. But when it comes to ancient attire, fabrics are often faded, fibers crumbling and designs unrecognizable.
Now, scientists are turning to forensic crime lab techniques to hunt for dyes, paints and patterns in prehistoric textiles.
The technique can not only reveal the beauty of the fabric, but also offers a relatively nondestructive method for analyzing how a piece was constructed, with what fibers and whether the designers used pigments or dyes.
"Forensic photography helps minimize damage by enabling us to sample strategically," said Christel Baldia, assistant professor in textiles at the Florida Institute of Technology in Melbourne.
Baldia worked with colleague Kathryn Jakes, a professor of textile sciences at Ohio State University, to develop the method.
Their approach uses ultraviolet and infrared imagers and filters normally used in crime labs to unveil stains, fingerprints, blood and body oils that cannot be seen in visible light.
This kind of technique works because some molecules absorb light in one wavelength but release it in a different one — sometimes one that the human eye cannot see. The phenomenon is called fluorescence and in forensic photography, this and other optical behavior is captured under infrared or ultraviolet lighting.
It turns out that some pigments (made from minerals) and some dyes (made from plant or animal material) fluoresce. The researchers turned the technique onto fabrics from ancient Native American people known as the Hopewell, who flourished in the Ohio River Valley between 1 A.D. and 500 A.D.
First, the team placed the artifacts under different lighting conditions, including daylight, ultraviolet light and infrared light.
Next, they photographed the fabrics using special film and light-filtering camera equipment. Then they examined the photographs for fluorescence.
