With one quick, tiny laser blast, ancient objects reveal secrets

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June 17, 2003 — Archaeologists digging in the field might soon have a new tool at their disposal. In addition to the traditional trowel and brush, enter LMnt1 (pronounced Element One): a travel-size laser analytical instrument. It’s a tool that can determine the elemental composition of an archaeological find in a few seconds.

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The invention is the fruit of joint collaboration between the Institute for Aegean Prehistory in Philadelphia and the Foundation for Research and Technology — Hellas, in Crete, Greece.

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“The technology has already been used by research labs for process monitoring in industry,” said Demetrios Anglos, the developer of the new application. “What we did, is that we used it in a more delicate application” for use on paintings and archaeological finds.

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The instrument is currently at the prototype stage, but is already being used for routine object analysis at the Institute for Aegean Prehistory’s Eastern Crete study center. Anglos’ team is working to reduce the size of the prototype. But it is also actively seeking partners to develop a professional product.

“We are looking for a manufacturer who would want to mass-produce it, a museum or any other organization who might want to use it,” said Dimitrios Tsamouras, technical consultant and the Innovation Relay Centre of Athens, a European Union funded office for technology transfer. Several companies have expressed interest so far, but no deal has yet been signed.

The instrument is based on a pulsed laser. The laser fires a pulse at the surface of the object, resulting in the ejection of a tiny quantity of material. The ablation measures 50 to 100 microns wide and less than 1 micron thick. It’s also white hot: more than 9,700 degrees Celsius. “The ablation produces a plasma gas which emits light,” Anglos said. “Thanks to our detector, we can find out what elements are present in the plasma and consequently, in the solid surface.” The procedure is based on Laser-Induced Breakdown Spectroscopy, a technique often referred to as LIBS.

The instrument can be used to find out what kinds of alloys were used in gold-colored paint. Details on paint composition can tell researchers where an object came from, and can precisely date an item. The composition of white paint on pottery, for example, can reveal whether it came from a palace or from a poor village. Thanks to this kind of elemental information, researchers can theorize on the period and provenance of any object. And museums can find out whether an old painting was once restored.

The instrument provides several advantages. First, the sample used is so small that the damage to the original is minimal. This is primordial in the case of paintings. Secondly, the object is portable. It’s the size of a small table, whereas other elemental analysis equipment can take up a whole room. Researchers at excavation projects often have large numbers of samples they want to analyze on site rather than bring them to the main lab. In addition, archaeological finds, particularly in Greece, are rigorously monitored by cultural authorities. Official permissions are needed to export a find for analysis in the United States or the rest of Europe. “Even sending it to Athens can be subject to strict regulations,” Anglos said.

Also, the process is relatively quick: ten-billionth of a second for the laser pulse and another microsecond or two for the light detector to do its work. Analyzing the data might take more time.

The downside might be the price. Right now, the prototype costs just less than $90,000 to build. Any potential industrial partner would have to re-engineer LMnt1 in order to make it cheaper. Cultural bodies like museums and archaeological research projects general operate on a limited budget.

“Not many institutions can afford anything more than $50,000,” said Christopher McGlinchey, conservation scientist at New York’s Museum of Modern Art. However, the price tag is smaller than more sophisticated elemental analysis instruments.

Staff at the Crete study center of the Institute for Aegean Prehistory (INSTAP) have been using the prototype in the field with encouraging results. “All you need to do is place the object being analyzed under the probe and the results appear on the screen,” said Philip P. Betancourt, INSTAP’s executive director. He added that unlike other techniques, this one doesn’t require any time-consuming sample preparation. In addition, it’s so easy to use, there is no need for a specialized technician to man the machine.

However, LMnt1 is not as accurate as some other methods. The instrument can indicate what elements are present, but not how much. “In the end, it doesn’t replace much more expensive and sophisticated equipment,” Betancourt said. “But we found it very helpful and easy to use in the field.”


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