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Ancient pigment could help solve modern crime

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Curtin University forensic researchers working with conservation scientists from the Indianapolis Museum of Art (IMA) have found a novel use for an ancient Egyptian pigment, revealing that it doubles as a dusting powder able to reveal traditionally tricky fingerprints in modern forensics.

The team demonstrated that micronised Egyptian blue pigment, a vivid and long-lasting pigment used in painted artefacts dating back millennia, also acts as a near-infrared (NIR) luminescent fingerprint dusting powder – providing a safe and simple way to reveal latent fingerprints on highly patterned and reflective surfaces.

Professor of Forensic and Analytical Chemistry and member of the Nanochemistry Research Institute within Curtin’s Department of Chemistry, Professor Simon Lewis, said the detection of latent fingerprints was still a critically important task for forensic investigators, helping to establish evidence of contact between the criminal, the victim and/or the crime scene.

“The most common approach to detecting latent fingerprints has been the use of dusting powders made from white, black or fluorescent powders that provide contrast against the surface,” Professor Lewis said.

“However, there remain many highly patterned and/or reflective surfaces that continue to prove troublesome, making it hard to see fingerprints.

“An alternative approach is to use dusting powders that exhibit near-infrared luminescence, which is invisible to the eye. Such powders can highlight ridge detail while avoiding interference.”

Fellow researcher Dr Gregory Smith, from the IMA, has used NIR imaging to locate Egyptian blue pigment on ancient artefacts for more than a decade.

“I’d always wanted to investigate Egyptian blue for fingerprints because it exhibits strong photoluminescence in the NIR region,” Dr Smith said.

“It’s also non-hazardous and very stable, with painted artefacts dating back several thousand years still showing strong NIR luminescence.”

Egyptian blue, also known as cuprorivaite, is the earliest known synthetic pigment. It was first prepared in ancient Egypt before 3200BC and was used extensively until the 4th Century CE, when its synthesis was apparently forgotten.

“The secret of how to make it was lost after the Roman Period, but then rediscovered in the 19th Century,” Dr Smith said.

Professor Lewis said the researchers compared commercially available fingerprint powders and micronised Egyptian blue pigment for their ability to reveal fingerprints on a range of surfaces.

They then used an inexpensive white light source to illuminate the prints and a slightly modified, consumer digital camera to photograph them. The prints dusted with Egyptian blue glowed brightly in the NIR under the white light, consistently outperforming the commercial powders on patterned and reflective surfaces.

“We found that the Egyptian blue could consistently develop the latent fingerprints, revealing good ridge detail in the NIR region,” Professor Lewis said.

Professor Lewis said further studies using a wider range of surfaces and fingerprint donors were required to establish the operational usefulness of the powder.

“The exciting thing about this is it enables us to detect fingerprints on surfaces that have been traditionally problematic with conventional powders,” Professor Lewis said.

“It also represents that intersection between art and science, where we can go backwards in time to find potential solutions for challenges into the future.”

The paper, Micronised Egyptian blue pigment: A novel near-infrared luminescent fingerprint dusting powder, has been published in the journal Dyes and Pigments.

Others involved in the research included Curtin Honours student Benjamin Errington and Mr Glen Lawson of Curtin’s Department of Physics, Astronomy and Medical Radiation Science.

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