Washington, Feb 5 : Engineering researchers at the University of Michigan in US, have developed a new device, which would use 'T-rays' - pulses of terahertz radiation, to reveal art work hidden beneath coats of plaster or paint in centuries-old buildings.
The team of researchers, which includes scientists at the Louvre Museum, Picometrix, LLC and U-M, used terahertz imaging to detect colored paints and a graphite drawing of a butterfly through 4 mm of plaster.
The researchers believe that T-rays can also be used to illuminate penciled sketches under paintings on canvas without harming the artwork.
"It's ideal that the method of evaluation for historical artifacts such as frescoes and mural paintings, which are typically an inherent part of a building's infrastructure, be non-destructive, non-invasive, precise and applicable on site," said John Whitaker, one of the research scientists involved in the project.
"Current technologies may satisfy one or more of these requirements, but we believe our new technique can satisfy all of them," he added.
According to Whitaker, terahertz imaging can reveal depth and detail that other techniques cannot.
"And it's not potentially harmful like X-ray imaging because terahertz radiation is non-ionizing. Its rays don't have enough energy to knock electrons off atoms, forming charged particles and causing damage, like X-rays do," he added.
According to G¨rard Mourou, a U-M electrical engineering professor emeritus, this technique will be especially useful in Europe, where historic regime changes often resulted in artworks being plastered or painted over.
This was common in places of worship, some of which switched from churches to mosques and vice versa over the centuries, he said.
"In France alone, you have 100,000 churches," said Mourou. "In many of these places, we know there is something hidden. It has already been written about. This is a quick way to find it," he added.
To help archaeologists examine a mural they discovered recently behind five layers of plaster in a 12th century church in France, the research team from the University of Michigan plan to take their equipment to that country in March.
This technique might also help to reveal Leonardo DaVinci's "The Battle of Anghiari," which is believed to lurk beneath other frescos at the Palazzo Vecchio in Florence, Italy.