U.S. engineers are collaborating with the Center for Research and Restoration at The Louvre Museum in France to use a terahertz device to find murals hidden behind plaster or paint for centuries. T-rays, or pulses of terahertz radiation, can 'illuminate penciled sketches under paintings on canvas without harming the artwork,' something which is not be possible with X-ray imaging technology. These researchers will have to work for many years. After all, there are 100,000 churches in France alone to investigate. And they all can contain art treasures. But read more...
You can see on the left an example of how this terahertz device is used to examine a mural recently discovered in a 12th century church in France and which was hidden behind five layers of plaster. (Credit: University of Michigan Photo Services) Here is a link to a larger version of this picture.
The team of researchers at the University of Michigan (U-M) includes Jae Bianca Jackson, a doctoral student in applied physics, and two professors of the Center for Ultrafast Optical Science (CUOS), Gerard Mourou and John Whitaker.
They've collaborated with engineers from Picometrix, LLC, who build and sell a variety of terahertz systems. The company states that "terahertz radiation can be used to image through materials yielding high spatial resolution and has the ability to resolve both time and amplitude information. It is safe for humans and can provide spectroscopic information, as well as produce images."
They've also worked with the Centre de recherche et de restauration des musées de France (C2RMF, site in French).
Here is a quote from John Whitaker about this T-ray technology. "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. Current technologies may satisfy one or more of these requirements, but we believe our new technique can satisfy all of them."
And why is this technology non-destructive? "Terahertz imaging can reveal depth and detail that other techniques cannot, Whitaker said. 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."
Gérard Mourou adds "he believes 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."
This research work has been published in Optics Communications, an Elsevier journal, under the title "Terahertz imaging for non-destructive evaluation of mural paintings" (Volume 281, Issue 4, Pages 527-532, February 15, 2008). Here is the abstract. "The feasibility of applying time-domain, terahertz spectroscopic imaging to the evaluation of underdrawings and paint layers embedded within wall paintings is demonstrated. Metallic and dielectric paint patterns and a graphite drawing are resolved through both paint and plaster overlayers using a pulsed-terahertz reflectometer and imaging system. We calculated the bulk refractive indices of four common pigments and used them to confirm color domains in a terahertz-beam spectral image of a painting."
Sources: University of Michigan news release, January 30, 2008; and various websites
You'll find related stories by following the links below.
6:36:10 PM
Permalink
|
