Like X-rays let doctors see the bones beneath our skin, "T-rays" could let art historians see murals hidden beneath coats of plaster or paint in centuries-old buildings, University of Michigan engineering researchers say.
T-rays, pulses of terahertz radiation, could also illuminate penciled sketches under paintings on canvas without harming the artwork, the researchers say. Current methods of imaging underdrawings can't detect certain art materials such as graphite or sanguine, a red chalk that some of the masters are believed to have used.
Very neat and something I hadn't heard of before. This is how it works:
The rays permeate the plaster, and some reflect back when there is a change in the material. When they bounce back and how much energy they retain depends on the material they hit. Different colors of paint, or the presence of graphite, for example, cause tell-tale differences in the amount of energy in the returning waves. A receiver measures this energy, and the scientists can use the data to produce an image of what lies beneath, Jackson explained.
Apparently it's been used on the space shuttle to check for subsurface cracks. It will be really great if they can get it to go even deeper. Not too long and we'll be reading books without opening them!