THz Nondestructive Imaging for Historical Arts

Abstract

Since historical artworks are unique, nondestructive and noncontact measurements are desired in the field of heritage science. Thus, electromagnetic techniques, such as radar remote sensing and X-ray tomography, are suitable for observing the internal structure of heritage objects. THz time-domain imaging allows the observation of the internal structure of a painting composed of preparation and support layers, which conservators desire to see even if they must take a small sample. The most important advantage of THz time-domain imaging is the ability to observe a cross-sectional image without cutting, as well as to obtain areal information at any depth from the surface. About 15 years ago, a portable, turnkey-type THz time-domain imaging system became commercially available, and the first on-site observation in a museum was carried out at the Uffizi Gallery in Florence, Italy, in 2008. Since then, THz time-domain imaging has been applied to historical objects and artworks, including Egyptian mummies, tempera panel paintings from the Renaissance, Japanese panel screens, and contemporary paintings on canvas. Case studies introduced in this chapter proved that THz time-domain imaging contributes to conservation planning by practical evaluation of the physical condition of artworks.