THz Spectroscopy for analysis of paintings

Recently terahertz spectroscopy has progressed rapidly and it is expected that its spectra are more material specific compared with those of mid-infrared regions. Since the materials used in art are basically mixtures and are composed with inorganic and organic materials, spectra obtained in mid-infrared regions are complicated. We have observed spectra of various historical and modern pigments and binders. Almost all historical pigments have fingerprint peaks, and binders also have specific spectra. Thus, THz spectroscopy can distinguish the pigments which have the same colour, and can distinguish binders used with the same pigment. THz spectroscopy can also identify the transparent body pigment in colour pigments. The scientific analysis is an important process in art conservation for collecting information of materials used in original work as well as in previous conservation processes. This work should contribute to art conservation as a new non-invasive examination method. Moreover, the first-ever THz spectra database of art materials can contribute to various other research fields such as the food and pharmaceutical industries, because materials are commonly used.