Colours of the "images of the floating world". non-invasive analyses of Japanese ukiyo-e woodblock prints (18th and 19th centuries) and new contributions to the insight of oriental materials

In the Edo (1615-1868) and Meiji (1868-1912) periods, Japanese woodblock prints were a commercial form of art that reproduced the everyday life of ordinary people (the ukiyo-e style). Since different dyes and pigments were used to produce these prints, changing over time, the knowledge of these materials can be very important for the history and the conservation of ukiyo-e prints. This study will present the results of the investigation of several woodblock prints, produced between the 18th and 19th centuries. The artworks belong to the Asian art collection at the Museum of Zaragoza (Spain). The aim of the study is the identification of organic colorants and inorganic pigments employed by Japanese printers, specially emphasising the introduction of new synthetic compounds in the 19th and 20th centuries. Because prints are fragile artworks, several non-invasive methods in a multi-analytical approach were employed, as hyperspectral imaging in the visible and NIR range (HSI), in-situ point-by point Diffuse Reflectance Spectroscopy (DRS), LED mu-spectrofluorimetry, and Fiber Optic Reflectance Spectroscopy in the near-infrared range (FORS NIR) and mid-infrared spectroscopy (MIR), combined with X-ray Fluorescence to confirm the presence of some elements. The identification of the diverse materials was made upon a dedicated database involving Japanese pigments, dyes, mixtures (blue, green, orange, purple colours) and papers. By combining all these methods, all the inorganic compounds were identified, and also some organic colourants, especially for the blue and red areas. Finally, a chronology of the use of the colourants in the ukiyo-e woodblock prints between 1700 and 1900 is proposed.