Non-invasive identification of pigments in Japanese coloured photographs

This paper describes the first systematic analysis of 19th century Japanese coloured photographs. This unique Japanese technique followed the diffusion of photography taken up by Westerners. The photos were coloured by the painters of the School of Yokohama from ukiyo-e prints ateliers and were sold to travellers returning home as a souvenir from Japan. Although there are several museum collections throughout the Western world, this artistic technique has never been thoroughly investigated, due above all to the fragility of the artworks. In this study 22 photographs and a photo album cover from the Museum of Cultures (Lugano, Switzerland) were analysed by non-invasive infrared spectroscopy in order to identify the painting materials. A preliminary survey was carried out on reference pigments used in Japan in the 19th century, some of which are the same as those used in Western Europe, but many are particular to the Japanese school of arts. The reference pigments were analysed after extraction procedures taken from traditional recipes. Modern pigments such as “aniline colours” were also considered. The results provided insights into the painting materials, for example identifying Prussian blue, gofun, yamahaji, enju, shio, and rhodamine. The data confirmed the use of albumen paper and detected the application of a beeswax-based varnish for conservation purposes.