江戸時代後期の絵画和紙試料のCuによる劣化

抄録

The effects of Cu-containing pigments on degradation of Japanese paper have been investigated. A hand-coloured wood-block print of the late Edo era is used as a naturally aged specimen. To clarify the degradation mechanism, sheets of modern Japanese paper painted with powdered malachite are aged in an environment of 353.15 K(80°C), 65%RH. Pigments are examined with XRD. Degradation of the paper is examined with a three-dimensional fluorescence spectrometer. Cu content in the specimen is measured by ICP-AES and EDS. The Cu concentrations of the cross-sections of naturally aged specimen decrease with increasing depth. In addition, the Cu concentrations at the same depth of the artificially aged paper increase with aging. These results show that the Cu species diffuse from the right to the wrong side of the paper. Although the green pigment of wood-block print contains Cu species and As species, only the Cu species has been detected in the fiber of the degraded part of the paper. The degree of degradation of the accelerated sample painted with malachite becomes higher than that of the unpainted sample. Therefore Cu is the main species that participates in the degradation of paper. The fluorescence intensity of the papers painted with malachite decreased with increasing aging time. This result shows that diffused Cu ions make impurity levels in the band gap of cellulose.