江戸時代後期の木版画に使われた鉛丹の変色と化学組成の変化

Abstract

The discoloration and chemical composition changes of red-lead used for wood-block print made in the late Edo period have been investigated. Both the chromaticity and lightness of red-lead decrease with discoloration, and its hue exhibits very little change. This is due to the reflectance decrease of red-lead in a long-wavelength range beyond the absorption edge of 580 nm. Red-lead is a mixture of Pb3O4 and β-PbO and has a grain size of 0.05-0.2 μm. The X-ray diffraction intensity of β-PbO considerably decreases with discoloration in comparison with that from Pb3O4. This result shows that β-PbO is more reactive than Pb3O4 in the mixture. The results of XPS measurement suggest that both lead chloride and lead carbonate exist in the surface layer of red-lead.