Non-invasive Optical Technical Identification of Red Pigments on Chinese Paper Notes

Abstract

Red pigments with bright colors were widely used in ancient Chinese painted pottery, books, antiques, calligraphy, and paintings. Herein, red pigments of traditional paper notes were investigated by non-invasive optical technology in order to enrich the Chinese historical pigments knowledge base. The results of laser Raman spectroscopy tests on five paper notes clearly identified the inorganic mineral pigments including ocher and cinnabar. Infrared spectroscopy measurements indicated that an artificial synthetic magenta was employed as the organic pigment. Inorganic and organic red pigments were applied together on the same samples 2 and 5 which can be speculated to serve an anti-counterfeiting function. In addition, SEM-EDS analysis of sample 5 clearly showed that the red pigment was composed of lead oxides and ZnS was added as color modulator. Combined with the abovementioned non-invasive techniques, analysis of printed pigments can provide a feasible method to authenticate and conserve paper notes.