A short but glorious porcelain glaze of Early Ming Dynasty: New finding of raw material and colorants in the copper red glaze

Abstract

Copper red glaze is considered to be Chinese unique high-temperature copper colored glaze. The sample of Hongwu underglaze red of the Ming Dynasty was analyzed by scanning electron microscopy (SEM), synchrotron radiation micro-X-ray fluorescence spectroscopy (SR-μ-XRF), synchrotron radiation micro-X-ray diffraction (SR-μ-XRD) and transmission electron microscopy (TEM), the results show that there are nano-scale metal copper particles in the diffusion layer of the glaze, and irregular copper sulfide particles at the bottom layer. The presence of metal copper nanoparticles shows the glaze red, but under the influence of black copper sulfide, the appearance of underglaze red is relatively dull and dark. It is assumed that the pigments in Hongwu underglaze red are natural copper ores due to the existence of irregular particles. Referring to the record of "Bright red clay" in ancient literatures, a mixture of cuprite and chalcopyrite are probably the raw materials, the exhaustion of which may be the main reason for the interruption of copper red glaze after the mid-Ming Dynasty.