Colouring mechanism and firing process of celadon from the Xiangzhou kiln in Anyang,China, from the 5th-7th century

The Xiangzhou kiln was the largest celadon kiln site in northern China from the Northern and Southern Dynasties to the Sui Dynasty (5th-7th centuries). In order to investigate the colouring mechanisms and firing process of two types of celadon (yellow-green and earthen-yellow glazes) from the Xiangzhou kiln, samples were tested and analysed using OM, ED-XRF, TD, SEM-EDS, LRS, XPS and UV-Vis-NIR. The study results show that most of the samples in the two enamels have different formulations. The celadon glaze of the Xiangzhou kiln contains a small amount of quartz, anorthite and other crystals. The yellow-green glaze is fired in a reducing atmosphere and the earthy yellow glaze is fired in an oxidising atmosphere. The colouring mechanism of the Xiangzhou kiln celadon is mainly dominated by the chemical colouring of ionic colouring and aided by structural colouring caused by the microstructure (bubbles, various crystals, fractal structures, etc.).     

Degradation mechanism of the Ru wares unearthed from the Qingliangsi site in Henan,China

The Ru kiln is a famous kiln that originated in the Northern Song Dynasty (960–1127 CE) in China. After nearly a thousand years of degradation, many ‘white spots’ have appeared on the Ru glazes, which have seriously damaged the visual aesthetic. Energy-dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction analysis (XRD), optical microscopy (OM), scanning electron microscopy-energy dispersive spectrometry (SEM–EDS), Raman spectroscopy, and angle-resolved spectrum system were used to systematically investigate the composition, microstructure, and degradation morphology of the Ru ware. The degradation mechanism of the Ru glaze was investigated, showing that the heterogeneity of the glaze microstructure resulted in different degradation morphologies. The weakest part determined the overall corrosion resistance. Fine crackles of the glaze provided a fast path for corrosion. The special soil environment at the Qingliangsi site was a key influencing factor leading to the ubiquitous and severe degradation of the Ru wares. The microstructure degradation caused by chemical corrosion provided complex light-reflecting interfaces, leading to the formation of ‘white spots’ on the surface. Combined with the influence of exotic contaminants, the color and texture of the Ru glaze significantly changed, and the appearance quality seriously declined.