Study on the microstructure of the multilayer glaze of the 16th-17th century export blue-and-white porcelain excavated from Nan’ao-I Shipwreck

Abstract The study aims to analyse the devitrification and multilayer structure of the glaze of the Zhangzhou export blue-and-white porcelain excavated from Nan’ao-I shipwreck in Shantou district, Guangdong province. Digital microscope, polarizing microscope and scanning electron microscope are applied to observe the glaze layer. X-ray Diffraction and X-ray Energy Dispersive Spectrometer are applied to analyse the chemical compositions of the glaze. Anorthite crystals are found in the outer glaze layer, which cause the decrease in transparency of the glaze. The appearance and chemical compositions of the multilayers of the glaze are different and cobalt pigments are located between the glaze layers. It is inferred that part of the 16th–17th century export blue-and-white porcelain produced by Zhangzhou kiln in Ming dynasty was glazed twice.