The success of early Chinese blue-and-white porcelains relied heavily on imported cobalt pigment from the West. In contrast to art-historical concept, which contains both typological evidence and literature records, it is assumed that imported Sumali blue was completely superseded by domestic Chinese asbolane ore based on the analytical results of the Fe/Mn ratio in imperial productions from the Xuande reign (1426 to 1435 CE) onward. Using a focused ion beam transmission electron microscopy technique to reassess this hotly debated question, we have identified two classes of residual submicron pigment particles in the blue glaze with diagnostic differences in morphology, chemical composition, and distribution behavior. Compared with the microstructural features of the blue-and-white porcelains of the Yuan and Qing dynasties, we show that a mixture of imported and domestic cobalt pigments was used for aesthetic reasons, indicating that the overseas supply chain of imported pigment remained consistent and adequate even though the authorities had terminated official trade and tributary activities after the death of Admiral Zheng He. This discovery further suggests that the globalized trading network and cross-regional industrial chain had been extensively established in the 15th century. Moreover, we provide analytical evidence against the fundamental assumption of the current Fe/Mn provenancing criteria, implying that the failures of previous chemical analyses can be attributed to elemental differentiation between the silicate glaze and the arsenic pigment. We propose an innovative method for directly assessing original mineralogic information from submicron residual pigment particles that provides a more reliable way to trace cobalt circulation and holds great promise for provenance studies.
Keywords: blue-and-white porcelains; ceramic archaeology; globalized trading network; residual pigment particles.