Compositional and Microstructural Evolution of Longquan Celadon from the Southern Song to Ming Periods: Implications for Color and Firing Behavior

This study examines technological change in Longquan celadon from the Dayao kiln-site area by asking three related questions: how body and glaze compositions changed from the Southern Song to the Yuan and Ming periods; how these compositional changes relate to glaze color and microstructure; and how firing-temperature data from representative ceramic bodies help to clarify firing practice within the sampled kiln sequence. Twenty celadon sherds from Jincun Dayao Bentou, Dayao Shantoucheng, Dayao Mulianyan, and Zhulongcun Panchuangkou were analyzed by energy-dispersive X-ray fluorescence spectroscopy (EDXRF), CIE L*a*b* color measurement, scanning electron microscopy (SEM), and high-temperature dilatometry. The results show that the Yuan-associated bodies in this sampled assemblage contain higher Al2O3 and K2O and lower SiO2 than the Southern Song and Ming groups, indicating a strengthened aluminum- and potassium-rich body system. Glaze chemistry records a staged rebalancing of the flux system: from the high-calcium condition represented by Northern Song reference glazes, through a transitional Southern Song state, to a stronger calcium-alkali character in the Yuan period, followed by a partial return toward a more calcium-rich recipe in the Ming period. Color measurement indicates that the Yuan samples generally have lower b* values, reflecting a reduced yellow component and a more bluish-green tendency; their relatively lower L* values also correspond to a darker glaze appearance, although this difference is less pronounced than that observed for b*. SEM observations of four representative cross-sections show glass-dominated glazes, anorthite-bearing body–glaze interlayers, and mullite-bearing bodies; the two Yuan representatives have thicker glaze layers and local phase separation, suggesting that their darker and more bluish appearance was produced by the combined effects of glaze chemistry, thickness, and microstructure. Firing-temperature data obtained from high-temperature dilatometry show that the representative samples were fired within a high-temperature range, while the variation between the two Yuan specimens suggests greater flexibility in firing practice during this period. Taken together, the data suggest that Longquan celadon underwent a non-linear technological reorganization, with the Yuan phase forming a key interval of compositional, microstructural, visual, and firing-related reconfiguration.