Strontium isotopic characteristics of the body and glaze formulas of the Jin Dynasty white porcelain from the Wanquansi site in Beijing
The Ding kiln is one of northern China's most representative white porcelain kilns of the 10th-13th centuries A.D.Many scholars have studied it extensively to reveal the complex changes in the formulas of white porcelain of northern China.The use of fluxes is an important issue in the study of ancient Chinese porcelain-making technologies,and several scholars have suggested that the Jin Dynasty was a critical period for the transformation of fluxes in the white porcelain from Ding kiln sites.However,there is still a lack of research on the formulas of the Jin Dynasty white porcelain,especially from the perspective of strontium isotopic analysis on the body and glaze formulas of the Jin Dynasty white porcelain from Ding kiln sites.The Wanquansi site in Fengtai District of Beijing is located within the Jin Zhongdu site,and samples of the Jin Dynasty white porcelain excavated from the site are consistent with the characteristics of Jin Dynasty white porcelain from Ding kiln sites in terms of forms.In our study,three methods—X-ray fluorescence spectrometry(XRF),multi-collector-inductively coupled plasma-mass spectrometry(MC-ICP-MS)and laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)—were employed to determine and analyze the compositions of the body and glaze and the strontium isotopic ratios of the white porcelain excavated from the Wanquansi site.Three kinds of raw materials used for making the Jin Dynasty white porcelain from the Ding kiln were identified,among which:the strontium isotopic ratio of the high-alumina clay raw material was around 0.73,that of the dolomitized limestone raw material was around 0.72 with a higher content of calcium,and that of the plant ash raw material was around 0.71;the content of strontium was around 1 000 μg/g.Through compositional analysis of the glaze layer and comparative study of the composition between the body and glaze,it was found that the glaze layer was mainly made from high-silica and dolomitized limestone raw materials,and was strongly affected by the partial melted body.According to the content of P2O5,which strongly correlates with the plant ash,it could be inferred that there might also be a certain amount of plant ash in the glaze.Compared with previous studies,our study expands on the following three aspects:1)no scholars have carried out scientific and technological analyses of the Ding kiln white porcelain excavated from archaeological sites in Beijing area yet,and we employed the method of combining the primary oxide contents with strontium isotopic ratios to determine the body and glaze formulas of the Ding kiln white porcelain excavated in Beijing area,which is more effective in indicating typical fluxes,such as wood ash and limestone,compared to the commonly-used method of determining the primary oxide contents only;2)a new understanding of using specific fluxes has been developed—when wood ash fluxes were used in porcelain bodies,the melted body might affect the elemental contents of the glaze and thus disturb the judgment of glaze flux types,and therefore,only after the elimination of the above interferences can the type of fluxes in the glaze be correctly judged;3)the differences between the Ding kiln white porcelain excavated from Beijing and those from Ding kiln sites were discussed,and it was concluded that there were two possibilities for the differences,namely,differences in production areas and/or a diversity of processes within the Ding kiln,mainly in the type of fluxes in the bodies—some kiln workers may have been more accustomed to using a mixture of wood ash and dolomitized limestone,while others preferred simple wood ash or high-potassium rock-based fluxes.This study supplements the data on the body and glaze formulas of the Jin Dynasty white porcelain from Ding kiln sites,enriches the understanding of the formulas for white porcelain-making of that period,confirms dolomitized limestone as the main calcareous flux for the body and glaze,and reveals the possibility of separate and independent sources of the wood ash-type fluxes for the body and glaze.This conclusion provides a basis for the study of the social economy and handicraft industry of the Jin Dynasty in Beijing area.
Wanquansi siteJin DynastyWhite porcelain of the Ding kilnFormulas of body and glazeStrontium isotopeFlux
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