Raman spectroscopy applied to early (ca. 1746-1754) English steatitic porcelains: a tentative study of compositions

Two pieces of unmarked English porcelainware, a vase and a coffee cup, were examined by Raman spectroscopy. The presence of both forsterite and enstatite was identified in the vase, and enstatite and diopside in the coffee cup, indicating that both articles contained magnesium. The glazes on the two objects were found to be different in chemical composition, as were the compositions of their on-glaze enamels used for their decoration. Residues of an organic binder were observed in the turquoise on-glaze enamels used to decorate both objects, indicating that either this colour was cold-painted onto these, or, more likely, a lead-based glaze fired at very low temperature was employed. From the data generated, together with the supporting historical information, it is now proposed that the two objects were decorated in different factories, most likely between ca. 1746 and 1754. The vase has been attributed to manufacture and decoration at Worcester during ca. 1753-1754, and the coffee cup is presently attributed to Bow manufacture and decoration in ca. 1746.