Ion beam analysis of Mosan enamels

Abstract

To continue to investigate the techniques and materials used to create Mosanenamels, 20 enamelled plaques from the Louvre Museum have been studied.These objects date from the 12th to the beginning of the 13th century.PIXE and PIGME measurements have been performed to determine thecomposition of both the glass and the metal phases in the plaque. The resultsare compared with those previously obtained at the British Museum in1993 and at our laboratory in 1999.Mosan and Rhineland enamellersused pure copper (98–99 wt%) for the metal support and three differentglass compositions. During the 12th century all coloured glasses, with theexception of the red glasses, are soda-lime silicates—with mineral sodiumsources—opacified by antimony compounds. The red enamels are potash-limesilicates—with wood ash potassium sources. A chronological evolution for theglass composition is hypothesized using this evidence. Changes in the glasscomposition occurred at the end of the 12th and the beginning of the13th century. The glasses are soda-lime silicates—using plant ash sodiumsources—opacified by tin oxides. Exactly the same chronological evolutionis observed for the contemporaneous production of Limoges enamels.Roman tesserae dating from the second to the fourth century AD have beenanalysed for a comparative study with Mosan enamels. The possibilityof a reuse of Roman glass tesserae for Mosan enamels is discussed forthe blue and green glasses. No evidence exists, however, linking the redenamels to the red tesserae as their compositions are completely different.