The evaluation of the oxidation state of colouring elements in ancient glass offers important information not only about colour, but also on the technology of the ancient glassmakers. Concerning iron, few information is published on the relative Fe3+/Fe2+ ratios. Furthermore, this type of measurements is challenging, due to the low ∑Fe contents of the glasses, typically in the range 0.3 – 1.0%. We have combined and compared the relative advantages of Mössbauer and XANES measurements to study a selected series of sixteen glasses - mainly from excavated primary and secondary production centres and dated to the first millennium AD - which provide a wide range of iron compositions. In addition, some of the glass samples were chosen to determine the differences in the relative Fe oxidation state in closely related glasses from a single production sequence. Good agreement between the two techniques was obtained for the more oxidised glasses (Fe3+> 70%). However, some significant differences were evident in the more reduced samples, with XANES suggesting higher Fe3+. The results on the decolorized glass indicate that Sb is more effective than Mn in oxidating iron. Primary natron glass from an early Islamic tank furnace at Bet Eli'ezer (Israel), shows a high level of Fe3+ in the bluish glasses, but greenish/olive samples - of essentially the same composition - appear less oxidized and hence originated in regions of the furnace with less access to air. Conditions in a primary furnace producing amber glass were highly reducing. A sequence of moils from a glass working furnace in London demonstrates progressive oxidation of the melt as the working campaign progressed. Iron in strongly coloured fourth century HIMT glass is very oxidised, due to the high content of Mn; the strong colour of these samples is due to their high iron content, but Fe3+ is more-or-less constant irrespective of the total amount of iron present. Primary chunk soda ash glass from the tank furnaces at Tyre (Lebanon), has an intermediate oxidation state, while a chunk from Banias (Israel) is fully oxidised, although manganese oxide has been added in both cases to oxidise and decolour the glass.

The oxidation state of early glass: a combined EXAFS and Mössbauer study and some applications

QUARTIERI, Simona
2012-01-01

Abstract

The evaluation of the oxidation state of colouring elements in ancient glass offers important information not only about colour, but also on the technology of the ancient glassmakers. Concerning iron, few information is published on the relative Fe3+/Fe2+ ratios. Furthermore, this type of measurements is challenging, due to the low ∑Fe contents of the glasses, typically in the range 0.3 – 1.0%. We have combined and compared the relative advantages of Mössbauer and XANES measurements to study a selected series of sixteen glasses - mainly from excavated primary and secondary production centres and dated to the first millennium AD - which provide a wide range of iron compositions. In addition, some of the glass samples were chosen to determine the differences in the relative Fe oxidation state in closely related glasses from a single production sequence. Good agreement between the two techniques was obtained for the more oxidised glasses (Fe3+> 70%). However, some significant differences were evident in the more reduced samples, with XANES suggesting higher Fe3+. The results on the decolorized glass indicate that Sb is more effective than Mn in oxidating iron. Primary natron glass from an early Islamic tank furnace at Bet Eli'ezer (Israel), shows a high level of Fe3+ in the bluish glasses, but greenish/olive samples - of essentially the same composition - appear less oxidized and hence originated in regions of the furnace with less access to air. Conditions in a primary furnace producing amber glass were highly reducing. A sequence of moils from a glass working furnace in London demonstrates progressive oxidation of the melt as the working campaign progressed. Iron in strongly coloured fourth century HIMT glass is very oxidised, due to the high content of Mn; the strong colour of these samples is due to their high iron content, but Fe3+ is more-or-less constant irrespective of the total amount of iron present. Primary chunk soda ash glass from the tank furnaces at Tyre (Lebanon), has an intermediate oxidation state, while a chunk from Banias (Israel) is fully oxidised, although manganese oxide has been added in both cases to oxidise and decolour the glass.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/2327026
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