Chemical analysis of Iron Age glass beads

Martina Bertini* & Eva M. Krupp

Iron Age Scottish glass beads represent a puzzling mystery of Scottish past. Although typologically similar specimens have been found in the south of England, it is likely that the Scottish beads are of very different provenance. The composition of the set of glasses is typically Roman, with high lime (> 8%), moderate soda (~16%) and high alumina (~3%). The homogeneity found in the pool also points to a high degree of standardization in the production of the raw glass, which is indeed the case of Roman glass. In this work we aim to identify and characterize the raw materials employed in the production, pigmentation and opacification of these glasses through analysis of trace metal composition. Miocro-destructive analysis using Laser Ablation-ICP-MS was performed for 33 elements, and correlations determined between the bulk and trace metal compositions in order to establish the provenance of the natural resources. The data analysis showed that different sources of raw materials can be identified on the grounds of the trace metal impurities introduced with them.

Martina is an enthusiastic PhD student in Analytical Chemistry for Archaeology at the Department of Chemistry at the University of Aberdeen. She graduated in Wood Technology and Engineering and later in Forestry Systems Management at the University of Florence and she started her work looking into archaeological materials in 2005 at the DI.S.T.A.F., Florence, under the supervision of Prof. Marco Fioravanti. After a few months training at the Opificio delle Pietre Dure (Florence) under the guidance of Dr Isetta Tosini, where she developed her interest for a wider range of archaeological materials and analytical techniques, she obtained a 9 months placement at the Department of Chemistry of the University of Aberdeen with Prof. Jörg Feldmann. She then started her PhD with Dr Eva Krupp, discovering  her passion for ancient glass when she was given the possibility to write her own proposal for her PhD studies, that she directed to the study of the secrets of Iron Age Scottish glass beads.