Evaluation of archaeological glass samples from the archaeological site of Vergina via a combination of analytical techniques and subsequent statistical analysis

The chosen subject falls within the domain of archaeometry and focuses on the study of archeological glass from the site of Vergina (Macedonia, Greece) using a combination of analytical techniques. Our goal was to answer certain archaeological queries regarding the provenance of the samples and, additionally, to investigate the necessary steps for organizing a holistic research approach for similar analytical problems and the ways of extracting the maximum amount of information from our results. A total of 18 samples from the excavation of Vergina were examined, including 17 glass fragments and glass paste samples as well as a clay matrix sample. The techniques chosen for the analysis of the samples were micro - X Ray Fluorescence Spectroscopy (microXRF), atomic emission spectroscopy using inductively coupled plasma (ICP-AES) and, finally, atomic absorption spectroscopy (??S). The statistical analysis of the results included a Student t-test for the determination of the correlation between the micro-XRF and ICP-AES/AAS techniques, as well as the application of hierarchical classification algorithms, cluster analysis and principal component analysis (PCA). Finally, regarding the clay matrix sample, we employed a three dimensional laser scanning technique in order to obtain an accurate digital model of its inner surface. One of the most important conclusions we reached was the determination of the site Pikrolimni (Macedonia, Greece) as the source of natron in the glass making process, based on the samples' K2O and MgO ratios. The high concentrations of Al2O3, Fe2O3 and MgO of the glass paste samples suggests they constitute by-products of the glass making process and also support the employment of recycled materials. Furthermore, sample 008, the only one exhibiting intense coloring, was found to owe its blue coloration to the high concentrations of Co (0,080%) and Cu (0,021%), elements known as common coloring agents in glass. Additionally, the statistical analysis of the elemental compositions before and after the cleaning of the glass fragments was keen in classifying the samples according to their prior proximity within the excavation site and also their state of corrosion. Finally, regarding the results of the clay matrix, we reached the conclusion that it was used for the smelting of small glass items, probably decorative elements or jewels. The inner surface of the molds did not exhibit any signs of modulation targeted in engraving certain pictorial elements onto the resulting item's surface.

Jaar van publicatie:2011

Trefwoorden:ancient glass, micro-XRF, ICP-AES, ICP-AAS, statistical analysis