Abstract: Archaeometric research on glass artefacts is continuously evolving and is converging towards a multidisciplinary research domain where different types of techniques are applied depending on the questions asked and the circumstances involved. The technique described in this work is optical spectroscopy. The benefit of this technique being the possibility of building up a knowledge database for a large amount of material in a relatively short period of time and with a relatively limited budget. This is of particular interest for the investigation of extensive and/or unexplored glass collections where a first-line analysis of artefacts could facilitate the selection of material needing further and more detailed examination. This publication explores the extent to which optical spectroscopy can be used for a first-line analysis of green coloured glass artefacts from the Roman period. It is shown that the colour coordinates calculated from the measured transmission spectrum could reveal information about the fragment under study. In particular it is shown that 1) based on the position of the calculated colour values on the colour diagram (CIE1931) one could easily know whether the artefact was coloured using only iron or if copper oxides were also present. In the case of the artefact owing its colour solely to the presence of iron, the distance between the measured colour values and the colour diagrams white point can roughly indicate the iron concentration of the sample; 2) artefacts that were fabricated under similar furnace conditions can also be identified on the colour diagram; 3) samples with identical compositions and fabrication conditions but with different sample thickness, gave rise to a variation in the colour coordinates, thus allowing optical spectroscopy to help identify fragments which might belong to the same object.

Abstract: Altare was in the medieval and post-medieval period an important glassmaking center in the Liguria region in Northern Italy. The first historical evidence of glassmaking in Altare is dated to the twelfth century. In spite of that, due to the continuity of glassmaking up to the present time and the contemporaneous intensive urbanization of the territory, no medieval glass from Altare or its immediate vicinity has been analyzed up to now. In this work, glass from archaeological excavations in the center of Savona, city with close ties with the glassmaking center, was studied. Glass fragments, dated from the tenth to the sixteenth century were selected from the collections of the Archaeological Museum in Savona and non-destructively analyzed with quantitative PIXE-PIGE. The resulting compositions, compared with known glass productions of the same time and evaluated on the basis of historical documents, offer an interesting panorama on the variety of glass circulation in Liguria. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract: The research on the use of obsidian in the Mediterranean is extensive but concerns almost exclusively volcanic glass from prehistoric and Bronze Age contexts. The consumption of obsidian during the Roman imperial period, however, has only occasionally received attention. Never a comprehensive account on what the Romans made in vitrum obsianum has been set up, nor have the sources exploited by them been examined. This paper provides a concise overview of the current knowledge on obsidian during the Roman imperial period and offers an introductory outline on potential research. The ancient writers inform us about the use of volcanic glass to create exclusive vessels, gemstones, mirrors and sculpture, but also about the creation of black appearing man-made glass initiated as a cheap and easier workable substitute of obsidian. The archaeological data on the other hand propose a more complex story with the occurrence of obsidian chunks in early Roman secondary glass workshops, and the bulky use of obsidian in late Antiquity to produce tesserae for the creation of wall and vault mosaics. Because it is extremely difficult to visually distinguish natural obsidian from man-made glass imitations we present in this paper data collected by means of non-destructive chemico-physical analyses SEM-EDX, portable X-ray fluorescence (p-XRF) and Raman spectroscopy to easily distinguish man-made glass from natural obsidian. In particular the use of portable instruments makes possible in situ analysis of objects in archaeological depots or museum collections to help defining distribution networks to better understand the shifting consumption patterns in Antiquity.