Raman and scanning electron microscopy and energy‐dispersive x‐ray techniques for the characterization of colouring and opaquening agents in Roman mosaic glass tesserae

Abstract

Mosaic tesserae, part of Roman villa floor decorations, from north-eastern Sicily and the Aeolian Islands, were analysed by means of micro-Raman spectroscopy and scanning electron microscopy-energydispersive x-ray techniques. Archaeologists considerate these 'villa' floor decorations (ranging from the 2nd century BC to the 4th century AD) as a stylistic product of North African workers or North Africanstyle design that were imported from abroad. Much attention is paid in the technology of glass making in order to understand the capability of local workers to produce the same glassy material. Since the other coloured tesserae are definitively recognized as polished limestones and/or calcscists of well-known Sicilian geological formations, the glassy materials could be hypothetically interpreted in the same way. Spectroscopic and mineralogical techniques were applied to the materials in order to define both the colouring and opaquening agents. Bindheimite (Pb 2 Sb 2 O 7 ), well known in past as 'antique yellow', was always found in both green and yellow glass tesserae, acting either as a colouring and/or an opacifier agent. Investigations were made in order to consider the possibility of local manufacturing techniques on the basis of widespread easy-to-find complex sulfide ore deposits in the area.

Non–Destructive Raman Analysis of Ancient Glasses and Glazes

“…Interesting studies dealing with the Raman characterization of historic glass were first published at the end of the 1990s and were initially mainly devoted to the analysis of pigments, in stained glass windows [48] as well as in nineteenth-century British glazed roof tiles [49]. The identification of colouring and opacifying minerals in ancient glasses, often accompanied by the identification of glass type, has been the object of a certain number of studies on Roman mosaic tesserae [50,51,52], a wide range of beads, rings and mosaic tesserae from Ifriqiya [52], on Omayyad tesserae [53] and on trade glass beads from South Africa [33] and the Far East [54]. Further studies have regarded the corrosion processes and the identification of degradation products of glass objects in museum deposits [55][56][57] and of stained glass windows [58,59].…”

Characterisation of inorganic pigments in ancient glass beads by means of Raman microspectroscopy, microprobe analysis and X‐ray diffractometry

“…Many reports have been published dealing with Raman spectroscopy on pigments in ancient manuscripts, 1 paintings, 2 faiences 3 or mosaics. 4 In this paper we present the identification of pigments in ancient glass beads by means of Raman microspectroscopy. Moreover, we demonstrate that Raman microscopy may provide information about the crystalline and the amorphous phases of the glass at the same time.…”

Raman spectroscopy in art and archaeology

“…It seems that completion of the technique with x-ray fluorescence (XRF) spectrometry is a good combination, especially as today in situ XRF instrumentation is becoming available. Examples of this approach are given by Rosi et al 6 and Ricci et al 7 The combination of Raman spectroscopy and scanning electron microscopy is discussed by Galli et al 8 Proton-induced X-ray emission (PIXE) is another option for elemental analysis, which can be combined with Raman spectroscopy. 9,10 In the paper by Ruiz-Moreno et al, 11 fluorescence spectroscopy is tested as a complementary technique for the analysis of pigments.…”