Ancient glass deterioration in mosaics of Pompeii

Abstract

The aim of the present project is to evaluate the deterioration degree of ancient glass surface used as mosaic materials (tesserae) in Pompeii's 'ninfei a scala'. Specimens come from the fountain in the 'Domus del Centenario' (Pompeii, IX, 8), built starting from the 1st century AD and have been studied within a broader project on the Domus involving archaeologists, engineers, geologists, chemists and materials scientists. Using data from both non-destructive analyses (OM, XRD, SEM-EDS and UV-VIS) and those requiring few milligrams of specimens (DTA-TGA and ICP-AES), a complete database of the tesserae based on classification by colour, materials characterisation and evaluation of their deterioration have been constructed. After characterisation, specimens were replaced in their original position in the mosaic using suitable mortars. One of the glassy tesserae that was analysed for surface deterioration gave interesting results. The glass, coloured opaque red from Cu 2 O micrometric crystallisation, turned green on the surface as a result of copper and lead leaching out and depositing as carbonate and sulphate salts. The glass production technology appeared to be very similar to that found in Nimrud (north Iraq) during the 8th century BC, the glass showing a similar chemical composition and deterioration. The identification of colour variations makes it possible to correctly read the decoration system and the archaeometric analysis will help to identify the site and production technique of materials.

Evidences of glass-ceramic white opaque tesserae from Roman age: A thermo-analytical approach

“…This is a significant finding that integrates the current knowledge about glass manufacturing in the Roman Age [5,8,10]: as far as the analyzed tesserae is concerned, it is reasonable to hypothesize that Roman craftsmen bought chunk, sheets or even tesserae of a relatively cheap, colourless and transparent glass and, in a second manufacturing step, deliberately heat-treated the raw glass to transform it in a glass-ceramic material to be used in the final form of opaque white tesserae. This hypothesis can be also supported by the observations of other authors, who found partially crystallized opaque glass tesserae [11,12].…”

A non-invasive study of Roman Age mosaic glass tesserae by means of Raman spectroscopy

“…2. Almost all of the Italian samples have already been the object of archaeometric studies dealing with specific historical and/or technological issues, most of which have been published (Abu Aysheh, 2006;Boschetti et al, 2007;Corradi et al, 2005;Macchiarola and Fontanelli, 2008;Macchiarola et al, 2006Macchiarola et al, , 2007Santagostino Barbone et al, 2008;Santoro et al, 2006). Table 2 contains selected chemical compositions determined by ICP-OES analyses (some of which during these previous analytical works, as referenced in the table).…”

“…Fragment MAC20 stands as an exception among the red samples; it belongs to a rare typology of red mosaic glasses found at Pompeii, which are strongly altered and have developed degradation products in the form of Pb-carbonates and Cu-oxides/hydroxides (Corradi et al, 2005), and a consequent greenish appearance (''turquoise'' color due to Cu 2þ ). Its chemical composition, extremely rich in copper (w9% CuO) and lead (w30% PbO), makes this sample more similar to European Iron Age opaque red (enamel) glasses than to Roman ones (Stapleton et al, 1999).…”

The Interaction Between a White Material Inside and Outside a Pottery Vessel From Eastern Ein-Shams, Egypt

“…Understanding the properties of ceramic artifacts can help care for them correctly [8] (Figs 2a and 2b). DTA gives a complete database based on classification by color, materials characterization, and evaluation of their deterioration [10].…”