Study of blue colour in ancient mosaic tesserae by means of thermoluminescence and reflectance measurements

Gallí, Anna; Poldi, Gianluca; Martini, M.; Sibilia, Emanuela; Montanari, C.; Panzeri, Laura

doi:10.1007/s00339-006-3588-y

Cited by 20 publications

(10 citation statements)

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“…The occurrence of some kind of crystallization of the siliceous matrix during time seems to have occurred, and this could account for the higher TSL efficiency observed in ancient samples. The observation of TSL features as a function of the cobalt and copper concentrations did not give evidence of any strong correlation, contrary to what previously supposed [3]. For what concerns copper, curve shape and peak intensity are independent on the amount of its abundance in the matrix, and its presence is nicely evidenced by a characteristic broad band in the reflectance spectrum centred at about 450-480 nm, due to the copper (II) d-d transitions [4].…”

Section: Methodscontrasting

confidence: 85%

“…The ancient blue tesserae, whose coloration is due to cobalt and copper ions, usually have relatively high TSL sensitivity that was tentatively attributed to the colour centres induced by specific colouring ions. Through reflectance measurements the identification of the colorant ions could be easily performed and interesting relationships between concentration of colorants and features of the reflectance spectra were observed [3,4]. …”

mentioning

confidence: 99%

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Thermoluminescence and visible reflectance spectroscopy applied to the study of blue‐green mosaic silica‐glass tesserae

Gallí

Poldi

Martini

et al. 2007

Phys. Status Solidi (c)

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We report the results of a series of measurements of Thermally Stimulated Luminescence (TSL) and visible reflectance spectrometry (vis-RS) performed on several modern blue-green silica glass mosaic tesserae. They were produced from the same matrix with different additions of colouring and opacifying oxides to get a wide shadow of blue colorations. This study follows others previously performed on archaeological mosaics, and aims at the understanding of the TSL emission of this class of glasses, particularly suitable for dating. The usefulness of the combined techniques for the identification of the metal ions responsible for the blue coloration in a given sample is confirmed as well as the positive role played by antimony in enhancing the TSL response. In general, however, the TSL characteristics of mosaic glasses depend on the glassy matrix and on its crystallisation degree rather than on the formation of colour centres associated to the introduction of colouring oxides. 1 Introduction Pure silica glass is colourless, with melting point at about 1400 °C. As a glass, it has an irregular lattice lacking in long-range order. Because of this irregularity, other elements can be incorporated into it, extremely changing its properties. This was indirectly achieved in antiquity as a consequence of the production technology (addition to the siliceous base of fluxes like soda potash and lead oxide to lower the melting point to 800-1000 °C and incorporation of stabilizers like lime, magnesia or alumina) or with a deliberate inclusion of colouring and opacifying ions (through copper, cobalt, manganese, iron, antimony and tin oxides). Most optical properties of glass depend on the presence of low concentrations of specific ions. For the characterisation of glasses, the chemical composition is therefore an important but non exhaustive starting point. Both TSL and reflectance measurements, strongly depending on the presence in the matrix of very small concentrations of impurities, have shown their potentiality and can add useful information to the optical properties of these materials. Ancient mosaic glasses are under study for their promising characteristics for TSL dating [1] and have been deeply analysed before [2]. The ancient blue tesserae, whose coloration is due to cobalt and copper ions, usually have relatively high TSL sensitivity that was tentatively attributed to the colour centres induced by specific colouring ions. Through reflectance measurements the identification of the colorant ions could be easily performed and interesting relationships between concentration of colorants and features of the reflectance spectra were observed [3,4].

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Section: Methodscontrasting

confidence: 85%

mentioning

confidence: 99%

Thermoluminescence and visible reflectance spectroscopy applied to the study of blue‐green mosaic silica‐glass tesserae

Gallí

Poldi

Martini

et al. 2007

Phys. Status Solidi (c)

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“…Figure 9b explains how the different profiles of the curves and the percentages of reflectance can be related to the contents of copper oxide in the matrix, responsible for the light blue chromatic shades, as well as to the presence of PbO, enhancing the brilliance of the tesserae and, therefore, resulting in higher lightness (Figure 9c). The dark blue tessera DR_B1 showed a completely different reflectance curve, consistent with those reported in the literature for tesserae coloured by the addition of cobalt [78,79]. A combined SEM-EDS and micro-Raman approach allowed an in-depth analysis of the micro-structures of the tesserae belonging to NCS-Blue category, and the results demonstrated that they were all (but DMS_10L and DR_B1) opacified with powdered bone ash.…”

Section: Colouring and Opacifying Agentssupporting

confidence: 86%

A Tale of Two Legacies: Byzantine and Egyptian Influences in the Manufacture and Supply of Glass Tesserae under the Umayyad Caliphate (661–750 AD)

Fiorentino

2021

Heritage

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The connection between Umayyad and Byzantine mosaic manufacture is a debated issue: on the one hand, Arab sources report that Umayyad caliphs received craftspeople and materials to adorn religious buildings from the Byzantine emperor; on the other hand, the reliability of these texts has long been disputed among scholars, and other possible influences have been hypothesised. Was early Islamic mosaic manufacture related to Byzantine tradition and to what extent? Were materials and artisans gathered from Byzantium and/or territories under the Byzantine control? Based on a multi-analytical approach, glass tesserae from Khirbat al-Mafjar, the Great Mosque of Damascus, and the Dome of the Rock have been analysed. Results speak of a tale of two legacies, demonstrating that, parallel to a continuity with the manufacture of glass tesserae in the late antique Levant—pointing, more specifically, to a re-use of materials from abandoned buildings—legacies other than Byzantine occurred. It emerged that Egypt definitively played a role in mosaic making during the Umayyad caliphate, acting as a supplier of skilled artisans and materials.

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“…The pioneering works by Bamford [71] and by Schreus and Brill [73] set the basis for the measurement of the absorption properties of a glass system in transmission mode. Subsequent works exploited the same method [12,16,75], using either sunlight or specific light sources, while other studies exploited the reflectance mode [76][77][78]. Both transmittance and reflectance, in fact, display the same electronic transitions [79].…”

Section: Glassmentioning

confidence: 99%

UV-Vis spectroscopy

Picollo

Aceto

Vitorino

2018

Physical Sciences Reviews

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Abstract UV-Vis reflectance spectroscopy has been widely used as a non-invasive method for the study of cultural heritage materials for several decades. In particular, FORS, introduced in the 1980s, allows to acquire hundreds of reflectance spectra in situ in a short time, contributing to the identification of artist’s materials. More recently, microspectrofluorimetry has also been proposed as a powerful non-invasive method for the identification of dyes and lake pigments that provides high sensitivity and selectivity. In this chapter, the concepts behind these spectroscopic methodologies will be discussed, as well as the instrumentation and measurement modes used. Case studies related with different cultural heritage materials (paintings and manuscripts, textiles, carpets and tapestries, glass, metals, and minerals), which show the usefulness of UV-Vis reflectance spectroscopy and microspectrofluorimetry applied to the study of artworks, will also be presented.

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Study of blue colour in ancient mosaic tesserae by means of thermoluminescence and reflectance measurements

Cited by 20 publications

References 9 publications

Thermoluminescence and visible reflectance spectroscopy applied to the study of blue‐green mosaic silica‐glass tesserae

Thermoluminescence and visible reflectance spectroscopy applied to the study of blue‐green mosaic silica‐glass tesserae

A Tale of Two Legacies: Byzantine and Egyptian Influences in the Manufacture and Supply of Glass Tesserae under the Umayyad Caliphate (661–750 AD)

UV-Vis spectroscopy

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