A Study of Glass Tesserae From Mosaics in the Monasteries of Daphni and Hosios Loukas (Greece)

Abstract

In this work 51 glass mosaic tesserae from decorations of the two Greek monasteries of Daphni and Hosios Loukas were analysed by inductively coupled plasma optical emission spectroscopy, electron microprobe analysis and X‐ray powder diffraction. On the basis of the chemical analyses, after discrimination between the tesserae of the original decorations and those from other periods, it was possible to outline the distinctive traits of Byzantine mosaic tesserae. In both the monasteries, the original mosaics were decorated with tesserae produced with plant ash based glass, either of the typical composition or a mixture with natron type glass. The samples from the Hosios Loukas decorations show a more homogeneous composition compared with those from Daphni. The major differences among the original samples are due to the presence of opacifiers and colourants.

Chemical characterisation of glass mosaic tesserae from sixth-century Sagalassos (south-west Turkey): chronology and production techniques

“…3C). Copper is the main colourant in conjunction with increased levels of iron and lead that seem to aid the precipitation of metallic copper within the glass matrices to obtain the deep red colour (Barber et al, 2009;Brill and Cahill, 1988;van der Werf et al, 2009). The red tesserae also exhibit elevated levels of chromium, nickel and arsenic relative to the other samples analysed in this study (Table 2).…”

“…Substantial amounts of lead oxide (w2e14%) accompany these colourants in the green and red and two of the peacock coloured samples and some lead is present also in the semi-translucent blue tesserae from the Roman Baths (for the significance of lead in red glasses see e.g. Barber et al, 2009). The highest amounts of lead, however, are found in the yellow tesserae where it acts as both the colouring and opacifying agent in the form of lead antimonate (Tables 1 and 2).…”

“…Similarly, older material seems to have been incorporated alongside medieval Byzantine tesserae in the eleventh-century CE mosaics of the monastery of Daphne near Athens. Differences in the type of tesserae used in the mosaics at Daphne and those of the roughly contemporary monastery of Hosios Loukas were ascribed to differences in the availability of glass and/or tesserae (Arletti et al, 2010). Studies such as these illustrate how the analysis of glass tesserae can offer fundamental insights into the supply and origin of materials, the chronological attribution of mosaics, and consequently about the organisation of mosaic workshops and artistic practices (James, 2006(James, , 2010.…”

“…Despite the vast amount of archaeological material from the later Roman and Byzantine world either in the form of mosaics in situ or from excavated collections of loose tesserae only a limited number of analytical studies of Byzantine glass tesserae have been carried out to date (Andreescu-Treadgold and Henderson, 2006;Arletti et al, 2010;Fiori et al, 2003;Freestone et al, 1990;Marii and Rehren, 2009;Shugar, 2000;Veritá, 2009). The present paper reports the analytical results of two sets of glass mosaic tesserae from sixth-century contexts at Sagalassos in Asia Minor.…”

The palaeo-Christian glass mosaic of St. Prosdocimus (Padova, Italy): archaeometric characterisation of ‘gold’ tesserae

“…Some authors have addressed the problem of classifying mosaic glass (Ruffini et al, 1999a(Ruffini et al, , 1999bVerità, 2000;Brill, 2002;Fiori et al, 2004;Andreescu-Treadgold et al, 2006;Vandini et al, 2006) and identified some important differences on chronological and geographical bases, starting with the use of various raw materials, colourants and opacifiers. However, a systematic and extensive study on glass mosaics has not yet been undertaken; those carried out so far (e.g., Freestone et al, 1990;Brill, 1999;Verità, 2000;Verità et al, 2002;Verità and Vallotto, 2003;Henderson, 2004;Verità and Zecchin, 2007;Boschetti et al, 2008;Arletti et al, 2008aArletti et al, , 2008bvan der Werf et al, 2009) mainly focus on a few samples coming from the same site, probably due to the value and availability of the material, often still in situ, and cover various periods of time, often not contiguous with one another. The possibilities offered by the specific case under consideration here e of working on more than 3000 loose tesserae characterised by a full range of colours e is an unique occasion for careful and precise analytical study on palaeo-Christian glass mosaics.…”