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L’usage de plomb dans les émaux est présenté à travers deux productions ; les émaux champlevés sur cuivre du Moyen Âge et celle des cuivres émaillés « dits vénitiens » de la Renaissance. Après une brève description de leur histoire, forme, style et technique de fabrication, les recettes verrières des émaux blancs et turquoise sont données ainsi que l’origine du plomb.

Un aperçu de l’usage du plomb dans les recettes de verres opaques et translucides du Moyen Âge et de la Renaissance est proposé. Ces données, consacrées essentiellement aux fausses gemmes, aux émaux et tesselles de mosaïque, sont comparées autant que possible aux analyses chimiques de verres dont nous disposons.

The materials uncovered in excavations in several provinces of the Roman empire provide important evidence to the frequent use of glass in most precious opera sectilia. Glass pieces imitating a dozen of ancient marbles and exotic stones have been identified in the collection belonged to Evangelista Gorga, samples of which were selected for analysis in order to obtain valuable information on the Roman glassmaking technology of the 2nd century AD, especially on coloration techniques. The monochrome and polychrome glass tesserae replicating precious marbles and rare stones were: porfido verde antico, litomarga verde, turquoise, pavonazzetto, gabbro eufotide, diaspro nero e giallo, semesanto, alabastro tartarugato, rosso antico, cipollino rosso, giallo antico, and onyx. XRF quantitative chemical composition was determined allowing the types of glass used and the colouring techniques to be identified. Results have been compared with similar data obtained by studies on coloured Roman glass and mosaic tesserae. Similarities and discrepancies are discussed and hypotheses are suggested on the technology of this extraordinary Roman production.

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This work aimed to investigate the origin of different red hues of Roman copper-based red opaque glass sectilia, to shed light on the production technology behind them. This objective was achieved by the depth study of the samples of glass sectilia, which decorated the villa of co-Emperor Lucius Verus (161&ndash, 169 AD). These were selected for analysis due to their abundance, the certainty of their date and of their different red and orange hues. Using OM (optical microscopy), colourimetry and FORS (fibre optical reflectance spectroscopy) spectroscopy, four red and four orange hues were individuated. A set of representative samples for each hue was analysed by EPMA (electron probe microanalyses) to detect any correlation between colour and chemical composition. Crystalline phases were investigated through high-resolution FEG&ndash, SEM (field emission gun scanning electron microscope), &mu, Raman spectroscopy and XRD, for the identification of colouring and opacifying agents and to understand how the different hues are affected by their shape, concentration and dimension. Sub-micrometric particles of metallic copper and cuprite crystals were identified as both the colouring and opacifying agents. These were not present in the same samples and were manufactured by two distinct colouring techniques, corresponding to two different glass chemical compositions. The size and the number of the colouring particles were the main factors that distinguished one hue from another. Although produced through different colouring techniques, some red samples appeared to be very similar to each other. These data enrich a period of the Roman age through some analyses and allow the identification of the type, as well as some of the production conditions of opaque red glass produced during 2nd century AD, which could be considered to be a period of transition from one technology to another.

The Villa del Casale at Piazza Armerina (Sicily) is world famous for its beautiful and extensive mosaic floors dating to the fourth-century A.D. Before a recent restoration of the Villa, it was possible to take a representative sampling of coloured glass and stone tesserae from the baths’ floors that were examined by chemical and minero-petrographic analysis, respectively, with the goal of determining the production-centre/s of the glass, and the provenance of the stones. The laboratory techniques used were SEM-EDS on polished sections, powder XRD and polarised OM on thin sections, extended to reference stones found in a Villa’s ancient storehouse. The obtained results had shown that the white and pinkish tesserae were exclusively made of local (from the Caltanissetta province) limestones, while the black ones were cut from an obsidian, likely of a Liparote origin; the turquoise and gold-leaf tesserae were exclusively made of glass manufactured according to the Roman and Byzantine tradition while both stone and glass were used for the dark and yellow hues (giallo antico was identified among stone yellow hues). As for the glass tesserae, the results of the chemical analysis of a few samples (mostly erratic) have allowed to date them to the fifth- to sixth-century and to the eighth- to ninth-century A.D. and thus to testify to a hitherto unknown ancient restoration of the Villa mosaics.

The so-called Venetian enamelled coppers are a group of objects produced in Italy during the 15th century. Up to now, about 300 objects have been recognized in private collections and in European and US museums. At the end of 19th century, a Venetian origin was suggested, but their provenance is still debated. In this study, the enamel compositions from 22 enamelled copper products from Italian and French collections have been analysed by invasive and non-invasive techniques. A comparison of the results with Tuscan and Venetian glass databases reinforces the suggestion of a Tuscan (most probably Florentine) origin for these works of art.

This study focuses on the Byzantine glass tesserae from Hierapolis (Phrygia, central Turkey). Fifty-seven samples of loose tesserae from two sites in the town (the theatre and the church of St. Philip) are analysed by particule-induced X-ray emission and particule-induced gamma ray emission and electron probe X-ray microanalysis to obtain the chemical composition and identify the colourants and opacifiers. The aims are to add new information to the scant knowledge of the Byzantine glassmaking technology, to constrain the chronology of the mosaics and to trace the supply routes of the tesserae. In the destruction layers of the theatre, tesserae produced following the Roman glassmaking technology (natron glass opacified by calcium and lead antimonate) were found. They were made using a Levantine 1 raw glass, generally attributed to the early Byzantine period (fifth to sixth c.). In the church, the samples attest a technological change from Roman tradition, and a complex pattern according to building history (two phases are attested, probably in the sixth and eighth to ninth c.), and a multiplicity of supply. Three glass types and some recipes not attested before in this chronological range for the production of tesserae are documented, such as the use of a local low-chlorine natron glass for the production of black and red tesserae, the blue colouring by a source of cobalt with zinc in a natron glass tessera and the opacification with tin oxide (both in a lead-free and in a high-lead natron glass), as well as with quartz.

The Basilica di Santa Croce (Basilica of the Holy Cross) is the major Franciscan church in Florence (Italy). Among the prominent masterpieces preserved in this church, there are 22 medieval stained glass windows. Between 2000 and 2013, the Opera di Santa Croce started a restoration campaign of six of the most important ones, dated 14th c. In this paper, the archaeometric data collected during the restoration campaign are reported. Two major base glass compositions (potash-lime-silica and soda-lime-silica) were identified by quantitative chemical analysis. Results are compared with similar investigations on Italian stained glass windows of the 14th-15th centuries and many similarities are highlighted. Some interesting "secrets" of the coloring techniques based also on multilayer glass pieces were revealed. Finally, SEM-EDS analyses allowed the main weathering glass phenomena to be investigated.

studio smalti dell'Altare di San Giovanni, Firenze

The considerable amount of research carried out up to present time in an attempt to understand the production technique of Egyptian blue frit is based on analyses of the ancient pigment and its laboratory synthesis. The fortunate finding in Roman Liternum of 1st century AD fragments of ceramic crucibles with adhering remains of a blue pigment allowed laboratory analyses (OM, XRD, SEM–EDS) to be performed on original production debris. The results confirm that the crucibles had been used for the synthesis of Egyptian blue frit and throw new light on the controversial issue of the Roman manufacturing technique of Egyptian blue frit. The results of the analyses indicate that the Egyptian blue frit was produced with a mixture of a local source of silica–lime sand, a fluxer (not identified) and copper scale; the crucibles were also made with local raw materials. The firing of the batch was performed at a relatively low temperature, probably around 850 °C and firing at higher temperatures would have hindered the formation of the cuprorivaite crystals. The analyses suggest that the evaporation of copper during firing of the batch attested in this study is one of the most critical parameters influencing the final blue pigment hue.

The results of an archaeometric trial study performed on an important finding of Renaissance maiolica (mid-15th to early 16th century) from the Ducal Palace of Urbino are presented. Mineralogical–petrographic data (XRD, OP, SEM–EDS) and chemical characterization (ICP/AES–MS: major and trace elements) of both ceramic bodies and glazes were compared with similar data provided on coeval maiolica found in archaeological excavations in Pesaro, now stored in the city's Municipal Museum, in order to verify an origin of the potteries from common (Pesaro) or different (Pesaro and Urbino) production centres. The results indicate that ceramic bodies were produced with quite similar illitic–calcareous clays, most probably taken from the same local Pliocene Formation. Similarities were also found concerning the glaze's glass (silica–lead), colourants (cobalt, copper and manganese) and pigments (lead antimonate and cassiterite).

Fifty-eight gold leaf tesserae from eight archaeological sites situated in the Byzantine Empire and two Early Islamic (one in medieval Palestine), covering the period that goes from the 4th c. to the 12th c., were analysed by EPMA, SEM-EDS and PIXE-PIGE to determine the composition of both the glass and the gold leaves. The good match until the 6th c. between circulating monetary alloys and the gold leaf compositions together with the type of glass used, provided criteria that can be used to date the tesserae fabrication. The data obtained allow newly produced tesserae to be distinguished from re-used ones. Because after the 7th c. the circulation of gold in the Byzantine Empire was less controlled, the same relationship is harder to establish. The results suggest the existence of workshops in the Eastern and Western part of the Mediterranean and a more advanced technology to manufacture a palette of glass colours for gold leaf tesserae in the Eastern region.

The enamels of the Altar of San Giovanni, from the Baptistery of Florence, were investigated using both non-invasive and micro-invasive analysis in order to elucidate the glass melting and colouring techniques. A few fragments detached from the altar and recovered by the restorers were analysed in cross-section by electron probe microanalysis. Moreover, non-invasive investigations by portable XRF allowed a large number of enamelled plaques to be investigated. The results showed a good agreement between the two techniques and made it possible to identify similarities or differences in the enamels of the three manufacturing periods of the altar.

Venetian enamelled glass is one of the most significant subjects of the art and technology of Renaissance glassmaking. These items were made in Venice from the second half of the 15th through the 17th centuries and were imitated in other European glassmaking centers during this period and again in Murano during the 19th century. Only a limited number of analyses of these masterpieces have been published up to now. In this paper the non-invasive PIXE–PIGE technique was applied to analyse the glass and enamels of eleven objects from the Louvre collection. The results disclose interesting details on the glassmaking technology and the raw materials and colourants used. The comparison between these data and the recipes in Venetian glassmaking treatises allowed identifying a group of objects corresponding to the genuine Venetian Renaissance production, while some discrepancies were found for other objects, probably being ascribable to a contemporary production outside Venice (facon de Venise) or to a 19th century Muranese manufacture.

The glass jewellery collection of Archduke Ferdinand II, today part of the Collection of Sculpture and Decorative Arts, Kunsthistorisches Museum, Vienna, Austria, is a rare example of early modern lampwork. The small glass items, made by shaping fine glass rods and tubes in front of the flame of an oil lamp, date from before 1596. Although lampworked glass objects must have been popular collectibles, only a few pieces have survived. Therefore, the examination of this collection is a unique opportunity for the study of sixteenth-century lampworking technology. The rarity of the glass objects limited the examination to non-destructive methods. Optical microscopy provided an overview of the glass colours and surfaces. Subsequently, non-invasive portable energy dispersive X-ray fluorescence analysis (XRF) was carried out to classify the glass types. Further invasive investigations were carried out with micro-invasive electron probe microanalysis (EPMA) and energy dispersive X-ray microanalysis in a scanning e...

A set of ten Millefiori glass fragments dating from the 17th century, originated from archaeological excavations carried out at the Monastery of Sta. Clara-a-Velha (Coimbra, Portugal), were characterized by X-ray electron probe microanalysis (EPMA), Raman microscopy and UV–Visible absorption spectroscopy. All glasses are of soda-lime-silica type. The use of coastal plant ash is suggested by the relatively high content of MgO, K 2 O and P 2 O 5 , as well as by the presence of chlorine. Tin oxide or calcium antimonate were the opacifiers used in the opaque glasses, cobalt in the blue glasses, copper in the turquoise glasses, iron in the yellow and greenish glasses, and iron and copper were found in the opaque red and aventurine glasses. Based on the concentrations of alumina and silica four different sources of silica were identified, allowing the classification of the glasses into the following compositional groups: low alumina ( cristallo samples with SiO 2 > 70 wt%, medium alumina (2–3 wt%), high alumina (3–6 wt%) and very high alumina (>6 wt%). Comparison with genuine Venetian and facon-de-Venise compositions showed that two fragments are of Venetian production, one of Venetian or Spanish production and the remaining are of unknown provenance. In two fragments the glass of the decoration is probably Venetian or Spanish but the glass used in the body is also of unknown provenance.

The study concerns the chromatic alteration of mosaic glass tesserae in the Sao Joao Chapel, Sao Roque Church in Lisbon. This precious chapel was commissioned by the King of Portugal, Joao V, in 1742. The polychrome marbles, stucco bas-reliefs, precious silver sculptures and three mosaic altarpieces were sent by ship to Lisbon. Alessio Mattioli, the glassmaker who produced the glass tesserae for the mosaics, was the famous inventor of new compositions for difficult colours in opaque glass such as red, orange, and the variety of flesh colours. In fact Mattioli succeeded in imitating the technique of painting to produce altarpieces that were “eternal”, or, at least, more durable in appearance than paintings. Our research is based on archive documents discovered in St. Peter's Fabrica in Rome concerning the decoration of the Sao Joao Chapel in the Sao Roque Church in Lisbon and the compositions of Mattioli's glass. The chromatic alterations producing conspicuous spots and shades of grey, brown, and white are similar to the alterations in many mosaic altarpieces in the Basilica di San Pietro in Rome, dating from the same period. The findings of the chemical analyses on glass and weathering products, are the first attempts to understand the weathering mechanism and to prepare a restoration and conservation plan.

The application of X-ray fluorescence to the study of the composition of ancient glasses has been limited by the large amount of material required for samples. In this paper the setting of a reduced sampling XRF method for the analysis of ancient glasses is described. The method involves the preparation of glass beads by melting the sample with lithium tetraborate flux. By means of reference and synthetic samples, the method allows regression curves to be set, covering broad ranges from ppm to high concentrations. By means of a single program, up to 31 elements of interest in the study of ancient glass are analysed. The reproducibility, sensitivity and reliability of the method are discussed. The results demonstrate that 0.2 g of glass is sufficient to obtain accurate and sensitive analyses for most of the elements of interest.

Portable energy-dispersive micro X-ray fluorescence spectrometry (-EDXRF) is a useful device for non-destructive chemical analysis of different materials. Despite its evident potential in the fields of glass analysis, only few archaeometric studies have been performed yet. In this work preliminary results on the analysis of different types of industrial glass by -XRF are presented in view to apply this method in industrial applications (monitoring of glass cullet, production quality control, classification of end products, etc.). The experimental results show a reliable qualitative recognition of detectable elements in the glass. A good correlation line intensity/concentration was verified for several important elements. Furthermore very low limits of detection were estimated for critical elements such as Fe, Cr and Pb.

Crystalline inclusions, commonly called stones, are very dangerous defects present in industrial glass products. Refractory materials of the furnace, raw materials and ceramic grains introduced with glass cullet, are the main sources of stones. To improve the quality of glass products, the understanding of the mechanisms responsible for the formation and the transformation of these defects is required. At the interface glass melt/stone surface several reactions occur leading to the formation of new glassy and crystalline micro-phases. These phases are usually studied by scanning electron microscopy and X-ray microanalysis on polished cross sections. Nevertheless SEM-EDX chemical analysis alone does not allow the complete identification of the different phases. In this work, the reactions occurring between refractory materials and the molten glass were studied with a micro-chemical and micro-textural approach completed by micro-structural investigation. Compositional and textural features were investigated by SEM-EDX and by μ-Raman spectroscopy. Raman spectra of pure crystalline well identified compounds were compared with those of the unknown phases. This technique allowed to identify the nature of the re-crystallized phases. The combined use of SEM-EDX and μ-Raman techniques revealed to be very promising in the study of the origin and in the characterization of stones in glass.

We report on micro-Raman spectroscopy as a tool to improve the quality of the industrial glass production. Crystalline inclusions, commonly called stones, are very dangereous defects present in industrial glass products. To minimize this technological problem, the detailed knowledge of the formation and transformation processes of these defects is required, and a complete identification of the different phases requires a multianalytical approach. Micro-Raman measurements were performed on a series of laboratory samples with different chemical compositions. Performing linear scanning and mapping of Raman features, we obtained a well-defined characterization of the evolution and nature of stones. In addition, information on the crystallization degree of the reaction layers was obtained by correlating the shape and intensity of the photoluminescence of Cr3+ impurities. Copyright © 2008 John Wiley & Sons, Ltd.

Quantitative chemical analysis is a powerful tool for the classification and discrimination of small glass fragments in forensic and archaeometric analytical issues. In the choice of the analytical method the small dimensions and the irregular shape of the fragments must be accounted for. Several accurate and highly sensitive instrumental techniques successfully employed for the chemical analysis of small glass samples (AAS, ICP-AES and FAAS) are destructive, and therefore unacceptable for these applications. X-ray analytical techniques such as WDXRF, EPMA and SEM/EDX provide means for rapid, non destructive and sensitive multi-elemental analysis of glass fragments. In this study the analytical sensitivity and accuracy of WDXRF, EPMA and SEM/EDX for the analysis of small commercial glass fragments are investigated. The results are compared and discussed in order to establish a relation between the minimum size of glass samples and the accuracy and sensitivity of the analytical methods.

The durability of glass depends both on its chemical composition and on the environment in which it is conserved. The glassy particles of smalt in samples from two sixteenth-century wall paintings in Rome were investigated to study the technology of glass melting and colouration, and the origin of the pigment discolouration. A potash–lime silica and an unusual soda–potash–lime silica were identified through analysis. These compositions were compared with recipes recorded in Italian medieval and Renaissance treatises that help understand the technology used in the preparation of smalt. The mechanisms of weathering are discussed in terms of glass durability in relation to its chemical composition and to aggressive environmental conditions. In the case of the two wall paintings studied here, smalt discolouration was found to be due to several factors: leaching of alkali, leaching of cobalt, formation of micro-cracks and glass corrosion.

Although Venice is regarded as being one of the most important centres of glass manufacture and trade in Western Europe, little is known about the origins of the Venetian glassmaking. Some archaeologists suggest there is a continuity in the history of glass making, in its transplantation from the Roman centres of the mainland (Altino and Aquileia), first to some islands of the lagoon, and later to the town. Some others, instead, think that there was no continuity at all and that the art of glassmaking was imported in Venice from the Islamic glass factories of the Middle East. Of great help in answering this and other technological questions is the information about the composition of ancient glass from well-dated excavations that allows to conclude on the early technology, sources of raw materials and long-distance trade. Some significant glass findings, including fragments of pots used for glass melting, were found on the island of Torcello and, more recently, in two emergency excavations in the historic centre of Venice. In this paper, the chemical composition of a large set of glass findings (and related materials) from the Venetian lagoon dating from the 7th to the 13th centuries is determined by X-ray microanalysis in order to throw new light on the glassmaking technology in the early centuries of the Venetian tradition. The results show that in this period there occurred a gradual transition from the Roman technique (a two-ingredient formulation with silica-lime sand and natron as a fluxer), towards the use of silica sand and soda plant ash. There is evidence, therefore, for a production continuity with the Roman period (melting pots and glass scraps with a natron-based composition), yet restricted to transparent blown items. No evidence was found for a local production of glass tesserae for the mosaics of the church of St. Maria Assunta in Torcello.

The original version of this article, unfortunately, contained error. Modifications have been made to the Introduction, Results and discussion, Conclusions and figure caption. The original article has been corrected.

Glass tesserae have been produced for use in mosaic decoration for more than 2000 years and constitute an important part of cultural heritage. They were applied to the architecture of pagan and religious monuments initially in the Mediterranean area, and later spread throughout the world. The paper examines the properties of vitreous mosaic tesserae, with particular reference to the techniques of glass melting, the colouring and opacification of glass pastes and smalti and the preparation of metal-leaf tesserae. Brief general information on the nature of glass, including its optical and mechanical properties and chemical durability are discussed and the manufacturing techniques and their development are described on the basis of historical sources and scientific analysis of finds. Particular reference is made to the different mixtures of raw materials used to make, opacify and colour glass in different centres of production in past centuries. The weathering mechanism of the tesserae is discussed, ...

The methodology of protecting the European stained glass windows against environmental risk (e.g. meteorological factors, air pollution, microorganisms) by means of an external glazing is not new. In spite of many scientific studies carried out in the last 20 years, some questions were still up for discussion. The European VIDRIO (2002–2005) project gave an answer to these questions. The research carried out by the different project partners established a new multidisciplinary approach aimed at evaluating the efficiency of the protective glazing systems and their effects on stained glass windows conservation, and finally at assessing the most appropriate strategy to preserve stained glass windows. Scientific results showed that the so-called isothermal glazing (i.e. ventilation by the air coming from the inside of the building) protected efficiently the ancient stained glass window from environmental attack (i.e. rain, pollutants, condensation, thermal shocks) with very limited secondary effects. The scientific research highlighted that its efficiency was strongly related to the technical design of the protective system. In particular, the ventilation and the size of the interspace had to be carefully considered. The research developed within the VIDRIO project was turned into general recommendations to the owners and practitioners on the best practice for the stained glass windows future conservation.

An archaeometric study was carried out on 40 gold leaf tesserae from mosaics in Italy dated 1st to the 9th century AD. Glass layers and gold leaf were both analysed by X-ray microanalysis. The main aim was the identification of the composition of the glass and of the gold leaf, in order to assess the variations in composition and nature of the tesserae in the examined period. The analytical results show that the tesserae were obtained with natron type glass; three compositional groups were identified, each characterized by a specific colour. The coexistence of colourless (antimony-manganese as decolourizer) and naturally coloured (manganese as decolourizer) glass in each mosaic suggests the simultaneous use of the two materials, probably related to aesthetic choices. The analyses of the gold leaves indicate the use of pure gold or of gold-silver alloys. The good matches between the compositions of the gold leaves and the analyses of contemporary gold coins in the late antique and byzantine samples (3rd–9th c.) suggest that the leaves were made by beating circulating gold coins. This, in some cases, can help the dating of the tesserae and a more precise information on the type of glass used in this period.

This work concentrates on the setting-up of conditions for the quantitative analysis of the composition profiles of major and minor components of float glass surfaces with an electron probe micro-analyser. Since surfaces are modified for depths of 10–50 μm, they have been studied both in polished cross-section and perpendicularly to the electron beam by varying its energy to investigate the near-surface region (0–3μm). The results demonstrate that combined use of the two methods supplies complete and continuous information on the quantitative distribution from large depths to the first layers of the float surfaces. The experimental conditions, sample preparation, in-depth and lateral resolutions, precision and accuracy of the methods are also investigated.

International audience; o prevent the soiling of glass window used in the built environment, the use TiO$_2$ coated products appears an important application matter. To test the cleaning efficiency and the sustainability of self-cleaning glass, a field experiment was conducted under real life condition, on a site representative of the background urban pollution. Samples of float glass, used as reference, and commercialized TiO$_2$ coated glasses were exposed to dry and wet atmospheric deposition during two years. The crossed optical, chemical and microscopic evaluations performed, after withdrawal, allowed highlighting a sensible difference between the reference and the self-cleaning substrate in terms of accumulation, nature, abundance and geometry of the deposit. This experiment conducted in real site emphasized on the efficacy of self-cleaning glass to reduce the maintenance cost

International audience; In order to analyse the self-cleaning mechanism of TiO$_2$-coated window float glass, a field experiment was conducted in Paris, at a site representative of background urban pollution. Two hydrophilic photocatalytic TiO$_2$-coated industrial glasses and a traditional float glass (reference) were exposed in unsheltered and sheltered condition for various time duration. The sheltered exposure allowed to study the soiling and self-cleaning mechanism without the disturbing effect of rain washing. In parallel, air filtrations were carried out in order to assess the chemical composition of airborne particulate.Analytical measurements were performed on the deposit and on the weathered glass layer. The analyses of the deposit on glass and of atmospheric particles on filters consisted in the determination of the organic fraction (organic carbon, particulate organic matter, water-soluble organic carbon), elemental carbon and the inorganic soluble fractions. The impairment of glass optical properties was followed by haze measurements. Investigation of the weathered surfaces was performed using EPMA and scanning electron microscopy (SEM)/EDX. Only a moderate weathering of the glass surfaces after 24 months of exposure was detected. The self-cleaning mechanism was evidenced by a significant decrease of the organic fraction in the deposit on the TiO$_2$-coated glasses.

In a previous paper the weathering of the internal surface of empty glass containers before filling was investigated. Several phenomena were identified and described such as leaching of modifiers, formation of a hydrated leached layer and of crystalline deposits mainly consisting of Ca-carbonates and Na-carbonates. Localised glass surface corrosion was sometimes also detected. The role of the storage conditions, time, temperature, relative humidity and concentrations of pollutant gases (CO2, SO2), in the weathering phenomena was highlighted [1]. In the present work the composition of the weathered glass layer and the nature of the crystalline deposits are investigated. Furthermore, in order to examine more closely the weathering mechanisms and their causes, the correlation between durability laboratory tests and chemical composition of soda-lime-silica glass are discussed. © 2008 Trans Tech Publications.

The stoichiometry of tin oxide incorporated in the bottom surfaces of float glasses has been studied by CEMS. Our results indicate the predominance in the investigated surfaces of the Sn(II) oxidation state, which is higher in the outer layer (some tens of nm) as compared to the inner one.

Metal leaf (gold, silver or their alloys) glass tesserae began to be used in wall mosaics in the first century AD (the first examples are in Rome) and their use has been uninterrupted up to day. The metal leaf could be obtained from circulating coins, jewellery or refining. According to various techniques that have changed over the centuries, the leaf was hot fixed between two glass layers. From an archaeological point of view, it is interesting to know when and where these tesserae were made, if they were new made or if they were reused tesserae recovered from earlier dismantled mosaics. The determination of the glass composition of the tesserae is not of great help in this connection, for the same kind of glass was used over long periods. Available information is still scanter for glasses produced between the 1st to 8th centuries when the batch of raw materials (a natural soda called natron and a silica-lime sand) was melted in large tank furnaces and chunks of raw glass were transported all over the Mediterranean to be remelted and shaped into manufacts in small pot furnaces. The SEM-EDS analysis is proposed in this study as a useful tool to investigate the composition of both the glass and the gold alloy in leaf tesserae from mosaics of the 1st - 9th centuries. The comparison of the composition of the gold leaf of the tesserae with that of circulating gold coins (for which an important analytical data base is available), adds further information to the glass analysis, allowing us to improve the dating of the tesserae and increase the knowledge that may result from scientific analyses. The results demonstrate that good quantitative analyses of the metal leaf can be performed and that metal leaves made of pure gold or gold-silver alloys were used.

When a glass is exposed to the atmosphere the combined action of water and environmental elements leads to the weathering of the glass surface. Both the chemical composition of the glass and the environmental parameters influence the mechanism of glass weathering mainly consisting in the formation of a layer of hydrated leached glass and salt deposits. The study of these phenomena is very important for both industrial and cultural heritage applications. In order to study the weathering mechanism of glasses exposed outdoor the chemical composition of the glass and the chemical and mineralogical nature of the reaction products should be determined. X-ray micro-analytical techniques such as scanning electron microscopy and X-ray microanalysis (SEM-EDS) and electron probe microanalysis (WD-EPMA) are traditionally employed in this type of investigation. Nevertheless particular compounds are hardly detected with this technique (for ex. nitrates) and no direct information can be obtained on the mineralogical features of the reaction products. Moreover, X-ray diffractometry (XRD) cannot be successfully used because of the very low amounts of deposited material. This work reports the results of a combined complementary X-ray fluorescence spectrometry (WD-XRF), SEM-EDS, WD-EPMA and μ-Raman spectroscopy (MRS) investigation on the surfaces of an industrial float glass and a glass reproducing the low-durable glass of ancient stained windows exposed sheltered outdoor for 6 months. The investigation enabled the identification and characterisation of different reaction products (soluble salts) confirming the need of this analytical approach for the study of the glass weathering process.

This work aims to characterise the chemical composition of Roman opaque red glass sectilia dated to the 2nd century A.D and to shed light on Roman glassmaking production of different shades of red, from red to reddish-brown. Due to the lack of technical historical sources for this period many questions about technological aspects still remain. In this project a multi-disciplinary approach is in progress to investigate the red glass sectilia with several red hues from the Imperial Villa of Lucius Verus (161&ndash, 169 A.D.) in Rome. First, colorimetric measurements were taken to identify the various red hues. The second step was chemical characterization of the samples and the identification of crystalline colouring phases. Particle Induced X-Ray Emission (PIXE) analysis was used to investigate the chemical composition of these glass samples, while the crystalline phases were identified by Raman Spectroscopy and Scanning Electrons Microscope with Energy Dispersive X-ray Spectrometry (SEM-EDS). Using SEM-EDS nanoparticles were detected as a colouring agent, the chemical composition and the morphology of which has been studied in depth. This information has been compared with the colorimetric analysis to establish any correlation with the different colour hues.