This PDF file contains the front matter associated with SPIE Proceedings Volume 8422, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

In this work a new approach to the physicochemical characterization of polychrome archaeological glasses through elemental maps is presented. It is the first time that elemental mapping both by Laser Ablation-ICP-MS and EPMAWDS was performed on ancient glass. The glass elemental mappings are here proposed as useful tools for a preliminary study of the overall pattern of a glass surface concerning each analyzed element. The visual inspection of the maps gives the distribution of the elements and their degree of homogeneity; this allows the identification of the correlations between elements, in order to get information about chromophores, opacifiers and their associated ores, as well as about the glass deterioration. The LA-ICP-MS quantitative elemental maps of 54 elements were performed on a glass sample area. The concentrations of the element oxides were visualized in pseudo-colors, both in 2D and 3D. EPMA-WDS elemental maps were performed on areas of surface and break-section of the samples, at the interface between bulk and decorations. LAICP- MS elemental mapping can be functional to the determination of the glass chemical composition patterns and of associations between elements, while WDS elemental mapping is mainly aimed to identify the distribution of crystalline phases or to visualize concentration gradients of elements at the interfaces of different areas, such as bulk and decorations. Both the techniques can be functional to the study of glass superficial weathering.

LA-ICP-MS is a well acquainted technique for the quantification of a wide range of minor and trace elements present in the glass matrix. The benefit to understand the changes in technological processes or the added value in assessing the provenance and chronology of the raw glass material is however rarely discussed. By selecting a set of 197 Roman black glass artifacts dating between the 1st and 5th century AD we aimed to contribute to this issue. The obtained data on the production of glass artifacts helps better understand the constantly evolving patterns in glass consumption throughout the Roman imperial period. The key trace elements linked with the sand generally show the use of Levantine and Egyptian raw glass to produce black glass artifacts and result in well defined clusters. These indications are evidence for the use of different raw glasses in the Roman Empire and therefore featuring the work of diverse workshops over time. Specific trace elements such as copper, cobalt and lead reflect the application of recycling glass in Roman times.

Opaque red glass has been extensively studied over the years, but its compositional complexity and variability means that the way in which it was manufactured is still not fully understood. Previous studies have suggested the use of metallurgical by-products in its manufacture, but until now the evidence has been limited. SEM-EDS analysis of glass beads from the early Anglo-Saxon cemetery complex at Eriswell, southeast England, has provided further insights into the production and technology of opaque red glass, which could only have been possible through invasive sampling. The matrix of the red glasses contains angular particles of slag, the main phases of which typically correspond to either fayalite (Fe2SiO4) or kirschsteinite (CaFeSiO4), orthosilicate (olivine-type) minerals characteristic of some copper- and iron-smelting slags. This material appears to have been added in part as a reducing agent, to promote the precipitation of sub-micrometer particles of the colorant phase, copper metal. Its use represents a sophisticated, if empirical, understanding of materials and can only have resulted through deliberate experimentation with metallurgical by-products by early glass workers. Slag also seems to have been added as a source of iron to colour ‘black’ glass. The compositions of the opaque red glasses appear to be strongly paralleled by Merovingian beads from northern Europe and Anglo-Saxon beads from elsewhere in England, suggesting that this technology is likely to have been quite widespread.

SEM-EDX and LA-ICP-MS analyses were performed on a set of early 17th century London glass fragments. The samples originate from two archaeological sites (Aldgate and Old Broad Street) where glass workshops were active in this period. The great majority of the samples are made of soda glass. Two distinct compositional groups are observed, each typical of one site of provenance. The samples originating from the Old Broad Street excavation feature a silica-soda-lime composition, with a moderate amount of potash. The samples from Aldgate are richer in potassium and feature higher amounts of trace elements such as Rb, Zr and Cu. The distinction between the two groups stems from different flux and silica sources used for glassmaking. A comparison with different European glass compositions of that time reveals no resemblance with genuine Venetian production, yet the composition of the Old Broad Street glass shows a close similarity to that of fragments produced ‘à la façon de Venise’ in Antwerp at the end of the 16th century. This coincides with historical sources attesting the arrival of glassworkers from the Low Countries in England and suggests that a transfer of technology took place near the turn of the century.

An extended set of 18th century glass vessels was analyzed by means of SEM-EDX (major and minor element composition) The fragmented archaeological objects were recovered from a latrine belonging to the early 18th century building phase of the nunnery of Clairefontaine, near Arlon (B). On the basis of typology and decoration, the major part of the vessels could be dated around the middle of the 18th century. Variety in color and weathering of the glass suggest differences in glassmaking recipes and in the composition and origin of raw materials. The results of the analysis show how two main compositional groups constitute about 90% of the analyzed glass set, and these are constituted by potash glass (transparent beakers) and high lime low alkali glass (green bottles). Next to these, a few potash-lime and soda glasses are also found. The type of alteration has also a clear relation with the original glass composition.

Raman spectroscopy is presented as a suitable and fast non-destructive technique to obtain qualitative information about glass samples of various origins (ancient and modern/industrial glass). A first application is the broad corpus of archaeological window glass that still needs to be investigated. For many sites, archaeologists have to deal with large collections of excavated glass samples and a selection of the most appropriate samples for chemical analysis is necessary. A fast classification can be made based on Raman spectra: different kind of glasses (Alkali-glass, High Lime-Low Alkali glass (HLLA)) have their own typical Raman signature. Even for glasses giving strong fluorescence, a classification is possible after a simple treatment of the Raman data. Raman spectroscopy has also been utilized to identify iron containing glasses. The effect of the iron content in glass samples is reflected on the topology of the Raman spectra: a strong link between the ratio of the Q₂/Q₃ vibration units of the silica tetrahedral structure is seen. Even (semi-) quantitative results can be determined from calibration lines if matrix effects are taken into account (similar glasses). In amber colored glasses, an extra peak ~415cm^-1 in the Raman spectra indicates the presence of a Fe-S chromophore. Finally, in the fluorescent signals of some yellow and red glasses two peaks of Zn-Se-Cd-S nanocrystals have been identified.

Absorption spectroscopy is the technique that measures the absorption of radiation as a function of wavelength, due to its interaction with the material. During a research project funded by our home university, we were able to investigate the possibilities of this technique to study ancient glasses. One of our main conclusions is that UV-VIS-NIR absorption spectroscopy is especially suited to characterize colored artifacts in terms of composition and furnace conditions. Moreover, for naturally colored window glasses, we have shown that this technique allows us to classify fragments based on differences in iron impurity levels. It is a semi-quantitative analysis tool that can be applied for a first-line analysis of (large) glass collections. Thanks to the commercial available portable instruments, these measurements can be performed at relative high speed and this in-situ if necessary. To illustrate the possibilities of this technique, we describe in this paper two case-studies. In a first test-case we analyze 63 naturally colored window glasses and demonstrate how groups with different iron concentrations can be identified by calculating the absorption edge position from the measured optical spectrum. In a second case-study 8 modern naturally colored and 31 intentionally colored Roman glass fragments are the point of focus. For these samples we first estimate which samples are potentially fabricated under the same furnace conditions. This is done based on the calculated color values. Finally we identify the type of applied colorants.

The aim of this paper is to draw attention to the potential usefulness of optical spectroscopy within the archaeological discourse. We therefore use the standardized color coordinates and the transmittance spectra in the region between 350- 1650 nm of nine fragmented Roman black glass artifacts from archaeological contexts in Avenches (Switzerland) and an intact piece from Tongeren (Belgium). Firstly, we demonstrate how the use of UV-Vis-NIR spectroscopy can help the archaeologist in understanding the various excavated features containing glass artifacts. The analysis of the optical spectra of Roman black glass artifacts demonstrates in the first place that an object has a very homogenous composition. The clustering of the different fragments with characteristic spectra permits to connect the pieces from various areas of an excavation to one single object or to several objects from the same batch. These results provide the archaeologist the possibility to merge recognized layers or to connect different features in the surrounding area. Secondly, we demonstrate how the use of UV-Vis-NIR spectroscopy can help improve the analysis process. This inexpensive method can facilitate a more convenient and purposive sampling by means of a preliminary inquiry, selecting the most interesting pieces out of a large group of artifacts suitable for chemical analysis.

In this paper we studied the transmittance spectra of a collection of several glass samples taken from a 16th century stained window of the Church of Our Lady in Bruges, Belgium. We recorded the optical spectra for all the samples in the region between 350 and 1600 nm. The goal of our research was to reveal information about the composition of the glass artifacts in a fast and non-destructive way. Analysis of the optical spectra allowed us in the first place to identify the type of colorants that were used. It was possible to recognize metal ions, such as Fe²⁺, Fe³⁺, Co²⁺, Mn³⁺, Cr³⁺ and Cu²⁺. Also colors made of metal nanoparticles, such as silver and copper colloids were successfully identified. The recognition of the coloring agents is of particular interest in dating the glass pieces. This is because some colorants were only used in certain periods. Green glass colored by chromium was produced only after the mid 19th century onwards. Our study showed that 3 of the 10 pieces were colored by this element and they originate as such from a later period. A second conclusion refers to the applied fluxing agent. By analyzing the spectral position of the first cobalt absorption band, we were able to classify the glass pieces as potash based (used in medieval times) or soda-based (used in modern times) and therefore to classify them as original or as restoration material. From the 10 blue colored samples, 7 of them were recognized as original material. Finally, for the naturally colored parts the analysis of the spectra allowed us to group them based on cobalt impurities.

The interdisciplinary study of ancient materials has become an increasingly common strategy, mainly because it has proved to be a highly rewarding approach to studying the age, provenance and production of archaeological objects. The results of such an approach sometimes also provide answers to questions relating not only to socio-cultural, economic or technological developments in a particular region or period (trade, innovation, production etc.), but also the conservation of the materials or artefacts in question. A number of analytical methods, ranging from microscopic to elementary analyses, have been successfully applied to determine the nature of materials and technologies used in the production, as well as to identify the provenance of ancient glass. As far as window glass and stained glass is concerned, the study of architectural context and art history – as well as the technological characteristics of materials – has proved to be most helpful in determining history, production and artistic importance of the objects under study. This paper discusses some of the multidisciplinary studies that the Vitrocentre Romont has conducted on early medieval window glass, stained glass and reverse glass paintings and illustrates the potential of a holistic approach in solving questions about materials, techniques, window design and conservation. It also addresses the limitations of the approach, which are often related to finding appropriate (i.e. non-destructive and possibly portable) methods for the analysis of sometimes extremely fragile stained glass windows.

Whatever the chemical composition and the origin (natural or man-made) or the surrounding environment is, glass materials undergo alteration processes leading to the modification of their structure and chemical composition. Similar alteration patterns can be observed in different historical glass types, especially alteration layers characterized by a laminated structure. The study of medieval stained glass windows (14th century AD, from Northern France) and Roman glass blocks (2nd century AD, from a shipwreck in the Mediterranean Sea) with several centuries of exposure in atmospheric and marine conditions, respectively, show that laminated features, commonly described at micro-scale (e.g. lamination), can also be found at the nano-scale (laminae) using TEM analysis on FIB ultra-thin section. These features develop on different alteration layers - in the gel layer for medieval glass and in crystalline secondary phases (smectites) for Roman glass - showing that the formation mechanisms vary according to the exposure environment and the chemical composition of the glass.

As far as Belgium and archaeological window glass is concerned, the most important site is the Dunes Abbey, a former Cistercian abbey near the Flemish coastline. The collection contains approximately 15,000 fragments dating from the 13th to the 16th century. This glass was exposed to atmospheric weathering while in situ for several hundred years, buried for up to 400 years, excavated by different individual excavators in different eras and for over half a century stored in uncontrolled conditions. Moreover, different conservation treatments have been applied to the glass. Due to this, the collection was in a friable condition and we assume half of it has already been completely lost. The remaining collection retains fragments whose condition ranges between almost perfectly preserved material to being completely weathered to the point that no original glass survives. In this research, an important asset is recognizing what has already been lost and maximizing what is still available. During recent conservation and stock making campaigns, the different weathering phenomena were separated into 9 groups based on empirical criteria and detailed registration. As a first step to further investigation of the weathering processes, quantitative SEM-EDX analyses are used to give better insight into the chemical composition of these groups. The aim is to bridge the gap between interpretative archaeologically and archaeological science and to develop a common terminology to evaluate the complexity of weathering phenomena in archaeological window glass collections which can be used as a tool for the assembling and interpretation of these collections.

Glass was used since the Roman age in the building envelope, but it became widely applied together with iron since the 19th century. Belgium was a major producer of window glass during the nineteenth century and the majority of the produced window glass was exported all over the world. Investigating the literature on the development of 19th century Belgian window glass production is therefore internationally relevant. In the 17th century, wood was replaced as a fuel by coal. In the 19th century, the regenerative tank furnace applied gas as a fuel in a continuous glass production process. The advantages were a clean production, a more constant and higher temperature in the furnace and a fuel saving. The French chemist Nicolas Leblanc (1787-1793) and later the Belgian chemist Ernest Solvay (1863) invented processes to produce alkali out of common salt. The artificial soda ash improved the quality and aesthetics of the glass plates. During the 19th century, the glass production was industrialized, influencing the operation of furnaces, the improvement of raw materials as well as the applied energy sources. Although the production process was industrialized, glassblowing was still the work of an individual. By improving his work tools, he was able to create larger glass plates. The developments in the annealing process followed this evolution. The industry had to wait until the invention of the drawn glass in the beginning of the 20th century to fully industrialise the window glass manufacture process.

Belgian Marbrite Fauquez opalescent glass is an innovative material developed at the take-off of the 20th century. S.A. Verreries de Fauquez produced this from 1922 onwards. Low maintenance requirements and appropriate properties in terms of hygienic aspects make these mass coloured glass plates popular as finishes for bathrooms, kitchens, hospitals, store fronts, decorative façade cladding,... Since production of Marbrite stopped in the 1960s, replacement of its applications in the framework of restoration procedures is almost impossible. Limited knowledge of the composition and production results in the lack of a proper conservation strategy. In order to improve the existing knowledge a historical research was conducted. Archive records including patents, literature, building specifications, plans, journals, advertisements, interviews with former directors of the glassworks, etc. were considered and evaluated. Onsite lifted samples of Marbrite glass were submitted to a laboratory investigation using optical and scanning electron microscopy. The results revealed crucial information about the original formula and components. This paper discusses the composition of Marbrite, a peculiar Belgian opalescent glass. This interdisciplinary research – a cooperation between the Vrije Universiteit Brussel and Royal Institute for Cultural Heritage – aims to improve the knowledge of Marbrite glass in order to develop repair and renovation techniques.

This paper presents recent work done on the application of Time of Flight Secondary Ion Mass Spectrometry (ToFSIMS), a high lateral resolution surface analysis technique, to the study of opacifying inclusions in ancient and historical glasses. A small selection of ancient glass samples have thus far been analyzed by this technique with great success. The combination of surface sensitivity and high lateral resolution offered by the technique is uniquely placed to address the detailed chemical composition of the opacifying inclusions themselves, without interference from the surrounding glass matrix. The research team seeks to further develop the use of ToF-SIMS for addressing issues of provenance and understanding the technological processes involved in adding opacifying inclusions to ancient glass, through further analysis of relevant material and through the production and analysis of replica opaque glasses. The technique itself will be discussed along with some of the preliminary results obtained and proposals for future work in this field.

Our knowledge of glass production in ancient Egypt has been well augmented by the publication of recently excavated materials and glass workshops, but also by more recent materials analysis, and experiments of modern glass-makers attempting to reconstruct the production process of thin-walled coreformed glass vessels. From the mounting of a prefabricated core to the final glass product our understanding of this profession has much improved. The small but well preserved glass collection of the Freer Gallery of Art in Washington, D.C. is a valid tool for examining and studying the technology and production of ancient Egyptian core formed glass vessels. Charles Lang Freer (1854-1919) acquired most of the material from Giovanni Dattari in Cairo in 1909. Previously the glass had received only limited discussion, suggesting that most of these vessels were produced in the 18th Dynasty in the 15th and 14th centuries BCE, while others date from the Hellenistic period and later. In an ongoing project we conducted computed radiography in conjunction with qualitative x-ray fluorescence analysis on a selected group of vessels to understand further aspects of the ancient production process. This paper will provide an overview of our recent research and present our data-gathering process and preliminary results. How can the examinations of core formed glass vessels in the Freer Gallery contribute to our understanding of ancient glass production and technology? By focusing on new ways of looking at old assumptions using the Freer Gallery glass collections, we hope to increase understanding of the challenges of the production process of core-vessel technology as represented by these vessels.