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The production of glass represented an important technological achievement, and it was the starting point for the invention of a large variety of materials, produced by processes involving melting, partial or total, and precipitation of new crystalline compounds during cooling. In particular, those crystallites built-in the glaze due to partial or total insolubility of some elements originally present in the melt (for instance some colourants and opacifiers), as well as those crystallites formed in the glazes resulting from the interaction of the melt and the ceramic surface are subject of the highest interest in the study of glaze technology. Finally, devitrification and weathering gives rise to precipitation of new crystalline compounds closer to the surfaces and interfaces. SEM-EDX and WDX have been traditionally used to obtain the chemistry of the glazes and the identification of the crystalline compounds present. However, it has some limitations identifying minute crystallites (below 0.5 micrometers) and polymorphs, which are of the highest interest in the study of historical glazes. Synchrotron Radiation micro-X-ray Diffraction has a small beam size adequate to obtain the structural information of submicron crystalline compounds and high brilliance, optimal for determining the crystallites even when present in low amounts. In addition the spatial distribution of the crystalline compounds present in the glazes fundamental for the study of the interaction between the ceramic and the glaze may be easily obtained. The identification of the microcrystallites formed in the glazes and their distribution across the glazes gives direct information on trends of the technology of production, stability and weathering of ancient glazes. In this study a collection of Islamic glazes from the 9th to the 13th century AD from different origins and obtained with different raw materials and production routes are studied. Unreacted grains, reaction compounds, crystallisations and alteration compounds as well as their space distribution are obtained. [ABSTRACT FROM AUTHOR]

The high analytical sensitivity and high spatial resolution of synchrotron radiation-based techniques, in particular SR-XRD and SR-FT-IR, allows the identification of complex micrometric mixtures of compounds that constitute the different layers of ancient paintings. The reliability of the measurements even with an extremely small amount of sampled material is very high, and this is particularly important when analyzing art works. Furthermore, the micro size (10×10μm for FT-IR and 30 to 50 μm squared spot size for XRD) of the beam enables one to obtain detailed compositional profiles from the different chromatic and preparation layers. The sensitivity of the techniques is high enough for the determination of minor and trace compounds, such as reaction and weathering compounds. We report here the identification of pigments in the Romanesque wall paintings found in situ in the church of Saint Eulàlia of Unha place in the Aran valley (central Pyrenees). During the first centuries of the second millennium numerous religious buildings were built in Western Europe in the Romanesque style. In particular, a great number of churches were built in the Pyrenees, most of which were decorated with wall paintings. Although only a few of these paintings have survived, they represent one of the most important collections of Romanesque art, both for their quantity and quality. A full identification of the pigments, binder, supports, and reaction and weathering compounds has been obtained. The results obtained, in particular aerinite as a pigment, indicate a clear connection between the paintings found in this Occitanian church and the Catalan Romanesque paintings from the south bound of the Pyrenees. [ABSTRACT FROM AUTHOR]