Stéphane Longelin

Performance of three different Si X-ray detectors for portable XRF spectrometers in cultural heritage applications

In this work, a study of detection systems in portable X-ray fluorescence (PXRF) spectrometry was performed. An assessment of various detectors and their influence on the measurement of trace elements in different bulk materials, from light to heavy matrices, was done. Four reference materials were analyzed: Orchard Leaves (NBS-1571); Bone Meal (NIST-1486); River Sediment (NBS-1645) and Free-Cutting Brass (NBS-1105). Detection limits were calculated for the elements present in the reference materials, quantitative calculations were performed for three known samples and a comparison was made for each detector. Three case studies were also performed in order to appraise the behavior of the detection systems: A paper document from 1909, a potassium alum/calcite mixture and a Portuguese coin.

Spectroscopic characterization of a masterpiece: The Manueline foral charter of Sintra

The foral charter attributed by D. Manuel I of Portugal, in 1514, to the village of Sintra was studied using Energy Dispersive X-ray Fluorescence spectrometry, Raman and Infrared micro-spectroscopies. A complete characterization of the pictorial materials used in the production of this masterpiece allowed the identification of iron gall inks used in the written text; pigments such as malachite, azurite, lead white, cinnabar, yellow ochre, gold, silver and carbon black in the illuminations and letterings; filler and binder used in the production of coloring materials and inks. Gum and calcium carbonate were the most recurrent binder and filler identified in this study. Silvering and gilding were mostly obtained by applying ground silver and gold on parchment.

New development on materials and techniques used in the heraldic designs of illuminated Manueline foral charters by multi-analytical methods.

In the illuminated foral charters commissioned by D. Manuel I, King of Portugal (1495-1521), heraldry played a prominent role. In this work, royal emblems corresponding to the third heraldic design, applied to the Charter of Couto de Teixedo, are studied by means of EDXRF, SEM-EDS, micro-Raman, micro-FTIR and HPLC-DAD to characterize the materials and techniques used to produce this masterpiece of Portuguese Renaissance. By comparing this data with the results previously obtained in other three charters, this research allows for the first time an accurate insight into the reformed manuscripts production, especially since the illuminated charters under consideration were all investigated on the basis of similar micro-spectroscopic techniques. Inks, metal coatings, pigments, organic dyes, fillers or extenders, and binding media are discussed, and their use enlightened by the politic and legal messages the foral charters had to convey. Parchment analysis allowed us to identify the animal species, and all undertaken processes along its preparation. HPLC-DAD allowed us to differentiate the gums used. CaSO4 was observed in the parchment as a degradation product of CaCO3 used in parchment production in the presence of metal sulfates coming from the ink. Pigments used in the different colors as well as some specific phases for some colors were identified. Silvering and gilding processes, metal caratage and silver oxidation compounds were also objects of the present study.

Development of a combined portable x-ray fluorescence and Raman spectrometer for in situ analysis

In this work, we have built a portable X-ray fluorescence (XRF) spectrometer in a planar configuration coupled to a Raman head and a digital optical microscope, for in situ analysis. Several geometries for the XRF apparatus and digital microscope are possible in order to overcome spatial constraints and provide better measurement conditions. With this combined spectrometer, we are now able to perform XRF and Raman measurements in the same point without the need for sample collection, which can be crucial when dealing with cultural heritage objects, as well as forensic analysis. We show the capabilities of the spectrometer by measuring several standard reference materials, as well as other samples usually encountered in cultural heritage, geological, as well as biomedical studies.

Blue Pigment Colors from Wall Painting Churches in Danger (Portugal 15th to 18th Century): Identification, Diagnosis, and Color Evaluation

Samples of blue wall paint layers from selected 15th to 18th century religious mural paintings from southern Portugal (Alentejo) have been analyzed using a multi-analytical methodology involving the combination of in situ visible spectro-colorimetry with microanalytical techniques such as optical and scanning electron microscopy and Raman spectroscopy. In situ analyses and micro-sampling were carried out in nine different churches, many in an advanced state of deterioration. The objectives of this study were: (a) to identify and compare the pigments that were used in the blue paint layers across the Alentejo region and through time by analysis of the elemental and mineralogical composition and pictorial techniques, and (b) to correlate the data between the actual color of the paint layer and the state of conservation of the pigments. For the paintings dated from the 16th century forward, the results show a generalized use of smalt blue. To a lesser extent, natural azurite was used despite the geological richness of the region in copper and pyrite ores. In only one painting was an optical blue made of carbon black and lime found. The pigments, pure or mixed with red and yellow ochres, were coarsely ground and used in different concentrations to create three-dimensional effects. These parameters as well as the presence of iron oxides in underlayer paints influence the colorimetric coordinates in the more transparent smalt blue paint layers. The state of conservation of the pigments plays an important role in the alteration of the paint color. A clear example of this is the fading of the smalt blue in several paintings due to lixiviation processes.

Spectroscopic Characterization of a Contemporary Indian Miniature Painting

A case study on a contemporary Indian miniature was carried out through the application of different spectroscopic techniques. Painting support, pigments, and dyes were largely characterized by means of energy dispersive x-ray fluorescence and Raman microspectroscopy directly on the artwork. Regarding golden motifs and silvered areas, for which these techniques have not provided enough information, scanning electron microscopy coupled with energy dispersive x-ray spectroscopy was used as a complementary technique. The painting support was identified as the Bombyx mori silk. Among the colorant matters, several pigments were identified such as chrome yellow, lithopone, hematite, lamp black, mica-titania pearlescent pigment, and tin-based metallic silver, and dyes such as phthalocyanine blue and the recent synthetic pigment red PR9 naphthol AS. All this materials will provide evidence in the support of the contemporary production of the artwork for future studies.

Characterization of glue sizing under calcium carbonate ground layers in Flemish and Luso-Flemish painting – analysis by SEM-EDS, μ-XRD and μ-Raman spectroscopy

This work regards the study of painting techniques in Portuguese workshops of the 15th and early 16th centuries, specifically addressing the methodology used on the preparation of ground layers. The influence of Flemish painting in Portugal is evident in stylistic and iconographic themes of that period. As regards the painting materials, we confirmed that this influence also extended to the ground layer technique. The use of a sizing layer with calcium sulphate or garlic to isolate the support from the calcium carbonate layer was verified by SEM-EDS but not confirmed by μ-XRD or μ-Raman spectroscopy. This work is part of a larger project, “The invisible ground layer and its influence in Portuguese paintings from the 15th and 16th centuries: a question to be settled”.

Microscopy and X-Ray Spectroscopy Analyses for Assessment of Gilding and Silvering Techniques of Portuguese Illuminated Manuscripts

The objects of this study are various local charters (cartas de foral, in Portuguese) granted by Dom Manuel I, King of Portugal (1495-1521), which substituted for medieval ones and were intended to achieve an administrative unification. These are luxuriously illuminated manuscripts, and our study aims at obtaining a better understanding of the gilding and silvering techniques applied to the parchments, in which the forais were written, between 1500 and 1520. The combined use of microscopy and X-ray spectroscopy analyses allowed us to identify the vestigial materials used for making the parchments, including products such as salt (NaCl), lime (CaO), pumice stone (SiO2+Al2O3), and chalk (CaCO3). Chalk was employed as a whitening agent to give the parchment its final color and opacity. Shell-gold and shell-silver mixed in with animal glue or gum binding media were directly applied on type 1 and 3 forais, while very thin gold leaves (<1 µm) were applied over lead-based tempera grounds (50-180 µm thick) in type 2 forais. Silver was always employed in its finest form without a further protective layer (thus its recursive state of corrosion), while gold was used in various alloy grades.

GREGÓRIO LOPES painting workshop: characterization by X-ray based techniques. Analysis by EDXRF, μ-XRD and SEM-EDS

Gregorio Lopes is one of the most famous Portuguese painters of the 15th–16th centuries. This work is a contribution to the study of his painting technique, specifically addressing the methodology used in the preparation of ground layers, which has never been carried out previously with this multianalytical method. For this purpose characterization of the ground layers of a selection of his paintings was carried out by micro-Energy Dispersive X-ray Fluorescence spectroscopy (μ-EDXRF), micro-X-ray Diffraction (μ-XRD), Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS) and complemented by micro-Raman spectroscopy. This work presents the results obtained on two altarpieces (c.1544) produced at the same period by this Portuguese artist. Ground layers are composed mainly of calcium sulfate — anhydrite and gypsum — and other compounds such as dolomite. Reference samples were prepared to obtain diffraction pattern of different percentage of gypsum and anhydrite and compared with the results from historical samples.

New insights into the red and green pigments in the illuminated foral charter of Setubal (1515) by combined use of μ-Raman and X-ray fluorescence spectrometry

The richly decorated foral charter attributed by D. Manuel I of Portugal, in 1515, to the village of Setubal, was studied using Energy Dispersive X-ray Fluorescence spectrometry and Raman micro-spectroscopy. An in situ characterization of the pigments used in the production of this masterpiece showed a very different pigment palette choice when compared to other similar Manueline charters. The red and green pigments are particularly puzzling, as the widely used mercury- and copper-based pigments, vermillion and malachite, respectively, were not found in the illuminated frontispiece. Instead, the cheaper lead-based pigment minium was used in the Kings flag, while a mixture of copper sulfates was found for the green color, identified by means of micro-Raman spectroscopy. This result led to a new look at the conception that only one Royal workshop existed for the elaboration of Manueline foral charters.