Time-resolved photoluminescence microscopy for the analysis of semiconductor-based paint layers

In conservation, science semiconductors occur as the constituent matter of the so-called semiconductor pigments, produced following the Industrial Revolution and extensively used by modern painters. With recent research highlighting the occurrence of various degradation phenomena in semiconductor paints, it is clear that their detection by conventional optical fluorescence imaging and microscopy is limited by the complexity of historical painting materials. Here, we illustrate and prove the capabilities of time-resolved photoluminescence (TRPL) microscopy, equipped with both spectral and lifetime sensitivity at timescales ranging from nanoseconds to hundreds of microseconds, for the analysis of cross-sections of paint layers made of luminescent semiconductor pigments. The method is sensitive to heterogeneities within micro-samples and provides valuable information for the interpretation of the nature of the emissions in samples. A case study is presented on micro samples from a painting by Henri Matisse and serves to demonstrate how TRPL can be used to identify the semiconductor pigments zinc white and cadmium yellow, and to inform future investigations of the degradation of a cadmium yellow paint

Les chancis des peintures de chevalet : étude des traitements de restauration actuels et proposition d’une alternative innovante

Les chancis de vernis et de couches picturales des peintures de chevalet à l’huile sont des altérations récurrentes induites principalement par l’humidité. L’article expose un état de l’art sur la restauration des peintures chancies à partir de substances transparentes filmogènes ou de solvants sous forme vapeur ou liquide. Pour les chancis de vernis, l’analyse par nanotomographie à contraste de phase de prélèvements restaurés selon des pratiques actuelles (application d’un solvant suivi d’un vernissage) démontre leur manque d’efficacité et surtout de durabilité. Trouver une solution pérenne constitue un enjeu de taille pour la restauration et la conservation des œuvres chancies. L’emploi du perfluoropolyéther développé dans le cadre de ce projet a été testé sur des échantillons modèles. Les analyses par spectrocolorimétrie et microtomographie X en absorption mettent en évidence son efficacité et sa réversibilité à l’échelle macroscopique et microscopique.The blanching of the varnish and paint layers in easel paintings executed in oils is a recurrent alteration mainly caused by humidity. This paper is a review of the restoration of blanched paintings using transparent film-forming substances or liquid or vaporous solvents. For the blanched varnish layers, analysis by phase-contrast nanotomography of samples restored by current practices (application of a solvent followed by varnishing) showed their ineffectiveness and, above all, their lack of durability. Finding a long-standing solution represents a serious challenge for the restoration and conservation of blanched paintings. The use of perfluoropolyether (PFPE), developed in the course of this investigation, was tested on selected samples. Spectrocolorimetry and X-ray microtomography demonstrated its effectiveness and reversibility on a macroscopic and microscopic scale

Les préparations des tableaux de Goya et de son entourage conservés en France

Les couches préparatoires de vingt-trois œuvres de Goya, de son entourage ou de sa suite, datées entre 1783 et 1843 et issues des collections françaises, ont été étudiées et analysées par microanalyse X à partir de micro-prélèvements. Cette recherche a permis de mettre en évidence trois catégories distinctes de préparations : une première où le blanc de plomb et le carbonate de calcium sont majoritaires ; une deuxième essentiellement à base de blanc de plomb et une troisième constituée de terres. Elles sont généralement colorées dans les tons beige, orangé ou rouge, en simple ou double application. Goya semble employer des couches de couleur rouge brique dans ses œuvres les plus anciennes, et plus claires à la fin de sa carrière. Ces résultats ont été confrontés avec d’autres œuvres de Goya et ont permis de contribuer, entre autres, à l’attribution à Francisco de Goya d’un autoportrait qui avait été auparavant attribué à son entourage.The preparatory layers of twenty-three works dated between 1783 and 1843 in French collections painted by Goya, his circle, or his followers, were studied, and analyzed by micro-analysis X from micro-samples. This study has allowed us to highlight three distinct categories of preparation: : a first one consisting mainly of lead white and calcium carbonate, preparations in which lead white is predominant and the third category consisting mainly of earths. The works studied in this corpus usually have colored ground layers in beige, orange or red tones, in single or double application. Goya seems to use layers of brick-red color in his oldest works and lighter grounds at the end of his career. These results have been compared with other works of the master and have contributed to, among other matters, the attribution of a self-portrait to Goya’s own hand that had been previously attributed to his circle

« Investigating the transition period from colored to white preparatory layers in 18th-century French canvas paintings: A retrospective study »

International audienc

Tiefenempfindlichkeit in der bildgebenden makro-RFA

Bildgebende makro-RFA findet in den letzten Jahren immer stärkere Verbreitung bei der zerstörungsfreien Untersuchung historischer Gemälde [1]. In dieser Technik wird die Oberfläche des Gemäldes schrittweise mit einem Röntgenstrahl von mehreren hundert Micrometern Durchmesser abgerastert. Dabei kann die Verteilung chemischer Elemente in Flächen von bis zu mehreren Quadratmetern untersucht werden. Durch die groβe Eindringtiefe der Röntgenstrahlen tragen nicht nur Elemente an der Oberfläche, sondern auch in tieferen Schichten, zu den aufgenommenen RFA Spektren bei, so dass auch Schichten untersucht werden können, die für das bloβe Auge nicht sichtbar sind. Diese Schichten können Aufschluss über Änderungen in der Kompositionen oder verworfene und übermalte Gemälde geben.Eine direkte Trennung der Signalen von der Oberfläche des Bildes und denen aus tieferen Lagen ist nicht direkt möglich, so dass es in machen Fällen fraglich ist, ob sich ein Element an der Oberfläche und in der endgültigen Komposition befindet.Um eine Tiefenempfindlichkleit zu erreichen haben wir einen RFA Scanner entwickelt der mittels mehrerer energiedispersiver Detektoren gleichzeitig Fluoreszensstrahlung mit vier verschiedenen Detektionswinkeln zwischen 25° und 45° registriert [2].Da die Absorption von Strahlung über die Weglänge im absorbierenden Medium und damit dem Detektionswinkel abhängt kann durch den Vergleich von Fluoreszensstrahlung die unter verschiedenen Detektionswinkeln aufgezeichnet wurde eine (begrenzte) Tiefenempfindlichkeit erreicht werden. Ähnliche Ergebnisse können durch den Vergleich der Intensitäten von Fluoreszenslinien unterschiedlicher Energie erreicht werden.Wir werden an ausgesuchten Fallstudien historischer Gemälde beide Ansätze miteinander und mit klassischen Tiefenprofilierungstechniken wie der konfokaler RFA [3] und Farbanschliffen vergleichen. [1] K. Janssens, M. Alfeld, G. Van der Snickt, W. De Nolf, F. Vanmeert, M. Radepont, L. Monico, J. Dik, M. Cotte, G. Falkenberg, C. Miliani, B.G. Brunetti, Annu. Rev. Anal. Chem. 6, 399 (2013).[2] M. Alfeld, K. Janssens, J. Dik, W. de Nolf, G. van der Snickt, J. Anal. At. Spectrom. 26, 899 (2011).[3] I. Reiche, K. Müller, M. Eveno, E. Itié, M. Menu, J. Anal. At. Spectrom. 26, 1715 (2012)

A multimodal study of smalt preservation and degradation on the painting “Woman doing a Libation or Artemisia” from an anonymous painter of the Fontainebleau School

International audienceThe blue pigment smalt, a synthetic potash glass tinted with cobalt, was widely used between the sixteenth and the eighteenth centuries. As part of a study on the alteration of smalt and the reconstitution of its original color, the painting: Woman doing a Libation or Artemisia (Fontainebleau school, 1570) was examined in which the artist used smalt as a blue pigment, which is now degraded. Noninvasive imaging was performed using macro-2D X-ray fluorescence and reflectance imaging spectroscopy to get an overview of the artist’s palette and its distribution. Samples prepared as cross sections were also analyzed by scanning electron microscopy coupled with energy dispersive spectroscopy, micro-X-ray absorption near-edge structure spectroscopy and synchrotron micro-X-ray diffraction imaging to determine the preservation state of the smalt as well as structural information on other pigments adjacent to smalt grains in individual paint layers, which could play a role in the degradation process. On the one hand, the study conducted on the alteration of smalt has shown that it is very weathered and mixed with hydrocerussite, which could be a factor that would facilitate the alteration. On the other hand, these analyses have made it possible to identify and locate the pigments used, which will be the basis for the virtual reconstruction of the color of the painting

Partially perfluorinated derivatives as powerful tool for the restoration of blanching easel paintings

Perfluorinated oligoamides/amines were prepared and characterized. They were evaluated then for easel painting restoration by filling pores resulting of the blanching. They were used on prepared mock-ups analysed by FEG-SEM for morphological changes and by spectro-colorimetry analysis for the restoration. Compared to DG6G900 , the new partially perfluorinated products DSTF and DSF are recommended as restoration products for blanching easel paintings

Synchrotron-based high angle resolution and high lateral resolution X-ray diffraction reveals lead white pigment qualities in Old Masters paintings

International audienceMicro-samples collected on 28 major paintings by Old European Masters dating from the Middle Ages to the late 19th c. were analyzed using Synchrotron-based X-ray diffraction. Two complementary analytical configurations were used at beamlines ID22 (high-angle resolution) and ID21 (high lateral resolution), in order to highlight markers of the different grades of the lead white pigments (mixture of cerussite PbCO3 and hydrocerussite Pb3(CO3)2(OH)2). Rietveld analysis and crystalline phases mapping at the micro-scale revealed the composition and microstructure of the pigments, shedding light on the preparation recipes and pigment choices of the artists through History

Microchemical analysis of Leonardo da Vinci’s lead white paints reveals knowledge and control over pigment scattering properties

International audienceLeonardo da Vinci (1452-1519) is a key artistic and scientific figure of the Renaissance. He is renowned for his science of art, taking advantage of his acute observations of nature to achieve striking pictorial results. This study describes the analysis of an exceptional sample from one of Leonardo's final masterpieces: The Virgin and Child with St. Anne (Musée du Louvre, Paris, France). The sample was analyzed at the microscale by synchrotron-based hyperspectral photoluminescence imaging and high-angular X-ray diffraction. The results demonstrate Leonardo's use of two subtypes of lead white pigment, thus revealing how he must have possessed a precise knowledge of his materials; carefully selecting them according to the aesthetical results he aimed at achieving in each painting. This work provides insights on how Leonardo obtained these grades of pigment and proposes new clues regarding the optical and/or working properties he may have tried to achieve