Thomas Calligaro

(Text in French) Lead compounds in historical paints probed by synchrotron radiation: synthesis, optical properties, and reactivity Techniques based on synchrotron radiation enable high resolution analysis of model samples or micro-fragments taken from paintworks. The research presented here relies on X-ray diffraction to probe the crystalline phases composing the historical inorganic pigments. The examples described show how combining synchrotron structural analysis with molecular probes can yield new information about the synthesis, implementation, and evolution over time of the complex composite systems that are ancient paint layers.

Gas optical emission enhanced by solid initiator (GENS) is designed to support the laser-induced breakdown spectroscopy (LIBS) technique for studying the impact of intense radiation beams on cultural heritage materials. GENS-LIBS generates plasma in the atmosphere using a metal target, which increases sensitivity while lowering laser irradiance. This method is designed to monitor gas emissions from ancient materials during intense radiation analysis, particularly under ion beam irradiation. The study focused on analyzing hydrogen gas emissions from lead white pigments mixed with linseed oil as a binder in paintings. The results show that the GENS-LIBS method has allowed us to quantify the hydrogen emission of lead white-containing paint layers exposed to 10 to 40 μC/cm2 of 3 MeV protons in a specially designed sealed cell. This technique permits the tracking of hydrogen and other light elements, such as oxygen and nitrogen, thus facilitating the follow-up of changes in the material composition of artworks. GENS-LIBS offers a promising method for safely analyzing and preserving valuable cultural heritage artifacts.

Collecter des informations chimiques sur les matériaux employés par Léonard de Vinci permet de mieux comprendre la matérialité de ses pratiques picturales et fournit de nouvelles informations pouvant contribuer à la conservation de ses œuvres. Mais les peintures de Léonard sont des systèmes chimiques complexes, assemblages hybrides de pigments minéraux et de composés organiques, notamment liants à l’huile. Ces pigments étaient obtenus par des voies de synthèses élaborées, puis mis en œuvre selon le savoir-faire du peintre. Les couches de peinture de Léonard constituent des milieux réactionnels actifs, au sein desquels des interactions chimiques peuvent entraîner la formation in situ de composés non originaux. Seule l’utilisation de méthodologies analytiques de pointe permet de surmonter ces défis. Cette communication présente des recherches récentes, fondées sur de telles méthodologies, visant à décrypter – au moins partiellement – l’origine et la mise en œuvre de certains matériaux de Léonard de Vinci, en particulier le pigment blanc de plomb, omniprésent dans sa palette.

La recherche sur les pratiques picturales de Léonard de Vinci a bénéficié d’une nouvelle technique d’analyse non invasive devenue, par le biais des développements informatiques, une technique d’imagerie : la cartographie de fluorescence X. Les apports de cette technique seront illustrés à partir d’exemples nous informant sur la genèse des œuvres, la connaissance de la palette, l’analyse des motifs de la composition souvent devenus peu lisibles en raison du vieillissement de la matière, ainsi que la technique de réalisation des carnations. Nous tenterons ainsi d’esquisser une évolution des pratiques du maître.

Scanning x‐ray fluorescence (MA‐XRF), Reflectance Imaging Spectroscopy (RIS) and Luminescence Imaging Spectroscopy (LIS) are scientific methods extensively used in the investigation of artworks in Cultural Heritage Science. Nevertheless, these three highly complementary imaging methods have never been implemented in a single instrument. In this paper, we present a scanning system that is the first to simultaneously combine MA‐XRF, RIS, and LIS techniques, generating spatially aligned hyperspectral datasets. The specifications of the instrument and of the collected datacubes are described, together with the processing pipeline developed for the coupled exploitation and interpretation. The operation of this instrument, combining XRF with RIS and LIS mapping in an extended range (400–2500 nm and 200–1000 nm, respectively), is exemplified on an anonymous test painting, studied previously. A focus on a restored area of this painting allows to illustrates the complementarity of the three aforementioned methods, for the visualization and characterization of pigments, varnish, and binders.

Non-destructive characterization of decorated porcelain artifacts requires the joint use of surface-analytical methods for the decorative surface pattern and methods of high penetration depth for bulk-representative chemical composition. In this research, we used position-sensitive X-ray Fluorescence Spectrometry (XRF) and Prompt-gamma activation analysis (PGAA) for these purposes, assisted by 3D structured-light optical scanning and dual-energy X-ray radiography. The proper combination of the near-surface and bulk element composition data can shed light on raw material use and manufacturing technology of ceramics.