Macro X-Ray Fluorescence (MA-XRF) scanning, multi-and hyperspectral imaging study of multiple layers of paintings on paneled vault in the church of Le Quillio (France)

International audienceDuring initial conservator's investigation of paneled wooden vault of the church in Le Quillio, 17th century paintings, hidden behind painted canvas nailed on the panels were discovered. A closer look on these paintings and some exposure windows showed the presence of an older paint layer. This layer corresponds to the first vault decoration, dating back all the way at the end of 15th century, existence of which was attested by written sources. However, the conservation state of the original pictorial layer was unknown, so it was not possible to make a decision to uncover it without further information acquired, preferably, non-invasively. Examination of different layers was performed by extracting, processing and cross-referencing the information from the complementary data obtained from MA-XRF scanning as well as multi-and hyperspectral imaging. This allowed to characterize the mineral composition of different layers and to attribute them respectively to the end of 15th century original painting, the 17th century overpaint and to the later 19th century interventions corresponding rather to a large retouching or restoration. Our study also showed the particularities of the mounting of panels, as some parts on the first decoration's paint seem to be partially discontinued between successive panels and may attest to the exchange of panels between different parts of the vault. This pilot study was conducted on an only small part of the large vault (0.4% of the 32 m 2). Further, more extensive investigations will be required to better understand this complex object and its complex history

Studio del cinabro: integrazione indagini XRF con SR-XRF e SR-XRD

Ad approfondimento ed integrazione dei risultati analitici già presentati, riguardanti la caratterizzazione in situ tramite fluorescenza a raggi X (XRF) dei materiali pittorici presenti su opere marmoree della collezione statuaria della Galleria Regionale di Palazzo Abatellis (Palermo), sono state effettuate ulteriori indagini su un campione di cinabro (HgS) caratterizzato da una colorazione nera. Tali analisi, condotte tramite misure XRF e XRD presso la beam line ID18 dell’European Syncroton Radiation Facility (Grenoble, Francia), hanno fornito informazioni complementari fondamentali per la corretta interpretazione dello stato di conservazione dello strato pittorico studiato

Casting Light on the Darkening of Colors in Historical Paintings

The degradation of colors in historical paintings affects our cultural heritage in both museums and archeological sites. Despite intensive experimental studies, the origin of darkening of one of the most ancient pigments known to humankind, vermilion (-HgS), remains unexplained. Here, by combining many-body theoretical spectroscopy and high-resolution microscopic x-ray diffraction, we clarify the composition of the damaged paint work and demonstrate possible physicochemical processes, induced by illumination and exposure to humidity and air, that cause photoactivation of the original pigment and the degradation of the secondary minerals. The results suggest a new path for the darkening process which was never considered by previous studies and prompt a critical examination of their findings

Degradation Process of Lead Chromate in Paintings by Vincent van Gogh Studied by Means of Spectromicroscopic Methods. 3. Synthesis, Characterization, and Detection of Different Crystal Forms of the Chrome Yellow Pigment

The painter, Vincent van Gogh, and some of his contemporaries frequently made use of the pigment chrome yellow that is known to show a tendency toward darkening. This pigment may correspond to various chemical compounds such as PbCrO(4) and PbCr(1-x)S(x)O(4), that may each be present in various crystallographic forms with different tendencies toward degradation. Investigations by X-ray diffraction (XRD), mid-Fourier Transform infrared (FTIR), and Raman instruments (benchtop and portable) and synchrotron radiation-based micro-XRD and X-ray absorption near edge structure spectroscopy performed on oil-paint models, prepared with in-house synthesized PbCrO(4) and PbCr(1-x)S(x)O(4), permitted us to characterize the spectroscopic features of the various forms. On the basis of these results, an extended study has been carried out on historic paint tubes and on embedded paint microsamples taken from yellow-orange/pale yellow areas of 12 Van Gogh paintings, demonstrating that Van Gogh effectively made use of different chrome yellow types. This conclusion was also confirmed by in situ mid-FTIR investigations on Van Gogh's Portrait of Gauguin (Van Gogh Museum, Amsterdam)