L’Islam vu par Carsten Niebuhr, voyageur en Orient (1761-1767)

En 1761, une expédition financée par le roi de Danemark quittait Copenhague pour le Yémen dans le but de répondre à des questions visant à éclairer certains passages de la Bible. Des six hommes qui étaient partis, un seul revint, Carsten Niebuhr, l’astronome-cartographe. À la mort de ses compagnons, il reprit la plupart de leurs tâches et publia à son retour deux ouvrages en allemand où l’Islam tient une place notable. Les éditions françaises étant anciennes et presque introuvables, il s’agit ici de mettre à la disposition des chercheurs une nouvelle traduction française des textes de Niebuhr relatifs aux religions orientales.Funded by the king, a Danish expedition to Yemen left Copenhagen in 1761 in order to collect information intended to throw light upon certain parts of the Bible. Out of the six men who left, only Carsten Niebuhr, the astronomer-cartographer, returned. After his companions’ death, he took over most of their duties and later published two books in German where Islam figures prominently. With French editions outdated and difficult to find, scholars will avail of a new French translation of Niebuhr’s writings about oriental religions

Thermal Reconversion of Oxidised Lead White in Mural Paintings via a Massicot Intermediate

Lead white is the most ancient and common white pigment used in mural paintings. However, it tends to blacken with time due to its oxidation to plattnerite (\b{eta}-PbO2). Chemical treatments were used but they can put the pictorial layers supports at risks. Hereby we address the possibility of thermally reconverting black plattnerite to white lead carbonates via a massicot (\b{eta}-PbO) intermediate, with a view to developing a restoration procedure using continuous wave laser heating. We first investigated the conditions (temperature, time, and environment) in which pure powders react, before studying mural painting samples. Experiments were made in ovens and TGA and XRD and SEM characterization were achieved. Litharge ({\alpha}-PbO) and massicot were obtained from plattnerite respectively between 564 and 567 {\deg}C and at 650 {\deg}C. Lead carbonates (cerussite, hydrocerussite and plumbonacrite) formed from massicot in wet CO2 below 100 {\deg}C in a few hours. Lastly, when heating plattnerite based mural painting samples, lead species reacted with binders and mortar, yielding massicot, plumbonacrite but also lead silicate and calcium lead oxides. This demonstrates the viability of thermal reconversion of darkened lead in mural, while raising concerns about the formation of several lead species by reaction with mural painting constituents

A combined non-invasive approach to the study of a mosaic model: First laboratory experimental results

This paper presents first laboratory results of a combined approach carried out by the use of three different portable non-invasive electromagnetic methods: Digital holographic speckle pattern interferometry (DHSPI), stimulated infrared thermography (SIRT) and holographic subsurface radar (HSR), proposed for the analysis of a custom-built wall mosaic model. The model reproduces a series of defects (e.g., cracks, voids, detachments), simulating common deteriorated, restored or reshuffled areas in wall mosaics. DHSPI and SIRT, already well known in the field of non-destructive (NDT) methods, are full-field contactless techniques, providing complementary information on the subsurface hidden discontinuities. The use of DHSPI, based on optical imaging and interferometry, provides remote control and visualization of surface micro-deformation after induced thermal stress, while the use of SIRT allows visualization of thermal energy diffusion in the surface upon the induced thermal stress. DHSPI and SIRT data are complemented by the use of HSR, a contact method that provides localized information about the distribution of contrasts in dielectric permittivity and related possible anomalies. The experimental results, made by the combined use of these methods to the identification of the known anomalies in the mosaic model, are presented and discussed here as a contribution in the development of an efficient non-invasive approach to the in-situ subsurface analysis of ancient wall mosaics

Contribution à l'estimation locale d'effusivité thermique par thermographie infrarouge stimulée

International audienceNotre laboratoire s'est spécialisé dans l'étude des altérations affectant les oeuvres d'art telles que les fresques [1,2]. L'effusivité thermique est une quantité thermophysique qui nous permet de repérer des altérations ou de mettre en évidence des contaminations d'espèces chimiques dans ces oeuvres telles que les sels hygroscopiques. Les deux approches présentées ici, basées sur l'analyse de la diffusion latérale de la chaleur suite à une excitation laser locale, permettent d'aboutir à une bonne estimation de cette grandeur thermophysique, ceci indépendamment de l'épaisseur des échantillons et sans prélèvement (ce qui est un atout pour l'analyse des oeuvres d'art)

Cyclododecane as a contrast improving substance for the terahertz imaging of artworks

This paper presents measurements of the terahertz properties of the art conservation substance cyclododecane, demonstrating that it can act as a contrast improving agent in the terahertz imaging of concealed wall paintings. Results are presented which show that the terahertz optical properties of cyclododecane are dependent on the rate at which it has cooled from the melt. Based on the results, a theoretical explanation of the contrast enhancement mechanism is postulated. The findings presented here may lead to the development of novel coating materials that could improve the quality of terahertz images in a variety of fields and not just in art conservation

Les couleurs des peintures murales romanes pyrénéennes : l’apport de l’étude des peintures conservées dans l’église Saint-Pierre d’Ourjout à Bordes-Uchentein (Ariège)

Après la mise au jour de peintures murales romanes dans l’abside de l’église Saint-Pierre d’Ourjout à Bordes-Uchentein, une étude sur la mise en œuvre et composition des peintures est menée associant la maîtrise d’œuvre conduite par Jean-Louis Rebière et le LRMH. Les analyses révèlent une peinture à sec après mise en place des tracés sur enduit frais. La palette est composée de noir de carbone, de carbonate de calcium, d’ocre jaune, d’ocre rouge, de vermillon, de minium mais aussi d’un pigment plus spécifique à cette aire géographique, l’aérinite. Le minium s’est manifestement transformé en plattnérite et en paralaurionite, conférant un aspect noir aux surfaces où il est employé.After the discovery of roman murals in Saint-Pierre d’Ourjout church (Bordes-Uchentein, Ariège), the architect and the « Laboratoire de recherche des monuments historiques » were asked to study the implementation and the composition of the paintings. The analyses allowed us to say that the paintings are not frescoes, even if the lines were realized in fresh coating. the colors are carbon black, calcium carbonate, yellow ochre, red ochre, vermilion, mimium, and also aerinite, a more specific pigment from this area. Minium certainly turned into plattnerite and paralaurionite, darkening surfaces where it was used