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

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)

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

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

Estudio técnico de las pinturas murales de Germolles: la contribución de las técnicas de imagen

[EN] The Château de Germolles is one of the rare palace in France dating from the 14th century. The noble floor is decorated with wall paintings that are a unique example of courtly love spirit that infused the princely courts of the time. After being concealed sometime in the 19th century, the paintings were rediscovered and uncovered in the middle of the 20th century and partly restored at the end of the 1990s. No scientific documentation accompanied these interventions and important questions, such as the level of authenticity of the mural decorations and the original painting technique(s) used in the medieval times remained unanswered. The combined scientific and financial supports of COSCH Cost Action and DRAC-Burgundy enabled to study Germolles’ wall paintings using some of the most innovative imaging and analytical techniques and to address some of the questions raised. The study provided significant information on the material used in the medieval times and on the conservation condition of the paintings. The data collected is vast and varied and exposed the owners of the property to the challenges of data management.[ES] El castillo de Germolles es uno de los raros palacios principescos en Francia que data del siglo XIV. La planta noble está decorada con pinturas murales que son un ejemplo único del amor cortés, ese espíritu que se divulgó en las cortes de la época.Ocultadas desde el fin del siglo XIX, las pinturas fueron descubiertas en la mitad del siglo XXy fueron parcialmente restauradas al finalde la década de 1990. No hay documentación científica queacompañelas intervenciones, y cuestiones importantesse quedaronsin repuesta, en particular el nivel de autenticidad de las decoraciones de las paredes, así como lastécnicaspictóricasutilizadasen laépoca medieval. El apoyo científico y económico de la Acción Cost COSCH y de la DRAC de Borgoña permitió elestudio delas pinturas murales de Germolles con algunas de las técnicas de imagen y analíticasmás innovadoras, con tal de responder a algunas de las cuestiones planteadas. El estudio proporcionó informaciónrelevante en lo que se refiere al material utilizado durante la Edad Mediay sobreel estado de conservación de las pinturas. La toma de datos es ampliay variada, y expuso a los dueños de la propiedad al desafío de la gestión de datos.This project would not have been possible without the financial support by DRAC-Burgundy and the COST Action TD1201: Colour and Space in Cultural Heritage (COSCH) (www.cosch.info) which the authors wish to sincerely thank.Degrigny, C.; Piqué, F.; Papiashvili, N.; Guery, J.; Mansouri, A.; Le Goïc, G.; Detalle, V.... (2016). Technical study of Germolles’ wall paintings: the input of imaging technique. Virtual Archaeology Review. 7(15):1-8. https://doi.org/10.4995/var.2016.5831SWORD18715Giovannoni, S., Matteini, M., & Moles, A. (1990). Studies and developments concerning the problem of altered lead pigments in wall painting. Studies in Conservation, 35(1), 21-25. doi:10.1179/sic.1990.35.1.21Manuel, A., Gattet, E., De Luca, L., & Veron, P. (2013). An approach for precise 2D/3D semantic annotation of spatially-oriented images for in situ visualization applications. 2013 Digital Heritage International Congress (DigitalHeritage). doi:10.1109/digitalheritage.2013.6743752Wefers, S., Reich, T., Tietz, B. and Boochs, F. 2016. SIVT – Processing, Viewing, and Analysis of 3D Scans of the Porthole Slab and Slab B2 of Züschen I. In: S. Campana, R. Sopigno, G. Carpentiero and M. Cirillo, eds, CAA2015. Keep the Revolution Going. Proceedings of the 43rd Annual Conference on Computer Applications and Quantitative Methods In Archaeology. Oxford : Archaeopress Publishing Ltd, pp. 1067-1080

Time-Gated Pulsed Raman Spectroscopy with NS Laser for Cultural Heritage

Raman spectroscopy, a non-destructive reference technique, is used in heritage science to directly identify materials like pigments, minerals, or binding media. However, depending on the material, the laser source can induce a strong fluorescence signal that may mask the Raman signal during spectral detection. This photo-induced effect can prevent the detection of a Raman peak. A pulsed Raman spectroscopy, using a time-gated detection and pulsed laser, is proven capable of rejecting the fluorescence background and working with the environmental light, which makes Raman spectroscopy more adapted for in situ applications. In this paper, we investigated how an ns pulsed laser can be an excitation source of Raman spectroscopy by focusing on different parameters of laser excitation and collection. With proper implementation, this pulsed Raman technique can be used for cultural heritage with an ns pulsed laser for the first time

Time-Gated Pulsed Raman Spectroscopy with NS Laser for Cultural Heritage

Raman spectroscopy, a non-destructive reference technique, is used in heritage science to directly identify materials like pigments, minerals, or binding media. However, depending on the material, the laser source can induce a strong fluorescence signal that may mask the Raman signal during spectral detection. This photo-induced effect can prevent the detection of a Raman peak. A pulsed Raman spectroscopy, using a time-gated detection and pulsed laser, is proven capable of rejecting the fluorescence background and working with the environmental light, which makes Raman spectroscopy more adapted for in situ applications. In this paper, we investigated how an ns pulsed laser can be an excitation source of Raman spectroscopy by focusing on different parameters of laser excitation and collection. With proper implementation, this pulsed Raman technique can be used for cultural heritage with an ns pulsed laser for the first time

Analyses de la polychromie des clefs de voûte du choeur de la cathédrale de Chartres

Analyse der Farbfassung der Schlusssteine im Chor der Kathedrale von Chartres, von Émilie Checroun, Vincent Detalle und Isabelle Pallot-Frossard Die Analyse der Farbfassung der Putze und der Schlusssteine erbrachte nicht nur Kenntnisse über ihre Zusammensetzung, ihre Pigmente und die dabei eingesetzten Techniken, sondern auch den Nachweis, dass es sich dabei um die originale Bemalung handelt.Analyses of the polychromy on the keystones in the choir of Chartres Cathedral, by Émilie Checroun, Vincent Detalle, Isabelle Pallot-Frossard The analysis of the polychromy of the revetments and the keystones permitted the identification of the components, pigments, and techniques used, and confirmed that this was the original decoration.L’analyse de la polychromie des enduits et des clefs de voûte permet non seulement de connaître les composants, les pigments et les techniques mises en oeuvre, mais aussi d’affirmer que ce décor est bien celui d’origine.Checroun Émilie, Detalle Vincent, Pallot-Frossard Isabelle. Analyses de la polychromie des clefs de voûte du choeur de la cathédrale de Chartres. In: Bulletin Monumental, tome 169, n°1, année 2011. La cathédrale de Chartres. Restaurations récentes et nouvelles recherches. pp. 27-28

Stimulated infrared thermography applied to thermophysical characterization of cultural heritage mural paintings

The purpose of this paper is to approach stimulated infrared thermography possibilities in terms of measuring longitudinal thermal diffusivity of mural paintings in situ. The measuring method principle is first submitted. It is based on temporal analysis of changes in the characteristic radius beams of spatial profiles of the photothermal signal, measured on the spot of the laser excitation. The feasibility of the method is demonstrated, thanks to a series of simulations. Lastly, the method enables to correctly estimate longitudinal thermal diffusivity in a test sample, and further in a fragment copy of “Saint Christophe” belonging to the Campana collection in the Louvre