Programme start: 2011

CICRP: Philippe Bromblet

Partnership(s): Bureau of Geological and Mining Research (BRGM), Historic Monuments Research Laboratory (LRMH), University of Paris 6

The purpose of this research is to develop a method of determining the origin of alabasters with the aid of isotopic tools. This soft material, primarily composed of gypsum (CaSO4, 2H2O), has been used in fine art sculpture from the Middle Ages to the Renaissance. Although the main supply sources in Europe are known (Spain, Italy, France, England etc.), it is at this time impossible to determine the precise provenance of the alabaster used in a given piece. It is thus a question of collecting samples from quarries and sculptures to carry out a feasibility study on the identification of the provenance of alabasters by the combination of different isotope dosages (S, O, Sr) along with the dosage of trace elements, the dosage of strontium and the examination of cathodofacies and the mineralogy. A first series of alabasters sampled from quarries (France, Spain) and sculptures from several French, English and Norwegian museums and monuments have already been studied and have yielded promising results.

Publications:

  • Poster presented at the European Geosciences Union congress in Vienna (Austria) in May 2011. Kloppmann W., Bromblet Ph., Leroux L., Cooper A., Worley N. and Guerrot C. (2011b), ‘Origin of European alabaster artworks assessed through isotope fingerprinting (S, O, Sr)’, European Geosciences Union General Assembly 2011, Vienna, Austria, 02–08 April 2011. Geophysical Research Abstracts, Vol. 13, EGU2011-3419.
  • Kloppmann W., Leroux L., Bromblet P., Guerrot C., Proust E., Cooper A.H., Worley N., Smeds S.A. and Bengtsson H.,’Tracing Medieval and Renaissance alabaster artwork back to quarries: A multi-isotope (Sr, S, O) approach’, accepted for publication (Oct. 2012) Archaeometry

Programme start: 2006

CICRP: Jean-Marc Vallet (director), Philippe Bromblet

Partnership(s): Aix-Marseille University; Paul Sabatier University, Toulouse; Historic Monuments Regional Department of Archaeology and Conservation (CRMH) Provence-Alpes-Côte d’Azur; Mercantour National Park

The purpose of the programme launched by the PACA Regional Archaeology Department is to establish the degradation kinetics of rock engravings in the Vallée des Merveilles (altitude of sites above 2,200 m) and to establish a predictive model for the evaluation of the risks and speed of total disappearance of the engravings using different benchmark cases. Its goal is to propose methods of conservation and restoration appropriate to the different cases encountered (site, lithotype, type of degradation).

Engraving

Washed out and eroded engraving, with the development of cyanophytes

(Vallée des Merveilles, photo J.-M. Vallet – CICRP)

The work began with a study on the origin of the red surface colouring on the engraved rocks. An on-site and laboratory investigation involving several lots of engravings has revealed that the engraved stones bore different colours (orange, red, purplish), apparently through different processes. Some of these colours were the result of the transformation of the rock bearing the engravings, while others were due to deposits of mater of varied origins. Currently the work is focusing on relative dating for these colourings and the development of different approaches towards understanding the degradation phenomena and their kinetics, with the aim of determining optimum conservation measures.

Publications:

  • Poster from the 14th International Clay Conference (Castellaneta Marina, Italy, 2009)
  • Poster from the 12th International Congress on the Deterioration and Conservation of Stone (New York, United States, 2012)

Programme start: 2003

CICRP: Philippe Bromblet, Jean-Marc Vallet

Partnerships: Meknes Faculty of Sciences (Morocco), CEREGE (Aix-Marseille University)

A joint venture was launched between the Meknes Faculty of Sciences, the city of Meknès and the CICRP to study the deterioration of the ramparts and main rammed-earth monuments of the ancient imperial city. Several sampling campaigns, a university thesis and specialist field investigations have been used to shed light on the materials and construction methods used, as well as assess the primary degradations and determine methods to improve the protection of these structures.

Morocco

Measurement of the speed of sound on a block of stone

before restoration (Volubilis, Morocco) (photo Philippe Bromblet)

Publications:

  • Bromblet P., Vallet J.-M., Ajakane R., Kamel S., Mahjoubi R. and Meunier J.D., ‘Caractérisation de l’enduit dégradé d’une muraille aqueduc de l’ancienne ville impériale de Meknès (Maroc)’, Minbar Ai Jamiaa, 7, Proceedings of the RIPAM 2005, 2007, pp. 236–246.
  • Ajakane R., Kamel S., Mahjoubi R., Vallet J.-M., Bromblet P., Meunier J.D. and Bouadid R. (2007), ‘Caractérisation des matériaux et de l’altération des remparts pour une restauration adaptée : exemple d’une muraille du contrefort de Hri Souani, Médina de Meknès, Maroc’, RehabiMed, 1st Euro-Mediterranean Regional Conference, Present and Future, Barcelona 12–15 July 2007, pp. 453–456.
  • Kamel S., Ajakane R., Mahjoubi R., El Faleh E.M., Vallet J.-M., Bromblet P., Meunier J.D., Noack Y. and Borschnek D., ‘Caractérisation des materiaux de construction des remparts de la medina de meknes : exemple de la muraille de Sidi – Baba (Meknès, Maroc)’, Echanges transdisciplinaires sur les constructions en terre crue, 2. Proceedings of the roundtable of Villefontaine 28–29 May 2005, Editions de l’Espérou, Montpellier, 2007, pp. 23–32.
  • Ajakane R., Kamel S., Mahjoubi R., Vallet J.-M., Bromblet P. and Meunier J.D., ‘Impact de l’altération météorique sur les murailles de la médina de Meknès (Maroc)’, Proceedings of the International Meeting on Mediterranean Architectural Heritage (RIPAM 2005), 26–28 Sept 2005, Meknès, ENSAM, pp. 119–120.
  • Ajakane R, Kamel S., MahjoubiI R., Vallet J.-M., Bromblet P., Bouabib R., Meunier J.D., Noack Y., Borschnek T. and Guillot H., ‘Preliminary studies on the degradations of the Medina’s ramparts of Meknès (Morocco)’, Proceedings of the 10th International Congress on Deterioration and Conservation of Stone, Stockholm, 2004.
  • Kamel S., Mahjoubi R., Arsalan S, Vallet J.-M. and Bromblet P., ‘Chantier expérimental de restauration sur un bâtiment de la Médina de Meknès (Maroc) en vue d’une méthodologie adaptée’, Proceedings of the international symposium Réhabilitation et revalorisation du patrimoine bâti, 23 and 24 May 2011, Skikda, Morocco, T2, pp. 770–782.

Programme start: 2011

CICRP: Philippe Bromblet

Partnership(s): French Heritage Partners Circle, Historic Monuments Research Laboratory (LRMH) (director), VICAT SA

The object of this programme is to tackle questions of restoration for facades decorated with natural cement based plasters in the Marseille region by proposing a restoration plaster suited to the supports and with colours and textures close to those of these 19th-century plasters.

It includes an examination of the sate of conservation and nature of the natural cement based plasters on Marseille facades, a documentary study on this industrial activity of the 19th and early 20th centuries, as well as visits to quarries (Roquefort-la-Bédoule etc.) and factories (ovens) to sample and analyse the raw materials in order to carry out the rare analyses found in the literature.

Facade decoration

Natural cement: facade decoration of the Eglise de la Mission de France carried out in 1860

by the company Désiré Michel, rue du Tapis Vert, Marseille (photo Philippe Bromblet)

The CICRP has participated in the sampling campaign and management of a documentary research initiative on the history of the manufacture of natural cements from the Marseille region.

Publications:

  • ‘Les enduits à base de ciment naturel à Marseille : Identification et restauration’, literature survey carried out by Claire Valageas, research analyst at the French Heritage Partners Circle, 2011.
  • ‘Histoire de l’industrie des ciments naturels dans la région de Marseille’, presentation by Claire Valageas for the ICOMOS technical days (2 and 27 April 2012, Paris) Les ciments naturels dans le patrimoine européen : histoire, propriétés, applications et conservation.

Programme start: 2010

CICRP: Philippe Bromblet, Jean-Marc Vallet (directors)

Partnerships(s): Mediterranean House of Human Sciences (MMSH), Aix-Marseille University, National Institute for Preventive Archaeological Research, Territorial Collectivity of Corsica (CTC)

For several years the CICRP has worked to gain a deeper understanding of the deterioration mechanisms affecting these granite monoliths, which at the beginning of the 1990s underwent a restoration effort that turned out to be unsuitable. The work has focused on monitoring the development of the degradation through observation and measurement of the speed of sound propagation as well as accelerated ageing specimen testing. The results obtained have shown that the degradation of the surface of carved stones had developed and that ethyl silicate combined with a waterproofing treatment (silane) seemed to offer better results in terms of durability than ethyl silicate alone or acrylic resins. The work in progress aims to determine which consolidation treatment would produce the best results in terms of durable preservation for the sculpted and highly fragile outer layer of these standing stones.

I Stantari

Corsican I Santari granite: view of the statue-menhirs (photo Philippe bromblet)

Publications:

  • Vallet J.-M., Bromblet P. & Bouillon N., ‘Du diagnostic à la conservation du Patrimoine archéologique en pierre en milieu isolé : quelle démarche adopter ? Exemple des statues- menhirs en granite d’I Stantari’, Proceedings of the roundtable CONSERVER, ETUDIER, PROTEGER LE PATRIMOINE EN MILIEU ISOLE, Mariana, 9-11 October 2008, in press.
  • Vallet J.-M., Bromblet P., Heddebaux E., Bouillon N., ‘Conservation of archaeological Megalithic sites under marine environment: example of the granitic menhirs at I Stantari (Cauria plateau, Corsica Island, France)’, Proceedings of the 12th International Congress on the Deterioration and Conservation of Stone, New York, 22–26 October 2012.

Programme start: 2009

CICRP: Philippe Bromblet (director), Jérémie Berthonneau (doctoral student 2010–2012), Jean-Marc Vallet

Partnership(s): Bureau of Geological and Mining Research (BRGM), Center for Interdisciplinary Nanoscience of Marseille (CINaM) (Aix-Marseille University), PACA Regional Council

This project forms the topic of a thesis (Jérémie Berthonneau) cofinanced by the BRGM, the PACA Regional Council and the CICRP, focusing on the role of clays in the deterioration of stone, and more specifically on the spalling affecting monuments built from Burdigalian molasses in the region. Petrophysical, petrographic and mineralogical profiles as well as hydric and hygric dilation tests have been carried out on the full range of samples taken from approximately 30 quarries and a few monuments. Field visits have been carried out to evaluate the durability of the stones studied in the regional heritage. These investigations have shown that there is a relationship between the clay content, the amplitude of the dilations and the alterability of the molasse. Qualitative and quantitative analyses of clay minerals are in progress using different methodologies (DRX and MET/EDS) on approximately 10 of the more alterable and clay-rich facies to determine precisely the impact of swelling clay materials and their location in the material in the development of spalling.

Publications:

  • J. Berthonneau, ‘Relationships between internal properties and durability in the “Molasse du Midi” limestone (South-East of France)‘, Euromat Colloquium, Montpellier 2011, summary and communication
  • J. Berthonneau, O. Grauby, A. Baronnet, D. Dessandier, P. Bromblet and J.-M. Vallet, ‘Role of swelling clay minerals in the spalling decay mechanism of the “Molasse du Midi” limestone (South-east of France)’, 12th International Congress on the Deterioration and Conservation of Stone, 2012.