Duration: 2002–2009

CICRP: Philippe Bromblet, Jean-Marc Vallet

Partnerships(s): Bureau of Geological and Mining Research (BRGM), Historic Monuments Research Laboratory (LRMH) and Olivier Rolland, restorer

This research programme, launched in 2002 on Bourges Cathedral, has subsequently benefited from financing for a duration of two years (2004–2006) under the National Research Project on the Conservation and Knowledge of Heritage (PNRCC) on the isotopic tracing of sulphate sources leading to the weathering of stone monuments.

The objectives were the following:

  • to specify the origins of the soluble sulphates responsible for the degradation of the stones
  • to identify and quantify the contributions of different sources identified, whether natural and internal to the stone (e.g. pyrite) or external (marine sprays), unintentional anthropogenic (urban atmospheric pollution) or intentional (plaster, Roman cement).

Different sites of investigation were selected for their environmental characteristics and their type of stone: the cathedrals of Bourges, Chartres and Marseille, and the châteaux of Chenonceau and of Versailles (garden).

The new aspect of the methodology concerns the use of a multi-isotopic ‘toolbox’ including the measurement of the isotopic signature of sulphur and oxygen constituting these solid sulphates (‘SO4’) and of the boron present in traces in the form of borates (‘BO3’). The isotopic analyses have been carried out on altered stone, mortar, plaster and black crust samples taken in different conditions from the different sites. The isotopic analyses have thus made it possible to shed light on the respective contributions of the sulphates originating from atmospheric pollution (classed under ‘black crust’) and from the materials (plaster, mortars). The use of isotopic dosages of sulphur and oxygen constitute a promising tool in determining the origins of sulphates associated with the degradation of stone.

Publications:

  • Kloppmann W., Rolland O. and Bromblet Ph., ‘Isotope study (S,O) of sulphate neoformations involved in the degradation of stones on Bourges Cathedral (France): internal versus external salt sources’, Proceedings of the 10th International Congress on Deterioration and Conservation of Stone, Stockholm, Sweden, 2004, p. 595–602.
  • Vallet J.-M., Gosselin C., Bromblet Ph., Rolland O., Vergès-Belmin V. and Kloppmann W., ‘Origin of salts in stone monument degradation using sulphur and oxygen isotopes: first results of the Bourges Cathedral (France)’, Journal of Geochemical Exploration, vol 88, 1–3, Jan–march 2006, GES-7, 7th International Symposium on the Geochemistry of the Earth’s Surface, 23–27 August 2005, Aix en Provence, p. 358–362.
  • Kloppmann W., Vergès-Belmin V., Gosselin C., Rolland O., Bromblet Ph., Vallet J.-M. and Dotsika E., ‘Isotope (sulphur, oxygen, boron) tracing of internal or external origin of sulphates involved in the degradation of French monuments (BOS project)’, Proc. of the 7th European Conference ‘Sauveur’, Safeguarded Cultural Heritage, Understanding & Viability for the Enlarged Europe, 31st may – 3rd June 2006, Prague, Czech Republic, 2007, vol. 1, p.437–440.
  • Kloppmann W., Vergès-Belmin V., Rolland O., Bromblet Ph., Vallet J.-M. and Gosselin C., ‘Néoformation de sulfates comme facteur de dégradation des pierres des monuments : détermination par traçage isotopique (B, O, S) des sources internes et externes du soufre’, Proceedings of the symposium Science des matériaux du patrimoine culturel, 6 and 7 December 2007, Paris, France, Techné, Special Issue, 2008, p.114–119.
  • Kloppmann W., Bromblet Ph., Vallet J.-M., Vergès-Belmin V., Rolland O., Guerrot C. and Gosselin C., ‘Building materials as intrinsic sources of sulphate: A hidden face of salt weathering of historical monuments investigated through multi-isotope tracing (B, O, S)’, (2011) Sci Total Environ, 409, pp. 1658–1669.

Duration: 2007–2010

CICRP programme steering: Philippe Bromblet (director) and Jean-Marc Vallet

Partnership(s): Center for Interdisciplinary Nanoscience of Marseille (CINaM), Paul Cézanne Aix University – Marseille III

The research efforts on the role of soluble salts in the alteration of materials have been carried out primarily in the context of the doctorate of Julie Désarnaud, student co-supervised by the CINaM and the CICRP. This doctorate, entitled ‘Alteration process of stones by cristallisation of soluble salts’, has been financed by a PACA regional grant.

This research has consisted in renewing the experiments carried out since 1920 (Taber, Correns etc.) that are at the root of the concept of cristallisation pressure. An experimental device was developed to measure the displacement induced by potential growth of the constrained faces of a KCl crystal submerged in a saturated solution in a controlled environment of T and HR and subjected to a known initial theoretical constraint on its upper face. The dimensions and weights of crystals are monitored before and after the experiment. The development of the height of the crystal is continuously monitored during the entire duration of the experiment by a displacement sensor. The experiment is carried out under different conditions (contact or near-contact of the mechanical constraint and the crystal, different rates of solution saturation etc.). In every case, the height of the crystal decreases progressively through the dissolution of the constrained summital and basal faces. The constrained faces have a higher solubility than the non-constrained faces and dissolve under mechanical constraint in every scenario, in accordance with Riecke’s principle as well as the general laws of crystalline growth. These experiments call into question the notion of crystallisation pressure as referred to in alteration phenomena of stone relating to soluble salts.

Publications:

  • Workshop CRYSPOM 1 organised by the École Nationale des Ponts et Chaussées in Paris in 2008, communication and publication of the summary ‘Crystal growth under mechanical constraint: new experimental results using KCl‘, J. Désarnaud, p. 1.
  • Workshop CRYSPOM 2 organised by ETH Zurich in 2010 at Brienz, Switzerland, communication and publication of the summary, ‘Growth and dissolution of a loaded KCl crystal: Impact and limit of the supersaturation rate‘, Desarnaud J., Baronnet A., Bromblet P., Vallet J.-M. and Grauby O., p. 1.
  • Désarnaud J., Baronnet A., Bromblet P., Grauby O. and Vallet J.-M. (2008), ‘Crystal growth under mechanical constraint: new experimental results using KCl’, Proceedings from the International Conference on Salt Weathering of Buildings and Stone Sculptures, 22–24/10/2008, Copenhagen, Denmark, Technical University of Denmark, 103–113.
  • Désarnaud J., ‘Mécanisme de croissance et de dissolution de cristaux de KCl sous charge, apport dans la connaissance des altérations des pierres par les sels’, thesis of Paul Cézanne Aix University – Marseille III, 2009, p. 197.
  • Désarnaud J., Baronnet A., Bromblet P., Grauby O. and Vallet J.-M., ‘Growth and dissolution of crystals under load: new experimental results on KCl‘, submitted to Crystal Growth & Design.

Duration: 2007–2011

CICRP: Philippe Bromblet

Partnership(s): Regional Archaeology Department and Regional Directorate of Cultural Affairs (DRAC), Provence Alpes Côte d’Azur; Vaucluse Archeology Department; Laboratory of Medieval Mediterranean Archaeology; Historic Monuments Research Laboratory (LRMH)

The purpose of this project is to study the use of Caromb stone in construction efforts from antiquity to the 19th century. This consists primarily in demonstrating how and why this stone became widespread over a large territory (Carpentras, Avignon, Aix) and was used as a substitute for other stone materials (Orgon stone), eventually itself giving way to other regional stones from the 19th century onwards (Crillon stone). This research, carried out in collaboration with historians, archaeologists and geologists, aims to compare samples with the provenance indicated in texts describing approximately 15 structures, and to study the principal characteristics and weathering behaviour of Caromb stone.

Publication:

Bernardi P., Bromblet P., Barret R., Vallet J.-M., Mignon J.-M. and Lise Leroux, ‘La production de pierres à Caromb (Vaucluse) : premiers résultats d’une enquête sur une industrie rurale au Moyen Âge’ (2008), Proceedings of the international symposium Pierres du Patrimoine Européen, Economie de la pierre de l’Antiquité à la fin des temps modernes, 18–21 October 2005, Château-Thierry.


Duration: 2006–2009 CICRP programme director: Philippe Bromblet, Jean-Marc Vallet

Partnership(s): University of Venice, Athens Institute of Geology and Mineral Exploration, Historic Monuments Research Laboratory (LRMH), restoration companies Lithos (Italy) and Pons-Asini (Germany), Algerian Ministry of Culture, the Supreme Council of Antiquities, the cultural heritage departments and the universities of Boumerdès (Algeria) and Meknes (Morocco)

From 2006 to mid-2009, the CICRP participated in a European Mediterranean cooperation programme entitled MEDISTONE (preservation of ancient MEDIterranean sites in terms of their ornamental and building STONE). The partners worked on the conservation of three large iconic sites: the ancient cities of Cuicul (Djémila, Algeria) and Volubilis (Morocco) and the stones of the Lighthouse of Alexandria (Egypt) retrieved from the water.

Three lines of research have been pursued: the identification of the origins of the stones used, the assessment of deterioration and the development of a stone reconstruction technique.

Publications:

This project gave rise to approximately 20 publications and communications. Several students have collaborated and a thesis was defended at the Université des Sciences de Meknès.

Dessandier D., Antonelli F., Bouzidi R., Bromblet P., El Rhoddani M., Kamel S., Lazzarini L., Leroux L., Vallet J.-M. and Varti-Matarangas M., Guide des pierres du site antique de VOLUBILIS (Maroc), (2010) Publications of Université Moulay Ismaïl, Edited by Saïd Kamel, p. 57.

Dessandier D., Bromblet Ph., Vallet J-M., Cadot-Leroux L., Akarish A., Nageh A. and Shoieb A., ‘Contribution to the study of the building stones and monumental sculptures of Alexandria lighthouse (Egypt)’, Proceedings of the 11th International Congress on Deterioration and Conservation of Stone, Toruń, Poland, org. by N. Copernicus University, edited by Lukaszewicz J. W. and Niemcewicz P., 2008, p. 1189–1196.


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.