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.