FrançaisCICRP – Centre Interrégional de Conservation et Restauration du Patrimoine
[CICRP - Interregional Centre for Heritage Conservation and Restoration]
Darkening of lead pigments
development of a new restoration technique using irradiation laser
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Program
Previous research works of CICRP have lead to understand the chromatic transformation of lead pigments as blackening or whitening; they were more particularly focussed on the behaviour of wall painting minium over natural ageing.
During the alteration, minium and lead white (hydrateous lead carbonate) generally change into secondary phases as PbO2 which blacken wall paintings colours. This phenomenon is considered as irreversible and depends on different factors as scientific references propose: the painting technique (a fresco, a tempera etc.), the environment (humidity, pollutants, temperature, sunlight etc.), and the microbial activity. Our results showed that the manufacture of minium is also able to favour the blackening because this worked pigment is generally made up of a mixture of lead oxide compounds (Pb3O4/PbO) and the lead monoxyde is very sensitive to alteration.
The current wall painting restoration techniques are quite inadequate. Some chemical treatments are sometimes done on blackened white lead but they can be inefficient and can weaken the support. No specific technique to minium restoration exists.
Our previous works along with other scientific studies showed that PbO2 could be chemically reduced under a thermal treatment with successive oxygen losses. The irradiation laser was notably able to reverse darkened pigment and brings back the original colour.
Our current work aims to:
- Find the most efficient laser source which permits this treatment and to adjust its main parameters (including wavelength, absorption coefficient)
- Develop an appropriate protocol of the darkened minium treatment including the treatment duration, the surface density of the power
- Verify the amplitude of the treatment: would the reversion be total or not? Does the treatment induce disorders? Would some complementary treatment be associated? Will the treatment increase or decrease the duration of the restoration?
You may download a poster on this program (only in french) PDF (971 kilo octets).
Research team on the irradiation laser technique
Dr. Sébastien Aze, Dr. Philippe Delaporte (L.P.3, U.M.R. 6182, CNRS -National Center for Scientific Research- Marseille).
Pr. Dr. Alain Baronnet, Dr. Olivier Grauby (CINaM -Nanoscience Interdisciplinary Center of Marseilles-, U.P.R. 7251, C.N.R.S. Marseille).
Dr. Vincent Detalle (LRMH -Historical Monuments Research Laboratory).
Dr. Jean-Marc Vallet (CICRP).
Publications
Aze S., Delaporte P., Detalle V., Grauby O., Vallet J.M., Baronnet A., "Towards the restoration of darkened red lead-containing mural paintings: a preliminary study of the a-PbO2 to Pb3O4 reversion by laser irradiation", International Conference on Lasers in the Conservation of Artworks, Madrid, LACONA VII, (17 – 21 /09/ 2007). In press.
Aze S., Delaporte P., Vallet J.M., Detalle V., Grauby O., "Le noircissement du minium dans les oeuvres peintes: vers une technique de restauration par irradiation laser", Congrès P.N.R.C.C. Paris, In press.
Aze S., Detalle V., Vallet J.-M., Pingaud N. "L'altération des pigments au plomb : étude du minium et de sa possible reconversion", L'Actualité Chimique, avril 2008, n°318, pp. 9-15.
Aze S., Vallet J.-M., Baronnet A., Grauby O. (2007), "Bungalow of the Moulay Imail's Berber favourite (Meknes, Morocco) : study of the polychromy on wooden pillars", Rencontre internationale sur le Patrimoine architectural méditerranéen, (RIPAM 2005), 26-28/09 2005, Meknès (Maroc), in Minbar Al Jamaia n° 7, Actes de la RIPAM 2005, Meknès, Maroc-2007, pp. 247-254.
Aze S., Vallet J.-M., Baronnet A., Grauby O. (2006), "The lighting of red lead pigment in mural paintings : tracking the physico-chemical transformations by menas of complementary micor-analysis techniques.", European Journal of Mineralogy, Volume 18, Number 6, November 2006, pp. 835-843.
Aze S., Vallet J.-M., Detalle V., Grauby O., Baronnet A. "Chromatic alterations of red lead pigments in artworks: a review", Phase Transitions, Volume 81, Issue 2-3 February 2008 , pages 145 - 154.
Aze S., Vallet J.-M., Detalle V., Pingaud N., Hugon P., Guivarc'h M., Pomey M., Baronnet A., Grauby O. (2006), "Le noircissement du minium en peinture murale : compréhension des phénomènes d'altération et premiers essais de restauration sous faisceau laser.", in Couleurs et Temps : La couleur dans la conservation et restauration., 12èmes Journées d'études de la SFIIC, Paris, Institut national du patrimoine, 21-23 juin 2006, pp. 280-291.
Aze S., Vallet J.-M., Grauby O., "Chromatic degradation processes of red lead pigment.", in 13th triennal meeting of the ICOM committee of conservation, Rio de Janeiro (Brazil) : September 22-28th 2002, pp. 549-55 (vol. 2).
Aze S., Vallet J.-M., Pomey M., Baronnet A., Grauby A., "Red lead darkening in wall paintings: natural ageing of experimental wall paintings versus artificial ageing tests", European Journal of Mineralogy, Volume 19, Number 6, November 2007, pp. 883-890.
Student reports
Aze, Sébastien, Altérations chromatiques des pigments au plomb dans les oeuvres du Patrimoine : étude expérimentale des altérations observées sur les peintures murales., Thèse de Doctorat en sciences de l'environnement, Université d'Aix-Marseille III, 208 pages.
Aze, Sébastien, Etude des altérations chromatiques du minium dans les oeuvres d'art : le cas des peintures murales., Mémoire de D.E.A. "Archéomatériaux", Université de Bordeaux III, U.F.R. Histoire de l'Art et Archéologie, 2001, 61 pages.
Delque, Mélissa, Décoloration des peintures murales à base de blanc de plomb : étude expérimentale sous vieillissement climatique., Mémoire de D.E.S.S. "Matériaux : élaboration, caractérisation et traitement de surface", 2001, Université Paul Sabatier Toulouse III, laboratoire de cristallographie (C.N.R.S.-U.M.R. 5563), 2 volumes, 73 pages.
Marfaing, Muriel, Processus de dégradation du minium utilisé comme pigment dans les oeuvres d'art : caractérisation et approche expérimentale., Mémoire de D.E.S.S. "Matériaux : élaboration, caractérisation et traitement de surface", 99 p.
Auzende, Anne-Line, Caractérisation des processus d'altération du blanc de plomb., 1998, 34 p.
Le Ho, Anne-Solenn, Etude et caractérisation de l'altération du minium dans les peintures murales., Mémoire de Maîtrise des Sciences de la Terre, Université Aix-Marseille III, Faculté des sciences et techniques de Saint-Jérôme et Université de Provence centre de Saint-Charles, 1998, 2 volumes, non paginés.
Page mise à jour le 17 juin 2008.
C.I.C.R.P. - Centre interrégional de conservation et restauration du patrimoine
Groupement d'Intérêt Public à caractère Culturel
- 21 rue Guibal - 13003 Marseille
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