New methodology for the elimination of corrosion in archaeological metal heritage: buffers, chelators, gels and emulsions
Keywords:
corrosión, metal arqueológico, soluciones tampón, quelación, geles, emulsionesAbstract
Elimination of corrosion in archaeological metal heritage has always been a challenge for conservators.
The proposal here presented tries to bring improvements towards a reasoned, individualised, selective and respectful restoration. The methodology includes soft, gelled and controlled physicochemical treatments with which it is possible to be highly selective in the elimination of corrosion products. By using controlled chelation within metal-safe pH buffer solutions, we can remove metal ions that are part of the corrosion metal salts but not the constituent metal atoms. In this way, the corrosion products are dissolved, leaving the original preserved surface visible. As no mechanical work is required, a level of cleanliness that is normally difficult to attain can be achieved. In addition, as it is a stratigraphic, slow and gradual process, the cleaning can be stopped at any time, depending on the intervention criteria and the needs of each case. This method has been used to remove copper chlorides, oxides and carbonates; iron chlorides, oxides and hydroxides; lead acetates, oxides, chlorides and carbonates, etc. It is also a method capable of removing surface layers, carbonate concretions and different kinds of salts. As it is non-toxic, the method is environmentally friendly and respectful of the conservator’s health.
Downloads
References
Ahedo, C. (2017): “The use of gel Systems for cleaning water — and solvent — sensitive paintings”. En L.V. Angelova, B. Ormsby, J.H. Townsend y R. Wolbers: Gels in the Conservation of Art. Archetype Publications. London: 356-359.
Angelova, L.V., Ormsby, B., Townsend, J.H. y Wolbers, R. (2017): Gels in the Conservation of Art. Archetype Publications. London.
Barrio, J. (2010): “La tecnología láser aplicada a los procesos de conservación y restauración de objetos metálicos arqueológicos”. Patrimonio Cultural de España 4. Ministerio de Cultura. Madrid: 79-98.
Bertholon, R. y Relier, C. (1990): “Les métaux archéologiques”. En M.C. Berducou (ed.): La conservation en archéologie. Masson. Paris: 163-221.
Borrós, S. y Agulló, N. (2006): “La técnica de plasma frío como herramienta en la restauración y conservación de Material Arqueológico”. En J. Barrio (ed.): Innovación Tecnológica en conservación y restauración del Patrimonio. Serie Tecnología y Conservación del Patrimonio Arqueológico, I. Universidad Autónoma de Madrid. Madrid: 64-73.
Cooper, M. (1998): Laser cleaning in conservation, an introduction. Butterworth-Heinemann. Oxford.
Cremonesi, P. (2004): L’uso di tensioattivi e chelanti nella pulitura di opere policrome. Il Prato, Collana i Talenti. Padova.
Cremonesi, P. (2010): “Rigid gels and Enzym cleaning”. En Mecklenburg, M. (ed.): Cleaning 2010. New insights in the cleaning of paintings. Universitat Politècnica de València: 179-183. <https://doi.org/10.5479/si.19492359.3.1>.
Cremonesi, P. (2015): El ambiente acuoso para el tratamiento de obras polícromas. Il Prato, Collana i Talenti. Padova.
Dean, A. (2004): Dean’s analitycal chemistry handbook. McGRAW-HILL, INC. New York.
Dorge, V. (ed.) (2004): Solvent gels for the cleaning of works of Art. The Residue Question. Getty Conservation Institute Publications. Los Angeles.
Faltermeier, R.B. (1998): “Colour changes induced when treating copper and copper alloy archaeological artefacts with the corrosion inhibitors benzotriazole and amoni-mercapto-thidiazole”. Scottish Society for Conservation and Restoration Journal, 9: 1-6.
Flores, M.LL. y Ferrazza, L. (2011): “Estudio y aplicación del agente quelante DTPA (ácido dietilentriamino pentaacético) como tratamiento de conservación y restauración a una obra de orfebrería con esmaltes”. En S. Díaz y E. García (coords.): IV Congreso Latinoamericano de Conservación y Restauración de Metal. Madrid, del 13 al 17 de septiembre de 2011. GEIIC. Ministerio de Educación, Cultura y Deporte. Madrid: 400-411.
Horie, C.V. y Vint, J.A. (1982): “Chalconatronite: a by-product of conservation?”. Studies in Conservation, 27: 185-186. <https://doi.org/10.1179/sic.1982.27.4.185>.
Huda, K. (2002): “A note of the efficacy of ethylendiaminetetra-acetic acid disodium salt as a stripping agent for corrosion products of cooper”. Studies in Conservation, 47: 211- 216. <https://doi.org/10.1179/sic.2002.47.3.211>.
Lange, N. (1999): Lange’s handbook of chemistry. 15th edition. McGRAW-HILL, INC. New York.
Mourey, W. (1987): La conservation des antiquités métalliques: de la foulle au musée. Éditorial LCRRA. Draguignan.
Organ, R.M. (1963): “Aspects of bronze patina and its treatment”. Studies in Conservation, 8, 1: 1-9. <https://doi.org/10.1179/sic.1963.002>.
Petrie, F. (1904): Methods & Aims in Archaeology. British Library. London.
Plenderleith, H.J. (1967): La conservación de antigüedades y obras de arte. Ministerio de Educación y
Ciencia. Dirección General de Bellas Artes. Madrid.
Pourbaix, M. (1966): Atlas of Electrochemical Equilibria in Aqueous Solutions. NACE International-Cebelcor. Houston-Brussels.
Rakanta, E., Zafeiropoulou, Th. y Batis, G. (2013): “Corrosion protection of steel with DMEA-based organic inhibitor”. Construction and Building Materials, 44: 507–513. <https://doi.org/10.1016/j.conbuildmat.2013.03.030>.
Rathgen, F. (1905): The Preservation of Antiquities. A handbook for Curators. Cambridge University Press. New York.
Richey, W.D. (1975): “Chelating agents, a review”. Studies in Conservation, 20: 229-234. <https://doi.org/10.1179/sic.1975.s1.038>.
Sánchez, R.M., Ibarra, I.J. y Roca, M.J. (2018): Fabricación y optimización de un sistema para limpieza superficial de metales por electrolisis: PLECO. Trabajo Fin de Grado. Grado en Ingeniería Química Industrial. Universidad Politécnica de Cartagena.
Scott, D.A. (2002): Cooper and bronze in Art. Getty Publications. Los Angeles.
Sease, C. (1978): “Benzotriazole: A review for conservators”. Studies in Conservation, 23: 76-85. <https://doi.org/10.1179/sic.1978.011>.
Selwyn, L. (2004): Métaux et corrosion. Un manuel pour le professionnel de la conservation. Institut canadien de conservation. Ottawa.
Sierra, J. L. y Buendía, M. (2018): “Gestión y conservación del conjunto monetario de la Fragata Nuestra Señora de las Mercedes: Restauración de 40.000 monedas”. En M.T. Doménech y A. Doménech (eds.): Third European Conference on electrochemical method applied to the conservation of artworks. Valencia, 28 de marzo de 2017. Editorial Universidat Politècnica de València. Valencia: 90-95.
Thouvenin, A. (1958): “Une nouvelle méthode de déchloruration des bronces antiques provenant des fouilles”. Revue Archéologique, 2: 180-182.
Traver, I. (2011): “Funcionalidad versus conservación en piezas de orfebrería destinadas al culto: el ejemplo del estudio y restauración de la cruz procesional de Tibi”. En S. Díaz y E. García (coords.): IV Congreso Latinoamericano de Conservación y Restauración de Metal. Madrid, del 13 al 17 de septiembre de 2011. GEIIC. Ministerio de Educación, Cultura y Deporte. Madrid: 315-326.
Volfovsky, C. (2001): La conservation des métaux. CNRS Éditions, Paris.
Wolbers, R. (2000): Cleaning Painted Surfaces, Aqueous Methods. Archetype Publications. London.
Wolbers, R. (2012): Macroemulsions/Microemulsions Workshop: New Methods of Cleaning Surfaces. Restauratoren Nederland, Reinwardt Academy. Amsterdam.
Wolbers, R. (2016): Nuevas posibilidades de los sistemas acuosos en los tratamientos de restauración. Retos y estrategias. Workshop. Instituto del Patrimonio Cultural de España. Ministerio de Educación y Deporte. Madrid.
Wolbers, R. (2017): “Gels, green chemistry, gurus and guides”. En L.V. Angelova, B. Ormsby, J.H. Townsend y R. Wolbers: Gels in the Conservation of Art. Archetype Publications. London: 3-8.
Wolbers, R. (2018): General cleaning materials and methods for wall paintings. Workshop. ESCRBCC. Barcelona.