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ABSTRACT
Tarnishing is one of the most crucial issues in the conservation of silver alloy objects. This phenomenon is relevant in the field of cultural heritage artifacts: although the blackish patina protects to a degree against ulterior corrosion effects, it significantly affects the aesthetical features of the artwork. Several different approaches are utilized for cleaning tarnished silver–copper alloy surfaces, including mechanical, chemical, electrochemical methods. The use of lasers is also reported. In this paper a dry approach based on the use of erasers is proposed and compared with traditional methods. The different methods were applied on silver–copper alloy mockups which had been artificially tarnished. They were compared based on the degree of sulfide removal and damage to the silver surface. Diagnostic investigations showed that the use of erasers for silver cleaning resulted in fewer surface modifications compared to traditional mechanical methods with an effective tarnish removal. The proposed method could be broadly considered a low-cost, adjustable, and fast one-step cleaning procedure. Finally, two case studies of application of the technique are reported: cleaning of three Islamic artifacts decorated with silver alloy inlay and of the silver letters on the North Door of the Baptistery of Florence.
RÉSUMÉ
La ternissure est une des problématiques les plus cruciales dans la conservation d'objets faits d'alliages d'argent. Ce phénomène est pertinent dans le domaine des artéfacts du patrimoine culturel: bien que la patine noirâtre protège à un certain point contre les effets d'une corrosion ultérieure, elle affecte de façon significative les caractéristiques esthétiques d'une œuvre d'art. Plusieurs approches différentes sont utilisées pour nettoyer les surfaces ternies d'alliages argent-cuivre, dont les méthodes mécanique, chimique, et électrochimique. On rapporte aussi l'utilisation de laser. Dans cet article, une approche sèche basée sur l'utilisation de gommes à effacer est proposée et comparée à des méthodes traditionnelles. Les différentes méthodes ont été appliquées sur des échantillons d'alliages argent-cuivre ayant été artificiellement ternis. Ils furent comparés selon leur degré de retrait des sulfites et de dommage à la surface d'argent. Des enquêtes diagnostiques ont démontré que l'utilisation de gommes à effacer pour le nettoyage de l'argent causait moins de modifications à la surface comparativement aux méthodes mécaniques traditionnelles avec un retrait efficace de la ternissure. La méthode proposée pourrait être considérée peu couteuses, ajustable, et comme étant un procédé de nettoyage rapide en une seule étape. Finalement, deux études de cas de l'application de la technique sont rapportées: le nettoyage de trois artéfacts musulmans décorés d'incrustations d'alliages d'argent et le nettoyage des lettres d'argent sur la porte nord du baptistère de Florence. Traduit par Monique Benoit.
RESUMO
O embaçamento é uma das questões mais importantes na conservação de objetos de liga de prata. Esse fenômeno é relevante no campo dos artefatos do patrimônio cultural: embora a pátina enegrecida proteja até certo ponto contra os efeitos de uma corrosão posterior, ela afeta significativamente as características estéticas da obra de arte. Várias abordagens diferentes são utilizadas para limpar superfícies de liga de cobre e prata manchadas, incluindo métodos mecânicos, químicos e eletroquímicos. O uso de laser também é relatado. Neste artigo, propõe-se uma abordagem seca baseada no uso de borrachas e se compara com métodos tradicionais. Os diferentes métodos foram aplicados em maquetes de liga de cobre e prata que haviam sido manchadas artificialmente. Eles foram comparados com base no grau de remoção de sulfeto e danos à superfície da prata. Investigações de diagnóstico mostraram que o uso de borrachas para limpeza de prata resultou em menos modificações de superfície em comparação com métodos mecânicos tradicionais com uma remoção eficaz de manchas. O método proposto pode ser amplamente considerado como um procedimento de limpeza em uma única etapa, de baixo custo, ajustável e rápido. Por fim, são relatados dois estudos de caso de aplicação da técnica: limpeza de três artefatos islâmicos decorados com incrustações de liga de prata e limpeza das letras de prata da Porta Norte do Batistério de Florença. Traduzido por Beatriz Haspo.
RESUMEN
El deslustre es uno de los problemas más cruciales en la conservación de objetos de aleación de plata. Este fenómeno es relevante en el campo de los artefactos de patrimonio cultural: aunque la pátina negruzca protege hasta cierto punto contra los efectos ulteriores de corrosión, afecta significativamente las características estéticas de la obra de arte. Se utilizan varios enfoques diferentes para limpiar superficies de aleación de plata-cobre deslustradas, incluidos métodos mecánicos, químicos y electroquímicos. También se informa sobre el uso de láser. En este artículo se propone un enfoque seco basado en el uso de borradores y se compara con los métodos tradicionales. Los diferentes métodos se aplicaron en maquetas de aleación de plata y cobre que habían sido manchadas artificialmente. Se compararon en función del grado de eliminación de sulfuro y el daño a la superficie de la plata. Las investigaciones de diagnóstico mostraron que el uso de gomas de borrar para la limpieza de plata resultó en menores modificaciones de la superficie en comparación con los métodos mecánicos tradicionales con una eliminación eficaz del deslustre. El método propuesto podría considerarse en términos generales como un procedimiento de limpieza rápido, ajustable y de bajo costo en un solo paso. Finalmente, se reportan dos casos de estudio de aplicación de la técnica: limpieza de tres artefactos islámicos decorados con incrustaciones de aleación de plata y de las letras plateadas de la Puerta Norte del Baptisterio de Florencia. Traducción: Amparo Rueda.
Acknowledgments
The authors thank Dr. Clarice Innocenti and Dr. Sandra Rossi, respectively former and current director of the Goldsmith Conservation Department of the Opificio delle Pietre Dure, for their support. Many thanks to conservators Dr. Stefania Agnoletti, Dr. Bruna Mariani, Dr. Mary Yanagishita and Dr. Paolo Belluzzo for fruitful discussions. Thanks to Dr. Massimo Medica and Dr. Mark Gregory D’Apuzzo of the Museo Civico Medievale, Bologna, to the Museo dell’Opera del Duomo, Florence, and to Dr. Francesca Pasquini and Dr. Aelmuire Helen Cleary for their advice in writing the paper.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Notes on contributors
Giulia Basilissi
Giulia Basilissi was born in 1987 in Florence. She has been conducting her studies in the field of conservation and restoration of cultural heritage, initially as a scientific diagnostician and then as a restorer. In 2009 she completed her undergraduate degree in technologies and diagnostic for conservation and restoration of Cultural Heritage – Università di Firenze, Florence, Italy, and, in the same year, she attended a trainee at the Institute of Applied Physics Nello Carrara (IFAC) – National Research Centre (CNR), Florence. In 2015 she completed a master’s degree in conservation of cultural heritage of metals and alloys, ceramics, waxes and glass, at the Opificio delle Pietre Dure in Florence. From 2015 to 2018 she worked as a freelance restorer-conservator. Since December 2018 she has worked as a conservator at the Direzione Regionale Musei della Toscana (Tuscany Museums), Florence. Address: Opificio delle Pietre Dure e Laboratori di Restauro, Viale Strozzi 1, Firenze 50129, Italy. Email: [email protected].
Annalena Brini
Annalena Brini is a conservator of cultural heritage, specialized in metal artworks (steel and iron, bronze, brass, gold, silver, lead) and archeological objects. In 1983 she obtained her master's degree in conservation and restoration of cultural heritage at the Opificio delle Pietre Dure (Florence, Italy), an Institute of the Italian Ministry of Cultural Heritage. In 1984 she attended a post-graduate specialization course in conservation and restoration of metal objects at the Opificio delle Pietre Dure (Bronze and Antique Weapons Department). In 2007, she obtained a bachelor's degree in technologies for the conservation and restoration of cultural heritage at the University of Tuscia, Viterbo, Italy. From 1984 to 2001, she worked as a freelance conservator for many museums and public institutions, gathering experience on different works of arts from archeological objects to modern sculptures. In 2001, she became a conservator at the Bronze and Antique Weapons Department of the Opificio delle Pietre Dure and, since 2004, she also teaches conservation and restoration tecniques at the Scuola di Alta Formazione e Studio (School of Higher Education and Scholarship of the Opificio). She has numerous publications related to her different projects. Actually she is involved in the research and restoration work conducted on the south door of the Baptistery of Florence, by Andrea Pisano and the roman bronze statue Vittoria Alata (Winged Victory) from Brescia. Address: As for Giulia Basilissi. Email: [email protected].
Andrea Cagnini
Andrea Cagnini is a chemist and completed his PhD in environmental science at the Università di Firenze, Italy, in 1996. From 2005 he has been working at the Scientific Department of the Opificio delle Pietre Dure, Florence, Italy. His work is focused on the archaeometric and conservative aspects of metal, glass, and stone artworks using different analytical techniques such as infrared and Raman spectroscopy, optical and scanning electron microscopy, and X-ray fluorescence spectrometry. During this period he was involved in many European and national projects and published more than 60 papers related to the conservation of cultural heritage in national and international journals. Address: As for Giulia Basilissi. Email: [email protected].
Cinzia Ortolani
Cinzia Ortolani is a conservator of cultural heritage, specialized in metal objects (goldsmith and silversmith artworks, enamels, archaeological objects). In 1997 she obtained a master's degree in conservation and restauration of cultural heritage at the Opificio delle Pietre Dure (Florence, Italy). In 1998, she took a post-graduate degree in the conservation and restoration of precious and non-precious metals at the Department of Goldsmithery and Glyptics. In 2012, she graduated with full marks in science for cultural heritage studies at the Faculty of Literature and Philosophy of the Università di Siena, Italy. Since 1999 she works as a conservator in the Goldsmithery Department at the Opificio delle Pietre Dure, Goldsmithery Department. Since 2004 she is a professor at the Scuola di Alta Formazione e Studio (School of Higher Education and Scholarship of the Opificio). She has attended various national conferences and published many papers on topics related to the conservation of goldsmith and silversmith artworks, enamels, and archaeological metal objects. Address: As for Giulia Basilissi. Email: [email protected].
Alessandra Santagostino Barbone
Alessandra Santagostino Barbone has been working as an external collaborator of the Scientific Department at the Opificio delle Pietre Dure since 2008, specialized in diagnostic investigations on stones, metals, ceramics, glasses, jewels and archeological artefacts. In 2001 she completed her degree in geological sciences at the University of Pavia (magna cum laude) with a thesis titled “The medieval glassware of the Gargassa valley (GE): petrological and archaeometric study of the production markers.” In 2002–2003 she won a scholarship at the University of Siena with the topic: “Archaeometric study of medieval ceramics from the castles of the southern Tuscany.” In 2007 she obtained a PhD degree from the University of Siena focusing on the topic: “Archaeometric study of roman, late-antique and low-medieval glasses: production technology and provenance.” Address: As for Giulia Basilissi. Email: [email protected].