Tailoring Cleaning Systems for the Removal of Bronze Paint and Soiling From a J.M.W. Turner Gilded Frame

ABSTRACT

This paper presents practice-based research designed to support the development and optimization of a successful cleaning methodology for an oil gilded J. M. W. Turner (1755–1851) frame in Tate's collection. The 3-dimensional ornate nature of this object posed additional challenges with respect to the development of a cleaning strategy, as the handling of gels on topographically complex gilded surfaces can be particularly problematic. Within a limited timeframe and without the use of sophisticated equipment, a comparative evaluation of a range of cleaning systems was designed to assess the efficacy of the removal of heavy soiling and bronze overpaint from this complex oil-gilt frame. This evaluation methodology entailed three different stages to better compare and select a suitable cleaning system. Free solvents, gels, and various emulsifiers were evaluated through empirical observation and documented using star diagrams (Excel radar charts), ultraviolet light, microscopy, and cross-section examination. The results indicated that hydrolyzed poly(vinyl acetate)-borate gels and modified silicone-based emulsions successfully removed the soiling and bronze overpaint while posing minimal risk to the oil gilded surface.

RÉSUMÉ

Cet article présente une recherche fondée sur la pratique conçue pour participer au développement et à l'optimisation d'une méthodologie de nettoyage réussie pour un cadre doré à l'huile de J. M. W. Turner (1755–1851) dans la collection de la Tate. La nature tridimensionnelle des ornements a posé des défis supplémentaires en ce qui concerne le développement d'une stratégie de nettoyage, puisque la manipulation de gels sur des surfaces dorées topographiquement complexes peut être particulièrement difficile. Dans un délai limité et sans l'utilisation d'équipements sophistiqués, l'évaluation comparative d'une gamme de méthodes de nettoyage a été conçue pour évaluer l'efficacité de l'élimination de salissures et de surpeints de bronzine épais de ce cadre doré à l'huile complexe. Cette méthodologie d'évaluation comportait trois étapes différentes pour mieux comparer et sélectionner une méthode de nettoyage appropriée. Des solvants libres, des gels et divers émulsifiants ont été évalués par observation empirique et documentés à l'aide de diagrammes en étoile (diagrammes radar Excel), de lumière ultraviolette, de microscopie et d'examen en coupe transversale. Les résultats ont indiqué que les gels de poly(acétate de vinyle)-borate hydrolysés et les émulsions à base de silicone modifiées ont réussi à éliminer les salissures et les surpeints de bronzine tout en présentant un risque minimal pour la surface dorée à l'huile. Traduit par Lucile Berthelot.

RESUMO

Este artigo apresenta o resultado de uma pesquisa prática para apoiar o desenvolvimento e a otimização de uma metodologia de limpeza bem-sucedida para uma moldura dourada de J. M. W. Turner (1755–1851) na coleção Tate. A natureza ornamentada tridimensional deste objeto apresentou desafios adicionais no que diz respeito ao desenvolvimento de uma estratégia de limpeza, pois o manuseio de géis em superfícies douradas topograficamente complexas pode ser particularmente problemático. Dentro de um prazo limitado e sem o uso de equipamentos sofisticados, uma avaliação comparativa de uma variedade de sistemas de limpeza foi projetada para avaliar a eficácia da remoção de sujeira pesada e tinta de bronze dessa complexa moldura de óleo-dourado. Esta metodologia de avaliação envolveu três etapas diferentes para melhor comparar e selecionar um sistema de limpeza adequado. Solventes livres, géis e vários emulsificantes foram avaliados através de observação empírica e documentados usando diagramas de estrelas (gráficos de radar do Excel), luz ultravioleta, microscopia e exame de seção transversal. Os resultados indicaram que os géis hidrolisados ⁣⁣de poli-(acetato de vinila)-borato e as emulsões modificadas à base de silicone removeram com sucesso a sujeira e a tinta de bronze, apresentando risco mínimo para a superfície dourada a óleo. Traduzido por Beatriz Haspo.

RESUMEN

Este artículo presenta una investigación basada en la práctica, diseñada para apoyar el desarrollo y la optimización de una metodología de limpieza exitosa para un marco de J. M. W. Turner (1755–1851) dorado al aceite en la colección de Tate. La naturaleza tridimensional del decorado de este objeto planteó desafíos adicionales con respecto al desarrollo de una estrategia de limpieza, ya que el manejo de geles en superficies doradas topográficamente complejas puede ser particularmente problemático. Dentro de un marco de tiempo limitado y sin el uso de sofisticados equipos, se diseñó una evaluación comparativa de una gama de sistemas de limpieza para evaluar la eficacia de la eliminación de la suciedad excesiva y repintes de pintura de bronce de este complejo marco dorado al aceite. Esta evaluación metodológica implicó tres etapas diferentes para comparar mejor y seleccionar un sistema de limpieza adecuado. Solventes libres, geles y varias emulsiones fueron evaluados a través de la observación empírica y fueron documentados usando diagramas de estrellas (gráficos de radar de Excel, luz ultravioleta, microscopía y examen de corte transversal. Los resultados indicaron que los geles hidrolizados de poli(acetato de vinilo)-borato y emulsiones a base de silicona modificada eliminaron con éxito la suciedad y los repintes de pintura de bronce a la vez que presentaban un riesgo mínimo para la superficie dorada al aceite. Traducción: Irene Delaveris; revisión: Amparo Rueda.

KEYWORDS:

• Oil gilding
• cleaning
• poly(vinyl acetate)
• borate
• hydrogels
• Shin-Etsu KSG 350z
• silicone
• emulsion

Acknowledgements

The author would like to thank the following people and organizations for their assistance and support for this project. Dr. Bronwyn Ormsby (Principal Conservation Scientist, Tate, UK) for assistance with project design, providing advice on cleaning materials and evaluation methodologies as well as guiding and editing the manuscript. Tate Conservation scientists Dr. Judith Lee, for advice on cleaning materials and Dr. Joyce Townsend, for assistance with interpretation of the cross-sections and editing of the manuscript. Dr. Lora Angelova (The National Archives, UK) for advice on the PVA-borax “gels.” Tate’s Frame Conservation team members Adrian Moore for advice on conservation approaches for Turner frames; Dr. Ivan Houghton for assistance with identifying the object as a Turner frame. Dr. Malgorzata Sawicki for sharing experience on the use PVA-borate “gels” for the cleaning of gilded surfaces and Kuraray Co Ltd. for generously providing samples of the hydrolyzed PVA polymers.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 A change in values of the gel’s surface pH was noted during the cleaning process – the initial gel’s 8.3 pH gradually dropped to 7.6 after being re-used 10 times. The change in pH points to an alteration of the gel matrix likely caused by the absorption of extraneous material including the acidic nature ofthe gilded surface which had an initial 5.5 pH, raising to 5.7 after cleaning.

2 The gel’s surface pH was measured during the cleaning process and noted to drop from 8.6 to 7.6. This change in pH suggests that an alteration to the gel’s matrix occurred, potentially caused by the absorption of overpaint, leading to syneresis reaction. There was no significant change in surface pH to the decorative surface, the 6.3 pH value prior to cleaning dropped (insignificantly) to 6.2 after the cleaning.

3 The gilding’s surface pH of 6.6 dropped to 6.2 after cleaning. This change in pH was caused by the removal of the overpaint and the exposure of the gilding and underlying layers, a more acidic surface.

Additional information

Notes on contributors

Inês Bravo

Inês Bravo is an Objects Conservator specialized in Gilded and Decorative Surfaces, that is currently working for the private sector in Portugal. She most recently held a two-year position at Tate, London, where she worked as a Frames Conservator. She has a BA(Hons) in Fine Arts from FBAUP, and a PGDip in Objects Conservation at City & Guilds of London Art School in 2017. Following her degrees she worked for museums, institutions, and private sector both in England and Portugal. Additionally, she is a committee member of the ICON Gilding and Decorative Surfaces Group. Address: Avenida Rodrigues de Freitas, 111. n65, 2 esq, Porto 4000-420, Portugal. Email: [email protected].