A review of the development and testing of Incralac lacquer

Abstract

This paper summarizes the development of commercial Incralac clear lacquer for outdoor copper alloys and reviews the research done in the 1960s with resulting formulations. The introduction of Incralac was groundbreaking for the coating industry and the product has been widely used to the present time. A review of minor formulation changes — mostly to comply with environmental regulations — is presented as well as discussion about how the components affect the overall performance. Originally developed for use on polished copper alloys, the product has been adopted for the protection of outdoor sculpture with varying results over the last few decades. This paper reviews the published performance testing of Incralac in the laboratory and in the field, discusses aging properties and removability, and provides a useful discussion about the challenges in evaluating the product in particular for its application to outdoor sculpture.

Résumé

Cet article présente un sommaire du développement du vernis incolore de la marque Incralac pour les alliages de cuivre d’extérieur, ainsi qu’un résumé de la recherche conduite dans les années 1960 et des formulations qui en ont découlé. L’introduction de l’Incralac fut révolutionnaire dans le monde de l’industrie des vernis de protection et le produit a depuis été utilisé à grande échelle. Les changements mineurs de formulations – principalement pour satisfaire des régulations environnementales – sont passés en revue et présentés avec une discussion sur l’impact que les ingrédients ont sur la performance générale du produit. Au départ développé pour des alliages de cuivre polis, le produit a été adapté pour la protection de la sculpture d’extérieur, avec des résultats discutables ces dernières décennies. L’article passe en revue les tests publiés sur la performance de l’Incralac au sein du laboratoire et sur le terrain, discute les propriétés de vieillissement et d’aptitude à l’enlèvement, et offre une discussion utile sur les difficultés liées à l’évaluation du produit, en particulier dans le cadre de son application à la sculpture d’extérieur. Traduit par Stéphanie Auffret et Bruno Pouliot.

Resumo

Esse artigo resume o desenvolvimento do verniz transparente comercial Incralac para ligas de cobre ao ar livre e sintetiza a pesquisa realizada nos anos de 1960 com composições resultantes. A introdução do Incralac foi inovadora para a indústria de revestimentos e o produto tem sido utilizado amplamente até hoje. Uma retrospectiva das mudanças das fórmulas secundárias – principalmente para cumprir a legislação ambiental – é apresentada assim como a discussão sobre como os componentes afetam o desempenho global. Desenvolvido expressamente para o uso sobre ligas de cobre polidas, o produto foi adotado para a proteção de esculturas externas com resultados questionáveis nas últimas décadas. Esse artigo apresenta os testes de desempenho publicados de Incralac em laboratório e em campo, discutindo propriedades de envelhecimento e remoção, e oferece debate útil sobre os desafios na avaliação do produto em particular para sua aplicação em esculturas ao ar livre. Traduzido por Sandra Baruki.

Resúmen

Este artículo resume el desarrollo de la laca comercial transparente Incralac usada en exteriores para aleaciones de cobre, y resume la investigación hecha en los años 1960’s de las fórmulas resultantes. La introducción en el mercado de Incralac fue innovadora para la industria del revestimiento y el producto ha sido ampliamente usado hasta el presente. Una revisión de cambios menores en las fórmulas – mayormente hechas para adaptarse a las regulaciones sobre la protección del medio ambiente – es presentada, así como también una discusión acerca de cómo los componentes afectan su desempeño en general. Evidentemente desarrollado para el uso sobre aleaciones de cobre pulidas, el producto ha sido adoptado para la protección de esculturas exhibidas al aire libre con resultados discutibles en las últimas décadas. Este artículo revisa las publicaciones sobre el desempeño de Incralac en las pruebas de laboratorio y en el campo, discute sus propiedades de envejecimiento y remoción, y ofrece una útil discusión acerca de los retos en la evaluación del producto, en particular para su aplicación en esculturas exhibidas al aire libre. Traductores: Ramón Sanchez Chapellín, y Vera de la Cruz Baltazar. Revisión: Amparo Rueda.

Keywords:

• Outdoor sculpture
• protective coating
• Paraloid B-44
• copper alloy
• maintenance
• lacquer
• review

Acknowledgements

The authors would like to thank Briana Feston, whose research while at the Getty Museum led to the early INCRA reports. We would also like to thank Valerie Greathouse, Magdalena Solano, and Olivia Stanton for extensive bibliographic assistance and translation. We thank our numerous colleagues who have shared their experiences and improved our understanding of Incralac’s use in conservation. Also, Jeff Wexler and Mindy Keefe (Dow Chemical) are thanked for sharing their insights and expertise on the Paraloid™ resins. We are thankful to James Michel at the CDA for historical references. Finally, we would like to thank Brian Considine, Jane Bassett, Tom Learner, and Alan Phenix for the support and encouragement they have provided in our research.

ORCID

ROSIE GRAYBURN http://orcid.org/0000-0002-1156-1378

Additional information

Notes on contributors

Julie Wolfe

Julie Wolfe has a BFA in Art History from the University of Illinois in Champaign-Urbana and an MA from Buffalo State College specializing in objects conservation with advanced training at the Harvard University Art Museums, Straus Center for Conservation. She is currently a Conservator at the J. Paul Getty Museum in Decorative Arts and Sculpture Conservation where she has worked since 2000. Address: The J. Paul Getty Museum, Decorative Arts and Sculpture Conservation, 1200 Getty Center Drive, Suite 1000, Los Angeles, CA, 90049, USA. Email: [email protected]

Rosie Grayburn

Rosie Grayburn obtained a joint PhD in 2015 from the University of Warwick, United Kingdom, and Universiteit Gent, Belgium, where she conducted research into conservation treatments and corrosion processes using novel time-lapse analytical methodologies. From 2015 to 2017, she was the postdoctoral fellow in Conservation Science within the Treatment Studies research area at the Getty Conservation Institute. She is currently Associate Scientist at Winterthur Museum and Affiliated Assistant Professor in the Department of Art Conservation, University of Delaware. Address: Department of Conservation, Winterthur Museum, 5105 Kennett Pike, Winterthur, DE 19735, USA. Email: [email protected]