An easy-to-use method for preparing paint cross sections

ABSTRACT

The optimized method for preparing paint cross sections described here advances our understanding of the structure of multilayered modern and contemporary paintings. Conducted in micrometer scale with nondestructive characterization, this method of sample preparation preserves the morphological integrity of the paint layers, while achieving a high-quality surface suitable for imaging and inorganic mapping studies. The preparation begins by positioning the paint cross section face down on a restickable, double-sided acrylic adhesive dot affixed to a glass slide. A molded nylon ring is then placed around the sample and filled with Bio-Plastic resin. After curing, the sample is released from the ring. The paint layers are fully exposed because the dot does not bond with the cured resin. The sample requires minimal dry polishing for a high-quality surface because the cross section is not fully embedded in the resin; instead, the face of the cross section sits at the resin’s surface. These samples can be prepared in one day. In this study, we obtained data from a single paint sample from the twentieth century painting The Big Egg (1968) by Ed Clark, from the Smithsonian’s National Museum of African American History and Culture (NMAAHC). At least 15 layers were identified from one paint sample and were characterized using digital microscopy and SEM–EDS.

RÉSUMÉ

La méthode optimisée de préparation des coupes transversales picturales décrite ici fait progresser notre compréhension de la structure des peintures modernes et contemporaines multicouches. Conduite à l’échelle du micromètre avec caractérisation non destructive, cette méthode de préparation d’échantillon préserve l’intégrité de la morphologie des couches picturales, tout en produisant une surface de haute-qualité adaptée aux études par imagerie et cartographie des éléments inorganiques. La préparation commence par le positionnement de la coupe transversale picturale face vers le bas sur une pastille d’adhésif acrylique double-face repositionnable collée sur une lame de verre. Un anneau en nylon moulé est ensuite placé autour de l’échantillon et rempli de résine Bio-Plastic. Après durcissement, l’échantillon est retiré de l’anneau. Les couches picturales sont entièrement exposées car la pastille ne colle pas à la résine durcie. Les échantillons requièrent un minimum de polissage à sec pour obtenir une surface de haute qualité car la coupe transversale n’est pas complètement incrustée dans la résine, la face de la section transversale se trouvant à la surface de la résine. Ces échantillons peuvent être préparés en un jour. Au cours de cette étude, nous avons obtenu des informations à partir d’un seul échantillon de la peinture du vingtième siècle Big Egg (1968) par Ed Clark, provenant du Smithsonian’s National Museum of African American History and Culture (NMAAHC). Au moins 15 couches ont été identifiées à partir d’un échantillon de peinture et ont été caractérisées par microscopie électronique et MEB-EDS. Traduit par Elsa Thyss.

RESUMO

O método aprimorado para preparar os cortes estratigráficos de pintura descritos nesse artigo aumentam nosso conhecimento da estrutura multilaminar de pinturas modernas e contemporâneas. Conduzido em escala micrométrica com característica não destrutiva, o método de preparação de amostras preserva a integridade morfológica das camadas de pintura, e ao mesmo tempo obtém uma superfície de alta qualidade própria para estudos de mapeamento inorgânico e de imagens. A preparação começa com o posicionamento da seção transversal da pintura voltada para baixo sobre um ponto de adesivo acrílico readerentes, de dupla face, afixado em lâmina de vidro. Um anel de nylon moldado é então colocado em volta da amostra e preenchido com resina Bio-Plastic. Depois de curada, a amostra é retirada do anel. As camadas de tinta ficam totalmente expostas porque o ponto não liga à resina curada. A amostra requer um polimento mínimo a seco para alcançar alta qualidade de superfície porque as seções transversais não estão completamente embebidas na resina; em vez disso, a face da seção transversal repousa na superfície da resina. Estas amostras podem ser preparadas em um dia. Nesse estudo, obtivemos dados de uma amostra simples da pintura do século XX, Big Egg (1968) de Ed Clark, do Smithsonian’s National Museum of African American History and Culture (NMAAHC). Ao menos 15 camadas foram identificadas a partir de uma amostra simples e foram caracterizadas através de microscopia digital e SEM-EDS. Traduzido por Sandra Baruki.

RESUMEN

El método optimizado para preparar secciones transversales de pintura que se describe aquí, mejora nuestra comprensión de la estructura de las pinturas modernas y contemporáneas de varias capas. Realizado en escala micrométrica con caracterización no destructiva, este método de preparación de muestras preserva la integridad morfológica de las capas de pintura, al mismo tiempo que logra una superficie de alta calidad adecuada para estudios de imagen y de mapeo inorgánico. La preparación comienza colocando la sección transversal de la pintura hacia abajo sobre un punto adhesivo acrílico de doble cara que se puede pegar a un portaobjetos de vidrio. Luego se coloca un anillo de nylon moldeado alrededor de la muestra y se llena con resina Bio-Plastic. Después del curado, la muestra se libera del anillo. Las capas de pintura están completamente expuestas porque el punto no se une con la resina curada. La muestra requiere un pulido en seco mínimo para obtener una superficie de alta calidad porque la sección transversal no está totalmente incrustada en la resina; en cambio, la cara de la sección transversal se asienta en la superficie de la resina. Estas muestras se pueden preparar en un día. En este estudio, obtuvimos datos de una sola muestra de pintura del siglo XX que pintaba Big Egg (1968) de Ed Clark, del Museo Nacional de Historia y Cultura Afroamericana del Smithsonian (NMAAHC). Se identificaron al menos 15 capas de una muestra de pintura y se caracterizaron mediante microscopía digital y SEM-EDS. Traducción: Amparo Rueda.

KEYWORDS:

• Ed Clark
• paint cross section
• SEM–EDS
• poly (vinyl acetate)
• modern and contemporary paintings

Acknowledgments

The authors gratefully acknowledge the support of our colleagues and fellows at MCI: Jessica Johnson, Christine France, Janet Douglas, Gwénaëlle Kavich, Stephanie Barnes, Christine Romano, and Christopher Wu. We also thank our colleagues Tuliza Fleming, Jacquelyn Serwer, and Renee S. Anderson at the Smithsonian’s NMAAHC, and Tim Rose and Tim Gooding at the Smithsonian’s National Museum of Natural History, and Jennifer Giaccai and Mathew Clarke at the Smithsonian’s Freer and Sackler Galleries of Art. Special thanks go to MCI Director Robert Koestler and Deputy Director Paula DePriest for their generous support of intern Elle Friedberg. Conservation of The Big Egg was funded by a grant from the Bank of America Art Conservation Project 2014–2016.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Jia-sun Tsang is a senior paintings conservator at the MCI, where she conserves paintings for Smithsonian museums. She holds an M.Sc. from the Winterthur/University of Delaware Program in Art Conservation and an M.Sc. in chemistry from Bowling Green State University, OH. Since 2007 her work has focused on the conservation and analysis of paintings from the visual art collections of the NMAAHC, and the installation of artworks for the grand opening of the museum in autumn 2016. She specializes in modern materials research and the conservation of modern and contemporary art.

Thomas Lam has a Ph.D. in ceramics from Alfred University, NY. After earning his Ph.D., he completed a postdoctoral fellowship at the National Institute of Standards and Technology. He is a physical scientist at the MCI, where he applies his knowledge of material science and characterization skills (including SEM–EDS, cathodoluminescence, X-ray fluorescence, and microfade testing) as part of the MCI technical studies team.

Elle Friedberg is a paintings conservation and analytical studies intern at the MCI (Suitland, MD), 2017–2018. Her current projects include optimizing paint cross section preparation techniques and assisting with preventive conservation at the NMAAHC. She is also a paintings conservation volunteer at the Smithsonian’s National Gallery of Art (Washington, DC). She received a B.A. from Wellesley College, MA, with a double major in chemistry and studio art.