AIC's 45th Annual Meeting

Historically, works of art on paper have proven challenging objects for scientific analyses. Due to the lower concentration of materials used in these works, sampling is not possible as removal of a sufficiently large sample would be visibly and irreversibly damaging to the work, necessitating in situ analysis methods. As a result, conservators and curators have come to rely upon close observation—at both the macro and micro level—as their primary means of differentiating drawing media. However, because this is a subjective approach and highly dependent on the experience of the observer, this is a challenging, if not impossible, task. Many drawing materials—particularly carbon-based drawing materials—are extremely similar in appearance. Visual distinction and identification is further complicated by the varied methods of application and manipulation artists employ. In 2016, the J. Paul Getty Museum presented the exhibition Noir: The Romance of Black in 19th-century French Drawings and Prints which featured drawings by Georges Seurat and Odilon Redon, among others. The works of these artists, deceptively simple in appearance, represent complex mixtures of black media including charcoals of varying hardness, assorted crayons, natural and fabricated chalks, ink, and pastel. In conjunction with this exhibition, curators, conservators, and scientists at the J. Paul Getty Museum and Getty Conservation Institute initiated a collaborative study to address the problem of accurate characterization of black drawing media. Specific research questions included: Is it possible to distinguish different types of black drawing media—such as chalk, crayon, and pastels—based on binder or clay content? Did the artists use fixative? If so, what is the composition and how was it applied? Have the media or fixative altered with age? To develop an effective, noninvasive, analytical framework for the study of drawings from the Museum’s collections, studies were conducted on mock-ups prepared with historic and modern artist’s materials to characterize the materials present and understand the complex media-substrate interaction. A suite of noninvasive techniques were utilized in this study. Micro-Raman spectroscopy was used to identify carbonaceous materials such as charcoal by examining two characteristic spectral features, the D band and G band. The ratio between the intensity of each band can be used to estimate the degree of crystallinity of the carbon species, which can then be matched to reference materials for proper identification.[1] Fourier Transform Infrared (FT-IR) spectroscopy was used to aid in characterization of organic binding media and fixatives, and to support the black media assignment made using Micro-Raman spectroscopy. X-ray fluorescence (XRF) was used to identify inorganic elements such as aluminum in chalks. In situ x-ray diffraction (XRD) was used to characterize minerals in clays. Collectively, these analytical techniques successfully characterized the materials used by the 19th century French artists, providing insight into the development of modern drawing. Additionally, this work provides a framework to address the need for noninvasive analytical methods to study low concentration materials in situ. 1. Coccato, A., J. Jehlicka, L. Moens, and P. Vandenabeele, Raman spectroscopy for the investigation of carbon‐based black pigments. Journal of Raman Spectroscopy, 2015. 46(10): p. 1003-1015.