Use of Imaging Spectroscopy and in situ Analytical Methods for the Characterization of the Materials and Techniques of 15th Century Illuminated Manuscripts

Abstract

This study combines site-specific in situ analytical techniques with non-site-specific reflectance imaging spectroscopy and multispectral infrared reflectography to characterize pigments and underdrawing materials in fragile, light-sensitive illuminated manuscripts. In situ methods implemented in this study included fiber optic reflectance spectroscopy and x-ray fluorescence, as well as multispectral visible and near-infrared reflectance imaging spectroscopy and multispectral infrared reflectography. Imaging spectroscopy was used to map areas having similar diffuse reflectance spectra, and the site-specific methods were used to further identify the primary pigments present. This combined approach was used to examine an illumination by Lorenzo Monaco (ca. 1370–1422 or after) and his workshop on the Praying Prophet, in the collection of the National Gallery of Art in Washington, DC (NGA), from an early-15th-century gradual on parchment (codex H74) currently at the Museo Nazionale del Bargello in Florence. The combination of the results along with microscopic examination led to a more complete understanding of the working methods used to create the Praying Prophet, including the primary pigments present and the two forms of underdrawing, ink and metalpoint. These results also allowed for a comparative examination of the primary pigments used in 13 other folios in codex H74. Multispectral infrared reflectography imaging and fiber optics reflectance spectroscopy confirmed that the primary pigments and preparatory drawing used in the NGA folio were consistent with those used in the other folios.

Résumé—Lors de cette étude, on a combiné des techniques analytiques in situ (spécifiques au site) avec l'imagerie spectroscopique par réflexion (non-spécifique au site) et la réflectographie infrarouge multispectrale pour caractériser les colorants et les dessins préparatoires sur des manuscrits enluminés fragiles et sensibles à la lumière. Les méthodes in situ utilisées ont inclus la spectroscopie à fibre optique par réflexion et spectrométrie de fluorescence X, ainsi que l'imagerie spectroscopique proche infrarouge et la réflectographie multispectrale infrarouge. L'imagerie spectroscopique a été utilisée pour démarquer les secteurs ayant des spectres de réflexion semblables et diffus, tandis que et les méthodes spécifiques au site ont été employées pour identifier plus précisément les colorants primaires présents. Cette double approche a été utilisée pour examiner ne enluminure, le Praying Prophet (le prophète en prière), par Lorenzo Monaco (circa 1370–1422 ou plus tard) et son atelier dans la collection de la National Gallery of Art à Washington, D.C., qui provient d'un graduel sur parchemin (codex H74) datant du début du XV^e siècle actuellement dans la collection du Museo Nazionale del Bargello à Florence. Les résultats combinés avec l'examen microscopique ont mené à une meilleure compréhension des méthodes de travail employées pour créer Praying Prophet, y compris les principaux colorants ainsi que les deux types de dessins préparatoires, l'encre et la pointe de métal. Ces résultats ont également permis l'examen comparatif des colorants primaires utilisés dans treize autres folios du codex H74. L'imagerie multispectrale à l'infrarouge et la spectroscopie à fibre optique par réflexion ont confirmé que les colorants primaires et le dessin préparatoire utilisés dans le folio de la National Gallery of Art étaient comparables à ceux utilisés dans les autres folios.

Resumen—Este estudio combina técnicas analíticas in situ, específicas al sitio, con espectroscopía de imagen de reflexión, no específica al sitio, y con reflectografía infrarroja multiespectral para caracterizar pigmentos y materiales del esbozo subyacente en manuscritos iluminados frágiles y sensibles a la luz. Los métodos in situ implementados en este estudio incluyen la espectroscopía de reflexión con fibra óptica y la fluorescencia de rayos x, así como también la espectroscopía de reflexión en los rangos del visible y del infrarrojo cercano y la reflectografía infrarroja multiespectral. La espectroscopía de imagen fue usada para mapear áreas espectro de reflexión difuso similar y los métodos específicos al sitio fueron usados para identificar mejor los pigmentos primarios presentes. Este enfoque en el que se combinan varias técnicas fue usado para examinar un trabajo de iluminación de Lorenzo Mónaco (c. 1370 – 1422 o posterior) y su taller sobre el Profeta Orante, de la colección de la Galería Nacional de Arte en Washington, D. C., de un gradual sobre pergamino de principios del Siglo XV (codex H74), actualmente en el Museo Nazionale del Bargello en Florencia. La combinación de los resultados con el examen microscópico llevó a un entendimiento más completo de los métodos de trabajo usados para crear el Profeta Orante, incluyendo los pigmentos primarios presentes y las dos técnicas usadas para los esbozos: tinta y punta de metal. Estos resultados también permitieron un examen comparativo de los pigmentos primarios usados en los otros trece folios del códice H74. La reflectografía infrarroja multiespectral y la espectroscopía de reflexión con fibra óptica confirmaron que los pigmentos primarios y el dibujo preparatorio usados en el folio de la Galería Nacional de Arte son consistentes con aquellos usados en los otros folios.

Resumo—Este estudo combina as localizadas técnicas analíticas in situ com as não-localizadas técnicas de espectroscopia de imagem e de reflectografia infravermelha multiespectrais para caracterizar os pigmentos e materiais sob a camada de pintura em manuscrito ilumados frágeis e sensíveis à luz. Métodos in situ implementados neste estudo incluiem a espectroscopia de reflectância de fibra óptica e fluorescência de raios-X, assim como multiespectral visível e espectroscopia de reflectância de imagem infravermelha e reflectografia infravermelha multiespectral. Espectroscopia de imagem foi usada para mapear as áreas que possuem espectros de reflectância difusa semelhante e os métodos localizados foram utilizados para identificar os pigmentos originais presentes. Esta abordagem combinada foi usada para examinar uma iluminura de Lorenzo Monaco (c. 1370–1422 ou depois) e sue workshop sobre o Profeta Rezar, na coleção da National Gallery of Art, em Washington, DC, a partir do início do século 15 em pergaminho (códice H74) atualmente no Museo Nazionale del Bargello, em Florença. A combinação dos resultados, juntamente com o exame microscópico levou a uma compreensão mais completa dos métodos de trabalho utilizados para criar o Praying Prophet (Profeta Orando), incluindo os pigmentos originais presentes e as duas formas de desenhos sob a pintura, a tinta e a gravação. Estes resultados também permitiram uma análise comparativa dos principais pigmentos utilizados em 13 fólios outros do códice H74. MS-TIR e FORS confirmaram que os pigmentos originais e desenho preparatório utilizados no fólio da NGA foram consistentes com os utilizados nos outros folios.

Keywords:

• imaging spectroscopy
• illuminated manuscript
• fiber optics reflectance spectroscopy
• x-ray fluorescence
• multispectral imaging
• infrared reflectography
• Lorenzo Monaco

Acknowledgments

We wish to thank M. Picollo (IFAC-CNR), M. Scudieri (Museo di San Marco), K. Morales, K. Schenck, and E. R. de la Rie (National Gallery of Art) for fruitful discussions, B. Paolozzi Strozzi and M. L. Palli (Museo Nazionale del Bargello) for allowing access to Codex H74, and R. Iannaccone (IFAC-CNR) for help with data collections in Florence. We acknowledge financial support from the Andrew W. Mellon Foundation and the Samuel H. Kress Foundation.

Additional information

Notes on contributors

Paola Ricciardi

Paola Ricciardi is a Research Associate in the Department of Manuscripts and Printed Books at the Fitzwilliam Museum in Cambridge. She earned her PhD in conservation science from the University of Florence, Italy in 2008. Her main research interest is the application of noninvasive analytical methods to the study of artists' materials, with a focus on pigments and binders used in illuminated manuscripts and other works of art. She performed the work presented in this paper during a Samuel H. Kress post-doctoral fellowship in imaging science at the National Gallery of Art. Address: Department of Manuscripts and Printed Book, The Fitzwilliam Museum, Trumpington Street, Cambridge CB2 1RB, UK. Email: [email protected]

John K. Delaney

John K. Delaney is the senior imaging scientist at the National Gallery of Art, Washington DC, where his research focuses on the development of in situ imaging methods for art conservation and the understanding of the optical properties of varnishes. He is also a research professor in the School of Engineering and Applied Science at George Washington University in DC. He received his PhD from the Rockefeller University and completed postdoctoral studies at the University of Arizona and the Johns Hopkins University School of Medicine. Address: DCL, National Gallery of Art, 2000B South Club Drive, Landover, MD 20785, USA. Email: [email protected]

Michelle Facini

Michelle Facini received her BA in art history from Towson State University (1996) and MS from Winterthur Museum/University of Delaware Program in Art Conservation (2002). She completed a Samuel H. Kress Fellowship at the Fine Arts Museums of San Francisco, followed by an Andrew W. Mellon Fellowship at the National Gallery of Art, Washington, DC. Michelle worked as a paper conservator at the National Archives and Records Administration prior to her current position as paper conservator at the National Gallery of Art. She has written in the past on the preservation of oversized works of art on paper and has been collaborating with conservation scientists for the past several years, investigating materials and techniques used in medieval manuscripts. Address: DCL, National Gallery of Art, 2000B South Club Drive, Landover, MD 20785, USA. Email: [email protected].

Lisha Glinsman

Lisha Glinsman received her undergraduate degree in Chemistry from the College of St. Rose in 1982 and her PhD in Chemistry in 2004 from the University of Amsterdam for her extensive work on XRF analysis of museum objects. From 1982 to 1984 she worked in industry as a plant chemist and 1985 to 1987 as a research chemist for the National Institute of Standards and Technology. She has been a conservation scientist at the National Gallery of Art, Washington, DC, since 1987 where her research focuses on noninvasive techniques for the study of museum objects. Address: DCL, National Gallery of Art, 2000B South Club Drive, Landover, MD 20785, USA. Email: [email protected].