The Coated Salted Paper Prints from the Eduard Isaac Asser Collection at the Rijksmuseum: FTIR and OCT Identification and Characterization

ABSTRACT

The Rijksmuseum holds four valuable albums with 187 photographs made by Eduard Isaac Asser (1809–1894), one of the first figures in photography in the Netherlands. Based on visual examination, most of these prints have been identified as salted paper prints with a coating, but they can be hard to distinguish from matte or glossy albumen prints, especially where the coating is thick. In order to be more accurate in our descriptions and to better understand Asser’s technique, a technical study of his work was conducted. Fourier transform infrared spectroscopy (FTIR) helped us to identify, to a certain extent, the nature of the coatings. Before the analysis, the prints had been described either as “shellac coated” or as “waxed,” based on their varying degree of sheen. FTIR identified a larger number of substances in the coatings: gum, protein, natural resin, and possibly starch. Optical coherence tomography (OCT) was also used to study the coatings. Because OCT has limitations when dealing with very thin layers, it was not always suitable for distinguishing coated salted paper prints from coated albumen prints. However, it did turn out to be a useful tool to explore the topography and structure of the paper supports and the coatings.

RÉSUMÉ

Le Rijksmuseum possède quatre albums importants contenant 187 photographies produites par Eduard Isaac Asser (1809-1894), une des figures pionnières de la photographie néerlandaise. Après examen visuel, la majorité de ces tirages a été identifiée comme étant des tirages sur papier salé avec un vernis, cependant ils peuvent être difficiles à différencier de tirages albuminés mats ou brillants, en particulier lorsque le vernis est épais. Afin d'être plus précis dans nos descriptions et de mieux comprendre la technique d'Asser, son travail a été examiné grâce à l'aide d'analyses techniques. La spectroscopie infrarouge à transformée de Fourier (IRTF) nous a aidés à identifier, jusqu'à un certain degré, la nature des vernis. Avant les analyses, les tirages avaient été décrits comme « vernis à la gomme-laque  » ou « cirés », selon leur degré de brillance. Or l'IRTF a identifié un grand nombre de substances dans les vernis : gommes, protéines, résines naturelles, et peut-être de l'amidon. La tomographie en cohérence optique (TCO) a aussi été utilisée pour étudier les vernis. La TCO atteint ses limites lorsqu'il s'agit de couches très fines, et n'était pas toujours adaptée pour distinguer des tirages sur papier salé vernis de tirages albuminés vernis. Cependant, elle s'est avérée être un outil utile pour explorer la topographie et la structure des supports papier et des vernis. Traduit par Elsa Thyss.

RESUMO

O Rijksmuseum possui quatro valiosos álbuns com 187 fotografias feitas por Eduard Isaac Asser (1809-1894), uma das primeiras figuras em fotografia na Holanda. Com base no exame visual, a maioria dessas impressões foi identificada como impressão em papel salgado com um revestimento, mas pode ser difícil distingui-las das impressões foscas ou brilhantes de albumina, especialmente quando o revestimento é espesso. Para ser mais preciso em nossas descrições e entender melhor a técnica de Asser, seu trabalho foi examinado com técnicas analíticas. A espectroscopia no Infravermelho por Transformada de Fourier (FTIR) nos ajudou a identificar, em certa medida, a natureza dos revestimentos. Antes da análise, as impressões eram descritas como “revestidas com goma-laca” ou “enceradas”, com base no seu grau variável de brilho.O FTIR identificou um número maior de substâncias nos revestimentos: goma, proteína, resina natural e possivelmente amido. Tomografia de Coerência Ótica (OCT) também foi usada para estudar os revestimentos. Como a OCT tem limitações ao lidar com camadas muito finas, ela nem sempre foi adequada para distinguir impressões de papel salgado revestido e impressões de albumina revestida. No entanto, acabou sendo uma ferramenta útil para explorar a topografia e a estrutura dos suportes de papel e dos revestimentos. Traduzido por Marcia Rizzo.

RESUMEN

El Rijksmuseum conserva cuatro álbumes de gran valor que contienen 187 fotografías realizadas por Eduard Isaac Asser (1809–1894), una de las primeras figuras de la fotografía en los Países Bajos. Basándose en un examen visual, la mayoría de estas copias han sido identificadas como papeles salados cubiertos con un aglutinante, lo que hace que sea muy difícil distinguirlos de una copia a la albúmina mate o una con brillo, especialmente cuando la capa de recubrimiento es muy gruesa. Con el fin de ser más precisos en nuestras descripciones y para entender mejor la técnica de Asser, su obra fue examinada con técnicas analíticas. La técnica de espectroscopia infrarroja transformada de Fourier (FTIR) nos permitió identificar, hasta cierto punto, la naturaleza de las capas de recubrimiento. Antes de los análisis, las copias se habían descrito como “recubiertas de shellac” o bien como “enceradas”, en base a los distintos niveles de brillo. FTIR identificó un mayor número de sustancias en esas capas: goma, proteína, resina natural y posiblemente almidón. La técnica de tomografía de coherencia óptica (OCT) fue empleada también para el estudio de estas capas. Dado que OCT tiene ciertas limitaciones a la hora de lidiar con capas muy finas, resultó no ser el método adecuado para distinguir entre una copia al papel salado recubierto y una copia a la albúmina recubierta. Sin embargo, fue una herramienta muy útil para explorar la topografía y estructura del soporte de papel y de las capas de recubrimiento. Traducción: Rosina Herrera Garrido; revisión: Amparo Rueda.

KEYWORDS:

• Photographic album
• salted paper print
• coated photograph
• Fourier transform infrared spectroscopy
• FTIR
• optical coherence tomography
• OCT
• Eduard Isaac Asser

Acknowledgments

The authors wish to thank the Conservation Department at the Rijksmuseum, especially Robert van Langh, Idelette van Leeuwen and Martin Jürgens; and, Mattie Boom, Curator of Photography. Also, thanks to Lénia Fernandes (Fotomuseum, Rotterdam) and Ioannis Vasallos (The National Archives, London) for their collaboration in preparing the mock-ups, and to Elena Bulat (Harvard Library) for facilitating their sample set to engross our FTIR spectrum library. Finally, thanks to Alison Bowers and Emma Webb, our generous English editors.

Disclosure statement

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

Notes on contributors

Rosina Herrera Garrido studied Paper Conservation in Madrid before she attended the Advanced Residency Program in Photograph Conservation in Rochester, NY (2005–2007). She was later a research fellow at MoMA (NY) and completed her Master’s in Art History in Valencia, Spain, in 2011. Since 2014, she works as Photograph Conservator at the Rijksmuseum in Amsterdam, The Netherlands. She is also a guest professor at the Polytechnic University in Valencia, Spain, and the Pablo Olavide University in Sevilla, Spain. She is currently writing a photograph conservation manual for students and professionals. Email: [email protected].

Suzan de Groot studied analytical chemistry at the Hogeschool van Amsterdam and graduated in 1996. Since 1996 she has been employed by the Cultural Heritage Agency of the Netherlands (RCE). She specializes in the identification of organic materials using Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. She is specialized in researching painting materials, but since 2012 the emphasis of her work has been on research into plastics in cultural heritage and in modern and contemporary art objects. Since 2014 she has been project manager of the Plastics project at the RCE. Email: [email protected]

Tom Callewaert-Dore, MSc was born in 1991. Following highschool education in Antwerp, he attended KU Leuven University and graduated Cum Laude in 2014 with a degree in physical chemistry. Since December 2014 he has been developing the use of OCT in material science applications in a PhD position at the Technical University Delft. Email: [email protected]

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Notes

1 Three types of albumen paper were produced: single coated, double coated and matte. The salted paper prints were sized, some with starch and others with gelatin. The prints sized with starch were coated with albumen, wax, gum Arabic, gelatin, casein, Dammar, shellac and collodion.

2 Elena Bulat provided us with a different set of salted paper prints coated with: shellac, dextrin, Dammar, albumen, sandarac, gelatin, gum Arabic, copal and beeswax.