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Wednesday, May 15 • 5:00pm - 5:30pm
(Research & Technical Studies) The Application of Surface Enhanced Raman Spectroscopy (SERS) and Gel-Sampling to Identify Synthetic Dyes Used on Hand-Colored Photographs

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Until the commercially successful introduction of chromogenic color prints by Kodak in 1935, colored photographic pictures mainly were produced by hand-coloring B. & W.-photographs, e.g. Daguerreotypes, albumen and gelatin-based prints (1). This was common practice with portraits on postcards (Figure 1). Until 1860, inorganic and natural organic pigments in a binding medium were applied. Later, inks, containing synthetic dyes were introduced. As many of these dyes are very light-sensitive, caution must be taken when exhibiting these artefacts. Little is known about the practice of hand-coloring. Therefore, a proper identification of these dyes would help to understand the coloration process and assess the risk of fading. Hydrogels, e.g. the “Nanorestore Gel”, or an agar gel, can be used to gently extract water-soluble dyes from the gelatin layer of a photograph, e.g. for cleaning purposes (2, 3). These gels could be useful for micro-sampling. Surface Enhanced Raman Spectroscopy (SERS) is a very powerful technique for dye identification, especially for synthetic dyes (4). The silver colloid, added to the sample taken from the object, can enhance the Raman signal up to a factor of 109, making it even possible to detect single molecules, e.g. crystal violet (5). According to research done by Doherty et al., methylcellulose films, doped with a silver colloid can be used to extract dyes from the artefact’s surface for analysis by SERS (6). In our research, this principle has been applied by doping the “Nanorestore Gel” and an agar gel, with colloidal silver (prepd. according to a description by Lee & Meisel (7). A small piece of the gel is immersed into the colloid and left there for a while to be impregnated by the colloid. During the short contact time (minutes) of a very small cube (area: c. 1 mm2) of the hydrogel, water-soluble dyes migrate into the gel and come into contact with the colloid. They then can be analyzed by SERS. This way, dyes on 4 hand-colored photographs from a private collection could be extracted and successfully identified by SERS. The spectra were measured with a Renishaw RAMAN microscope with a 785 nm Laser. In order to identify the dyes, their Raman spectra were compared with spectra taken from the RCE’s large reference collection of synthetic dyes. The red dye in the roses on the postcard in Figure 1 turned out to be eosin. *Corresponding author Many historic gelatin-based photographs show silver mirroring, the formation of colloidal silver at the surface, caused by redox cycling of silver in the gelatin layer (8). The silver mirroring on some of these photographs was shown to function as a SERS-active substrate, enhancing the Raman signal of the dye in contact with it.

avatar for Han Neevel

Han Neevel

Senior Researcher Conservation Science, Cultural Heritage Agency of the Netherlands
Han Neevel is research scientist at the Cultural Heritage Laboratory of the Cultural Heritage Agency of the Netherlands, location Amsterdam. He also holds an appointment as guest lecturer in dyestuff & photographic chemistry at the University of Amsterdam (UvA). He received a PhD... Read More →

avatar for Inez van der Werf

Inez van der Werf

conservation scientist, Cultural Heritage Laboratory, Cultural Heritage Agency of the Netherlands
Inez van der Werf is conservation scientist at the Cultural Heritage Laboratory of the Cultural Heritage Agency of the Netherlands, location Amsterdam. She was trained as a paintings restorer at the Istituto Superiore per la Conservazione ed il Restauro in Rome and received a PhD... Read More →
avatar for Katrien Keune

Katrien Keune

research scientist/associate professor, Rijksmuseum Amsterdam/University of Amsterdam
Katrien Keune is research scientist at the Rijksmuseum Amsterdam, Netherlands. She also holds an appointment as Associate Professor of Chemistry at the University of Amsterdam (UvA) and contributes to the Netherlands Institute for Conservation, Art and Science (NICAS) at a scientific... Read More →
avatar for Veronica Biolcati

Veronica Biolcati

intern, Technical Studies Research Laboratory, Getty Conservation Institute
Veronica Biolcati is an intern at the Technical Studies Research Laboratory of the Getty Conservation Institute. Her research interests include the investigation of the materials and techniques used for painting, the application of new methods and technologies for the scientific study... Read More →

Wednesday May 15, 2019 5:00pm - 5:30pm EDT
Nehantic/Pequot/Paugussett Rooms Sky Convention Center, Mohegan Sun
  Specialty Session, Research & Technical Studies
  • Track Research & Technical Studies
  • Ticketed Included in Main Registration
  • Authors in Publication Order Veronica Biolcati, Katrien Keune, Inez van der Werf
  • Abstract ID 19162
  • Tags Hand-colored photographs,Surface Enhanced Raman Spectroscopy,Hydrogels,Sampling,Synthetic Dyes,Identification