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Wednesday, May 15 • 4:30pm - 5:00pm
(Research & Technical Studies) Effects of Binder Layer and Bath pH on Pt-Ag Replacement Reactions as Applied to Photographic Toning Practices

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Nineteenth-century paper-based photographic images consist of metallic nanoparticles embedded in carbohydrate or protein matrices, where the properties and local environments of these particles determine the aesthetic tonality of the print. Salted paper prints and gelatin printed-out prints are both silver-based processes that naturally produce prints with a reddish-brown coloration. From an early date, photographers manipulated the tones of these photographs with the use of precious metal baths containing gold or platinum salts. As in modern nanochemistry, traditional chemical photographic printing methods require tightly controlled reaction conditions to influence product morphology and access specific optical properties. In this study, a suite of silver prints toned with platinum was generated following historic recipes and analyzed by X-ray fluorescence spectroscopy, scanning electron micrography, and colorimetry to investigate the interplay between metal content and perceived tone. Thin sections of the samples were also prepared by focused ion beam milling and imaged using scanning transmission electron micrography to visualize the metal particles in situ. Prints toned in an acidic platinum bath undergo galvanic replacement of silver for platinum, converting nanoscale aggregates of silver to evenly distributed bimetallic particles that impart a neutral gray hue. Those toned in an alkaline platinum bath experience metal deposition, which increases the print’s optical density. For gelatin prints, these reaction mechanisms are further influenced by the protonation state of the binder layer. Detailed analysis of laboratory-created samples and mechanistic understanding gained through parallel solution experiments lead to insights into traditional photographic printmakers’ working methods and can help direct the long-term care of original objects. Additionally, understanding the implications of these synthetic methodologies for current nanotechnology fields, such as paper-based sensors and supported nanocatalysts, is an important consequence of this work.

avatar for Joan M. Walker

Joan M. Walker

conservation scientist, National Gallery of Art
Joan M. Walker received a Ph.D. in Inorganic Chemistry in 2015 from Indiana University, where her research focused on the interaction between metallic nanoparticles and proteins under visible light excitation. After a brief internship in the Conservation Science Department at the... Read More →

avatar for Alline Myers

Alline Myers

physical scientist, National Institute of Standards and Technology
Alline Myers is a Physical Scientist in the NanoFab Operations Group. She received a B.S. in Physics from North Carolina State University, an M.S. in Physics from Penn State, and a Ph.D. in Materials Science and Engineering from North Carolina State University. Alline has extensive... Read More →

Keana Scott

physical scientist, National Institute of Standards and Technology
Keana Scott is a Physical Scientist in the Materials Measurement Science Division at the National Institute of Standards and Technology (NIST). Keana graduated from the California Institute of Technology in 1991 with a B.S. in Engineering and Applied Sciences. She completed her Ph.D... Read More →
avatar for Ronel YL Namde

Ronel YL Namde

Conservator, National Gallery of Art
Ronel Namde is a Photograph Conservator at the National Gallery of Art in Washington, DC. She graduated from the Winterthur/University of Delaware Program in Art Conservation in 2015 with a specialization in photographic materials. She received her BA in Anthropology from Yale University... Read More →

Wednesday May 15, 2019 4:30pm - 5:00pm 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 Joan M. Walker, Ronel Namde, Keana Scott, Alline Myers
  • Abstract ID 18705
  • Tags salted paper prints,gelatin printed-out prints,X-ray fluorescence spectroscopy,scanning transmission electron micrography,platinum toning