Silver Gelatin Printing-Out, Silver Gelatin Developing-Out, Resin Coated (RC), Photo-Stat

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Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated January 2012
Contributor: Amy Brost, Stephanie Watkins

The Photographic Materials Conservation Catalog is created and maintained by the Photographic Materials Group of the American Institute for Conservation for the convenience of the membership. The treatments, methods, or techniques described herein are provided for informational purposes. The reader assumes responsibility for any application results or interpretation of information.

Silver Gelatin Developing-Out, Resin Coated (RC), Photo-Stat

Papers with silver sensitized emulsion layers were used widely for pictorial image making, documentation, and copying processes into the 21st c. Silver-gelatin's market dominance was replaced by digital image technology. Silver-gelatin processes are still used by photographic artists.

Historical Facts
Invented: 1871, Richard Leach Maddox; 1878 improvements, Charles Harper Bennet
Important Development Dates:

  • 1874 Commercial production of gelatin for DOP
  • 1885 Commercial coating machines
  • 1894 Baryta layers added to commerical DOP papers, 1900 introduced to Kodak papers

Historic and Contemporary Practitioners: As one of the most widely used processes in the 20th c., just about anyone working in this period did work with silver-gelatin at one time or another whether amateur, professional, or copyist.

Identification Characteristics
Image layer: The image is within the emulsion layer. It can either be partially within the paper structure as with printing-out processes, or on top of a baryta layer as with developing-out processes.
Color: Pristine silver gelatin printing-out photographs can range in color from warm browns to cool purples because of the nature of the development of the photolytic silver strand. Pristine silver-gelatin developing-out photographs are generally monochromatic, blue-black and white in appearance. Both processes can be toned to different colors with the addition of a toning process during development, using other minerals such as selenium or gold.
Support: Silver-gelatin emulsions can be applied to numerous types of substrates including paper. Paper substrates used in direct contact processes are usually sized to withstand the numerous immersion baths required during processing.

Basic Process Overview
Image creation in all silver halide processes involves sensitizing a substrate with silver halide, and exposing it to light, which breaks the bond between the silver and the halide. The silver ion is then reduced to become free silver, which creates the dark areas of a photographic image.

The silver gelatin developing-out process involves exposing and developing a negative, which can be placed into an enlarger. Light is passed through the negative onto sensitized photo paper, which is then chemically developed-out. The exposed paper is developed (to reduce the silver ions), stopped (to stop the reduction/darkening), fixed (to remove the unexposed silver salts), and washed (to remove any trace chemicals from the previous baths).

Housing and Storage Considerations

  • Silver gelatin prints should be stored in good quality paper-board folders, to protect from light, dust, and handling. They can also be stored in plastic film folders and sleeves, such as uncoated, unplasticized, virgin polyester terephthalate, poly(ethylene), and poly(propylene). Materials that pass the Photographic Activity Test (P.A.T.) will provide suitable housing for these types of photographs.
  • An ideal temperature and humidity are 68 degrees F (20 degrees C) +/- 2 degree drift and 50% +/-5% variation over 24 hours.

Emergency Recovery Tips
Handling wet paper can cause damage such as nicks, abrasions, and tearing. Mold can develop on or within the papers and emulsion layers.

Helpful Treatment Techniques, Things to Know, and CAUTIONS!

Electronic Media Resources: WEBLINKS, AUDIO, DIGITAL
Regarding Historic Material:

Regarding Contemporary Practice:

Printed Resources: BOOKS, ARTICLES
Regarding Historic Material:

  • Adams, Anselm. 1950. The Print : Contact Printing and Enlarging. New York: Morgan & Morgan.
  • Coe, Brian and Mark Haworth-Booth. 1983. A Guide to Early Photographic Processes. London: Victoria and Albert Museum
  • Crawford, William. 1979. The Keepers of Light. New York: Morgan & Morgan. p. 199-212
  • Eaton, G. T. 1965. Photographic Chemistry in Black-and-white and Color Photography. Hastings-on-Hudson, N.Y.: Morgan & Morgan.
  • Funderburk, Kit. 2007. A Guide to the Surface Characteristics: Kodak Fiber Based Black and White Papers. Rochester, NY: Kit Funderburk self-published
  • Gray, G. G. 1987. "From Papyrus to RC Paper: History of Paper Supports." Pioneers of Photography: Their Achievements in Science and Technology. Eugene Ostroff, ed. Springfield, VA, The Society for Imaging Science and Technology: 37-46.
  • Hendriks, Klaus B., with Brian Thurgood, Joe Iraci, Brian Lesser, Greg Hill. 1991. Fundamentals of Photograph Conservation: A Study Guide. Toronto, Ontario: Lugus Publications for the National Archives of Canada
  • Lavedrine, Bertrand (with Jean-Paul Gandolfo, John McElhone, and Sibylle Monod). 2007 (French version), 2009 (English Version). Photographs of the Past: Process and Preservation. Los Angeles, CA: The Getty Conservation Institute
  • Reilly, James M. 1986. Care and Identification of Nineteenth-Century Photographic Prints. Rochester, NY: Eastman Kodak
  • Wentzel, F. and L. W. Sipley. 1960. Memoirs of a Photochemist. Philadelphia: American Museum of Photography.

Regarding Contemporary Practice:

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