Gum Bi/Dichromate

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Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated April 2011
Contributor: 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.

Gum Bi/Dichromate (also called Photo-Aquatint)

Historical Facts
Invented: 1839 by Mungo Ponton; 1855 Alphonse Louis Poitevin added carbon pigment to colloids; 1858 John Pouncy used watercolor (color pigment with gum)
Historic Practioners: Heinrich Kuhn, Hans Watzek (Austria); Leonard Misonne (Belgium); Robert Demachy, C. Puyo (French); ; Rudolph Duhrkoop, Hugo Erfurth, Theodor & Oskar Hofmeister (Germany); Jose Ortiz Echague (Spain); Alfred Horsley Hinton, Alexander Keighley, Alfred Maskell, F. J. Mortimer (UK); Edward Steichen (USA)
Contemporary Practioners: Christina Z. Anderson, Steven Livick, Keith Taylor, Katherine Thayer (died, March 2011), Sam Wang (USA)

Identification Characteristics
Image layer: Gum prints are pigment and hardened gum, albumen, or proteins, therefore, the media sits on the surface of the paper. At times, the image can appear soft-edged or blurred, and the image layer grainy or granular. Sometimes offset registration can be seen in multiple layer gum prints resulting from expansion and contraction of the paper during multiple washing and re-sizing procedures.
Color: Gum prints are the color(s) of the pigment(s) chosen by the photographer, therefore, bright, bold colors can be achieved with gum printing. Multiple-layer printing of color is possible. Sometimes the blue layer in a gum print is a cyanotype.
Support: Paper type can vary, however, the fibers and surface texture of the support are visible under magnification. The print surface can look matte unless heavily sized or varnished.
Analysis: X-Ray fluorescence can analyze elements in colorants chosen and chromium. For historical samples, mercury (from a mercuric chloride fungicide) might also be detected.

Housing and Storage Considerations
Gum prints should be stored in good quality paper-board folders, as a watercolor is stored, to protect from light, dust, and handling.
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
Gum prints can be frozen for later recovery if necessary. The gum is hardened during exposure and undergoes extended washing during processing. Therefore, gum prints should be able to withstand extended periods of immersion in water. Handling wet paper can cause damage such as nicks, abrasions, and tearing. Mold can develop on the prints.

Helpful Treatment Techniques, Things to Know, and CAUTIONS!

Electronic Resources:
Regarding Historic Material:
GEH Notes on Photography (Print):
GEH Notes on Photography (Process):
Robert Wulfert: Chronology:

Regarding Contemporary Practice:
Alternative Photography (How To):
Analog Photography Users Group (APUG):
Hamish Stewart (How It Works):
Keith Taylor (Three Color Gum #2):
Katherine Thayer (Notes on Process): (died 2011, may be inaccessible)
Katherine Thayer (Technical Notes): (died 2011, may be inaccessible)
Sam Wang (Three Color Gum):

Printed Resources: BOOKS, ARTICLES
Regarding Historic Material:
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
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

Regarding Contemporary Practice:
Anderson, Christina Z. 2007. Alternative Processes Condensed. (self-published)
Barnier, John. 2000. Coming Into Focus: A Step-by-Step Guide to Alternative Photographic Printing Processes. San Francisco, CA: Chronicle Books
Farber, Richard 1998. Historic Photographic Processes. New York, Allworth Press p. 150-176
James, Christopher. 2008 (2nd ed.). The Book of Alternative Photographic Processes. Florence, KY: Delmar Cengage Learning Langford, Michael. 1981. The Darkroom Handbook. New York: Dorling Kindersley Limited
Scopick, David. 1991. The Gum Bichromate Book, 2nd Edition. Stoneham, MA: Focal Press
Wang, Sam. 2011. Sam Wang: Four Decades of Photographic Exploration. China: Jiangsu Arts Press

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