Assignment 1-Gum Dichromate

Stephanie Chace 

Gum Dichromate Prints #15

Edward Steichen (American, born Luxembourg, 1879–1973)
The Flatiron, 1904, printed 1909
Gum bichromate over platinum print, 47.8 x 38.4 cm (18 13/16 x 15 1/8 in.)
The Metropolitan Museum of Art, Alfred Stieglitz Collection, 1933 (33.43.39)
 Image © The Metropolitan Museum of Art, New York

Key elements that distinguish the gum dichromate process include the below:

This photographic process utilizes gum arabic rather than other common binders such as egg whites/albumen, gelatin or glues as the colloid that binds pigments. It is the combination of coating the paper with differing ratios of pigment, gum and potassium, ammonium or sodium dichromate that yields an intended result by the photographer. This process was viewed as unique due to the allowance of experimentation with the gum, pigment and dichromate ratios which artists could employ to express their personal vision for an image (Vila, Centeno, Barro, & Kennedy, 2013).

The  basic process is as follows: 

"Once a sheet of paper is coated with gum, pigment and a dichromate mixture it drys and is exposed to light through a negative that is in contact with the paper. The dichromate acts as a light sensitive component causing, in the exposed areas the hardening and in solubilization of the gum that traps pigment.

After exposure the pigment coated paper is place in a water bath and the unexposed areas soften and dissolve revealing the white paper substrate and forming the light tones of the image. The gum in the exposed areas harden and remain intact as a pigmented colloid layer make up the darker tones in the image" (Vila et al., 2013).

The inventor and other important photographers associated with the process are:

   The  gum dichromate process was invented by John Pouncy in 1858. Alphonse Louis Poitevin of France had done some earlier work with the dichromated colloid which established the workable principle that set the stage for using dichromated colloid. The technique was typically used by pictorialists  and artist who viewed the technique as a high art form.  Some notable artists who employed the this technique were Edgar Degas, Edward Steichen, Gertrude Kasabier, and Alvin Langdon Coburn (Scopick, 1978). 

Tips on how to identify and date examples of the process are listed below:

To identify with the naked eye look for the following qualities: Images that have contrast, and are grainy, yet soft in an impressionistic style. Mid tones stand out but not if the image is processed on rough paper. Artists have also printed platinum or silver based photographs to achieve delicate details and subtleties as well as using pigment colors that impose the look of a chalk and or charcoal drawing (Vila et al., 2013).

When looking at an image that is magnified, look for flat appearance, absence of tonal definition or very abrupt high contrast in tone shifts from light and dark. In addition, paper fibers and pigment particles are easily recognized. This process was commonly used between 1894-1930’s ( “Gum Dichromate,” 2015).

Preservaation concerns:

Viewed as an process that  maintains a stable image very little or no fading occurs because of the use of pigments for the final image. Dichromate prints also escape the occurrence of cracking because the gum arabic is seldom applied too thickly unlike in the case of carbon and woodburytypes . Those two processes use a binder made of gelatin which is applied thickly and often does crack (Riley, 2009).

References

Vila, Anna., Centeno, Silvia A., Barro, Lisa., Kennedy, Nora W. (2013)  Understanding the gum dichromatic process in photographs: A literature review and technical study. Studies in Conservation, 58 (3), 176-188.

Gum Dichromate. (2015). http://www.graphicsatlas.org/identification/?process_id=342)  

Reilly, James (2009) Care and Identification of 19th Century Photographic Prints. Rochester New York: Rochester Institute of Technology  

Scopick, David (1978). The Gum Bichromate Book . Rochester, NY: Light Impressions.