Gum Dichromate Prints: A brief procedure by Todd Walker
The paper to be used for Gum (Gum Dichromate) printing needs to be a sturdy, preferably rag, paper which will stand soaking in water for an hour or more without losing its strength. If you plan to register several printings, the quality of the paper should be of the best and the paper should be pre-shrunk by soaking in very hot water for 10-15 minutes and drying thoroughly before sizing or commencing to sensitize the paper.
If it is important to have the highlights of the print without staining from the pigment being used, the paper shold be sized (sealed) so that the color does not penetrate into the fibers of the paper. The paper is first saturated with a 1 percent solution of alum, dried, then sprayed with starch, dried, washed and re-dried. A diluted acrylic gesso coating, or a gelatin coating may also be used.
After the paper has been properly prepared it is ready to sensitize. A small amount of Gum Arabic is measured out (1/2 ounce of the liquid will easily coat an 11" x 14" print). Watercolor pigment is added to make a transparent wash of the desired color. When this has been thoroughly mixed with the gum, an equal volume of saturated dicromate solution is added to the pigmented gum. THE AMMONIUM DICHROMATE OR POTASSIUM DICROMATE IS POISONOUS AND SHOULD BE HANDLED WITH EXTREME CARE !!! The solution is thoroughly mixed and then coated onto the dry, previously prepared paper with a brush. The paper is completely dried, at which time it is then ready to expose.
Exposure is by contact with the negative under daylight or similar light source to that useful for blueprint or diazo prints. Exposure time is determined by test strips using the same pigmented gum mixture. Changes in the gum, dichromate, or pigment mixture will affect the exposure.
Development is in cool tap water. The print is immersed in the tray, with gentle agitation, for several minutes and then carefully floated face down, for at least five minutes and possibly as long as several hours, to develop the image to its desired point.
The print is then dried by hanging in a cool place. It may then be recoated, re-exposed, redeveloped, and redried again and again until the desired effect is achieved.
Dry Pigment Measurements for Gum Dichromate Prints
Ivory Black 5.0 grams
Van Dyke Brown 4.0 grams
Burnt Umber 4.0 grams
Pthalocyanine Blue .6 grams
Pthalocyanine Green 1.0 grams
Alizarin Crimson 1.2 grams
Cadmium Red 3.0 grams
Hansa Yellow .5 grams
Chocolate Brown Oxide 4.0 grams
Thioindigo Violet .6 grams
Ferrite Lemon 4.0 grams
Titanium Dioxide (white) 5.0 grams
These are some "good" and "bad" water color pigments for gumprinting in terms of permanent vs. fugitive (colors in the finished print) - (presented) somewhat in order of (the) preference (of Todd Walker):
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GOOD: Cadmiums - Red, Orange, Yellow Cobalts - Yellow, Blue, Violet Chinese White - Zinc White Cerulean Blue Yellow Ochre Burnt Umber Alizarins - Red (Crimson, Lake, Scarlet) Ivory Black Lampblack Manganese (Blue, Violet) Naples Yellow Permanent Carmine Pthalocyanines - Blue, Green Raw Sienna Burnt Sienna Red Oxide Vermillion - Heavy, sometimes turns black Viridian Strontium Yellow
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BAD: Carmine - fugitive Chromes - anhydrous Ultramarine - changes Prussian Blue - erratic Hooker's Green - coarse, fugitive Magenta - fugitive Moss Green - chromete Olive Green - coarse, chromete Rose Madder - thin Emerald Green - poison Van Dyke Brown - coarse, fugitive |
The preceding information is from class handouts in the Non-Silver Photography class, ART 444, taught by Todd Walker at the University of Arizona in the Fall semester of 1984.
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This page was last updated August 22, 2001.