Gum bichromate process
Gum bichromate (or dichromate) printing involves creating a working emulsion made of three components: Gum arabic, A dichromate, (usually ammonium or potassium) and a pigment
The emulsion is spread on a support, such as paper, and allowed to dry. A negative or matrix is then laid over top the emulsion and exposed to a UV light source. Usually a contact printing device or a sheet of heavy glass to ensure even, constant contact is employed. The light source will harden the dichromate in proportion to the densities of your negative. After exposure, the paper is placed in a series of plain water baths and allowed to develop until the unhardened portions of the emulsion have dissipated.
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| Dichromate ammonium |
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| Gum Arabic |
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| Pigments |
Gum prints tend to be multi-layered images sometimes combined with other alternative process printing methods such as cyanotype and platinotype. A heavy weight cotton watercolor or printmaking paper that can withstand repeated and extended soakings is best. Each layer of pigment is individually coated, registered, exposed and washed. Separation negatives of cyan, magenta, and yellow or red, green, and blue are used for a full-color image.
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| Michel Herin |
The Digital attempt
The Gum bichromate process is a 19th century process which has historical values and unrepeatable features that can only be achieved with the original print process, even though, digital softwares let us play, experiment and give an idea of the process. This is my Digital attempt using Photoshop.
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