Alternative Photography Workshop - Gum Bicromate Process

A program presented to the students from Photography department of Cleveland Institute of Art (CIA) - during Creative Fusion Residency / Cleveland Foundation, USA (2015)

An introduction to the gum bichromate process

At first glance, the gum bichromate process looks amazingly uncomplicated. However, to nearly every one of my students who has been seduced by the process, and for those artists who are dedicated to it, gum is one of the most complex in the alternative genre. Gum bichromate printing is certainly seductive due to its limited chemistry, simple water development, and unlimited color potential with watercolors of the artist’s choice. Gum printing is quite flexible and easily combined with other processes and graphic disciplines.

Overview

Gum bichromate (or dichromate) printing involves creating a working emulsion made of three components:

Gum arabic
A dichromate (usually ammonium or potassium)
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.

gum bichromate printing

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.

Documentation: http://www.alternativephotography.com/an-introduction-to-the-gum-bichromate-process/