Gum Bichromate Experiment

I have had this image sitting on my desk for ages and wanted to share it as an illustration of the (partially finished) art process. So many of my Google+ Artist friends share their drawings and paintings, and I think this fits in that category, although it a photograph.

This is a gum bichromate treatment of a photo of my grandmother. Gum bichromate is an alternative film-based technique that I learned in a workshop at Gallery 44, which thankfully still promotes antiquarian processing.

The image here is in its rough state, and you can see the masking tape that attached the image for exposure, as well as the pigment brush-strokes that given the impression of having been painted by Francis Bacon (of the screaming popes).

From Fox Talbot to Robert Demachy, from the Lumière brothers to Heinrich Kühn, the bichromate process has a long and varied history spanning well over a century. After falling out of common use for an extended period of time, a resurgence in gum printing began again in the 1970′s through the writings and work of a new generation of artists. It is essentially a modified watercolour. This one was done on Arches paper and has a heavy, antique feel to it.

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

Gum arabic
A dichromate (usually ammonium or potassium)

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 hardens the dichromate in proportion to the densities of the 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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