Workshop: Gum Bichromate Printing by Ellie Young
Gold Street Studios, Trentham East
22 & 23 August 2014
Gum Bichromate process allows colour printing from black & white contact negatives in numerous colours. Paper is coated with pigment, dichromate and gum Arabic, registered, exposed to ultraviolet light. Exposure to light hardens the gelatin proportionate to the varying density of the negative.The print is then placed in a bath of water to allow the soluble gum, excess dichromate, and pigment to wash away. Colour layers are built up by repeating the coatings with careful registration.
In 1839 Mungo Ponton discovered light sensitivity of dichromates. William Henry Fox Talbot later found that colloids such as gelatin and gum Arabic became insoluble in water after exposure to light. In 1858, John Pouncy used colored pigment with gum Arabic to create the first color images.
There is a high degree of artist control in this beautiful print making process.
During the workshop you will create a number of images. The following issues and many others will be covered:
- CMYK negatives for control of colour and contrast
- Alignment / registration of negatives
- Ways of coating the paper
- Different colour pigments that can be used
- How to build up and control colour during processing