The Historic Processes
Gum Bichromate Prints
This process is known more informally as 'Gum Printing' and dates back to the earliest beginnings of photography. Three separate scientific discoveries in the mid 1830's came together to bring the process to life. Although deceptively simple, it can also be maddeningly frustrating and temperamental. It is however the one old process that is most open to artistic interpretation. Taking advantage of digital technology I am now able to create a negative from a digital image which is then printed on transparency paper. This is then contact printed onto a piece of watercolour paper that has been painted with a mix of gum arabic, watercolour pigment and a sensitiser. This is then exposed to UV light and during this exposure the mixture of pigment, dichromate and gum arabic hardens in direct proportion to the amount of light it receives through the negative. The exposed paper is then washed in water, where the unusued mix is washed off. Further layers of different colours or densities are subsequently added to increase the depth and look of the print, until I am satisisfied.........or it goes in the bin!
This process, was also discovered in the mid 1830's by English astronomer and scientist Sir John Herschel. It was however considered mainly as a means of reproducing notes and diagrams, as in 'blueprints'. This process remained in use well into the 20th century to produce low cost copies of drawings etc. The process is relatively similar to gum prints, although usually only one layer is produced, using two different chemicals mixed together. Once exposed, and then washed in water, the resultant print has that traditional blue colour. It can then either be toned to a different colour, using items as simple as tea or coffee, or additional layers of a different process, such as gum printing, can be added on top of the original layer.