Gum Bichromate Alternative Photo-printing Workshop

Conducted by Tanima Das

On the River

For the River

By the River

Gum bichromate is a 19th century a alternative photographic printing process using gum arabic, watercolor and light sensitizer, potassium dichromate or ammonium dichromate and light source as sun or UV tube lights. Gum Arabic is mixed with watercolor pigment and a photosensitive substance called ammonium or potassium dichromate, and brushed onto watercolor paper. When exposed to light in contact with an enlarged negative, where the light hits the most, the gum hardens the most and creates the shadow areas of the image. Where the light hits the least, the gum and pigment wash away proportionately, leaving the highlights of the image.  The ” development” of the print is carried out by merely plain water. In the water bath, the image reveals itself over a period of time little by little, as the unexposed highlights first wash away and then the softer midtones also dissolve off in various depths. What results is an image that looks surprisingly continuous tone. This exposing and development process could be carried out for two or more times, with development and drying steps after each exposure creating layer upon layer. This produces a much richer print. For a tricolor print there must be three layers – blue, yellow, and magenta.

Requirements

Ammonium Bichromate
Potassium Bichromate
Distilled Water 2 liter
Gum Acatia
Food Gelatin or Better quality Bacto company Gelatin
Formaldehyde. 200 ml,
small quantity of Alcohol as preservative.
Water colours, camal ivory black artist colours, camal lamp black, Camal Magenta, camel crome yellow, or lemon yellow,  Patho Blue ( Reevs ),
Lab necessities
one Borosil Beaker
Two injection syringe
2 clay bowls
Flat 2 inch and one 1 inch brush
One thermal Flask ( should not be used for other purposes)
one steel vessel
2 doses plastic clips
some sharp pins
some rope to hang the prints
a3 size lab trays to wash prints
One or more joined desk to work on, for demonstration and people to work on,
Minimum 2 A3 size glass sheets.
2 hair drier
one water heater.
Minimum 2 plastic jars.
surgical gloves
Other Needs
A4 size gateway paper
Printer
Water colour or printing paper,
one toilet area for developing and washing print

Step Table

UV light box

Mixing colour with gum and ammonium dichromate

applying a layer of gum dichromate for a single layer print

A coat of gelatin before placing the first layer

The paper needs to be dried before applying gum dichromate for printing.

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Comments
One Response to “Gum Bichromate Alternative Photo-printing Workshop”
  1. It’s truly amazing what someone with and idea and some creativity can accomplish from the own comforts of home. The printing process isn’t that hard. A few carefully selected materials and tools, a little know how and your all set.
    http://www.orlandoprinter.com

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