This method gives by far the greatest colour range to be easily obtained on paper prints. By using four readily available colour couplers in various combinations, together with a common colour developer,- almost any colour image can be obtained, and can be readily repeated if the solutions are carefully prepared. It is a means of obtaining particularly rich warm blacks and browns.

Solutions Required

Colour Developer.

Sodium metabisulphite 5 gm
p-diethylaminoaniline sulphate 10 gm
Water, to 00 cc

Genochrome or Activol 11 gm
Water, to 100 cc

Calgon 2 gm
Sodium carbonate (anhyd.) 17 gm
Sodium formaldehyde sulphoxylate 5 gm
Potassium bromide 1 gm
Water, to 1000 cc

Coupler Solutions

Magenta: p-nitrobenzyl cyanide 0-5 gm
Alcohol 100 cc
Yellow : Acetoacet-2:5-dichloranilide 2 gm
Alcohol 100 cc
Blue-green: 2:4-dichloro-1-naphthol 1 gm
Alcohol 100 cc
Blue: 1-Naphthol 1 gm
Alcohol 100 cc

These stock solutions will keep reasonably well in brown bottles if filled to the neck and well corked, but the working solution must be mixed immediately before use as it is unstable. The working solution is prepared by mixing three parts of Developer (i) or (ia) with 100 parts of Developer (ii) and then adding ten parts of Coupler solution. Suitable mixtures of coupler for a complete spectral range are:

Magenta 8
Yellow 2

Magenta 5
Yellow 5

Magenta 2
Yellow 8

Stock solution

Yellow 5
Blue-green 5

Stock Solution
Blue-green 8
Magenta 2

Blue-green 5
Magenta 5

Blue-green 5
Magenta 8

(The blue image obtained with the mixed couplers is not as bright as the image obtained from the blue coupler, but can be used if the number of solutions is to be kept to the minimum.)

Fixing Bath.
Hypo 200 gm
Water, to 1000 cc

First Bleach.
Potassium ferricyanide 50 gm
Potassium bromide 20 gm
Water, to 1000 cc

Second Bleach.
First bleach 30 cc
First Bath 70 cc

The fixing and first bleach baths will keep well, but the second bleach has a life of only a few minutes, and must therefore be mixed just before use.

Processing Procedure
Direct development of the latent image in the colour developer is possible, but the more reliable method is to develop the latent image in a normal print developer, fix and wash, and convert the silver image to silver bromide, fog it, and then colour develop. The colour developer produces a light silver image in addition to the dye image and this can either be left in to give a rich 'tinted' image, or it may be removed to leave the bright dye image. The following time-table is suggested:

First Developer 2 minutes 20C
Stop Bath 1 minute 20C
Fix 10 minutes 20C
Wash 30 minutes
First Bleach ---------
Wash 5 minutes
Fog 1 minute 1 ft from 100W lamp
Colour Developer 5 minutes 20C

If the silver image is to remain:

Wash 5 minutes
Fix (in fixing bath given) 5 minutes
Wash 20 minutes

or if the dye image only is required:

Wash 20 minutes
Second Bleach -------
Wash 20 minutes

Notes on Processing

1. The first development should be full, but fog must be avoided. If necessary, extra bromide or an antifoggant should be added to clear the highlights.

2. The first fixer must be fresh or colour stains will be produced.

3. Bleaching times are not given as these will depend on the condition of the solutions and the print density. Both first and second bleach stages should be long enough to completely remove the black silver deposit.

4. Continuous and vigorous agitation during colour development is essential. or the shadows will be of low density and will have no gradation.

5. Washing times given may need alteration, depending on the weight of the paper base and on the efficiency of the washing system. Too little washing between first fix and first bleach will destroy the light densities, and too little before or after colour development will produce stained highlights. If in doubt, wash longer. The dyes produced by colour development are sensitive to acids, and acid solutions after colour development should be avoided. Also, like the majority of dyes, they may fade on exposure to strong sunlight for long periods.

From the British Journal of Photography Annual 1965, first published in an earlier Almanac in the 1930's.
It's an easy process and works very well.