Toning Bromide and Gaslight Prints 
CoprerR Toninc.—Various shades from red to violet- 
brown are obtainable by this process, which is based on the 
deposition of red cuprous ferrocyanide on the image with the 
simultaneous formation of white silver ferrocyanide. It is 
actually an intensification process; therefore, the primary 
image must not be developed too far. 
Single solution (Ferguson) : 
Cupric sulphate, 10% sol. 106ccm 1 oz., 5dr: 
Potassium citrate, 10% sol. 800ccm 13 oz. 
Potassium ferricyanide, 
10% sol. 94ccm  loz.,3dr. 
This solution will keep and does not stain plates or papers; 
the colours are dependent on the length of immersion. Sed- 
laczek gives the following formulas for various tones, and, 
as the baths will not keep well, they should be mixed just 
before use. In all these formulas, the quantities of the solu- 
tions should be added to the stated amount of water in the 
order given: 
Potassium citrate, 10% sol. 250ccm 334 02. 
Cupric sulphate, 10% sol. 40 ccm 290 min. 
Ammonia alum, sat. sol. 100 ccm 14 oz. 
Potassium ferricyanide, 
10% sol. 30 ccm 218 min. 
Water 750 ccm 12 oz. 
This gives red or violet-brown tones with clear whites. 
Ammonium oxalate, sat. sol. 200 ccm 3% 
Cupric sulphate, 10% sol. 40 ccm 290 min. 
Ammonium carbonate, 
10% sol. 10 ccm 72 min. 
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