Copper Toner is a general purpose toner that acts by deposition of copper metal. It is capable of producing a variety of colors ranging from warm brown to chalk red. The exact tone that is obtained depends upon the length of time the paper is immersed in the toning bath, and the type of paper used. Almost all papers can be used with this toning bath, although fiber based papers are best, resin coated papers work nicely also.

CHEMICAL SAFETY
POTASSIUM ferricyanide: In spite of the fact that this compound contains cyanide, it is not particularly toxic. The reason is that the cyanide groups are bound to the iron atom and are not free to act as a poison. The cyanide groups can be released as hydrogen cyanide gas if the potassium ferricyanide is placed in a strong acid solution: however the copper toning process does not call for acid. To dispose of excess potassium ferricyanide (solid or in solution) wash the material down the drain with excessive amounts of water.

MIXING THE STOCK SOLUTIONS
NEVER USE METAL UTENSILS OR CONTAINERS IN MIXING, STORING OR USAGE OF ANY TONER.

Stock Solution A

Chemical	Amount	Units
Water (68°F/20°C)	600	ml
Copper Sulfate	4	g
Potassium Citrate	16	g
Water to make	1000	ml

Place the water in the storage container or a mixing container and add the Copper Sulfate. Stir until the solid completely dissolves. Next add the Potassium Citrate and stir until the solid dissolves. Add water to bring the volume of the solution up to 1000 ml. Stir the final solution thoroughly.

Stock Solution B

Chemical	Amount	Units
Water (68°F/20°C)	600	ml
Potassium Ferricyanide	3.3	g
Potassium Citrate	16	g
Water to make	1000	ml

Mix the chemicals in the order given, in the same manner as directed for Stock Solution A.

MIXING THE WORKING SOLUTION
Mix the working solution just prior to toning. To prepare the working solution, mix equal volumes of Stock Solutions A and B. Do not dilute the working solution. Discard the working solution after a working session.

TONING THE PRINT
All toners work best if the print is fixed with a non hardening fixer. Immerse the fixed and washed print in the undiluted toning solution in a plastic tray. If you start with a dry print, be sure to presoak it in water. The longer the print is immersed in the toning solution, the more the tone will appear as a red hue. If the print is allowed to remain too long in the bath the whites will turn pink. Determine the toning time with test strips. Rinse the toned print in running water for 20 minutes.

REFERENCE
Classic Toning Methods, Peter Hughes (Reichelt), Mastering Black-and-White Photography, p.49.
Copper Toner Kit No. 06-0010, Photographers' Formulary (800-922-5255).

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