Formulary Potassium Ferricyanide (Bleach) Powder - 10 grams

Potassium Ferricyanide 10g - by Photographers Formulary.

The compound has widespread use in blueprint drawing and in photography (Cyanotype process). Several photographic print toning processes involve the use of potassium ferricyanide. Potassium ferricyanide is used as an oxidizing agent to remove silver from negatives and positives, a process called dot etching. In color photography, potassium ferricyanide is used to reduce the size of color dots without reducing their number, as a kind of manual color correction. It is also used in black-and-white photography with sodium thiosulfate (hypo) to reduce the density of a negative or gelatin silver print where the mixture is known as Farmer's reducer; this can help offset problems from overexposure of the negative, or brighten the highlights in the print.

Safety Precautions:

• The bright red crystals or powder should be free from any yellow powdery coating.
• Store the compound in a cool, dry place, and protect from light and air.
• Keep the container tightly closed and do not heat strongly solid or solutions.
• Use with adequate ventilation.
• Wear safety glasses and rubber gloves to avoid contact with the compound.