This 4 ounce jar of Potassium Ferricyanide by Jacquard is a red salt that is used in conjunction with Ferric Ammonium Citrate to create sensitizer stock for Cyanotype printing. An antique photographic process, Cyanotype has been used since the mid-19th century for producing Prussian blue monochromatic prints especially in the biology field. This remarkably simple process employs two inexpensive chemicals and sunlight/UV. Prints can be made on any natural fiber including paper, cotton, silk, wool, wood and more. Avoid ingestion, inhalation and contact with skin.