Cyanotype is the original sun-printing process and one of the earliest photographic techniques ever developed. Discovered in 1842 and distinctive for producing rich, Prussian blue monochromatic prints, Cyanotype was used well into the 20th century as an inexpensive method for reproducing photographs, documents, maps and plans (hence the enduring architectural term “blueprint”), as well as for making impressions of biological specimens in the field (“photograms”).
Cyanotype may be used to create detailed prints from virtually any object that casts a shadow: tools, toys, plants, leaves, stones, sand, string, lace, etc. Simply place the object on the sensitised surface and expose to sunlight (UV). By using a digitally-printed photographic negative (an inverted black and white photo inkjet-printed onto a transparency*) instead of an object, cyanotype may also be used to create full-resolution photographs on paper or fabric. Great for photographers, mixed media artists, printmakers, quilters, kids and more, the cyanotype process is easy, forgiving, quick, magical and fun. Harness the power of the sun—a great group activity for any age!
Potassium Ferricyanide is a red salt that is used with
Ferric Ammonium Citrate for cyanotype.
Ferric Ammonium Citrate is a light-sensitive iron salt that is used with
Potassium Ferricyanide for cyanotype.
Any natural surface, including cotton, linen, silk, canvas, wool, paper, wood and leather.
Add approximately 2 tablespoons/40 g of Potassium Ferricyanide to 1.7 cups/400 ml of water to create Stock Solution A. Add approximately 1/2 cup/100 g of Ferric Ammonium Citrate to 1.7 cups/400 ml of water to create Stock Solution B. Allow to fully dissolve over 24 hours. Stock solutions have long shelf lives and should be stored in a cool, dark place.
Mix Stock Solutions A & B in equal parts to create the cyanotype sensitizer. Mix only the amount you immediately need, as the sensitizer is stable just 2-4 hours. Coat paper or fabric with the sensitizer and allow to dry in the dark. Once dry, make exposures in sunlight (1-30 minutes, depending on conditions) or under a UV light source, placing objects or a film negative on the coated surface to create an image. (Note: over-exposure is generally preferred to under-exposure. The print should look bronze in color after an adequate exposure). Process prints in a tray of cold water. Wash for at least 5 minutes and allow to air dry. During washing and drying, cyanotypes will oxidize to their final, deep blue color. To instantly oxidize the print to its final color, submerge in a dilute bath of hydrogen peroxide after washing, then rinse and dry.
*The chemicals used for cyanotype are inexpensive and go a long way. Despite their perhaps alarming names, both are safe to handle and mix. That said, care should be taken to avoid ingestion, inhalation and contact with skin.