Cyanotypes

By Steph Koehnen

In the early 1840’s, countless scientists or scientifically-inclined men (and a few women) experimented with chemistry to make photographic images. Sir John Herschel developed one of the first viable and permanent processes in 1842, the cyanotype—after the Daguerreotype, of course. He found that by mixing ferric ammonium citrate (then called ammonio-citrate of iron) with potassium ferricyanide and coating paper with the mixture would produce bright blue images that could be made permanent merely by soaking in water. The ferric ammonium citrate is the light-sensitive part of the solution and the potassium ferricyanide gives the blue color.

 

The cyanotype photographic process received short-lived popularity and was largely forgotten for almost a century. However, its alternative use was largely popular—blueprints. Since the cyanotype is a contact process, it works to copy notes and drawings, as well. This process is incredibly easy—to produce a good cyanotype, abide by the following procedure:



By Steph Koehnen

1.      Obtain a contact negative (a negative the size of the desired print) or simply gather objects with interesting shapes

2.      Mix solutions A and B together in equal parts. Solution A is the ferric ammonium citrate and B is the potassium ferricyanide (it is VERY important not to let solution B sit in the sun or any light brighter than room-light; heating potassium ferricyanide results in the release of cyanide gas, which is poisonous).

3.      Using a crosshatch pattern, paint the mixed sensitizer onto a piece of watercolor paper. The color will appear a bright yellow-green.

By Steph Koehnen

4.      Lay the contact negative or objects on the paper and expose in the sun. If a negative is used, a sheet of glass will need to be laid on top to ensure proper contact and focus. Printing times will vary from 5-40 minutes, depending on the intensity of the sun and the temperature; bright, warm days will need the shortest times whereas cold and cloudy days will require longer printing times.

5.      Since there is no certain exposure time, a color shift in the emulsion will be the determinant. The color of the emulsion will change from the bright yellow-green to a deep green to a blue-green and is finally ready when it is a light blue-gray.

6.      After the exposure, simply remove the negative or objects from the paper and immerse the paper in a bath of cool water (65-68˚F). A yellow pigment will be released—this is the unexposed sensitizer. Empty the water bath and refill with water; repeat until no more sensitizer is removed from the photo or 5-10 minutes have passed. Hang the photo to dry on a clothesline and your cyanotype is done!

For more information on cyanotypes or to see more examples, stop by the CSS photo lab in T4412 or look through the gallery at the Alternative Photography website. The above information comes from experience and Christopher James’ The Book of Alternative Photographic Processes.

James, Christopher. "The Cyanotype Process." The Book of Alternative Photographic Processes. Clifton Park, NY: Delmar Cengage Learning, 2009. 148-74. Print.