As you read more and more about photography, you’ll realize that most analog or film photography works a lot with silver. In both black & white and color photographic film, silver halides capture the light from the scene. With Daguerreotypes, silver salts recorded the light.
There are other ways to make a photograph without silver – one such way is the cyanotype. You’ll know these by their ‘Cyan’ (blue) color. Read on to learn about the history, the recipe, and how to create a cyanotype negative image.
Cover photo by Sandie Clarke
History of the Cyanotype
The cyanotype was born in 1942 from research into an iron compound that could record light. Sir John Hershel, a chemist, inventor, and experimental photographer, continued an idea that his father pursued. He wanted to record the infrared wavelengths of the electromagnetic spectrum. John’s ideas also drew from Johann Döbereiner’s use of Iron Oxalate, an iron compound that recorded light, yet one that needed more tinkering.
A version that Hershel found that worked the best came to him from Alfred Smee. He was also a chemist and inventor who had separated a form of potassium ferricyanide by using electrochemistry. He created ferric ferrocyanide by mixing it with ammonium ferric citrate and exposing it to sunlight. This deep blue came to be known as Berlin or Prussian Blue.
Like many creations throughout history, the inventor isn’t the one who is credited for making the invented item famous. While Hershel experimented with the chemicals, a family friend spent 18 years creating what would become the first photography book (one with photos inside). Anna Atkins, a biologist, and botanist created Photographs of British Algae: Cyanotype. It was a book of printed plant and textile specimens that inspired others to complete similar studies.
Unfortunately, Hershel never patented the cyanotype process. It only started receiving commercial success in the year after his death in 1872. Since its invention, cyanotypes have been used to document items in photogram printing, and for art. Here, contact printing allowed negatives to be printed and replicated in the signature deep blue. A similar process is still used in replicating construction plans, known as the blueprint.
How Are Cyanotypes Made?
To make a cyanotype chemical solution, you need three ingredients:
- - ammonium iron (III) citrate
- - potassium ferricyanide (AKA Red Prussiate of Potash)
- - (distilled) water
These three are found online in separate forms or mixed especially for cyanotype photography.
Sample Recipe
The cyanotype solution is made easily in daylight. To ensure the cyanotype solution is useable for a long time, store the chemicals in brown bottles in a cool, dark area.
To make ammonium iron (III) citrate solution, use 25g and then add distilled water to make 100 ml. Do the same with potassium ferricyanide, but use 10g instead and bring it up to 100 ml.
When you are ready to use the chemical solutions to create cyanotypes, mix the amounts in a bottle in a ratio of 1:1. This will last between a few hours and a few days.
When mixed, coat the solution evenly over paper (over 250 gsm), textile, wood (or any porous material) with a roller or wide brush in a dim light.
Leave to dry in a dark place. It takes about an hour to air dry, but for the impatient, a hair dryer is possible. Keep it in the dark until ready to expose it (an old lightproof bag from photographic printing paper is best).
How To Make the Cyanotype Image
There are two ways to make a cyanotype image; a Photogram or from a negative. A photogram is creating an image by placing items on top of the sensitized paper. To print from a ‘negative’, the negative must first be printed the same size as the paper or image. For best results, an acetate negative from a digital file. This way, the cyanotype is created through contact exposure.
For both processes, sandwich the paper at the bottom, the photogram items/negative, and then heavy plastic or glass. A clip frame works well. The package then requires exposure to UV light. This can be direct sunlight, or a tanning bed if needed. Depending on the strength of the light, it could be ready in minutes or hours. As a rule of thumb, it is ready for washing and fixing when the highlights start turning blue, yet it is difficult to overexpose.
To ensure the cyanotype doesn’t keep processing, it needs to be washed and fixed. You can wash in still or running water, but it works better faced down in a dim room. The wash removes the yellow-green-looking iron salts from the unexposed areas. It also starts the oxidation of the exposed areas. When the highlights are white, or blue run-off finishes, the wash is complete.
You can let the print dry, or you can increase the oxidation with an acid bath. It is important not to touch the exposed side of the print. An acid bath consists of 2% citric acid and 0.3% hydrogen peroxide. After the bath, wash the print again, then place it on a flat surface to dry. A wet-adhesive tape works well.