A cyanotype is a printing process that creates a blue image, best used to reproduce other images. The key ingredient in this process is the use of iron instead of silver. This process was discovered by Sir John Herschel in 1842 and was effectively the first, and long lived (nearly a century), means of photocopying. The process is similar to others that had been created some years before. This one was created accidentally due to an unreliable alchemist during Herschel's attempts at creating a direct photographic method in natural color.
During that time period blues as well as other vivid colors were very desired which instantly attracted attention to this new found method. Herschel's impact on the world would not yet be known - for nearly a century this method was used for photocopying blue prints (hence the derivation of the word).
For more detailed information on Sir John Herschel and the discovery of Cyanotypes, please read:
During that time period blues as well as other vivid colors were very desired which instantly attracted attention to this new found method. Herschel's impact on the world would not yet be known - for nearly a century this method was used for photocopying blue prints (hence the derivation of the word).
For more detailed information on Sir John Herschel and the discovery of Cyanotypes, please read:
It works through creating photosensitive ferric ferrocyanide ions through the use of ferric ammonium citrate and potassium ferricyanide. The chart below shows how different reactants comes together and the results on the cyanotype process. As iron has two states, Iron(III) and Iron(II) – which is noted with how many valance elections they have, there are different results. Different colors are obtained with the difference between ferricyanide and ferrocyanide (which might look the same but one is spelled with an ‘i’ and the other an ‘o’.
Reactant | Ferricyanide Iron (III) | Ferrocyanide Iron(II) |
Ferric Salts Iron(III) | Ferric ferricyanide Prussian yellow/brown Soluble, easily oxidizes and reduces via green (Prussian green) intermediates to Prussian blue | Ferric ferrocyanide Prussian Blue Highly insoluble, most stable product, to which all the others eventually revert |
Ferrous Salts (II) | Ferric ferrocyanide Turnbull’s Blue (same as Prussian Blue) | Ferrous ferrocyanide Prussian white Insoluble and colorless, readily oxidized by air to Prussian blue. |
To make the solution for cyanotypes you use the following to make two solutions, A and B.
Solution A: Distilled water at ~21 degrees Celsius 100 ml
Ferric ammonium citrate (green) 25 g
Solution B: Distilled water at 21 degrees Celsius 100 mil
Potassium ferricyanide 10g
After making those solutions you then combine them together and have approximately an hour to work with the solutions. By coating the print papers with one coat of the combined solution and allowing to dry you can prepare a page for taking an image.
depending on the strength of the sun. If it is cloudy up to an hour might be required. For my experimentation I remained outside for half an hour and still my image didn’t not come through as best as it could have. On a good day, exposure can be only ten to fifteen minutes.
It is important to understand that if the exposure is not long enough the image will not stick to the paper. This is a different experience from previous experiments. When fixing in previous experiments there is some fading or bleaching to the darks of the image. Things that were very dark, near black were bleached into dark browns. However the image remained on the page. Failure to have the right exposure time for cyanotypes can lead to all out disappearing images, completely disheartening.
There is another way to create a cyanotype that we did not perform because of the toxicity of the process. It uses Ammonium Iron(III) Oxalate, Potassium Ferricyanide and Ammonium Dichromate. Mixed together with 100 ml of distilled water and you have a solution that makes cyanotypes. When made in closed quarters the toxic process can lead to death. And as we don’t want anyone to die, I’ll only provide the ingredients and not the amounts. Use the traditional method stated above to make nice Prussian Blue Cyanotypes.
After a cyanotype is created the darks are represented in blues. It is where the term blueprint came from because cyanotypes were used primarily to reproduce images such as architectural plans. They had much less use in the art world. However, to darken the colors and give it a nicer look, if you don’t want the blues, you can tone your image.
Cyanotype Demonstration:
There is tea toning that involves using a dark tea (4-5 bags of black tea) bath and soaking your image until you are satisfied with the results. The tannic acid in the tea will react with the iron salts and thus darken the tones to a navy blue or blue-black. However, while the darks darken, the highlights or white areas will also darken a little, turning a bit brown with the color of the tea. If droplets fall on picture or pool on the surface you can get water rings that will alter the image. I rinse my image after tea toning and then held it up to hand dry a little to prevent further rings from developing. [I had a ring developing but I caught before it had a change to fully dry. I rinsed and re-soaked the image in the tea bath and then rinsed it again before drying.]
Another method of toning a cyanotype is Redevelopment toning. To redevelop tone, you must first bleach the image in an ammonia or borax bath. This will remove the blue. Then exposing it to a tea bath, the tannic acid will react with the iron salts as they still remain on the image. The image will redevelop with brown black color. The process creates ferric tannates. If you desire a red brown color, further soak the image in a bath of sodium carbonate.
For more information regarding cyanotypes, I found this book segment to have a good amount of detail and instruction into the preparation of type 1 and type 2 cyanotypes
Historic photographic processes
By Richard FarberAnother iron process is Van Dyke and uses silver. For more information on the Van Dyke process, please see Van Dyke Blog Entry.
In my experience, I enjoyed this process but it was very disappointing to see most of my image fade away with the first wash. The sun really needs to be out and shining bright for a good image to stick. I would like to try this again as making the two solutions and then combining them makes a really easy single application and then the fixing process is even easier by rinsing it. However, if there isn’t any sun than there isn’t any point. I don’t have enough patience to develop them for a full hour or however long it would take without any sun, unless I was doing something else in between that time. This is a process that I consider doing with my son when he gets a little older. (I tried salted prints with him, papers prepared in lab before taking them home, and he wasn’t really interested).
Overall, I really like the blue tones, though albumens brownish tones are very nice as well, and I’m quite a fan of the Van Dyke clarity (please see other blog entries for further information on these processes). If I did this again I would probably try the redevelopment toning just to see how it comes out.
very helpful. Thank you
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