Ferric Ammonium Citrate for Cyanotype
Ferric ammonium citrate is one of the two components required to prepare the photosensitive emulsion used in the cyanotype process.
When dissolved in water, it produces what is known as solution A, which is then mixed in equal parts with solution B —prepared with potassium ferricyanide— to create the final emulsion used in this historical photographic process.
Cyanotype is a technique based on the reaction of photosensitive iron salts which, when exposed to sunlight or ultraviolet light, produce the characteristic blue image known as Prussian blue.
Preparing Solution A
A common formula for preparing cyanotype solutions is:
Solution A
25 g ferric ammonium citrate diluted in 100 ml distilled water
Solution B
15 g potassium ferricyanide diluted in 100 ml distilled water
The final emulsion is obtained by mixing equal parts of both solutions just before applying it to the surface.
There are many variations of this formula, and many artists prefer to experiment with different proportions to adjust contrast or the intensity of the blue.
Storage of Ferric Ammonium Citrate
Ferric ammonium citrate is sensitive to environmental humidity. If not stored properly, it may harden or clump, indicating that it has absorbed moisture.
To ensure proper storage:
Under proper conditions, it can be stored for long periods without losing its properties.
Suitable Surfaces
The emulsion prepared with ferric ammonium citrate and potassium ferricyanide can be applied to different types of surfaces:
The behavior of the emulsion depends largely on the type of paper used. Highly absorbent papers may produce softer images, so it is often recommended to work with sized papers or those intended for printmaking.
Blue Intensity in Cyanotype
During washing, the image initially appears with a lighter blue tone that gradually intensifies as it oxidizes.
Adding a small amount of hydrogen peroxide to the wash water can accelerate this process and increase the intensity of the characteristic cyanotype blue.
Related Products
To prepare the full emulsion you will also need:
You can find more products, kits and chemicals for alternative photographic processes in our cyanotype and solar chemistry section.
