Bernd Hutschenreuther shares his experiments with a two-bath cyanotype process—a rapid variation of the traditional method—using ammonium ferric citrate and potassium hexacyanidoferrate(III). The paper is coated, dried, and exposed to UV light before being developed in a red blood lye salt solution, causing the exposed areas to turn blue within seconds. A final rinse with water, optionally enhanced with hydrogen peroxide, refines the image. This minimalistic and efficient process closely resembles a formula once explored by Herschel.
For beginners to the cyanotype process start here instead. This is for experienced and advanced users only. Read the MSDS (Material Safety Data Sheet) before attempting to use chemicals and use the correct safety equipment.
The cyanotype process was discovered by Sir John Herschel. Being a scientist he experimented with several ways to make cyanotypes. The two-bath cyanotype process formula was sourced from Cyanotype separate process by Roger Deuber, Kantonsschule Baden. The document is a pdf in German and can be found here.
Another source that was used was the German Wikipedia. This quote is from Cyanotype Original process from the German Wikipedia and translated using a free translator:
“In Herschel’s original method, the light-sensitive layer on the paper consisted of potassium hexacya-
nidoferrate(II) (yellow blood-leach salt) and ammonium iron(III) citrate. Later, potassium hexacya-
nidoferrate(III) (red blood leach salt) was used.
Development: The iron(II) ions react with potassium hexacyanidoferrate(II) (red blood-leach salt)
in the developer solution and initially form water-insoluble Berlin white on the photographic paper.
This is then converted into insoluble Berlin blue by atmospheric oxygen or hydrogen peroxide.
Coating the paper: The paper is coated with a light-sensitive solution of ammonium iron(III) citrate.
Exposure: Blue or violet light excites an electron of the negatively charged citrate ion, whereby
iron(III) ions are reduced to iron(II) ions.”
Using this information, Bernd started his experiments.
“It is very exciting to read the old Texts from 1842 to 1860.”
The two-bath cyanotype formula Bernd used
I did not have the yellow salt (Kaliumhexacyanidoferrat(II)), so I used the red one instead (Kaliumhexacyanidoferrat(III)).
- Solution 1: 2 g ammonium ferric citrate to 10 ml water
- Solution 2: 1.5 g red blood lye salt to 50 ml water, about 3-5% solution is sufficient for developing. I try to
work in a minimalist way.
Paper:
I used 1 sheet of watercolour paper. I used Agave paper.
Step-by-step formula:
The process is relatively quick.
Step 1: Coat the paper with solution 1 (ammonium-iron-III-citrate), it is light-sensitive, so do this in the dark and also let it dry in the dark.
Step 2: Expose the paper for approximately 15 minutes under LED UV light or in sunlight, the time varies depending on the light source and its intensity. The colour of the exposed area changes from light yellow to brown.
Step 3: After exposure, develop the print using solution 2. Brush the developer solution over it with a very soft
brush or let it run directly over the exposed paper. The colour changes to blue in a few seconds. This is very fast compared to the classic cyanotype process.
Step 4: After developing, rinse the print. If you like, you can add a few drops of hydrogen peroxide solution to the rinsing water. It helps to intensify blue faster. Do not rinse too vigorously.
Good luck and leave a comment if you have tried this.
Sources for the two-bath cyanotype formula
Cyanotype separate process by Roger Deuber, Kantonsschule Baden. Pdf in German.
Robert Hunt: PHOTOGRAPHY (Internet Archive.org, Third Edition, 1853, Seite 51, in
ENCYCLOPEDIA METROPOLITANA, englisch)
Robert J. Bingham: PHOTOGENIC MANIPULATION, P ART I, 1850, Seite 60, Cyanotype (Internet Archive.org, englisch)
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Hi Henrieke,
i tried several things.
Using the two-step process, I achieved better results, but there are indeed additional factors to consider. The main advantage is that the coated paper can be used for a longer time. The mixed solution paper degrades earlier.
I do not make large pictures and I do not see strokes, except I made them by purpose.
I also wanted to try the first cyanotype processes.
I appreciate your work, too.
The results with coated paper were not so good in my case in camera.
All processes have different properties, and so all have advantages and disadvantages.
Best regards
Bernd
To me the advantage is a smoother blue with more midtones. I use a brush to get uneven results like a painting. I can use it in camera.
A main thing is that the process depends on PH. And om.paper. If you want a blue print, mixed solution is better.
An advantage is in my case that the coated paper does not change so much. It is longer usable.
I like the process. Herschel used it only for a short time. He switched to the mixed solution.
My goal was to test it.
And also to use it in camera. Shorter time is good there.
Hello Bernd,
I assume that these two steps only make sense if you expose the first layer (ammonium ferric citrate) with an overhead projector or a halogen lamp, which according to Robert Deuter means an exposure time of 80 seconds. That is an enormously short exposure time! I’ll give the halogen lamp a try.
I tried your recommendation and exposed the paper coated with ammonium ferric citrate for 15 minutes and then developed it with potassium hexacyanoferrate(III).
I wonder what the advantage of an additional step of this “Two-Bath Cyanotype Process” could be? I think with an additional step and the same usual exposure time – in this case 15 minutes – you can mix solution A+B at the same time and have less work with coating, developing etc.
The only advantage would be to shorten the exposure time, according to Robert Deuter. Everything else makes no sense to me. But, maybe I have overlooked something?
Oh yes, I forgot to mention something: If you develop with a brush, you get streaks and an uneven result. That doesn’t happen to me with the ready-mixed A+B solution. The result is an even shade of blue. No streaks.