Tests de cyanotypes

Functional description

For several years now, I've been interested in silver photography and the chemical processes that transform light into images. We're all familiar with silver salts, which have been used in silver photography for as long as photography has existed, both in film and in photography, but cyanotype is a little-known photographic technique that is very easy to produce and gives very interesting results.

However, you do need to take a few safety precautions when handling the products, since like most photosensitive products used in photography, those used to produce cyanotypes give off vapors that are harmful to health. So, set up in a well-ventilated area, and put on your goggles and gloves to minimize the risks.

Although less well-known than silver salts for photography, cyanotype was a very popular technique for reproducing technical diagrams and schematics... blueprints.

First cyanotype photogram by Anna Atkins, botanist and photographer. c. 1843.

Demonstration

Project completion stages

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Step #1

First, to create a cyanotype, we need to prepare a 20% solution of ferric ammonium citrate and an 8% solution of potassium ferricyanide.

20% ferric ammonium citrate solution:

100ml distilled water
25g ferric ammonium citrate

8% potassium ferricyanide solution:

100ml distilled water
10g potassium ferricyanide

For my first tests, I divided the measurements by 10 to obtain just 20ml of final solution.

Step #2

Once both solutions have been prepared, mix in equal parts to obtain the desired quantity to cover the surface to which you wish to apply your cyanotype. Everything should be done in an environment with little or no ultraviolet radiation.

Solution A+B 1:1

Sheet of paper covered with a thin layer of the magic solution

Let it dry...

Step #3

!!!VERY IMPORTANT!!!
Otherwise our cyanotype disappears at the end.

Once the surface is dry, we print our image to be transferred in grayscale on acetate. The technique creates a negative of our image, so we need to invert the colors before printing if we want to retain luminosity... the whites (transparent) will be dark blue, while the blacks will be white.

We then place our acetate on our surface and expose it to ultraviolet light for a few minutes. It's a good idea to place a pane of glass over the acetate to keep it glued to the printing surface.

UV exposure.
After a few minutes, you can start to see the blue appear.

After about 15 minutes. (Under-exposed... should have been 20-30 minutes)

Exposure times can vary from 2 minutes to several hours, depending on the strength of the light. You'll need to experiment with several exposure times before achieving the desired contrasts.

Finally, the magic moment occurs when we put our cyanotype under running water. The yellow disappears and the blue doubles in intensity.

The end result is dry and crinkly