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A Guide To Cyanotypes

With the weather being bright and sunny these past few weeks and with spring on the horizon, I thought I'd re-visit a process that I fell in love with during my university years. The Cyanotype process. Here, I will be documenting each stage of the process step by step, just in case any visitors to my website feels inspired and wants to join me in trying this distinctive way of printing.

A Brief Background Information

Cyanotype is a photographic printing method that produces prints with a distinctive Prussian-blue colour.

The process was developed in 1842 by the scientist and astronomer Sir John Herschel, who employed it to reproduce notes and diagrams (the technology would be widely used in architecture and engineering until the mid-20th century, hence the term “blueprint”). The first to adopt this technique in photography was botanist and photographer Anna Atkins. She published a volume of algae cyanotypes that is considered to be the first ever book with photographic images.

What you need for producing around 50 prints in A4 format:

  • 20 g of green ferric ammonium citrate

  • 8 g of potassium ferricyanide

(These chemicals can be bought online as a cyanotype set)

  • 200 ml of water (preferably distilled)

  • Scales

  • Graduated cylinder

  • Paper (mustn’t contain acids and must be quite thick)

  • Two 100 ml bottles or containers and one 200 ml bottle or container (preferably made from brown glass)

  • Washing-up bowl

  • Brush or sponge without metallic parts

  • Glass sheet at least as big as the piece of paper you’re using

1. Preparing the solutions

First of all, make sure you’re in a well-ventilated part of the house/studio without a lot of sunlight. Then, prepare your work surface by covering it with newspaper or plastic to prevent the solutions from staining the surface. Next, dilute the ferric ammonium citrate in a container with 100 ml of water (Solution A), and dilute the potassium ferricyanide in another container with the same amount of water (Solution B). As mentioned above these chemicals can be purchased in power form together as a printing set. Leave both solutions somewhere dark and dry for at least 24 hours. The solutions can be stored in this state for up to 6 months but, for best results, you should ideally use them within a few weeks.

2. Preparing the emulsion

To prepare the emulsion, mix equal proportions of the two solutions in an opaque container. This procedure should be carried out in a room that doesn’t let any sunlight in, but it doesn’t have completely dark. Once mixed together, the solutions must be used as quickly as possible to prevent colour intensity and sensitivity from diminishing. Ideally, prepare just the right amount of emulsion that you need for your project. As a rule of thumb, 200 ml of emulsion (100 + 100 ml) will cover about 50 sheets of A4, half that for A5 and so on.

3. Coating the paper

Continuing to work in your room without sunlight, pour the emulsion onto a small tray. Then, using a brush or sponge, spread it all over the paper. The goal is to cover the paper as evenly as possible so that there are no streaks or stains.

The ideal paper for cyanotype is thick and strong (it will have to withstand immersion in water), like that used for watercolour painting , but you can try out other types of paper to see how they affect the process. I have personally used printing paper, the likes of Somerset white works best for me. I have also experimented with homemade papers but they proved to be too thin to withstand the washing process at the end. Once covered in emulsion, the sheets will take around 30 minutes to dry.

4. Exposure

When the sheets are dry, the real printing process begins. Place a sheet in direct sunlight and immediately place the objects that you intend to “photograph” on its surface, covering everything with a sheet of glass. Exposure is the most critical phase of the whole process. Sunlight is variable and unpredictable: season, time of day and position with respect to the sun influence the length of exposure, which can be anything from 3-4 minutes to 15-20, depending on the type of paper. It’s therefore best to do an initial test in which you expose an image and then cover more and more of it every 2 minutes. In sunlight, the colour of the print will immediately start to darken, but you need to wait until it starts to turn a dull brown colour before the print is ready.

5. Developing and drying

Once you’ve finished exposing the image, place the print in a washing-up bowl and rinse it with running water until the yellow sheen has been washed away to leave an intense blue hue. Next, hang the print to dry in the shade for about an hour. Once dry, the image will be set on the cyanotype. It’s best to store prints out of direct sunlight to prevent fading, but if they do fade, simply leave them in the dark for a few days and they’ll regain their original tone.

6. Disposing of leftover chemicals

Leftover chemicals can be washed down the drain in small amounts with lots of water to dilute them.

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