Cyanotype Printing – How to Make a Cyanotype Blue Print

What is a Cyanotype?

Cyanotype Printing is a 19th-century camera-less photographic printing process that produces a distinctive, monochrome, Prussian blue-and-white image. Discovered in 1842 by Sir John Herschel, it is one of the earliest photographic techniques and is famous for being used to create “blueprints” for architectural and engineering plans.

How to make Cyanotype Prints

Paper or fabric is coated with a solution prepared by mixing Green Ferric Ammonium Citrate solution and Potassium Ferricyanide solution immediately before use. Objects, like feathers, leaves or film negatives are placed on the dried material and exposed to sunlight. The UV light triggers a chemical reaction that creates an insoluble blue pigment called Prussian blue while the areas covered by the objects remain unexposed.

The Cyanotype Chemicals Pack sold by George Weil contains 100g Potassium Ferricyanide and 200g Green Ferric Ammonium Citrate. Although the chemical names may sound alarming, they are relatively low in toxicity when handled correctly and are widely used for educational and artistic cyanotype printing. Potassium Ferricyanide is stable under normal cyanotype conditions but should never be mixed with strong acids, as this can release highly toxic hydrogen cyanide gas. As with all art and craft chemicals, sensible precautions should be taken: wear rubber gloves and safety goggles, and avoid inhaling chemical dusts when weighing powders.

This recipe will make approximately 50 x A4 Cyanotype prints:

1. Add 20g Green Ferric Ammonium Citrate to 100ml water (distilled if possible) and stir until dissolved. Tap water with high chlorine or iron content can cause premature shifting or spoilage of the liquid mix.
2. In a separate container, add 10g Potassium Ferricyanide to 100ml water (distilled if possible) and stir until dissolved.
3. Mix equal quantities of each prepared solution in a third container. Once mixed together, the sensitiser is best used the same day for the most consistent results, although it can sometimes remain usable for several days if stored in a tightly sealed opaque container.

Instructions and tips:

1. The chemicals can stain, so protect your work area from splashes. Do not expose the chemical to UV light or sunlight until you are ready to print. Ordinary light bulbs are fine but some fluorescent lighting may also affect your prints.
2. Choose your material. Cyanotype prints work well on paper, card, and finely woven natural fabrics such as cotton and silk. Using a brush, paint the chemicals onto the material, making sure that your work area is dimly lit. Leave the treated material to dry in a dark place such as a cupboard.
3. Place a stencil such as a film negative, leaf, feather or cardboard cut-out onto the dry chemical treated material. The stencil needs to be as flat as possible to prevent it casting a shadow and therefore ghosting. Place a sheet of glass (if you have one) over the top of the stencil to ensure contact with the surface and expose the sandwich to UV light.
4. You can use natural sunlight or a UV lamp and exposure times can vary from a few minutes to several hours, depending on how strong your light source is.
5. During exposure the uncovered areas gradually change from yellow-green to a “burnt” olive or silvery grey colour. Once washed, these areas oxidise to the characteristic deep Prussian blue. Areas covered by the stencil will not develop and wash away in the final rinse to expose the image.
6. When the print has been exposed, it should be rinsed under running water until all the unexposed chemicals are removed. Continue rinsing until the yellow-green colour has disappeared and the water runs clear. Hang the print to dry.

Try our Cyanotype Blue Printing Kit to get you started.