Cyanotype is a photographic printing process that gives a cyan-blue print. The process was popular in engineering circles well into the 20th century. The simple and low-cost process enabled them to produce large-scale copies of their work, referred to as blueprints. Two chemicals are used in the process:
- Ammonium iron(III) citrate
- Potassium ferricyanide.
The English scientist and astronomer Sir John Herschel discovered this procedure in 1842. Though the process was developed by Herschel, he considered it as mainly a means of reproducing notes and diagrams, as in blueprints. It was Anna Atkins who brought this to photography. She created a limited series of cyanotype books that documented ferns and other plant life from her extensive seaweed collection. Atkins placed specimens directly onto coated paper, allowing the action of light to create a silhouette effect. By using this photogram process, Anna Atkins is regarded as the first female photographer.
This recipe makes approximately 50 8×10 inch prints. The cyanotype is made up of two simple solutions:
- Solution A: 25 grams Ferric ammonium citrate (green) and 100 ml. water.
- Solution B: 10 grams Potassium ferricyanide and 100 ml. water.
1. Mixing the chemicals
Dissolve the chemicals in water to make two separate solutions. Add Ammonium ferric citrate to water into one container and Potassium ferricyanide to water in another. Stir with a plastic spoon until the chemicals dissolve. Mix equal quantities of each solution together in a third container.
Unused solutions can be stored separately in brown bottles away from
light, but will not last very long once they have been mixed. Dispose of
any unused chemicals in a sensible and environmentally friendly way!
Your work area
Your floors, carpets, walls, work surfaces, clothes and skin can be stained by the chemicals. Cover all possible areas,
use rubber gloves and an apron or an old shirt to work in. If you have
the space, choose an area where you can spread out. Ordinary light bulbs
or tungsten light is safe to use, but UV light will affect your prints. Some fluorescent lighting may also affect your prints.
2. Preparing the canvas
Using a brush, simply paint the chemicals onto the material.
Paper, card, textiles or any natural material can be used to print on.
Decide how big your print is going to be, and cut your material to size.
Make sure your working area is dimly lit, or lit with a low-level
tungsten bulb. Once the material is coated, leave it to dry in the dark.
3. Printing the cyanotype
Print a cyanotype by placing your negative (to reproduce a
photograph) or object (to make a photogram) in contact with your coated
paper or fabric.
Sandwich it with a piece of glass. Expose the sandwich to UV light. Natural sunlight is the traditional light source, but UV lamps can also be used. A photogram can also be made by placing items on the surface. Plants, decorative items or other objects can be used to create silhouettes or interesting shapes. Exposure times can vary from a few minutes to several hours, depending on how strong your lightsource is or the season where you are printing.
4. Processing and drying
When the print has been exposed, process your print by rinsing it in cold water.
The wash also removes any unexposed chemicals. Wash for at least 5
minutes, until all chemicals are removed and the water runs clear.
Oxidation is also hastened this way – bringing out the blue color. The
final print can now be hung to dry and be admired.
In a cyanotype, a blue is usually the desired color; however, there are a variety of effects that can be achieved. These fall into three categories: reducing, intensifying and toning.
Reducing is the process of reducing the intensity of the blue. Sodium carbonate, ammonia, Clorox, TSP, borax, Dektol and other reagents can be used to do this. A good easily obtained reducer is Sunlight laundry detergent. When using a reducer it is important to pull the cyanotype out of the weak solution and put the cyanotype into a water bath to arrest the bleaching process.
Intensifying is the strengthening of the blue effect. These reagents can also be used to expedite the oxidation process the cyanotype undergoes. These reagents are Hydrogen Peroxide, Citric Acid, Lemon Juice, and Vinegar.