On Tuesday we did cyanotype printing in a workshop led by Matt Lee and Smriti Mehta who gave an artist’s talk back in November. The activity was very enjoyable and it gave me a great number of ideas for working in the future. It seemed a good way of sketching out ideas in a completely different medium to those I usually use bringing fresh inspiration.
The workshop was simple and direct with easy to follow instructions which made for an experience that can practically be taken away and done elsewhere without difficulty. I particularly liked the way we collaged transparency images. I do not usually like collage, but this method seemed to me to have a purposefulness and elegant flexibility that engaged me more than I thought it would have. The source materials we were given were both of high quality and coherent, taken from the British Library Qatar Foundation project.
For more information: https://en.wikipedia.org/wiki/Cyanotype
- Acetate sheet with tracing paper.
- Images printed on acetate. The images were printed using a laser printer. However, an inkjet can be used so long as the acetate is made specifically for use with such printers. In the case of inkjets, it is best to print black with colour and not just greyscale to ensure the print layer is dense enough for a sufficiently contrasted negative.
- Chemicals: potassium ferrocyanide and ferric ammonium citrate for preparing the paper. Citric acid for washing or developing the print. Hydrogen peroxide can also be used as well as lemon juice, and vinegar.
- The chemicals can be bought from Amazon for around £20 and the two bottles make up a very large quantity of sensitised paper.
- Watercolour paper. Heavy paper absorbs the sensitising fluid more readily and dries more quickly and flat.
- Sponge brush, easier to use and delivers a more even coating of sensitiser than a normal brush.
- UV lamp or sunlight.
The image was built up using the acetate prints fixed to a sheet of acetate using sellotape. [the tape does tend to show a little in the final print as it absorbs a small amount of UV light, but the effect is negligible or not at all.
It is best to avoid layering one piece of print over another as the thickened acetate and over-layering of print ink can create areas where light is unable to pass through properly and spoil contrast and composition. It is best, where possible to cut and fit pieces together.
The paper is sensitised using a solution made of the two chemicals in a ratio of 1:1. Make sure the measurement is as accurate as possible. The made-up solution will last a while but it is best to use it the same day. It can be used to prepare lots of sheets of paper which can be stored in a light tight box for several days. Around 20ml of each solution to make 40ml was ample for around 20 A4 sheets of paper.
When coating the paper, the solution can be spread using the sponge brush. The best results appeared with one or two coats. I preferred using two light coats making sure the first is dry before applying the second.
The paper is left to dry thoroughly before printing. It is best to leave sensitised paper in as dark a place as possible. In the studio, the fluorescent lights fogged many of the sheet to varying degrees. The less fogging results in a deeper, richer Prussian blue and better contrasts. It is best to store in a sealed black bag or box and keep away from daylight altogether.
The negative is placed with the inked surface facing the paper. This way, the edges of the images have maximum sharpness and definition. The two layers are then covered with a piece of glass. Perspex can be used but it is not advisable as acrylic absorbs more UV that glass increasing exposure times. The glass presses the negative and paper together to ensure there is no light leakage which can give rise to blurred images (not altogether undesirable with some images). The paper is now ready for exposure. Whether exposed under a lamp or sunlight, the whole sandwich needs to be supported by a flat surface such as a board.
The prints were exposed in UV boxes for around 15 minutes. Prints can also be exposed in sunlight, even on a cloudy day, but in the case of the latter, the exposure time may be much much longer. It is all a matter of experimentation.
When the paper surface has turned grey, the print is ready to be washed. Again, trial and error is best for ascertaining exposure times. Much depends on the light source, the negative and paper as well as the thickness of sensitising coat. We were unable to assess the correct exposure because the lightboxes were closed, so a time based on experience was used of around fifteen minutes.
Initially, prints come out dark and indistinct. When washed in the citric acid, the image was fully developed after around one to two minutes. Any longer and the image may start to bleach. The concentration of the citric acid bath also determines the colour of the print and the richness of the dark areas. The developer is best made up using distilled water as calcium in hard water affects the reaction.
Other reagents can be used for developing including vinegar, hydrogen peroxide, lemon juice. Each one can result in different intensity and hue of blue.
The print is finally thoroughly washed in water, preferably running water until no more colour runs off it.
The print is then hung and left until dry. It can also be put between blotting papers. Water colour paper will dry flat whereas other papers such as cartridge have to be put under a heavy weight.
The print can be left as cyan or toned using a variety of toners, all of which contain tanning which binds with the iron to give varying hues of brown to black.
When toning, the print has to be bleached first.
- Sodium carbonate
- Bleach can also be used but it does tend to destroy the paper base.
- Tannic acid
- Pyrogallic acid
The image is bleached until the image just disappears and then thoroughly washed to avoid losing highlight details. It is then soaked in the toner and left until the desired colour and saturation is reached.
Some toners darken the paper base more than others. Those that do, need more contrasty negatives to ensure the image has a good tonal range.
If archiving properties are desired, neutral ph, natural fibre papers such as linen and cotton are best. But the sensitising solution will adhere to any absorbent surface. Non porous materials need to be coated with gelatin first.
Cyanotypes fade with prolonged exposure to light. The original tone can often be restored by placing the print in the dark for a while.
Printed cloth (natural materials such as silk, cotton and linen) should be washed by hand with a soap that does not contain phosphates as this turns the cyan to yellow.