Invented by Sir John Herschel in 1841, Cyanotype, or more commonly known as 'sun printing' is an alternative photographic process. It is a printing process that does not use silver gelatin paper and is often used in traditional darkroom printing, although you do not need a darkroom to create them. The Cyanotype is also known as a blueprint. The characteristic of Cyanotypes is the vivid Prussian blue colour of the print. In the cyanotype printing process, paper or other materials, are coated with a sensitising solution of ferric ammonium citrate and potassium ferricyanide. After drying, the sensitised paper is contact printed with negatives printed on transparencies, or other objects, then placed in the sun or under a UV (Ultra Violet) light source. Once exposed, the image is soaked in water to get rid of surplus sensitizer and to develop the image. This is known as 'dry cyanotype'.
To create some of the images in my gallery, flowers and foliage were placed on watercolour paper, coated with the sensitizer, and exposed to sunlight whilst still wet. This gives a very different outcome, especially if you add things like a spray or water, lemon juice, vinegar, salt or sprinkles of colour from spices such as turmeric. These are known as 'wet cyanotypes' and are exposed for much longer, sometimes up to 24 hours and beyond, to get the best imagery, colour variations and detail possible. The great thing about creating cyanotypes using the wet technique is that you never quite know what you are going to get at the end of exposure and the developing process. No two images are ever the same, even if you use the same botanicals in an identical design.
Cyanotypes are archival and should last for years. They are best displayed away from direct sunlight, which could cause some fading. If any fading does occur, the image can be placed in a dark place for 24/48 hours and the colour should deepen again.
The image below on the left is a traditional 'dry cyanotype, and the one on the right has been sun printed while the sensitiser was still wet.