Sun prints are photographic prints created by exposing paper (or other materials) coated with light-sensitive chemicals to the sun or other ultra violet (UV) light source. Most of these processes go back to the origins of photography in the first half of the nineteenth century. One of the earliest of these is the cyanotype process.
The cyanotype process, the effect of light on Iron salts, was first discovered by the scientist and astronomer Sir John Herschel (1792-1871) in 1842. However, he did not use it as a photographic process but as a method of reproducing diagrams and written text. These reproductions became known as blueprints, and were the main means of reproducing plans, designs, etc until modern reprographics took over.
One of the early exponents of cyanotypes was Anna Atkins (1799-1871) who used cyanotype reproductions of ferns, plants, and seaweed in her book Photographs of British Algae: Cyanotype Impressions (1843). It was also the first book to be published that included photographs.
Cyanotype photography became popular during the 19th century, but fell out of fashion as photography improved and other processing methods took over.
According to the Guinness Book of Records, the largest cyanotype was created by Stefanos Tsakiris on 18 September 2017 in Greece. It measured 2877.72 square feet (276.64m2). It was created in Thessaloniki’s port area to promote artistic expression and collaboration in the city.
A modern variation of this process has become known as the wet cyanotype. The invention of this process has been credited to Krista McCurdy, who started exploring it around 2015 in order to “to achieve a wide variety of colors and visual textures that are completely unlike the traditional blue and white cyanotype print.” Wet cyanotypes extend the usual cyanotype process. The paper is coated with the sensitiser as normal. However, once the paper has dried, water and a range of other chemicals, such as vinegar, turmeric, salt, and soap bubbles are added in addition to the subject of the print prior to exposure.
The exposure time for these prints is often considerably longer than for standard cyanotype, and can extend to several hours. The final print contains a much wider range of colours and textures.
The prints are still processed using water in the way as standard cyanotypes.
Lumen prints date back to the earliest forms of photography. A substrate coated with a light-sensitive coating is exposed to the sun and then developed and fixed.
Unlike cyanotype prints, for which you need to prepare sensitised paper, Lumen prints are created using vintage black and white photographic paper.
The paper is exposed to sunlight for an extended period of time – no enlarger of dark room is needed. No development of the print is done, as would be normal in for a black and white development, but it is just fixed using a standard fixer, such as sodium thiosulphate.
The great advantage of this process is that it does not matter whether the photo paper is out of date or even fogged – a great way to recycle expired photo paper.
The colours of the final print depend on the specific photographic paper used.
Cyanolumen prints combine the alchemy of cyanotypes and lumen prints. A sheet of black and white photographic paper is coated with cyanotype chemistry, and exposed to sunlight or UV light.
The chemistry of the black and white paper reacts to both the cyanotype chemistry (and visa-versa) as well as to the sunlight.
Both resin-coated and fibre-based paper can be used. Also the cyanotype solution can be left to dry or used wet with addition items added - just like a wet cyanotype.
After exposure, the paper is washed in water, for the cyanotype, and then fixed, for the photographic paper.