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.
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.
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.
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 then exposed to sunlight for an extended period of time
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.