The Cyanotype
Cyanotype printing is one of the earliest photographic processes, first developed in 1842 by the scientist and astronomer Sir John Herschel. This technique, known for its deep blue tones, was adopted as an efficient way to reproduce technical drawings and photos. This is the origin of the word “blueprint”.
Cyanotype of British algae - Anna Atkins
British botanist Anna Atkins is considered the first person to publish a book illustrated with photographs, Photographs of British Algae: Cyanotype Impressions (1843), which documented plant and algae using the process. It is thought that this was the first book to be illustrated with photographs rather than hand drawings.
Cyanotype on paper, ceramic and glass
The cyanotype process is one of the simpler ‘alternative photography’ methods, requiring very little specialist equipment. When mixed, ferric ammonium citrate and potassium ferricyanide produce a photosensitive solution that can be applied to paper, glass, or fabric. Once dried, the coated surface is exposed to ultraviolet light, such as sunlight, triggering a chemical reaction that creates the signature blue hues.
Variations in tone are achieved by blocking light from reaching parts of the surface, either by placing objects on top or using film negatives. After exposure, the print is rinsed in water to wash away the unreacted chemicals, revealing the image which can take up to 24 hours to fully develop (or sped up if you are impatient like me with some hydrogen peroxide).
Every cyanotype print is unique, shaped by variations in exposure time, brushstrokes, and environmental factors. That is in part what makes it such a enjoyable, if not incredibly frustrating at times, process.