Cyanotypes use the light sensitive properties of iron salts to give a blue and white image when exposed in daylight. The cheapness of the process led to its being used to reproduce technical drawings that became known as blueprints.
The first book made using photography was Anna Atkins, Photographs of British Algae: Cyanotype Impressions, (1843). I have been making cyanotypes from plants for over 20 years. This site contains a small selection of my work.
215 Appleton Avenue, Great Barr, Birmingham, B43 5QE, UK