cyanotype

A cyanotype photogram is the “original” sun-printing process, one of the earliest photographic techniques. Discovered in 1842 and distinctive for producing rich, Prussian blue monochromatic prints, Cyanotype was popular well into the 20th century as an inexpensive method for reproducing photographs, documents, maps and plans (hence the enduring architectural term “blueprint”) and famously, for making impressions of biological specimens in the field (“photograms”).