The cyanotype process was introduced by Sir John Herschel in 1842 to develop photographic images using a solution of iron compounds (Ammonium iron(III) citrate) creating a blue tinted print on paper or cloth. The relatively simple and inexpensive process became popular with engineers who needed to create large-scale copies of their work plans, still known today as blueprints. Edward Curtis frequently made
cyanotype work prints in the field. Cyanotypes deteriorate easily when exposed to environmental factors, and thus, few of Curtis's work prints survive.
