Author Archives: Karen Keehr

Do not adjust the color on your screen. These photographs really are blue. They are called cyanotypes and can be easily recognized by their uniform, bright blue color. Cyanotypes are created using light sensitive iron salts as opposed to silver salts used in more traditional black and white photograph.

Sir John Herschel developed the cyanotype process in 1842 using ferric ferrocyanide (sometime called Prussian blue) and ferrous ferricyanide (also known as Turnbull’s blue). Due to their unusual blue color, cyanotypes failed to gain popularity for commercial use. They did, however, become somewhat accepted during the 1890s and early 1900s with amateur photographers who found cyanotypes easy and cheap to make. Cyanotypes were often used to proof negatives and to make photograms of leaves and plants. Architectural drawings and blue prints use a process similar to cyanotypes. Continue reading →