Cyanotype Process

The cyanotype process was one of the first non-silver technologies invented to create photographic images.  Cyanotypes are most recognizable for their continuous Prussian Blue tone.

Sir John Herschel (1792-1871) was a British scientist, astronomer, and chemist.  Herschel invented the use of “hypo” as a fixing agent in photography by first discovering the ability of hyposulfite to dissolve otherwise difficult to dissolve silver salts.  Herschel also developed the use of sensitized paper for photographic processes.  In 1842, Herschel invented a cheap, easy, and relatively non-toxic photographic method called cyanotype.  Although Herschel developed the cyanotype process, he had little interest in producing photographs.

 

Cyanotypes’ Prussian Blue color is created by using a mixture of ferric ammonium citrate and potassium ferricyanide.  These two chemicals are mixed and used to sensitize paper by painting the paper with the chemical mixture in the dark.  A photographic negative is placed on top of the sensitized paper before exposing it to ultraviolet light.  When the iron salts on the paper are exposed to ultraviolet light, or sunlight in most cases, they are reduced to their ferrous state, which, when oxidized, creates a high contrast, easily identifiable blue image.  Once the image has been exposed by the ultraviolet light, the paper is washed with water to remove un-oxidized iron salts.

Anna Atkins (1799-1871) was a British botanist and photographer.  In 1843, Atkins printed and published a scientific reference book of botanical specimens called “British Algae: Cyanotype Impressions”.  Rather than using a photographic negative, Atkins created her algae images by placing plant specimens directly onto the sensitized paper.  Atkins’s book was the first published book to be illustrated with cyanotypes.

“The difficulty of making accurate drawings of objects as minute as many of the Algae and Confera, has induced me to avail myself of Sir John Hershel’s beautiful process of Cyanotype, to obtain impressions of the plants themselves, which I have much pleasure in offering to my botanical friends.” – Anna Atkins, October 1843 

Today, cyanotypes are still used, but primarily for architectural and mechanical drawings, typically called “blueprints”.  The cyanotype photographic process produces a relatively stable print, ensuring that the prints will last for a long time with minimal fading and little preservation necessary.

References:

Ritzenthaler, Vogt-O'Connor, Zinkham, Carnell, & Peterson (2006). Photographs: Archival care and management. [referred to as P:ACM] Chicago: Society of American Archivists.

James, C. (2002). The book of alternative photographic processes. Albany, N.Y.: Delmar Thomson Learning.

http://venetianred.net/2010/05/08/anna-atkins-mistress-of-blueprint-manor/

http://www.getty.edu/art/gettyguide/artMakerDetails?maker=1542&page=1

http://www.nationalmediamuseum.org.uk/~/media/Files/NMeM/PDF/Collecti   

ons/Photography/CyanotypeProcess.ashx

http://www.sciencecompany.com/The-Cyanotype-Process-W164.aspx

http://www.getty.edu/art/gettyguide/artMakerDetails?maker=1917

http://www.sciencelogs.com/2012/10/anna-atkins.html

Anna Atkins’s Photographs of British Algae:

http://www.flickr.com/photos/nypl/sets/72157610898556889/detail/