What is a cyanotype?
A cyanotype is a photographic print in Prussian blue. Here is who invented it, and what Anna Atkins made with it, from the Getty Museum.
What it is
“Cyanotype is an antique photographic printing process distinctive for producing Prussian blue monochromatic prints.” [Jacquard, Cyanotype FAQs]
“A cyanotype—a type of photogram—is made by laying the subject material directly on top of a regular piece of writing paper (British Whatman Turkey Mill paper in Atkins’s case) that has been coated with iron salts of ferric ammonium citrate and potassium ferricyanide.” [Getty Museum, Anna Atkins, British Algae]
Who invented it
“Sir John Herschel (1792-1871), a confidant of William Henry Fox Talbot and scientific colleague of Atkins’s father, John George Children (1777-1852), had invented the process.” [Getty Museum, Anna Atkins, British Algae]
“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”).” [Jacquard, Cyanotype Chemistry]
Herschel’s paper on the process was read to the Royal Society on June 16, 1842 and published in its Philosophical Transactions that year (Crossref record).
Anna Atkins
The Getty’s essay is about Anna Atkins’s Photographs of British Algae: Cyanotype Impressions, made by laying plant specimens on coated paper. It says:
“British Algae is recognized as the first book of photographs.” [Getty Museum, Anna Atkins, British Algae]
“The exposed parts of the paper turn a stunning Prussian blue while the parts covered by the specimen remain white.” [Getty Museum, Anna Atkins, British Algae]
On how well the prints last, the same essay says:
“It turned out to be one of the most permanent processes as well.” [Getty Museum, Anna Atkins, British Algae]
Why blueprint
“Developed in the mid-19th century, cyanotype was quickly embraced as an inexpensive method for reproducing photographs, documents, maps and plans (hence the enduring architectural term “blueprint”).” [Jacquard, Cyanotype FAQs]
Make one
The steps are on how to make a cyanotype. For a photograph, make the negative first.
On your phone: Cyanotype
For iPhone and iPad.
The app shows your photo as a cyanotype print first, in seven looks, with print sizes and matte borders, so you can see the blue before you coat anything. Then it exports the digital negative at full resolution: black and white, inverted and mirrored, and for 4 × 5, 5 × 7 and 8 × 10 paper at the resolution that prints at the paper’s size. It all happens on the device. There is no account, and the app makes no network connections.
How this was checked
Statements about the process, its chemicals, safety and history are quoted word for word from the maker’s instructions (Jacquard), the Getty Museum and the Photographers’ Formulary safety data sheets, and linked where they appear (checked ). Where we could not fetch a source for a fact, we left the fact out, so this section gives no concentrations or amounts of chemicals: use the instructions and safety data sheet that come with what you buy. The digital negative tool is compared by an automated test with the Cyanotype app’s own code. If something here is wrong, tell us at a@noshu.net.