Unit 23: Photographic Media Historical process - Cyanotypes

Cyanotypes is an old historical photographic process which gives a cyan blue print, and was discovered by Sir John Herschel in 1842.  It was initially used by engineers to make blueprints but following that, it was Anna Atkins who popularised this simple and cost effective process in the photographic world.  She made a number of books documenting plant life.  She produced cyanotypes by placing algae directly on to the paper and exposing them to light to create a silhouetted effect.

To produce a cyanotype you need equal amount of two chemicals - ammonium iron citrate and potassium ferricyanide.  These photosensitive solutions need to be applied to paper or cloth and then dried in a dark room/cabinet. An image can be produced by exposing the chemical coated paper to ultraviolet light like the sun and by placing a contact negative or a digital image printed on acetate on top of the paper.  The longer the image is exposed to the light the darker the image will turn out. It's recommended to to expose between 10-20 minutes to get a good level of detail in the image.  Once the correct exposure time is achieved then the paper needs to be rinsed off under running water to wash off all the chemicals.      

Images below show how cyanotypes can vary a great deal in colour and intensity.  Image on the right is one of Anna Atkins famous plant cyanotypes.


     




So we decided to produce our own cyanotypes in college.  The first image is the result of too much exposure in the sun.  The colour has intensified, resulting in loss of detail.

I feel much happier with the second image as I spent less than ten minutes out in the sun.   There's plenty of definition and it pretty much resembles the original image. I feel even the inverted image on acetate looks quite good.  This is a lovely old process with some room for experimentation.  It's all trial and error like a lot of things but I would love to try this again and, maybe do something similar to Anna Atkins.