“Experimenters have found that if this spectrum is thrown upon a sheet of sensitive paper, the violet end of it produces the principal effect: and, what is truly remarkable, a similar effect is produced by certain invisible rays which lie beyond the violet, and beyond the limits of the spectrum, and whose existence is only revealed to use by this action which they exert.”
The Pencil Of Nature, Henry Fox Talbot.
To create a cyanotype, paper is coated with Potassium Ferricyanide and Ferric Ammonium Citrate. When the paper is exposed to ultraviolet light (usually from the Sun), a chemical reaction takes place resulting in an insoluble blue dye know as "prussian blue".
If an opaque object is placed upon the paper, blocking sunlight, these parts of the paper will return back to white once the paper is developed.
Essentially cyanotypes are light prints, bridging the gap between traditional printing methods and photography (light writing).
Every day, between the 01 April and 17 December 2012, I made one cyanotype marking one spin of the Earth on it's axis, capturing sunlight on paper before the Earth was cast back in to shadow at night.
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