Some of my works:

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In the Cyanotype process the resulting deep blue is due to the sensitivity of some iron salts to ultraviolet light.  Sir John Herschel developed the process in 1842 and just one year later Anna Atkins used cyanotypes of ferns and algae as the illustrations for her botanical books.

The process is quite simple: under safelight (a tungsten bulb) the paper is hand coated with the photosensitive solution and allowed to dry completely. A suitable object  is then placed over the sensitized paper and the exposure, usually several minutes long, can be performed under direct sunlight. Unexposed salts are then washed out in a water bath, while the parts that received enough sunlight become that deep blue.

Some serendipity in chemical reactions and fantasy can help in obtaining more interesting images.