Cyanotype of Himanthalia Lorea, c 1843.

This cyanotype is taken from a book of algae published by Anna Atkins (1799-1871), a pioneering figure in photography, and her friend, Anne Dixon (1799- 1864). Atkins is credited with having produced the first book to use photographic illustrations. The 'blueprint' proces used to make the image employs ferric salts to produce a light sensitive solution coated onto a sheet of paper. After exposure it is permanently fixed by washing in water. The image is white on a blue background, and is highly durable and stable.