Cyanotype or blueprint was invented by Sir John Herschel, astronomer and scientist. On June 16, 1842, he gave a lecture on one of his discoveries. He established that certain iron compounds react under the influence of sunlight. And produced an image; by smearing a sheet of paper with a brown-green mixture of chemicals, putting a negative on it and exposing it in the sun. Subsequently rinsing the paper with water resulted in a positive blue image that was preserved and did not fade under the influence of light. Herschel believed he had made one of the most important inventions in the field of photography. Shelf life of photographic images was one of the most difficult things in his day.
Blueprint or Cyanotipie are contact prints. The blue color can vary in tone due to lighting or changing the solutions of the chemicals. The type of paper used for printing also influences the color and atmosphere of the image.
The size of the image depends on the size of the object or negative that is placed on the prepared paper.
For example, I made a series of prints of large leaves that I picked and printed. Those leaves become negatives in which the veins form a play of lines that reveal a beauty of structures in their blue print.
'Just as we like to chase something pleasant that flight for us , so we like to look at blue, not because it pushes on us, but because it pulls us along.'
J.W. Goethe, Color theory