Cyanotype photography is an early photographic technique, where a prepared negative image is placed onto a sheet of high quality watercolour paper, which has been previously coated with a photosensitive solution. It is then exposed in sunlight, and washed to reveal the print. Because of this they are sometimes called `sun prints`. The print is often taken from a larger image and reduced down, producing a very detailed image in a wonderful indigo blue colour. This is where the word `blue print` originates from.