Cyanotype photography involves first coating paper with a special solution and drying it in the dark.
An object (e.g. a photo negative or a leaf) is then placed on the paper which is then exposed to the sun or other UV light.
When ready, the paper is rinsed with water to stop the development process. It will turn blue where the light hit the paper but remain white in areas that were blocked out.
Wet cyanotypes use the same process but the coated paper is typically first sprayed with water or diluted vinegar. Other things like salt, turmeric or soap bubbles are sometimes added.
The exposure to UV is often much longer than more traditional blue and white cyanotypes. This approach creates different textures and variations in colour.