Sunprints® are cyanotypes which are produced by exposing light sensitive paper to ultraviolet light such as that produced by the sun. Sunprints® are merely one among many photographic printing processes, and the concept is very old, since only the most basic of equipment is required to make a Sunprint®. Some professional photographers create cyanotypes in the course of their work, and they also make a popular classroom activity to get children thinking about photography and the arts.
Although the concept of the cyanotype is quite old, Sunprints® were actually developed by the University of California, Berkeley's Lawrence Hall of Science, which sells them in kit form for people who want to explore the art. Sunprint® kits contain sheets of paper which have been covered in a solution of ammonium iron(III) citrate and potassium ferricyanide. When these chemicals are exposed to sunlight, they react, forming ferric ferrocyanide, also known as Prussian Blue, a brilliant blue dye which cannot be washed out. The kits typically also contain a clipboard for stabilizing the paper on, along with plexiglass to help keep objects in place as a Sunprint® is made.
Obviously, simply exposing a sheet of Sunprint® paper to sunlight wouldn't make a very interesting image, as the entire print would turn a uniform shade of blue. To make Sunprints®, people place various objects between the paper and the source of light, ranging from car keys to leaves. Many people like to make Sunprints® of natural items such as leaves and feathers, but any sort of roughly flat item, including one's hand, will do. The paper typically starts out with a faint bluish tint, turning white as it is exposed to UV light. When the exposure is finished, the paper is rinsed in water, and a print will slowly emerge.
Some photographs make Sunprints® of transparencies of other work, such as photographs taken with film, especially if they shoot in black and white. The rich blue color of a cyanotype can transform a transparency into a haunting and unusual image. Others experiment with exposures of an assortment of items, and some people like to move objects around to create nuances of shading and a sense of movement. This very basic printing process can be utilized in a wide range of ways.
If you want to make Sunprints® on your own, you should be able to find a Sunprint® kit at a science store, museum shop, or children's store in your area. Numerous companies make variations on the official Sunprint® kit which may have names like “Solargraphics” and “Sun Exposures.” The process of making Sunprints® is very fun, and safe for artists of all ages.