Cyanotype printing, also known as sun printing, is a technique which was discovered in 1842 by scientist Sir John Herschel. At the time, it was used primarily to reproduce engineering and architectural drawings. When the botanist Anna Atkins learned of the process, she used it to document plant life from her collection, and is credited with bringing the process to the world of photography.
The process is fairly simple. Chemically treated surfaces like paper and fabric are exposed to sunlight, a chemical reaction takes place, and you’re left with fascinating silhouettes on beautiful blue backgrounds. While this normally requires mixing chemicals, pre-treated papers are available, making it easy and safe to involve children.