Cyanotype

In 1842, the scientist and astronomer Sir John Herschel invented a new process for reproducing his notes. By combining sunlight and an iron salt solution on photo-sensitive paper, a Prussian blue image was created. Just a year after Herschel’s invention, a family friend, the botanist Anna Atkins used the technique to create copies of algae specimens, which she combined into an album. (Atkins is often credited as the first woman photographer.) In the following years, the cyanotype was used to copy architectural and engineering plans, and the distinctive blue tint gave rise to the term “blueprints.”