Cyanotype (also known as blueprint) is a photographic contact printing process developed in 1842 by the English scientist Sir John Herschel. It is known for its distinctive Prussian blue colour. When this mixture is applied to paper or fabric and exposed to (sunlight), the salts react with the light and form iron(III) hexacyanoferrate(II) — or Prussian blue. The paper is then washed in water, leaving the unexposed areas white and the exposed areas blue. Pattern is probably Art Nouveau (c. 1890–1910) – organic lines, flowers, asymmetrical but flowing shapes.