The cyanotype (from Ancient Greek κυάνεος – kuáneos, “dark blue” + τύπος – túpos, “mark, impression, type”) is a slow-reacting, economical photographic printing formulation sensitive to a limited near-ultraviolet and blue light spectrum, the range 300 nm to 400 nm known as UVA radiation. It produces a cyan-blue print used for art as monochrome imagery applicable on a range of supports, and for reprography in the form of blueprints. For any purpose, the process usually uses two chemicals: ferric ammonium citrate or ferric ammonium oxalate, and potassium ferricyanide, and only water to develop and fix. Announced in 1842, it is still in limited use even in this digital age.