Cyanotype is a very early photo printing technique, invented 1842 by English scientist Sir John Herschel, in which images can be made on UV sensitised paper using iron compounds, sunlight and water. The process produces images in various shade of blue. The technique was originally used by architects and engineers to copy technical drawings known as 'blueprints'. It's a way of making photographic images without a camera, though many contemporary artists now use digital negatives
