Gelatin silver prints are black-and-white photographic prints that have been created using papers coated with an emulsion of gelatin and light-sensitive silver salts. After the papers are briefly exposed to light (usually through a negative), a chemical developer renders the latent image as reduced silver, which is then fixed and washed. This technique was first introduced in the 1870s and is still used today. Most twentieth-century black-and-white photographs are gelatin silver prints. They are known for being highly detailed and sharply defined prints with a distinguishable smooth, even image surface.