Developed in the 16th century, etching is an improvement on the copperplate engraving technique. In the etching process, a metal plate (usually copper) is covered with an acid-resistant coating and an etching needle is then used to scrape lines, hatch marks, etc. into the base to expose those areas that are to appear in color on the printed image later on. The plate is then treated with acid, which etches the metal in the exposed areas. After the remaining coating has been removed, the plate can be used as a gravure printing plate. Etching is still used widely today as an artistic technique.