Etching is related to engraving, but uses acid (rather than a burin or graver) to incise a metal plate along lines scratched into the plate’s surface. A metal plate is coated with an acid-resistant film, into which the artist draws with an etching needle to create the lines to be printed. When the plate is submerged in acid, the acid bites the plate in the exposed lines and areas. The longer the exposure to the acid, the darker the line when printed. Etching is an intaglio process.