An intaglio technique in which the surface of the plate is covered with an acid resistant material called ground. The image is drawn into this to expose the metal underneath. The plate is then immersed in an acid bath. Only the exposed parts of the plate are bitten (etched) away by the acid. The depth of the etch is controlled by how long the plate is in the acid and how strong the acid is. The most deeply bitten lines will hold the most ink and be the darkest areas of the print.