Any slightest scratch or mark that disturbs the surface of a highly polished plate of metal will hold printer’s ink and can be printed. Any method of which a design composed of such printable marks is made is called an Intaglio process.
The three basic types of Intaglio work are dry-point, engraving, and etching. In dry-point the surface of the plate is torn by a sharp point thrust in to the surface and dragged along it, the tool is held like a pencil. In engraving, V-shaped trenches are cut into the surface of the plate by a tool called a Graver or Burin, which is pushed along the surface. Etching is a process by which lines are chemically eroded in the surface of a metal plate. The polished plate is covered with a specially prepared ground, the principal of which is wax. The grounded plate is then blackened with smoke. The artist draws his design on the blackened ground with a point or etching needle. In theory, the etcher presses just hard enough on the point to scratch through the ground, but not dig in to the plate.