Etching is a traditional form of relief printing. The process uses strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal. The plate is then put through a high-pressure printing press together with a sheet of paper (often moistened to soften it). The paper picks up the ink from the etched lines, making a print. This process can be repeated many times before the plate us worn out.