Intaglio printing is the opposite of relief printing, in that the printing is done from ink that is below the surface of the plate. The design is cut, scratched, or etched (using an acid bath) into the plate which can be copper, zinc, aluminum, or plastics. The printing ink is rubbed into the incisions or grooves, and the surface is polished clean. Unlike surface printing, intaglio printing—which is actually a process of embossing the paper into the incised lines—requires considerable pressure. Intaglio processes are probably the most versatile of the printmaking methods, as various techniques (engraving, etching, drypoint, aquatint, soft ground, and mezzotint) can produce a wide range of effects.