Mezzotint is an elaborate form of engraving on copper that produces a tonal print and is unique in that a completely black ground is engraved first, then the image is worked from dark to light. A curved serrated tool called a rocker is used to engrave a ground into a copper plate. This engraves a fine line of dots into the plate, as well as raising a burr of copper proud of the surface. The whole plate is covered so an even, uniform texture is created that feels like fine sandpaper to the touch. It is the depth of the dots as well as the height of the burrs that hold ink, producing a deep velvet black tone. To fully ground a 30x20cm plate takes around 36 hours. Then using a variety of scrapers, blades and burnishers the image is selectively scraped and burnished back to produce a tonal design. The deeper the indented areas remain, the darker it will print. Where the plate is polished smooth, no ink will adhere so will appear as highlights.