So called because it was used to reproduce paintings with the full range of greys. The process starts by roughening a copper plate with a rocker (a tool with varying numbers of teeth) to give it a burr all over the plate. This plate will print a rich, velvety black when completely roughened.
To achieve the greys and lights up to white tones, the burr is removed with a scraper or flattened with a burnisher until the required tone is achieved. It is a lengthy process but the tonal range that can be achieved is what gives mezzotint its softness and it is particularly suited to dramatic effects of light and dark (chiaroscuro).
Very high pressures are required to print mezzotint properly and this means that plates wear quickly. Editions of prints are therefore small as the quality of the blacks and greys diminishes quite quickly due to press wear.