Mezzotint
Mezzotint is a monochrome printmaking process of the "intaglio" family. It was the first printing process that yielded half-tones without using line- or dot-based techniques like hatching, cross-hatching or stipple. Mezzotint achieves tonality by roughening a metal plate with thousands of little dots made by a metal tool with small teeth, called a "rocker". In printing, the tiny pits in the plate retain the ink when the face of the plate is wiped clean. This technique can achieve a high level of quality and richness in the print. "Mezzotint" is often combined with other "intaglio" techniques , usually etching and engraving. The process was especially widely used in England from the eighteenth century, to reproduce portraits and other paintings. It was somewhat in competition with the other main tonal technique of the day, aquatint. Since the mid-nineteenth century it has been relatively little used, as lithography and other techniques produced comparable results more easily. Robert Kipniss and Peter Ilsted are two notable 20th-century exponents of the technique; M. C. Escher also made eight mezzotints. History. The mezzotint printmaking method was invented by the German amateur artist Ludwig von Siegen (1609–). His earliest mezzotint print dates  to 1642 and is a portrait of Countess Amalie Elisabeth of Hanau-Münzenberg. This was made by working from light to dark. The rocker seems to have been invented by Prince Rupert of the Rhine, a famous cavalry commander in the English Civil War, who was the next to use the process, and took it to England. Sir Peter Lely saw the potential for using it to publicise his portraits, and encouraged a number of Dutch printmakers to come to England. Godfrey Kneller worked closely with John Smith, who is said to have lived in his house for a period ; he created about 500 mezzotints, some 300 copies of portrait paintings. British mezzotint collecting was a great craze from about 1760 to the Great Crash of 1929, also spreading to America. The main area of collecting was British portraits; hit oil paintings from the Royal Academy Summer Exhibition were routinely, and profitably, reproduced in mezzotint throughout this period, and other mezzotinters reproduced older portraits of historical figures, or if necessary, made them up. The favourite period to collect was roughly from 1750 to 1820, the great period of the British portrait. There were two basic styles of collection: some concentrated  on making a complete collection of material within a certain scope, while others aimed at perfect condition and quality (which declines in mezzotints after a relatively small number of impressions are taken from a plate), and in collecting the many "proof states" which artists and printers had obligingly provided for them from early on. Leading collectors included William Eaton, 2nd Baron Cheylesmore and the Irishman John Chaloner Smith. Light to dark method. The first mezzotints by Ludwig von Siegen were made using the light to dark method. The metal plate was tooled to create indentations and parts of the image  that were to stay light in tone were kept smooth. This method was referred to as the ‘Additive method’; that is, adding areas of indentations to the plate for the areas of the print that were to appear darker in tone. This technique meant that it was possible to create the image directly by only roughening a blank plate selectively, where the darker parts of the image are to be. By varying the degree of smoothing, mid-tones between black and white can be created, hence the name "mezzo-tinto" which is Italian for "half-tone" or "half-painted". Dark  to light method. This became the most common method. The whole surface (usually) of a metal, usually copper, plate is roughened evenly, manually with a rocker, or mechanically. If the plate were printed at this point it would show as solid black. The image is then created by selectively burnishing areas of the surface of the metal plate with metal tools; the smoothed parts will print lighter than those areas not smoothed by the burnishing tool. Areas smoothed completely flat will not hold ink at all; such areas will print "white," that is, the color of the paper without ink . This is called working from "dark to light", or the "subtractive" method. Jacob Christoph Le Blon used the dark to light method and invented the three and four-color mezzotint printing technique by using a separate metal plate for each color. Le Blon's color printing method applied the [RYB color model] approach whereby red, yellow and blue were used to create a larger gamut of color nuances. In Coloritto, Le Blon refers to red, yellow and blue as 'Primitive' colors and that red and yellow make orange; red and blue, make purple/violet; and blue and yellow make green  (Le Blon, 1725, p6). Printing. Printing the finished plate is the same for either method, and follows the normal way for an intaglio plate; the whole surface is inked, the ink is then wiped off the surface to leave ink only in the pits of the still rough areas below the original surface of the plate. The plate is put through a high-pressure printing press next to a sheet of paper, and the process repeated. Because the pits in the plate are not deep, only a small number of top-quality impressions (copies) can be printed before the quality  of the tone starts to degrade as the pressure of the press begins to smooth them out. Perhaps only one or two hundred really good impressions can be taken. Detailed technique. Plates can be mechanically roughened; one way is to rub fine metal filings over the surface with a piece of glass; the finer the filings, the smaller the grain of the surface. Special roughening tools called 'rockers' have been in use since at least the eighteenth century. The method commonly in use today is to use a steel rocker approximately five inches wide, which has between 45 and 120  teeth per inch on the face of a blade in the shape of a shallow arc, with a wooden handle projecting upwards in a T-shape. Rocked steadily from side to side at the correct angle, the rocker will proceed forward creating burrs in the surface of the copper. The plate is then moved – either rotated by a set number of degrees or through 90 degrees according to preference – and then rocked in another pass. This is repeated until the plate is roughened evenly and will print a completely solid tone of black. Tone. Mezzotint is known for the luxurious  quality of its tones: first, because an evenly, finely roughened surface holds a lot of ink, allowing deep solid colors to be printed; secondly because the process of smoothing the plate with burin, "burnisher" and "scraper" allows fine gradations in tone to be developed. The scraper is a triangular ended tool, and the burnisher has a smooth round end – not unlike many spoon handles.