The early forms of intaglio printmaking, engraving and etching, were purely linear in approach. The medium was much in need of a tonal process, and it was discovered in the mid-seventeenth century in the form of mezzotint, the very name which ,from the Italian mezzotinto ('half tint') claims the achievement of the middel range of tones.
The frist stage of producing a mezzotint requires the entire printing surface of the copper plate to be roughened to a texture similar to fine sandpaper, consisting of tiny troughs and peaks in the metal which will between them hold enough ink even after the plate has been wiped - that it will print an even and velvety black. In the very early days of mezzotinting this microscopically chewed-up texture was achieved by running a spiked roulette again and again over those areas of the plate where dark shadow was required. Now, it is generally found to be far more effective that it is far more effective to work up an even ground over the entire plate. For this purpose a tool called a rocker was used, in shape like a broad chisel with a curved and serrated end to the blade. The rocker is then worked gradually in one direction over the surface of the plate leaving a series of dotted lines scored in the copper. Each recessed dot forces up a tiny amount of displaced copper, and it is this bloom of fragile peaks, known as the burr, which will hold the ink in such a way as to give early impressions a superb velvety quality in the darkest tones. When the entire plate has been rocked in one direction the process is repeated again and again in ever more directions. The more coverage the better - 40 being the recommended number but any amount after that only improving results.
When the plate is ready, the artist prepares to work on every patch of it except those which are required to print a solid black. His method is that of smoothing away to varying degrees the fragile burr. For drastic results he uses a scraper and for gentler effects the burnisher, a narrow tongue of metal which by steady rubbing rubbing can impart its own smoothness to the copper below. The dark greys will receive only the gentlest attention from the burnisher, while the pure whites will be scraped and then burnished until the copper gleams smooth again with no trace remaining of the rocker's teeth.
It is the pale grey areas, just short of the white highlights, which show the most characteristic signs of the mezzotint. Here all the raised burr has been burnished away, leaving none of the velvety mezzotint quality. All that remains is the clear-cut toothmarks of the rocker in those few directions in which it happens to have been pressed most deeply into the metal, appearing therefore as faint lines made up of thin dashes.