A mezzotint is also usually made on a copper plate. A texture, or groundwork, is worked on the copper plate with a tool resembling a cabinet maker's toothed plane iron, except it is rounded at the end. The teeth are very fine, ranging from forty to one hundred and twenty to the inch in different tools. This tool is called a "Bercier," or "rocker." The rounded edge allows the tool to be rocked across the plate, the rocking motion causing the teeth to form indentations in the copper. The rocking has to be continued until the surface of the plate is completely covered, and it then presents an appearance like velvet. Rocking in from forty to sixty directions is necessary to cover the plate properly. The durability of a mezzotint plate depends entirely upon the pressure put upon the rocker, and the depth to which it penetrates the copper. After the ground is thus laid, the outline is sketched in on the rocked surface, which takes the pencil easily, and then with steel scrapers and burnishers the light and middle tints are worked down, leaving undisturbed the portions of the surface where the strongest blacks are to be. From time to time, a print is taken from the plate, to note the progress of the work, which advances slowly to the finish. On account of the length of time necessary for the laying of the ground and the scraping of the plate, many artists hesitate to attempt mezzotint plates. There are very few men in this country to-day who do mezzotint engraving, which, considering the results to be obtained, seems somewhat surprising.
For flesh tones, drapery, and landscapes it has no equal. The velvety richness of the blacks, the beautiful gradations of the middle tones, and the extreme delicacy of the light tints give the artist a power of expression not obtainable by any other method of engraving. Besides this, as the engraving is done on the bare copper, the artist can see at all times the progress of his work without having to take off the wax ground as he must in making an etching. This is a great advantage, for as the effect of each stroke can be plainly seen on the plate, the element of uncertainty which always attends the production of an etching is entirely eliminated, and it is then simply a question of skill with the scraper. The difficulty of obtaining rockers is one great drawback. I doubt if one could be obtained in New York to-day. The teeth have to be very accurately cut, and a perfect tool has a value to an engraver that cannot well be estimated. The lack of demand has prevented their manufacture in this country, but they could be made here by any fine tool maker.