The mezzotint process was invented in 1625 by Ludwig Von Siegen. Today, the surface of the mezzotint plate is prepared in exactly the same manner as in the 17th century. A polished copper plate is roughened with a tool called a rocker, a sort of curved knife with sharp steel teeth and a wooden handle. The rocker is literally rocked back and forth on the surface of the copperplate until the tiny bite marks homogenize and create a uniform rough grain or ground. If the plate were inked and printed at this stage this roughened ground would produce a solid, velvety fully saturated dark.The design is formed by the patient extraction of the lighter tones from this ground. This is done by scraping and flattening the rough grain with burnishers and scrapers. As more and more of the grain is removed and flattened, the smoother the surface becomes. A perfectly smoothed area will produce a white or very light tone, while areas left fully rough will produce the velvety darkest tones that mezzotint engravings are so famous for. The inking and printing of mezzotint engravings requires care because of the fragility of the ground and the number of relief planes created by scraping and burnishing the plate surface. Full color printing is possible by either multi-plate printing or by applying all of the individual colors onto the plate together (a`la poup’ee). In both methods the excess ink on the plate must be carefully wiped off using starched cheesecloth, while insuring that sufficient ink is left in the roughened areas to create the tone. The white areas are wiped completely free of ink. In the a`la poup’ee method all of this is done while taking care not to blend adjacent colors into one another. Mezzotint edition sizes are generally smaller than with other intaglio printmaking techniques. This is due to the delicate nature of the ground into which the image is engraved. Edition sizes may be increased by steel or nickel plating the copper mezzotint plate.