These two images were created using a copper plate, rolled with hard ground (a bitumen-like medium) and etched with a sharp implement. Submerged in ferric acid for about 20 minutes, the exposed lines are further etched. White areas are then painted with bitumen and the plate sprayed with acrylic (in lieu of the aquatint process) and submerged for another five or so minutes. Turpentine is used to remove the hard ground and bitumen prior to printing. This site, Non-toxic Printmaking, has several alternatives to the traditional methods.
Before the plates are printed, the edges are filed at an angle of 45 degrees to prevent cutting the wool mats. The plates are warmed before inking, to reduce the amount of ink used and to make the ink more fluid and movable. After gentle wiping with tarlatan, the plates are polished with paper and put through the printing press.