Shell steel
Granierstahl , mezzotint knife , also weighing iron is a crescent-shaped perforated steel tool that the roughening of for low pressures in the mezzotint (= mezzotint serves plates used).
The 3–5 cm wide Granierstahl is moved back and forth crosswise over the pressure plate until it is roughened evenly and over the entire area. This means that a homogeneous black area appears in the print. The drawing is then polished out of this black plate as a white highlight.