The effect of Leoni's prints depends on the extraordinary range of engraved marks to distinguish texture and form. He developed a subtle technique of using the engraving tool (burin) not only to capture the sharpest detail of eyebrow or moustache, but to stipple dots that modelled every nuance of flesh with texture as soft as if it were rubbed chalk.
Leoni used an engraving tool (burin) to carve lines and dots directly into the surface of a copper plate.
Ink was forced into the engraved marks and the inked plate laid on the flat bed of a heavy roller press.
The inked plate was rolled through the press with a piece of paper laid on top of it. The new print was hung up to dry.
Illustrations from A. Bosse, Traicté des Manieres de graver..., 1645