Drypoint closely relates to engraving except the carving creates a burr—metallic ridges flanking the artist's marks. The burrs hold ink and create a subtle feathering on initial prints, but they subsequently wear down after several passes through a printing press.

Excerpt from

Emily Schiller, Visions of America exhibition gallery text, 2016.

TOAH- http://www.metmuseum.org/toah/hd/drpt/hd_drpt.htm