Engravings best suited to this style of painting are mezzotint or aquatint, though fine lithographs are used.
"Young's Demonstrative Translation of Scientific Secrets"
Daniel Young
This is, however, prevented by the aquatint ground, which allows the mordant to circulate only in the channels around the resinous particles of which it consists, and thus produces a grain precisely as in ordinary aquatinting.
"Photogravure"
Henry R. Blaney
Article in Wilson's Magazine, 1890-1891. Notes on Photo-aquatint.
"Photogravure"
Henry R. Blaney