Intaglio (Italian, "to incise") includes engraving, etching, and mezzotint, among other techniques. Reversing the relief process, in intaglio the artist cuts the lines to be printed, rather than cutting away the nonprinting surfaces. Although it is an ancient process, intaglio did not come into use in Europe for printing illustrations until the fifteenth century. Engraving allowed the scientific or medical artist to create a more precise and detailed line in a metal plate — copper at first, but later steel — than was possible in relief. Intaglio printing requires much more pressure than relief, since the ink is held in recessed grooves instead of on the surface of the plate, and so illustrations could not be printed on the same press as the text.

Etching, a less arduous process developed in the early sixteenth century, uses acid to cut into the plate, which allows the artist much greater freedom to create a line. Easily combined with engraving, it became the intaglio process most favored by artists. Another type of intaglio process, the mezzotint (Italian, "half-tint") allowed an artist to create the middle range of tones between black and white. In a laborious process, the overall ground is laid down with a rocker. The resulting velvety quality made mezzotint ideal for portraits but too imprecise for scientific and medical illustration.


Robert Hooke
Detail from: Micrographia, 1665
The New York Public Library

Images of these items illustrate but a few of The New York Public Library's major holdings in science and medicine as well as items from other institutions which were featured in the exhibition Seeing Is Believing,on view from October 23, 1999—February 19, 2000 at the Humanities and Social Sciences Library, and related publication.


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