glossary of terms in map history
In printing, the product of a single pull from a printing press, and by extension the quality of that product (as in “good impression”). More specifically, one instance of a single-sheet image printed on one side, generally from copper plate but also from wood block and lithography. It is possible to refer to one instance of a multi-sheet map as an “impression,” but this is borderline inappropriate.
Reference to instances of printed images as “impressions” is preferred over “copy” (which has connotations of manuscript reproduction). Note that bibliographers have a quite different meaning: ¶impression2.
¶ impression (2)
A set of printed materials produced in an act of printing, such as the original print run of a book. Although it forms one rung in the formal bibliographical hierarchy of edition/impression/issue/state, cartobibliographers have tended in the past to be quite loose in its application. To avoid confusion with impression1, Tanselle (1982, 9–10) suggested that impression2 be replaced by printing.
The printing of images from incised surfaces: the ink rests within the incisions. Historically, relief printing has been accomplished through copper plates and perhaps, in the nineteenth century, steel plates. Several techniques are used to incise lines within the matrix: engraving, etching, acquatint, and mezzotint.