In modern printing systems, ink is pressed directly onto paper from plates of photographic paper or film, which carry an image of a finished page; the ink adheres only to the parts of the photographic plate which will show up in print, as was earlier done with raised type.

Since the turn of the twentieth century, the lettered parts of plates were made by photographing actual metal plates of finished type--the exact type of plates which, in earlier days, would have been inked themselves. In linotype machines that cast type with metal, the typesetter inputs text at a keyboard. The machine sets up a row of pre-made models (or "matrices") of letters. When the row is finished, it pours a quick-setting alloy over the row, which cools to form a metal row of type; this row is then dropped into place on the plate.

Obviously, the process of...