In three kinds of printing—relief, intaglio, and planographic—illustrations are often produced by the halftone process, in which a plate is made by photographing through glass marked with a network of fine lines (see also photoengraving). A usual form of color printing is by the Ben Day, or Benday, process, invented by New York printer Benjamin Day, which utilizes celluloid sheets to achieve proper shading and color. Printing in colors is sometimes done, as excellently in Japan, by applying inks of different colors by hand to the printing surface, but usually a separate printing surface is used for each ink.
In full-color printing four standard colors are used—yellow, cyan (a hue between blue and green), magenta, and black—the first three being the complementary colors of blue, red, and green. Other colors are produced by printing one color over another, as green by printing cyan on yellow. Black is used to print the text accompanying the illustration, and it is often used as a fourth color in the illustration itself to add strength and detail.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.