In addition to plates made by either line or halftone process, combinations of the two are frequently used, as, for instance, where decorative pen work is used to embellish a halftone picture, or where lettering is to be used in connection with a halftone and form part of the same plate. These plates made up of both line work and halftones are known as combination plates or double-prints, depending upon the way they are produced. In both cases, negatives are made of both the halftone and fine copies.
Combination plates are made by combining the halftone and line negatives together and making one complete print on the metal.
Double-print is used where the surface is covered with halftone screen, either the line or halftone negative is printed on the metal, the other is superimposed on it.
The Benday process, so called, is the use of mechanical appliances for adding lines or stipples to either drawings or plates. Its use is very extensive in the making of tint blocks or color work, used either in connection with line or halftone key plates.
The highlight process, possible only with certain kinds of copy, is a modification of the halftone in which, by manipulation of the time of exposure and the screen when making the negative, the halftone stipples are lost and in this way halftones are produced in which there are pure whites, without the necessity of the finisher cutting them by hand.
Benday Engraving
Color Engravings.
Let us assume that we have a painting or a drawing in colors from which it is desired to produce a set of printing plates to produce that drawing in facsimile. Under the old method of procedure, lithography, it would have been necessary to make a stone for each of the colors, which would mean, roughly speaking, from twelve to eighteen stones to reproduce it—it will be understood that this means the finished print must go through the press once for each color. This would mean twelve to eighteen impressions to get the desired result. The expense of doing this limited the use of lithography.
