18. Ben Day process.—By the use of a sheet of celluloid having a raised design, known as a Ben Day screen, it is possible to introduce the pattern of the screen into any part of a zinc etching. The parts of the negative that are not to take the pattern are pro tected by sheet, or by being treated with a liquid resistant to the ink. By this means grays may be introduced on a plate printing black; light pinks may similarly be shown on the red plate. This process makes zinc etchings available for a wide range of color work.
Many Ben Day plates closely resemble hand stip pling or line work. In •the Moon Coupe advertise ment, the illustration is made by the Ben Day process.
19. forms cannot be printed as soon as made up, or where permanent plates are wanted, any form, cut or plate may be duplicated as many times as needed. By means of the electrotype, advertisement may be reproduced and distributed to all the periodicals in which it is to appear, thus insuring uniformity of display and clear printing.
The ordinary electrotype is wax-molded, the mold being dusted with graphite and submitted to electrolysis. The resulting film of copper is backed with lead. So-called nickel types, or nickel-plated electrotypes, are used on long runs and'in color print ing. They may be used with any colored ink without disintegrating, thus preventing the color change that takes place in some inks when the printing is done from an electrotype.
20. Stereotypes and is the process employed in many newspaper offices to dupli cate forms. Advertisements in the larger news papers must conform mechanically to the restrictions of the stereotyping process. In general, body-type smaller than six point should be of an open face; cuts should be free from minute detail, and no half-tones of finer screen than 80 to 100-line are adaptable.
The method of stereotyping is simple. A sheet of paper pulp is beaten into the face Of the form or pressed into it by means of a roller. The impressed
sheet, called the "matrix," is placed in a mold and molten type, metal is poured in. If the plate is to run on a rotary press, the mold is curved to conform to the curvature- of the press cylinder.
When an advertisement is to be run in a number of newspapers that have stereotype foundries, it is more economical to forward the papier-mache matrix than the plate itself. Even a large matrix can be mailed as first-class postage for a few cents.
21. Mechanical the various modern methods of-reproduction, certain mechanical processes are constantly employed.
"Stripping" enables the operator to join parts of different photographs or drawings into one cut or to combine photo-engraved and etched surfaces. In stripping, the film is removed from the glass plate to which it was originally attached. The stripped film can then be trimmed and placed where desired.
An engraving or other picture having a back ground that shades off gradually is termed a "vig nette." Vignetted half-tones are difficult to print, especially on a platen press, as the shading tends to cloud under heavy impression, while a light impres sion gives only a shadowy effect. This difficulty is overcome by using the silhouetted half-tone, made possible by the "routing" process.
Routing consists in cutting away those parts of an engraving that are to be below type height. Often it is necessary to rout out blank spaces so that they will not smudge the paper in printing. In zinc etch ings the entire background may be routed out so as to insure clearness.
Reverse cuts are those in whidh the impression is exactly the reverse of that in the drawings. "Re verses" are made by reversing the negative. The term is also applied to plates in which the blacks and whites are reversed.