PRINTING ART IN ADVERTISING 1. Relation of printing to advertising.—Except for a small amount of word-of-mouth advertising, printing must be relied upon to deliver the advertis er's message. Without some mechanical means of multiplying the written message, extensive advertis ing would of course be impossible.
In view of the practical importance of the subject, the advertiser should possess a fair knowledge of the work that can be performed by printing processes.
2. Standard flat-press bed.—Inasmuch as the print ing art, as applied to advertising, embraces a variety of processes, it is well to note the number and sequence of the steps which an idea may take before becoming permanently embodied in print.
Many presses now in use retain the flat bed. Platen presses bring the type against a flat bed; cyl inder presses rotate a cylinder against a flat form. The rotary press commonly used in newspaper of fices departs from the use of a flat bed by employing a curved form that rotates with and against the im pression cylinder.
3. Offset process.—The tendency of ink to transfer under pressure is the basis of the so-called "offset" process—one of the later developments of the print ing art. The plate with the form to be printed does not meet the paper directly. The impression is made on a rubber roller and transferred from this to the paper.
By means of the offset process, rough papers, such as those with "antique" finish, may be used as readily as smooth papers. This is of particular advantage in the printing of half-tones. Reproduction of delicate shades of color is also made possible by this process. Admirers of the offset process claim for it superiority over lithography in the production of soft yet distinct color effects.
Since offset work requires special plates, the first cost for short runs is necessarily high. For large runs, the rapidity with which the work can be turned out greatly reduces the unit cost.
4. Multicolor process.—The multicolor process is based on the theory that any color may be produced from the three primary colors—red, yellow and blue —singly or in combination. Three plates, each carry ing one of these colors, are used, one after the other; the resulting picture will contain nearly every varia tion in colors. •
It was found that the three-color process could be improved by the addition of a fourth plate carrying black. This is especially advantageous on long runs, since it permits more rapid printing and imperfect register is less apparent than when but three plates are used. The paper is fed from rolls thru the cyl inders; inks of the desired colors are fed from different fountains and distributed by individual sets of rollers, each color going to its appropriate form.
The colored sections of the Sunday newspapers are familiar examples of multicolor presswork. Many catalogs, printed in one and two colors, carry inserts in multicolor.
5. Lithographic in colors calls for great exactness in execution. Not only must the presswork be accurately done, but the colors must be chosen with the eye of the skilled artist. In lithog raphy a satisfactory effect is seldom obtained with three or four colors, as is the case in other color pro cesses. In the finer grades of lithographic work, ten or more impressions age necessary.
Lithographic printing is commonly done on a press similar to those on which printing in colors by other processes is done. The stones holding the impres sions are first dampened and then inked. The ink rollers have a calf-skin surface instead of one of glue composition. For each color desired a separate stone is used.
6. of distinctly artistic value can be done in photogravure. In this process, an intaglio printing plate is used. This plate carries no sharply incised lines, but is marked by many minute depressions. In printing, these depressions produce the shadows, the high parts of the plate showing white.
To produce a plate in photogravure, the photo graphic sensitive film upon which the picture has been taken is imposed upon a metal plate. The plate is then developed and the picture bitten into the metal with mordant. From the resulting plate, impressions may be taken in substantially the same manner as from a copper plate: ' Of late years this process has been adapted to a cheaper grade of printing, called rotogravure from the fact that the printing is done on rotary presses. Rotogravure is much used for pictorial supplements of newspapers.