The Press., 1892-03-10
BOOK ILLUSTRATION.
A LUCID exPLANATioN OF SOME
 DIFFERENT PROCESSES.

DIFFERENT PROCESSES
 How Many of the Fine Pictures i'm Books. Magazines and Papers Are Produced. The Difference Between Cheap and Costly Work Made Plain to Buyers. With the increasing use of half tone work and the numerous processes for book illustration that have been devel- oped or adapted during the past ten or | fifteen years, there has steadily grown a tendency on the part of publishers, proc | ess men, and in some instances among critics. to apply entirely inappropriate | names to the reproductions that are mis- | leading in the extreme and cannot but do an injury to the better classes of work | by giving their names to processes much their interiors in quality.
 Let us first consider the ordinary half tone photoengraving of which so much has lately been seen in the way of illus trations for the higher class periodicals and works of an art and technical nature. We shall find that these prints all render l the half tone of the original; or, to be less technical. show the various degrees l of light and shade in masses of color. | differing in degree, butin flat tints. pro duced by breaking the original subject, 1 may have been either wash drawing. painting in color, portrait from life or view from nature, into and immense number of dots, obtained by photograph ing through the fine meshes of 8 ruled | glass in manner not necessary of de- l scription here.
 The resulting picture is transferred to l plate; the chemical action is proceeded with and the half tone plate that results shows the picture in relief and the en- tire surface of the plate mass of fine points or dots, separated by fine furrows running in transverse directions. the points in relief being the printing sur faces. The plate being blocked on wood or metal to render it of the same height as type, it is linked up with a roller in the same manner that type is. and the ink, adhering to the points, is impressed into the paper that is brought in contact with them in the printing press.
 | THE HALF TONE. ENGRAVING.
 1t should here be noted that the points or dots making up the printing surface of the plate, being all of the same height the amount of ink deposited on the paper is of the same depth or thickness from each and every printing point, and it naturally follows that variations in the light and shade making up the picture | are dependent on the number and size of such dots within given radius: thus heavy shadow ill a picture printed from relief plate will be seen to be com l posed of large number of these dots often so close together as to merge into one another. while lthe high lights are the result of preponderance of the clear transverse lines that serve to sep arate the dots more widely, only show ing them sufficiently to give form and color to their object @ -s
 The above are the principal points of Identification of a print made from a half tone type plate in relief. and are easily to be distinguished from pictures produced from intaglioIplates. There is still another kind of half tone relief work. however. that is not so easily dis tinguished. and this is the photogelatine or heliotype and kindred processes, which in rendering the gradations of color do not cut them Hp into dots. but lay the ink in smooth masses of different tones on the paper from surface of gelatine. PRINTING FROM AN INTAGLIo PLATE.
 The photogravlre is printed from an intaglio plate, and is not capable of be ing used in type press under any con ditions 1t can. only be successfully printed by an expert, and where with a relief plate the office boy might 'kick off, say 1000 day, or the steam cylin. der press 10000. the expert printer with his intaglio plate would not produce above 200 good impressions. The intaglio plate is filled while warmed with a hard, stiff ink. which isf pressed into every depression. and after the high lights of the plate are carefully wiped off," by hand, the plate is run through the press, in connection with the paper. and the latter lifts from the sunken sur face of the plate all the ink it has pre- viously received, holding it on the sur face of the paper in masses of color that differ in depth and consequently in tone, according to the depth of intaglio in diff ferent parts of the plate, the result of which is series of graduations from the pure high light of the clear paper to the rich. veIvety black of solid body of ink spread over the surface of the paper and not pressed into it.
 The grain. too. of this plate, instead of. being composed of noticeable cross hatchings of lines and dots, is d scarcely discernible tooth that is obtained by peculiar chetiiica action on the metal plate before the picture to be etched is transferred thereto. Carbon tissue being the medium through which the transfer is made and the finished print very closely resembling in most of it's features that beautiful pigment. it is wonder that the feeling of those in- terestsd in seeing justice done to all has not been more forcibly expressed on this subject before. a
 name that would answer the pur- pose and still be neritorious, is the old title photoglyph, as it applies to all plates which give reproductions from re- lief surfaces, while photogravure is properly used only in the opposite con- nection. Let all, then, who know bet ter. be honest enough to call things what they are and thus dowhat they can to avoid further complication of the already multitudinous. collection of pro