Gravure


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Gravure

 

a basic printing technique, one in which the printed copy is taken from plates on which the ink is in recessed printing elements. In gravure the various depths of the printing elements on the plate change, depending on the intensity of highlights and shadows in the work being reproduced. This is why layers of ink of different thickness are formed on the printed copy and the finest gradations and transitions of tones are created. This is the advantage of gravure over other types of printing in reproducing color pictures.

Gravure was first used in the mid-15th century. Until the mid-19th century there were only hand methods for preparing printing forms by engraving the recessed printing elements on metal plates with special cutting tools and other instruments (cut engraving, mezzotint, and drypoint). Chemical methods of engraving—aquafortis, aquatint, and soft lacquer—were also used. At that time the technique of reproducing demanded large expenditures of labor and time, and the degree of accuracy in reproducing an original depended on the artistic and technical skill of the artist-engraver. At the end of the 19th century a method was developed for photomechanically transferring a picture to the surface of a metal plate and then chemically etching the printing elements. Printing from these forms was done on hand-operated machines.

Rotogravure was invented in 1910. It is characterized by mechanized printing on rotary machines to which liquid ink is applied. The ink from the white (nonprinting) elements of the plate is removed by a doctor blade. The plates for rotogravure are made photomechanically, using a screen. On a sheet of pigmented paper, first a screen, then a retouched tone diapositive is copied. The image (copy) obtained is set into the polished and degreased copper surface of a form cylinder with a pigmented-gelatinous layer toward the copper. The image is rolled against the cylinder with a rubber roller in a pigment-transfer machine, and then it is developed with warm water. The water dissolves the part of the layer of gelatin that did not harden during copying. The hardened part of the gelatin layer remains on the surface of the cylinder in the form of a relief, completely reproducing the gradation of tones. The copper form is etched to different depths by aqueous solutions of ferric chloride. Liquid ink is brought to the surface of the form in the printing machine and fills its depressions. The inks for gravure are prepared in readily evaporating solvents, including toluene, benzene, and butyl acetate. The copper plate lasts for 25,000 to 30,000 impressions. In order to increase this number, the form is covered electrically with a thin layer of chromium (0.004-0.005 mm). In the 1950’s large-scale illustration and especially multicolor gravure developed rapidly. Small-volume sheet-fed machines (5,000-6,000 monochromatic prints per hour) were replaced by highly productive roller multicolor machines (15,000-20,000 multicolor prints per hour). Still later, they were replaced by multisectional printing equipment with automatic regulating and control equipment and devices that make it possible to obtain sheets that are gathered and sewn.

Gravure is used mainly in mass production with a large number of color illustrations—in mass circulation magazines such as Ogonek and Sovetskii Soiuz, albums with photographic illustrations, postcards, portraits, and insets in books. Gravure is also used in printing identical packing tags and labels for manufactured goods, especially using transparent film. Books are only rarely prepared by gravure, since texts reproduce worse by this method than by letterpress and planographic printing. This is a result of distortion of letter shapes by the screen and a certain degree of blurring of the liquid ink on the paper. Long-range prospects for gravure include programmed control of developing pigmented copies, automatic systems for etching printing plates, and automated control of ink viscosity. The first light-sensitive pigmented paper has been created in the USSR, and a method is being developed for preparing a light-sensitive copying layer for gravure on a nondistorting base—that is, on a film whose use will completely eliminate distortion in the plate-making process.

REFERENCES

Grigor’ev, G. K., and N. I. Siniakov. Proizvodstvo form glubokoi pechati. Moscow-Leningrad, 1950.
Fel’dman, B. A. Tekhnologiia proizvodstva massovykh illiustrirovannykh zhurnalov. Moscow, 1956.
Efremov, S. V., V. A. Strugach, and V. A. Dubinskaia. Glubokaia pechat’. Moscow, 1961.
Siniakov, N. I. Teknologiia izgotovleniia fotomekhanicheskikh pechatnykh form. Moscow, 1966.

O. I. SOPOVA

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