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letterpress printing

flexography, form of rotary printing in which ink is applied to various surfaces by means of flexible rubber (or other elastomeric) printing plates. The inks used in flexography dry quickly by evaporation and are safe for use on wrappers that come directly in contact with foods.

In flexography, the desired imagery or lettering is engraved in the form of tiny indentations, or cells, onto a flexible rubber plate by means of plastic-molding techniques. Liquid ink is flooded onto a rotating ink-metering roller while a blade inclined at a reverse angle to the direction of rotation shaves any surplus ink from the ink-metering roller. The remaining ink is rolled onto the rubber printing plate, which is affixed to a rotary letterpress cylinder, and the plate’s tiny indentations receive and hold the ink. The inked plate then transfers the image or type to paper (or some other material) that is held on an impression cylinder.

Flexography has been widely used as a quick and economical way of applying simple designs and areas of colour to a wide variety of packaging materials, such as paper and plastic containers (including waxed-paper ones), corrugated-cardboard boxes, tape, envelopes, and metal foil. The inks used can be overlaid to achieve brilliant colours and special effects. Among the fluid inks used in flexography are aniline inks (aniline dyes dissolved in alcohol or some other volatile solvent), polyamide inks, acrylic inks, and water-based inks. These are superior to oil-based printing inks because they adhere to the surface of the material, while oil-based inks must be absorbed into the material.

A modern printing press that uses UV technology
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printing: Flexography

In the late 20th century flexography began to find new and significant applications as an alternative process used in newspaper printing presses. This was because of the simplicity and ease of the flexographic ink-distribution system, which only requires a single roller to determine the thickness of the ink applied, in contrast to the 10 or so rollers needed in conventional newspaper presses using oil-based inks. New water-based flexographic inks promised further advantages in newspaper printing, since such inks do not transfer to the hands of newspaper readers (a familiar problem with newspapers) and do not present the toxic-waste disposal problems associated with oil-based inks.

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printing, traditionally, a technique for applying under pressure a certain quantity of coloring agent onto a specified surface to form a body of text or an illustration. Certain modern processes for reproducing texts and illustrations, however, are no longer dependent on the mechanical concept of pressure or even on the material concept of coloring agent. Because these processes represent an important development that may ultimately replace the other processes, printing should probably now be defined as any of several techniques for reproducing texts and illustrations, in black and in color, on a durable surface and in a desired number of identical copies. There is no reason why this broad definition should not be retained, for the whole history of printing is a progression away from those things that originally characterized it: lead, ink, and the press.

It is also true that, after five centuries during which printing has maintained a quasi-monopoly of the transmission or storage of information, this role is being seriously challenged by new audiovisual and information media. Printing, by the very magnitude of its contribution to the multiplication of knowledge, has helped engender radio, television, film, microfilm, tape recording, and other rival techniques. Nevertheless, its own field remains immense. Printing is used not merely for books and newspapers but also for textiles, plates, wallpaper, packaging, and billboards. It has even been used to manufacture miniature electronic circuits.

The invention of printing at the dawn of the age of the great discoveries was in part a response and in part a stimulus to the movement that, by transforming the economic, social, and ideological relations of civilization, would usher in the modern world. The economic world was marked by the high level of production and exchange attained by the Italian republics, as well as by the commercial upsurge of the Hanseatic League and the Flemish cities; social relations were marked by the decline of the landed aristocracy and the rise of the urban mercantile bourgeoisie; and the world of ideas reflected the aspirations of this bourgeoisie for a political role that would allow it to fulfill its economic ambitions. Ideas were affected by the religious crisis that would lead to the Protestant Reformation.

The first major role of the printed book was to spread literacy and then general knowledge among the new economic powers of society. In the beginning it was scorned by the princes. It is significant that the contents of the first books were often devoted to literary and scientific works as well as to religious texts, though printing was used to ensure the broad dissemination of religious material, first Catholic and, shortly, Protestant.

There is a material explanation for the fact that printing developed in Europe in the 15th century rather than in the Far East, even though the principle on which it is based had been known in the Orient long before. European writing was based on an alphabet composed of a limited number of abstract symbols. This simplifies the problems involved in developing techniques for the use of movable type manufactured in series. Chinese handwriting, with its vast number of ideograms requiring some 80,000 symbols, lends itself only poorly to the requirements of a typography. Partly for this reason, the unquestionably advanced Oriental civilization, of which the richness of their writing was evidence, underwent a slowing down of its evolution in comparison with the formerly more backward Western civilizations.

Printing participated in and gave impetus to the growth and accumulation of knowledge. In each succeeding era there were more people who were able to assimilate the knowledge handed to them and to augment it with their own contribution. From Diderot’s Encyclopédie to the present profusion of publications printed throughout the world, there has been a constant acceleration of change, a process highlighted by the Industrial Revolution at the beginning of the 19th century and the scientific and technical revolution of the 20th.

At the same time, printing has facilitated the spread of ideas that have helped to shape alterations in social relations made possible by industrial development and economic transformations. By means of books, pamphlets, and the press, information of all kinds has reached all levels of society in most countries.

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In view of the contemporary competition over some of its traditional functions, it has been suggested by some observers that printing is destined to disappear. On the other hand, this point of view has been condemned as unrealistic by those who argue that information in printed form offers particular advantages different from those of other audio or visual media. Radio scripts and television pictures report facts immediately but only fleetingly, while printed texts and documents, though they require a longer time to be produced, are permanently available and so permit reflection. Though films, microfilms, punch cards, punch tapes, tape recordings, holograms, and other devices preserve a large volume of information in small space, the information on them is available to human senses only through apparatus such as enlargers, readers, and amplifiers. Print, on the other hand, is directly accessible, a fact that may explain why the most common accessory to electronic calculators is a mechanism to print out the results of their operations in plain language. Far from being fated to disappear, printing seems more likely to experience an evolution marked by its increasingly close association with these various other means by which information is placed at the disposal of humankind.

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