Printing

Summary

Printing includes a wide variety of increasingly computerized technologies engaged in the transference and manipulation of images—both words and illustrations—from one surface to another. Surfaces range from paper to glass to metal and even apparel. With the emerging demands of the information age, as millions of agents engage in moving information and maintaining accurate records, printing technology has evolved into a cornerstone industry.

Definition and Basic Principles

Printing refers to the applied technologies of reproducing texts, specifically the storing and distribution of data. In many ways, printing is an invisible technology despite being surrounded by evidence of its application. It might be assumed that given the rapid rise in digital technology, specifically the unprecedented storage capability of digital technologies and the ubiquitous presence of personal computers, that printing has become obsolete. Although the computer has revolutionized printing, the demand for the organized and controlled transference of information still relies on printing. From publishingbooks, magazines, and newspapersto commercial applicationslabels, manuals, banking checks, forms, letterhead, glassware, and clothingprinting is central to a culture that relies on maintaining records and disseminating information. Unlike more prominent applied technologies—such as steel manufacturing or auto making—printing maintains its low profile because, unlike those industries, printing concerns are more likely to be smaller, privately owned, independent industrial facilities that seldom employ more than fifty workers.

Nearly all commercial nondigital printing involves one of five basic processes—lithography, screen, flexography, letterpress, or gravure. Digital technologies have reshaped printing, and microtechnology has allowed printing to diversify into data management and web-based systems. With the advent of desktop publishing and laser printing, text manufacture and information display became part of personal computing with texts that, unlike those produced in the twentieth century by the typewriter, look professional.

Background and History

Given the impractical and unreliable methods of the ancient oral cultures (memory and verbal communication), the desire to print information has a long history. Papyrus, the first practical printing system, dates to 6000 BCE. The earliest developments in printing, woodblocks used to transfer images and symbols to cloth, date to first-century China. Additionally, advances in paper production in the Far East were brought to Europe in the twelfth century with advances in movable type, efficient systems of reproducing text using revolving stone tablets and numbered boxes of handset type, often made of wood. In the early fifteenth century, German metalworker Johannes Gutenberg perfected an efficient system of movable type technology using durable type pieces made of a lead and tin alloy.

It is impossible to overestimate the impact of movable type. It enabled information to be more rapidly shared, and science, philosophy, and literature enjoyed unprecedented prosperity. The printing press has been credited with making the Renaissance possible. Knowledge could accumulate across generationsscientists could build on each other's work, books could circulate widely, governments could maintain public records, education was readily accessible, writers had authority over their work, reading became a private act, and languages became part of national culture. Over three centuries, the basic technology of Gutenberg's printing press remained unchanged, save for being driven by progressively more energy-efficient meansfirst steam then electricity. In the closing decades of the twentieth century, however, printing began to redefine image reproduction and text manufacturing to accommodate the rapid strides in information gathering and display offered by digital technologies.

How It Works

Offset. By far the most common process for commercial printing is offset lithography, which includes the mass-quantity, high-speed production of mail-order catalogs, newspapers, directories, weekly magazines, and books. The process is designed for competent and speedy production. It involves spools of paper that weigh upwards of a ton and machines capable of printing more than one thousand impressions every minute.

First, the text to be printed must be converted to plates, a process that involves photo emulsion. This is the same process as photography in that the negatives of the text are exposed to controlled light that passes through the negative and triggers a chemical reaction that transfers the transparent image to a thin flat plate, most often made of zinc or aluminum. The process moves to the press run. Because oil and water do not mix, the plate surface is broken down into two areas, the image area, which repels water (and thus remains dry and can absorb ink), and the nonimage area, which accepts water and is not part of the reproduced image.

Ink is distributed to the prepared plates through high-efficiency rollers. The plates are rolled first with water and then with ink. The ink adheres to the image, and the water rollers keep the ink off the nonimage area. The plate is then pressed to a rubber blanket, transferring the image quickly and cleanly. High-speed presses then roll the paper across the rubber blanket. The paper never touches the plate, thus the term offset. Because the paper, once through the press, is wet, the paper then passes through a gas oven at a temperature near 400 degrees Fahrenheit to dry it. Then it is quickly run through a refrigeration unit to cool the paper to avoid smudging.

Rotogravure Printing. The other most widely used industrial printing process (accounting for roughly 20 percent) is rotogravure, or intaglio, printing, in which the image or text is cut into the surface of a rounded (hence “roto”) printing plate. The image is formed from the sunken surface of the plate. Each cylinder can hold the image of up to sixteen pages of text. As the cylinder is turned at high speeds, the roll of paper (or fabric, foil, or plastic) is fed continuously across its surface, in which computerized stressors maintain the registration controls necessary to transfer the images. The paper is passed across the image cylinder. After that, the paper is passed through high-temperature driers to help set the ink quickly.

Although the process is more technologically sophisticated and expensive than offset, gravure is more cost-efficient (state-of-the-art presses can run as fast as three thousand feet per second), and the reproduction is more consistent, better detailed, and of finer resolution. The tempered plates are more durable than the rubber blankets used in offset. The only drawback to gravure from an industry standpoint is the time it takes to prepare the cylinder plates, a process called diffusion etching, which involves a thick copper mask and an acid bath to achieve the appropriate cut in the cylinder.

Applications and Products

Printing applications figure in virtually every industry. These industries are routinely held together through the reproduction and dissemination of printed materials. Marshall McLuhan, one of the pioneer theorists in communication and language, predicted the inevitable end of the age of print and the evolution of the paperless office in the 1950s. However, despite the innovations of the last generation of printers driven by digital technology, reproducing and storing data through printing processes has only increased in application.

Lithography. Offset lithography, introduced more than a century ago, is the predominant technology for commercial printing. Sheet-fed offset printing is cost-effective and produces reliably clean images and text because the rubber blanket that transfers the image adheres tightly and precisely to the texture of the printing surface. Color-control reproduction is entirely directed by computerized settings that blend the inks at tremendous speed. Although the color reproduction is not fine point, the types of printing that use lithography offset—daily and weekly newspapers, most weekly magazines, advertising and informational brochures, and most paperback books—are not designed for long-term usage and do not require precise image reproduction.

Gravure Printing. Given its history (the process of cutting designs into soft metallic plates was first used by Renaissance artisans interested in fine and expensive engravings), it is not surprising that gravure printing is used for printing projects that, while requiring a significant number of rungs, have more of an aesthetic element than those created with offset printing applications. These include commercial bags and boxes that bear the trademark logo of a company or store; decorative wrapping paper; labels; mass-mailing glossy inserts; Sunday newspaper inserts, high-end glossy commercial and department-store catalogs, and monthly magazines; specialty limited-run printing, such as ornamental wallpaper rolls, art prints, publicity posters, or commemorative postage stamps; and, finally, printing runs that involve delicate fabric. Because of the durability of the cut plates, gravure printing is also used in the production of long-term forms and applications.

Flexography. Developed in the early 1900s and popularized with the invention of cellophane during the Great Depression, flexography created a new industry for food packaging. Flexography is a variation of rotary printing using an image carrier made of flexible rubber or a soft plastic plate with raised image designs. It accounts for just about 15 percent of commercial printing applications. Flexography is particularly attractive for high-demand printing work that is less ornamental and more functional. It is based on a simple three-stage technology—an in-feeding unit feeds materials such as cardboard or film, a printing unit delivers high-speed drying ink which is spread by passing the medium through a series of distribution rollers, and the outfeed unit rewinds the printed material to send to the appropriate plants. Spools of candy wrappers, for instance, would be rewound and sent to the factory. Flexographic printing is versatile in its applications. It is widely used to produce cardboard products, product wrapping, corrugated boards, plastic film, and medical, sanitary, and food packaging. Because printing on cellophane using the gravure process proved prohibitively expensive, flexography made cellophane printing cost-effective.

Screen Printing. As with other printing technologies, screen printing is based on a simple principle that dates back to ancient China. The idea is to transfer an image by passing ink through openings in a precut stencil. A stencil is attached to a piece of fabric stretched on a metal or wooden frame. A squeegee-like device is used to force ink through the stencil opening, and then the material, most often paper or fabric but also metal, plastic, or wood, is fed and pressed under the stencil and then removed for drying. Although originally used for producing elaborate wallpaper designs and shop signs in the 1800s, screen printing is now used for short-run projects that require high-quality resolutionphotograph reproduction, clothing lines and silk-screen work, cardboard cartons, and even microcircuits for computer systems.

Ink-Jet Printing. With the rise of personal computers and the emergence of digital printing in offices, ink-jet printing is becoming the most familiar and most versatile application of printing technology. Given the resources of computer programs and the speed at which such software is marketed (any description of existing ink-jet printing technology will quickly become obsolete), the applications of ink-jet printing are bound only by the resources of the technological imagination. The basic premise—the transfer of images and text using digital data memory and on-screen formatting to create individual and personalized printing—puts printing skills in the hands of anyone with a computer. The effects are clear and readable but relatively low resolution. High-quality resolution is seldom the aim.

In ink-jet printing, computers create the desired effect by controlling the spraying of individual drops of ink by using electronic impulses. Although used most frequently with paper for high-speed reproduction of information within a large or small office network, ink-jet printing can also be used with corrugated board, plastic, and fabric. Newer developments in this technology have led to handheld inkjet printers that allow users to print labels on numbers directly on products ranging from traditional surfaces such as plastic and glass to concrete.

3D Printing. Three-dimensional (3D) printing is a type of rapid prototyping technology that involves creating a physical object from a virtual model. Though 3D printing was possible in the 1980s, its applications were limited. In the early twenty-first century, 3D printing expanded from functional prototypes to medical care, automotive manufacturing, weapons, food, and more. As technology evolved, 3D printers became available to the average consumer. Hobbyists, mechanics, and educators purchased these printers, primarily those using thermoplastic material.

Careers and Course Work

Courses in mechanical engineering, chemistry, physics, computer science, mathematics, and graphic communication account for the foundational requirements for students interested in careers in printing. Career opportunities and requirements for long-term success in printing have dramatically changed in the twenty-first century. The US Department of Labor cites increasing computerization and the declining volume of printed matter due to the availability of computerized data storage as reasons for the decline. The most promising career opportunities in larger commercial printing firms are geographically concentratedCalifornia, Illinois, Massachusetts, Texas, Michigan, and the Washington, DC, Chicago, and New York City metropolitan areas account for over one-third of such facilities.

Training for most hourly wage printing jobs (technicians and operators) is on-site and job-specific. Production workers, printing machine operators, and manual laborers who load and maintain the presses typically have associate's degrees, specific vocational training, or bachelor's degrees (most often in engineering). However, significant career advancement is best secured through knowledge of computer skills, desktop publishing, journalism, and digital graphic design. Upper-level-salary jobs require familiarity with business administration and marketing.

Social Context and Future Prospects

A casual glance at a contemporary department store or shopping mall, office complex, bank, hospital, or local government building confirms the place of print technology. Although seldom acknowledged, the printing industry defines a twenty-first-century consumer culture. The advent of computerized printing techniques has reshaped the employment profile away from manual work into prepress design and computerized formatting, and digitalized data banks have drastically cut into the volume of printed material produced. Printing and printed materials remain central to most service industries and business enterprises.

Newspapers have suffered dramatically because of competition from Internet news sources and television. Despite the advent of electronic books and readers, the book industry is solid—up to one million books are published annually—and magazine publishing maintains a healthy market share. Researchers have estimated that before the end of the twenty-first century, the enormous volume of data required by an information-hungry global community will be entirely digitalized, virtually eliminating the need for paper and printing for data retrieval. That same technology will increase printing efficiency, reliability, and safety and provide other, wide-ranging printing applications.

Bibliography

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Connolly, Kate Bertrand. "New Digital Printing Technologies Boost Packaging Benefits." Packaging Digest, 20 July 2020, www.packagingdigest.com/digital-printing/new-digital-printing-technologies-boost-packaging-benefits. Accessed 20 May 2024.

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Kuznetsov, Yuri V. Principles of Image Printing Technology. Springer, 2021.

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