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EncyclopediaofJournalismPrinting.pdf

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Encyclopedia of Journalism

Printing

Contributors: Frank J. Romano

Book Title: Encyclopedia of Journalism

Chapter Title: "Printing"

Pub. Date: 2009

Access Date: January 22, 2019

Publishing Company: SAGE Publications, Inc.

City: Thousand Oaks

Print ISBN: 9780761929574

Online ISBN: 9781412972048

DOI: http://dx.doi.org/10.4135/9781412972048.n312

Print pages: 1122-1128

This PDF has been generated from SAGE Knowledge. Please note that the pagination of the online

version will vary from the pagination of the print book.

http://dx.doi.org/10.4135/9781412972048.n312

Printing is the reproduction of text and images in quantity on paper. Modern printing has become highly so- phisticated and more digital in nature and has been transformed from art to science. New digital printing processes combine the use of advanced pre-media systems (preparation of content for printing or publishing), lasers, plates, presses, inks, papers, electronic controls, and digital imaging and printing systems.

Origins

Printing from movable (or exchangeable) type appeared in China and Korea in the eleventh century. The old- est known printed rather than manuscript text was printed from clay in Korea in 1397 A.D. In 1440, Johannes Gutenberg of Mainz (Germany) introduced printing with ink on paper to the Western world with his invention of movable cast metal type mounted on a converted wine press. Until Gutenberg's invention, all books in the West were laboriously handwritten or copied by scribes. Changes in press construction evolved slowly until the first all-metal press was built in England by the Earl of Stanhope early in the nineteenth century. Expanded use of printing was spurred by the growth of book and newspaper publishing and the need to produce more copies of publications faster. During the Industrial Revolution the job (or platen) press and the cylinder press were developed. The first successful cylinder press, in which a rotating cylinder was used to press the paper against a flat type bed, was the steam-powered press built in London by German inventor Frederick Koenig. It was used for the Lon don Times in 1814 and was capable of producing 1,100 sheets per hour. Cylinder presses provided the speed for high-capacity magazine, newspaper, and book printing.

Mechanized Printing

American Richard Hoe manufactured the first rotary press in 1846. The first such press was installed at the Philadelphia Public Ledger. Early models produced 2,000 impressions per hour. The first web (roll-fed) press was developed by American William Bullock in 1856. These early web presses delivered 15,000 signatures (multiple pages printed on one large sheet) per hour, printed on both sides. A device for folding the papers as they came from the press was added in 1875.

Letterpress printing (metal type) was replaced by offset lithography in the 1960s.

Lithography

The basic principle of lithography—“stone writing”—is based on the principle that oil-based ink and water do not mix. It was discovered by Alois Senefelder of Munich about 1798. Working on a highly porous stone, he sketched his design with a greasy substance that adhered to the stone. He then wet the entire surface with a mixture of gum arabic and water. It wet the blank or nonimage areas, but the greasy image repelled the ink. An ink made of soap, wax, oil, and lampblack was rolled on the stone. This greasy substance coated the image but not the moist blank area.

Senefelder called his invention “chemical printing.” Artists used lithography to make reproductions of art- work—drawings and paintings.

The first steam-driven press for lithography was invented in France in 1850, and introduced in the United States by Richard Hoe in 1868. Direct rotary impression for lithography was introduced in the 1890s using grained zinc and aluminum metal plates to which images were hand transferred from stones using starch- coated transfer sheets.

In 1906, the first “offset lithographic” rotary press began printing sheets in Nutley, New Jersey, an invention

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of Ira Washington Rubel. offset lithography transfers the image from the plate to a rubber blanket and then to the paper.

Digital Imaging

The age of electronics and computers changed the way printed products were created and produced. The first printing production operation to be affected was typesetting with the introduction of the Intertype Fotoset- ter in 1949 and the Photon in 1954. offset lithography did not need metal type and this accelerated the growth of photo offset preparation. In 1950, the PDI Electronic Scanner was introduced for color separations. To print color photographs, they must be “separated” into cyan, magenta, yellow, and black plates. Neither technology advanced until the 1970s, when the video display terminal (VDT) or television screen and computers were combined to improve electronic typesetting, and Electronic Dot Generation (EDG) and digital magnification expanded electronic typesetting.

The digital revolution in typesetting began in 1985 with the introduction of the plain paper typesetter and the film imagesetter. In 1985 the imagesetter and Raster Image Processor (RIP) fostered the development of de- vice-independent prepress systems known as Desktop Publishing that displaced the device-dependent Color Electronic Prepress System and even tually replaced conventional prepress systems.

Platemaking advances began with laser plate-making in 1975; laser engraved cylinders for flexog-raphy (printing from raised plastic plates) and engraving assists for gravure (printing from cells etched into the plate) in the 1980s; computer-to-film in the 1980s; to computer-to-metal plates in 1991.

Each modern printing process has three main operations: Prepress, Press, and Postpress. The first and last steps are very similar for all printing processes. The prepress step involves preparing text and graphics for printing. Before the introduction of electronics and computers in printing, most prepress operations were man- ual using handset type and/or typesetting machines, process cameras for making page films, film processing, manual color correction, film assembly, and page and signature layout (multiple pages on one plate). Digital imaging technology has replaced all of these manual metal and photomechanical operations; pages are now created and assembled on computer screens using desktop software.

Postpress or finishing is the operation for cutting, folding, assembling, and binding sheets into final form—and it is largely unchanged.

On the other hand, the press or printing step uses presses that are different for each printing process. There are two major classifications of printing processes: (1) plate, pressure or impact processes such as offset lith- ography, letterpress, flexography, gra vure, and screen printing; and (2) plateless or dynamic processes such as electrophotography, inkjet, ion, or electron charge deposition, magnetography, thermal transfer printing, thermal dye sublimation, and elec-trocoagulation. It is predicted that newspapers will be printed using these new printing processes.

Plate printing processes use mechanical printing presses to exert the heavy pressure needed to transfer ink to paper and are the processes used to support long-run (many copies) magazines, news papers, books, packaging, and other printed products.

Plateless printing systems are used for copying and digital printing. They produce an image during each cycle of the printing device. The image can be the same or can be changed from cycle to cycle. This feature en- ables digital printers to print vari able information such as coding, addressing, and personalizing promotions and documents. The printing speed, however, is slower than plate processes, but there is no plate loading and no drying time. Therefore they are used primarily for short runs, on-demand, and/or variable information printing.

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Ink-Based Printing Processes

All printing processes are concerned with

• Image or printing areas, • Nonimage or nonprinting areas.

After the text and imagery have been prepared for reproduction (the prepress step), each printing pro cess has definitive means of separating the image from the nonimage areas. Ink-based or conventional printing has four types of printing processes:

1. Planographic—printing and nonprinting areas are on the same plane surface and the dif- ference between them is based on chemical properties—ink is either accepted or reject- ed. Examples are offset lithography, collotype, and screenless printing.

2. Relief—the printing areas are on a raised surface and the nonprinting areas are below the surface. Examples are letterpress and flexography.

3. Intaglio—the nonprinting areas are on a plane surface and the printing areas are etched or engraved below the surface. Examples are gravure and steel-die engraving.

4. Porous—the printing areas are on fine mesh screens through which ink penetrates, and the nonimage areas are a stencil over the screen to block the flow of ink. Examples are screen printing and stencil duplicating.

Planographic-Offset Lithography

Offset lithography uses thin aluminum metal or polyester plates with the image and nonimage areas on the same plane. There are two basic differences between offset lithography and other processes: (1) it is based on the fact that oil (ink) and water do not mix, and (2) it uses the offset principle in which ink is transferred from the plate to a rubber blanket on an intermediate cylinder, and from the blanket to the paper on an impression cylinder.

On a lithographic printing plate, the printing areas are ink-receptive and water-repellent, and nonprinting areas are water-receptive and ink-repellent. When the plate mounted on the plate cylinder of the offset press is rotated, it comes into contact with rollers wet by a water or dampening solution and rollers wet by ink. The dampening solution wets the nonprinting areas of the plate and prevents the ink from wetting these areas. The ink wets the image areas that immediately are transferred to the blanket cylinder. The inked image is transferred by pressure to the paper as the paper passes between the blanket cylinder and the impression cylinder.

“Offset” is not a process. Letterpress and gravure (and even digital printing) can also be printed using the offset principle. A main advantage of the offset principle is that the resilient rubber blanket produces a clearer impression on a very wide variety of paper surfaces and other materials with both rough and smooth textures. Also, it extends plate life and reduces press make ready (the process of setting up the press for printing by loading plates, paper, and ink).

Both sheetfed and web (roll-fed) presses are used. Sheetfed lithog raphy is used for printing advertising col- lateral, books, catalogs, greeting cards, posters, labels, packaging, folding boxes, decals, coupons, trading stamps, and art reproductions. Also many sheet fed presses can perfect (print both sides of the paper, which is also called duplexing) in one pass through the press. Web offset prints on rolls of paper and is used for print- ing business forms, daily and weekly newspapers, inserts, advertising lit erature, long-run catalogs, books, encyclopedias, and magazines.

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Relief-Letterpress

Letterpress is the method of printing Gutenberg invented in 1440 and has been used for job and commercial printing. It is a relief method of printing that can print from cast metal type, molded duplicate plates (still used for some package printing), or photopolymer plates on which the image or printing areas are raised above the nonprinting areas. Viscous oil-base and ultraviolet (UV) inks are used. The ink rollers come in contact with the raised areas only, and the inked image is transferred directly to the paper. Commercial letterpress has declined in use because too much time was consumed in makeready (building up of the press form so both the light and heavy areas print with the correct impression). Letterpress makeready is a manual process that is very skill- and time-intensive and therefore very expensive. It is one of the main reasons that the letterpress has declined in use. It is still used for corrugated carton printing, imprinting, and numbering. Four types of presses were used: platen, flatbed cylinder, rotary, and belt. Letterpress is making a comeback in specialty printing using photopolymer plates and UV inks on narrow web presses.

Relief-Flexography

Flexography is a form of rotary web relief printing like letterpress but using flexible rubber or resilient pho- topolymer relief plates, and fast-drying low-viscosity, solvent-based, water-based, or UV-based inks fed from an anilox inking system (rollers with many cells in them to facilitate ink delivery). Most flexographic presses are webfed in three basic approaches: stack, in-line, and central impression cylinder presses. Almost any material that can go through a web press can be printed by flexography—decorated tissue, plastic bags, pressure sensitive labels, corrugated board, and materials such as foil, cellophane, polyethy lene, and other plastic films. It is well suited for printing large areas of solid color with high gloss and brilliance. The growth of flexography parallels the expansion of the packaging industry, especially flexible packages. Development was based on the central impression cylinder press, laser-engraved ceramic anilox ink metering sys tems, laser-imaged photopolymer plates, and water-based and UV inks.

Intaglio-Gravure

Gravure image areas consist of cells or wells etched or engraved into a copper cylinder, while the unetched surface of the cylinder represents the nonprinting areas. The image cylinder rotates in a bath of ink. The ex- cess is wiped off the surface by a flexible steel doctor blade. The ink remaining in the thousands of recessed cells forms the image by direct transfer to the paper as it passes between the plate cylinder and the impres- sion cylinder. Three types of processes are used for making gravure printing cyl inders: (1) chem ical etching produces cells of the same size or area with varying depths; (2) elec tro mech anical en graving produces cyl inders with cells that vary in area and depth; and (3) direct digital laser etching pro duces cells of vary- ing area and depth. Gravure printing produces excellent reproductions of pictures, but slightly ragged type. The high cylinder-making cost usually limits use to very long runs. The use of halftone and film-less gravure has reduced these costs and made gravure competitive in certain shorter run markets. Gravure is used for long runs of newspaper supplements, circulars, magazines, catalogs, as well as special products such as wall paper and packaging. Cylinders can be reused many times. Many magazines and catalogs are hybrid publications—part gravure and part lithography. The long-run editorial sections are gravure and the short-run geographic, demographic, and advertising sections are printed with offset lithography. All pages are then as- sembled in automated bindery systems.

Porous—Screen Printing

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Formerly known as silk screen, this method once employed a porous screen of fine silk, nylon, dacron, or stainless steel mounted on a frame. Many materials are now used to make the stencil, which is produced, manually, photomechanically, or electronically. Printing is on a wide range of substrates under the screen by applying ink with a thick consistency forced through the fine mesh openings with a rubber squeegee. The pro- duction rate, once limited by the drying time of the ink, has been in creased by the development of automatic presses, im proved dryers, and new UV inks. Most presses are flatbed. Rotary screen presses speed up pro- duction considerably because they allow continuous operation. Screen printing usually can be recognized by the thick layer of ink and is used for fabric, apparel (especially T-shirts), signage, and specialty materials.

Lithography, letterpress, flexography, gravure, and screen printing account for the majority of all reproduction on paper and special substrates; however, digital printing processes are making rapid inroads because of their ability to more effectively handle very short runs and variable information printing.

Digital Printing Processes

Copying and digital duplicating are also called reprography or reprographics. For fewer than 100 copies, the copier has been the fastest and most economical method of reproduction—if only hard copy originals are available. Above 100 copies, highspeed copiers and/or duplicators are used, but these are now mostly digital printers and can accept hard copy or digital files. Reprography is used extensively by in-house printing de- partments and quick printing shops. The only method for making copies of documents before 1940 was the photographic print called a photostat, that was time-consuming, and expensive. In the 1950s the 3M Ther- mo-Fax used heat to make copies. The Xerox 914 in the 1960s was the first to introduce plain paper copying using electrophotography (toner). Subsequently, a number of photocopying systems were developed, such as photo-based diffusion transfer processes that were popular in Europe. Electrophotography (toner) has domi- nated the copier market, but inkjet printing is making inroads.

Electrophotography, also called xerography or electrostatic printing, is based on electrostatic transfer of toner to and from a charged photocon-ductor surface. Copiers use electrophotographic coatings such as selenium, cadmium sulfide, zinc oxide, or organic photoconductors to produce the images in the copier. The photocon- ductor converts light energy (photons) into electrical energy (electrons). These coatings are charged with a corona discharge in the dark and lose the charge on standing or when exposed to light, such as that reflected from the white areas of an original or by a laser or other light source. The image areas that remain charged are developed with an oppositely charged dry powder or liquid toner and are transferred from the electropho- tographic surface onto plain paper using electrostatic attraction. The electrophotographic coating is cleaned and can be re-imaged many times. Color copiers use similar principles but they have four or more colored toners rather than one. The term digital press implies a higher level of operating speed and capability for pro- duction applications.

Copiers are no longer manufactured as such. The function of copying a hard copy original is now performed by multifunction printers (MFPs). These devices incorporate a scanner, a digital printer, and a Digital Front End (DFE) to accept files. They can scan, print, fax, and copy. Fewer and fewer copies are made as more and more files are sent to these devices for printing. MFPs may be black-and-white (also called monochrome) or full color. Printers theoretically produce originals, and copiers produce copies—but the term copy is used in both cases.

Duplicating

Before copiers and digital presses, copies of pages in quantities from 50 to 5,000 were produced on offset lithographic duplicators. There were offset presses in sizes up to 12 by 18 inches (A3+). The offset duplica-

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tor was the mainstay of the printing industry and allowed many entrepreneurs to start printing companies. Copier/duplicators were once small offset presses with online polyester plate-making. Over time they became high-speed copiers that “photographed” paper originals, and today they are digital printers. Stencil and spirit duplicators are based on the mimeograph that was invented by Thomas Edison and marketed by Albert Blake Dick. They work by forcing ink through a porous stencil and produce copies on plain paper. New versions of these printers use digital files to image the stencils.

Digital Prepress

Prepress processes advanced from metal assembly to paste-ups to film. New filmless digital imaging process- es create page images directly on printing plates for conventional printing, or directly on plateless presses from computer files. These are called computer-to- or direct-to-printing processes. The three types of filmless digital printing processes are (1) computer-to-plate (CTP), (2) computer-to-plate-on-press (DI for direct imag- ing), and (3) computer-to-print (digital printing). All categories use essentially the same prepress digital files output from page composition software, page de scription languages, and raster image processors (RIP) to drive the lasers or imaging systems of the marking devices.

Digital Printing

Conventional printing uses plates that contain the text and images to be reproduced in quantity on a mechan- ical press that feeds inks to the plates and exerts heavy pressures to transfer the inked images to paper or other substrate. Digital printers apply copier and new digital technology and use dynamic image carriers. Each cycle of the printer transfers a fresh image to the substrate. It can be the same or different than the previous image. This feature makes it possible to print variable information from print to print, which conventional print- ing cannot do. It also allows electronic collation which assembles all pages of a publication in order. Digital printing is used for short-run, on-demand printing (print immediately), but the speed for larger and longer-run documents is slower than plate processes.

Digital printing began in 1970 with the introduction of inkjet printing, followed by electrophotographic (EP) laser printers in 1978; color electronic laser printers in 1993; and many EP and inkjet color printing presses introduced since 1995. Other digital printing technologies are Magnetography, Thermal Transfer, Thermal Transfer Dye Sublimation, and Inkjet printing.

Printing today is digital in some manner and all printing technologies accept digital files. Static printing uses an image carrier (plate or cylinder) that makes every impression exactly the same. Digital printing refers to any printing process that does not use a fixed-image image carrier (a plate, for example). The process is based on the regeneration of printed information for each and every impression of a particular job. Toner, sol- id ink, and inkjet (in all its forms) are considered digital printing. DI printing (imaging plates on-press) or CTP (imaging plates off-press) are digital in nature, but not digital printing. Over time, offset lithographic plates will be imaged on reusable image carriers on-press and the age of “plateless” conventional printing will begin.

Computer-to-Print (EP) Systems

All purely digital printing systems accept digital files and thus become computer-to-print digital printing sys- tems. They may use electro photographic photoconductor, inkjet, ion- or electron-charge deposition, magne- tography, thermal transfer, and thermal dye sublimation technologies, among others. They are called variable data printing systems because each impression is regenerated and can then include personalized information

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from a database. Each impression is an original. A copier makes a second-generation copy.

A modern roll-fed printing press used in the production of newspapers.

Source:http://iStockphotos.com/fotogaby.

Magnetography and electron deposition printing use special magnetic toners to produce the printed images. In these processes, there is less need for heat to fuse the toner, and thus a wider array of papers may be used, especially when litho is used for pre-printing.

Thermal transfer uses thermal print heads that melt spots of dry thermoplastic ink on a donor ink ribbon and transfer them to a receiver to produce color labels, logos, wiring diagrams, bar codes, and other similar prod- ucts. Thermal dye sublimation printers are like thermal transfer printers except the inks on the donor ribbons are replaced by heat-activated dyes. The thermal head converts the dyes to gas spots that condense on the receiver.

Inkjet systems use jets of ink droplets driven by digital signals to print directly on paper or other substrates. The first plateless digital printing system was an inkjet imager introduced in 1970. Two types of inkjet systems are in use:

• Continuous inkjet (CIJ) • Drop-on-demand (DOD)

Continuous inkjets are used for direct mail and transactional printing, digital color proofing, and variable infor-

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http://istockphotos.com/

mation on-press color printing systems at speeds up to 1,000 feet/minute.

Drop-on-demand inkjets are divided into Thermal, Piezo, and Solid Ink/Phase Change digital printing sys- tems.

Thermal inkjet uses heat and piezo inkjet uses pressure to create droplets of ink.

Solid ink begins as a solid and is melted to produce drops. Inkjet systems are rapidly gaining in use, especially since new inks have been developed with light- and water-fastness properties for printing on different sub- strates. There are also large format web-fed and flatbed printing systems used for producing displays, murals, outdoor exhibits, posters, and paneled billboards. Water-based (aqueous), solvent, and UV inks are used de- pending on the printer type. Early water-based inkjet inks used dyes; today many use pigments.

Press Configurations

Printing presses and digital printers are either sheetfed or roll-fed (also web-fed and continuous feed). Sheetfed presses are used for commercial printing where lightweight and heavyweight paper stocks can be easily changed. Roll-fed presses are used for printing longer runs on lighter-weight stocks for magazine, cat- alog, and newspaper publications.

Presses and printers are further categorized by the sheet size (40-inch presses can print eight pages on one side of the sheet at one time) and roll-fed presses use the width of the roll and the cut-off in defining size. Most publication roll-fed presses cut and fold the paper into units called signatures that contain 4 to 64 pages. Most packaging roll-fed presses are roll to roll.

The printed newspaper is facing many challenges—from electronic readers and distribution to blogs and mo- bile news access. As print circulation declines and page sizes shrink, newspaper printing is projected to move to digital printing (toner, inkjet, and other methods). These devices do not use plates that print many copies of the same content. Digital printers allow printing of individualized newspapers with information aggregated for one person. Journalism arose because of the printed newspaper and today extends into television, radio, and the web. But the printed newspaper will metamorphose from a mass-produced publication to one that is more personalized and the technology to produce it is at hand.

• ink • printing • printers • digital imaging • sublimation • engraving • reprography

Frank J. Romano http://dx.doi.org/10.4135/9781412972048.n312 See also

• Automation • Graphics • Layout • Magazine Design

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• Newspaper Design • Type and Typography