Unit 2 Basic Printing Methods

Transferring an image from one material to another is called printing. This process plays an essential role in visual communications.

Printed matter is produced by eight basic processes.

1．Relief or letterpress printing.

2．Gravure or intaglio printing.

3．Planographic or lithographic printing.

4．Screen-process printing.

5．Photographic printing.

6．Heat transfer printing.

7．Xerographic printing.

8．Ink jet printing.

Each process will be described in more detail later. They all can produce printed matter in single color and in full color. The first three methods account for most printed matter produced each year.

Relief or Letterpress Printing

When ink is applied to a raised surface and paper is pressed against the inked surface, the ink is transferred to the paper, Figure 1-2. Relief and letterpress are terms that describe printing methods that use this principle. The rubber stamp is a device that prints by the relief or letterpress method. It transfers ink from a raised surface to paper. Typewriter elements, also print in this way.

Foundry type, Monotype, Linotype, and Ludlow are used by the letterpress printer to transfer letters and numbers to paper, Figure 1-3. The plates of wood cut, wood engraving, linoleum block, and photoengraving can also be used in letterpress printing. Their raised surfaces can print photographs and illustrations as well as letters and numbers.

Relief or letterpress printing is the oldest printing method. Before 1980s, a wide variety of letterpress plates were used on several types of presses to print a rich and varied assortment of products including newspapers, books, and magazines.

IMAGE REVERSAL. As you can see, the principle of printing from a raised surface is not difficult to understand. There is one problem to consider, however. Look at Figure 1-2 again. Note that the shape of the raised surface that printed the letter P on the paper is“wrong reading”or backwards. The raised surface was purposely prepared this way so that it would print a“right reading” image on the paper.

Gravure or Intaglio Printing

Relief printing transfers ink from a raised surface to paper. The gravure process is just the opposite. In gravure printing, ink is transferred from a lowered surface to paper. The image area of a gravure plate is cut below or into the surface of the plate, Figure 1-4.

Intaglio is another name for gravure. Figure 1-4 also illustrates the gravure or intaglio process. The entire surface of the plate is inked and then wiped clean. This leaves ink in the lowered areas of the plate. Paper is then pressed against the plate and ink transfers to it.

Paper is flexible. It can bend and stretch to get into the lowered areas of a gravure plate. Figure 1-5 shows how ink is transferred to the paper.

Karl Kleitsch is generally credited with inventing the gravure process in 1879. In 1894, he developed a press that could print from etched copper cylinders instead of flat plates. Within twenty years gravure cylinders were being used to print a variety of products including a portion of New York Times.

Today both flat and cylindrical gravure plate are used on a variety of presses to print Sunday newspaper supplements, magazines, major mail order catalogs, stamps, and even paper money. Much of our printed fabric is also produced by gravure.

IMAGE REVERSAL. Like the raised image on a relief plate, the lowered image on a gravure plate must also be prepared in reverse. Look at Figure 1-4. Note the shape of the lowered surface that printed the letter P. It is“wrong reading” or backwards. The lowered surface was purposely prepared this way so that it would print a“right reading” image on the paper.

Planographic or Lithographic Printing

To print from a flat surface is also possible.Planographic and lithographic are both terms that describe methods of printing from a flat surface.

Planographic printing is based on the principle that grease and water do not mix. The process works this way. First, a greasy image is placed on a flat plate. The image may be drawn directly on the plate with a grease pencil. It may also be placed on the plate photographically instead.

Next, water is applied to the plate. The water will cover the non-image area of the plate. Water will be repelled from the image area because WATER AND GREASE DO NOT MIX!

The entire plate is then coated with ink. Ink is a greasy substance and adheres to the greasy image. Ink is repelled from the wet areas of the plate because WATER AND GREASE DO NOT MIX!

Paper is then pressed against the surface of the plate and the inked image is transferred to the paper. The process of printing from a flat surface is shown in Figure 1-6.

Planographic or lithographic printing prints from a plane or flat surface, one neither raised nor depressed. The printing image is formed chemically by making some areas of the plate grease receptive and water repellent, while others remain water receptive and grease repellent.

OFFSET PRINTING. Lithographic printing is often called offset printing. Unlike plates for letterpress and gravure (which have their printing surfaces shaped to form the desired image), the printing image on a lithographic plate simply rests upon the plate's surface. The image can rapidly wear away when paper rubs against it during the printing process. This is especially true when the plates are used on high-speed printing presses. To minimize wear the image on the plate is first offset (transferred) to a rubber blanket, Figure 1-7(A). Note that the right-reading image is reversed on the blanket. Figure 1-7(B) shows how the paper receives the image from the blanket. The paper does not make contact with the printing plate. The entire offset lithographic process is diagrammed in Figure 1-7(C).

Alois Senefelder of Germany discovered the lithographic printing method in 1796. He printed directly on paper from a grease image applied to a heavy piece of limestone. Stone lithography is slow and tedious.

Today a wide variety of lithographic plates is used on high-speed offset presses and duplicators to print more products than any other printing method.

Screen Process Printing

Another printing method is to print by forcing ink through openings or holes in a stencil, Figure 1-8. One common type of stencil printing is screen-process printing. This method is also called stencil printing, screen printing and silk screen printing.

STENCILS. The stencil controls what is to be printed. Basically a stencil is nothing more than a thin sheet of paper, film, or other nonporous material with lettering or a design cut through. The lettering or design is right reading, not reversed. Stencils for screen-process printing may be hand cut from paper or film, prepared photographically, or painted directly on the screen.

PRINTING SCREENS. A stencil with open areas representing the desired image must be adhered to a screen. A screen is a piece of woven material, such as silk, nylon, dacron or stainless steel mesh, stretched tightly over a wooden or metal frame. The frame serves as the printing press in screen process printing. A simple printing frame is shown in Figure 1-9.

THE PRINTING PROCESS. Screen-process printing is easy to understand. After paper is placed under the printing screen, ink with a paint-like consistency is applied to the top of the screen. Finally, the ink is spread and forced through stencil openings onto the paper below the screen. This is done by pulling a rubber squeegee over the screen. The screen process of printing is illustrated in Figure 1-10.

The idea of applying decorations to objects by stenciling is very old. Evidence shows that stenciling techniques were widely used in China to decorate pottery and other objects.

Screen-process printing developed rapidly during the early twentieth century. A wide variety of stencil materials has been developed over the years. Today, just about any surface of any shape or size can be printed using screen-process methods.

Heat Transfer Printing

Heat transfer or sublimation printing is not a new process. However, not until recently has the technique grown rapidly. Today, heat transfer printing is used to print fabrics.

Have you ever used a pressing iron to print a novelty design on your T-shirt? If so, you have used heat transfer printing.

Modern heat transfer printing starts with a special ink and, in some cases, special paper. The design or pattern is printed on the paper usually by a gravure process. The paper can be a special thermo-printing type, film coated paper, or a ground wood, clay coated type. Use either sheet or roll stock.

The dried, printed image is placed over the cloth and heat is applied. At about 199℃ the ink goes from a solid to vapor (sublimates). This causes the dyes to go into the fibers of the cloth and color them.

The modern heat transfer printing machine is capable of printing 1000 meters of cloth per hour. A skilled operator is needed to supervise and adjust the machine.

Ink Jet Printing

Ink jet printing is a non-contact printing process. No printing surface such as type, plates made by photographic means, or film is needed.

Copy to be printed is prepared by computer. A minicomputer in the ink jet printer controls ink jets in the printing head. On command, microscopic droplets of ink emerge from the jets to print characters and images.

The printing head is a series of single jets. The most common used printing head has up to 1280 jets spaced at 0.0083 in.

The ink droplets are created in the system. They are either permitted to impact on the moving web of paper, or are deflected into a reservoir when no printing is desired. Deflected ink is reused. Printing is done in one pass of the paper under the ink jets.

The process, as developed by one company, is known as DIJIT (Direct Image by Jet Ink Transfer). However, the most common name for it appears to be ink jet printing. Its greatest use is in direct mail printing, personalized book publishing, addressing system and proofing.

Key Technical Terms

letterpress printing 凸版印刷

Linotype 莱诺机铸行铅

foundry type 手拣铸造活字

Ludlow 拉得鲁标题铅

monotype 莫诺机铸活字

wood engraving 木雕版

wood cut 木刻版

intaglio printing 凹版印刷

gravure printing 凹版印刷

photo engraving 照相蚀刻版

offset press 胶印机

lithography 平版胶印

blanket cylinder 橡皮滚筒

impression cylinder 压印滚筒

planographic printing 平版印刷

blanket 橡皮布

plate cylinder 印版滚筒

dampening system 湿润系统

linoleum block 亚麻油毡板

screen-process printing 丝网印刷

stencil 孔版，镂空版

xerographic printing 静电印刷

Supplementary Reading

New Trends in Media Market

Publication Printing

The biggest part of conventional printing is publication printing, covering almost 50 per cent of the total market of printed products. Common for publication printing is that the publishers are depending on that the consumer pays for every single copy. The publisher has to find the most cost effective way to get as many copies as possible sold to the public.

In printed publications direct printing and material costs generally represent some 10 to 20 percent of the total costs of the product. Depending on how the product is distributed, the distribution costs can be even higher than the printing costs. In the future it will be possible to deliver books, and later also full color magazines, as digital data that can be loaded to an electronic screen, looking like a book or magazine. At least single color text books will achieve the same quality as printed text. For both publisher and consumer this will be a very significant way to produce text information. Full color pictures are still more difficult as they need very big data capacity. In a quite near future this will probably also be solved.

For the publisher this means that the main problem will be to charge the customer for the publications. This will be solved on Internet, CD-ROM and similar digital media. One problem that will remain is that the digital publications are very easy to copy, and even if copying is made more difficult it will be very difficult to prevent pirate copies from entering the market.

Advertising Printing

Advertising printing stands for about 40 percent of the total printing market. For the advertising printing it is typical that the print buyer and the target group for the information are not the same. The print buyer pays the printer and distributor for delivering advertising material to the target group. For the advertising market it is most important to develop distribution channels where the advertisements meet their target groups.

It is known that the increase of TV channels has lead to changes in behavior of the viewers. When the consumer has many commercial channels he tends to change channel when there is a commercial break in the program. This means that the commercial will lose its effect, and at the same time the TV channel will lose its viewer. Thus the increase in TV channels has a negative effect on TV media. The effect of digital TV is not yet seen, but experience with increasing number of commercial channels has affected interest in digital TV negatively. A fact is that in some countries increase in TV channels has led to increasing advertising in magazines and newspapers. A result of growth in the overall advertising market, and of the problems advertisers have to find their target groups on TV, is that advertising printing will continue to grow.

Digital Printing

Digital printing has entered the market during the last years, and significant development in the digital printing technology will happen during the next years. Digital printing today is, however, more to compare with high volume office printing than with conventional printing.

For the reader the digital print is identical to the conventional print. The print is built from ink and paper and seen by the eye in exactly the same way. The big difference is how the print is produced.

In conventional printing the information on the printing cylinder is either on offset plates or gravure cylinders. The prints in a print run are all identical. In digital printing every copy can be different as the information on the printing cylinder changes from one sheet to the next. This means that the press must be programmed and controlled by a computer. The initial programming work is big and the transferring of data to the printing cylinder makes the press significantly slower than conventional presses. Prints can, however, be made on demand, and there is less waste in digital printing.

Digital printing is today most suitable for short runs. In this area it has also generated new printed products, which previously were too expensive to produce. The printing machines are also relatively small and their productivity relatively low.

In the future, however, digital presses will develop, and their speed and productivity will make them competitive with conventional printing. Today they have taken some small jobs from sheet fed offset, but in the future their competitive ability will gradually develop to bigger products. This does not mean that the total volume of printing on paper changes. In the future there will also be combinations of conventional and digital printing. The conventionally printed products will be complemented by digitally printed elements.

When the media market turns digital, the techniques for printing on paper will develop too. Pre-press operations will in the future be totally filmless. The techniques for making printing cylinders will regardless of printing method utilize digital technology. This will reduce make ready times, and make it easier to change the printed information. The use of digital technology makes it possible to produce short runs competitively. By combining different printing methods it will also be possible to make demographic print runs, where every copy is different. This development of conventional printing is necessary to keep it competitive in the future.

Exercise

Q&A

1．List theeight basic printing processes. Describe each briefly.

2．Illustrate major differences among relief, intaglio, planographic and screen-process printing.

3．Describe the basic steps involved in printing from a raised, lowered, and flat surface, and with a stencil.

4．List four kinds of type that are used in letterpress printing and name four kinds of relief plates.

5．Explain why the raised image on type and relief plates and lowered image on gravure plates must be prepared in reverse.

6．Identify the grease receptive and water receptive areas on a lithographic plate.

7．Explain why the image on a lithographic plate is transferred to a rubber blanket during the offset process.

8．Describe three techniques for preparing a stencil for screen-process printing.

9．Describe the function of each of the major parts of a screen-process printing frame.

Complete the Sentences by Filling in the Blanks

1．________ printing is often called offset printing. Unlike plates for ________and________ (which________ their printing surfaces________ to form the desired image), the printing________ on a lithographic________ simply rests upon the plate's surface. The image can rapidly ________when paper rubs against it during the________ . This is especially true when the plates are used on high-speed printing presses. To minimize wear the image on the plate is first offset (transferred) to a ________.

2．Ink jet printing is a ________printing process. No printing surface such as ________, ________made by________ means, or ________is needed.

3．________is prepared by computer. A minicomputer in the ink jet printer ________ink jets in the printing head. On command, ________of ink emerge from the jets to print characters and images.

Put the following into Chinese

Digital printing is today most suitable for short runs. In this area it has also generated new printed products, which previously were too expensive to produce. The printing machines are also relatively small and their productivity relatively low.

In the future, however, digital presses will develop, and their speed and productivity will make them competitive with conventional printing. Today they have taken some small jobs from sheet fed offset, but in the future their competitive ability will gradually develop to bigger products. This does not mean that the total volume of printing on paper changes. In the future there will also be combinations of conventional and digital printing. The conventionally printed products will be complemented by digitally printed elements.

When the media market turns digital, the techniques for printing on paper will develop too. Pre-press operations will in the future be totally filmless. The techniques for making printing cylinders will regardless of printing method utilize digital technology. This will reduce make ready times, and make it easier to change the printed information. The use of digital technology makes it possible to produce short runs competitively. By combining different printing methods it will also be possible to make demographic print runs, where every copy is different. This development of conventional printing is necessary to keep it competitive in the future.