Biermann Ch. Handbook of Pulping and Papermaking

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474 23. PRINTING AND THE GRAPHIC ARTS

This type of ink (such as soy bean oil vehicle) is

used in newsprint, but tends to smudge.

Evaporation of the ink vehicle leaves the

solid ink with rosin esters and metal binders

behind; this is used in magazine and catalog

grades using letterpress or heat—set web offset

printing. To keep heating costs relatively low,

solvents with low boiling points, but not so low as

to be unsafe, are used. The ink further sets by

cooling to ambient temperatures.

Oxidation

drying oil with multifunctional

carboxylic acids and alcohols left on the paper

surface after the vehicle is absorbed into the paper

may promote polymerization. Heavy metals

(cobalt, manganese, lead) may promote oxidation

with atmospheric oxygen.

UV or electron beam radiation curing causes

monomers or prepolymers in the vehicle to form

polymers; it is useful with acrylics. This method

does not have much use with paper, but is often

used for metal and plastic substrates to avoid the

use of large ovens.

Infrared hardening (heat—setting), precipita-

tion of binders, gelation, and cooling of hot

thermoplastic inks used in electrostatic printing

(photocopy and laser printers) are other mecha-

nisms used less often, but are increasing in use.

The use of volatile organic solvents improves

the speed of ink dying; however, more and more

environmental restrictions are being placed on the

use of these materials. Vapors must be trapped

and recovered and incinerated. Also, these mate-

rials have the potential to explode if

the

vapors are

concentrated.

Ink mileage or coverage

Ink mileage is the amount of paper that can

be covered by a certain mass of ink to achieve a

specified print density under operating conditions

of a press. It is measured in English units of

square inches per pound of ink. It is a measure of

the ink requirement and varies with the type of

paper. For example, one manufacturer's black ink

for lithographic work covers 275,000 (square

inches per pound) for uncoated paper; 375,000 for

dull coated; 380,000 for litho coated; and 425,000

for enamel coated. On the other extreme, metallic

or opaque white inks have only about one—half of

this coverage.

Critical

ink

properties

Some of the properties of interest of inks

include viscosity, ink tack, the length of ink,

pigment particle size distributions, avoidance of

particle clumping, opacity, color and color

strength, gloss, and drying rate. Some of these

parameters depend on colloid chemistry, general

opacity and filler theory, color theory, and other

topics discussed elsewhere in this book in regard

to paper. These analogies should not be ignored.

Ink viscosity, ink yield point, and thixotropic

properties are all important properties for ink flow

and transfer rates which are dictated by the end

use.

Nondrip paints containing silicic acid are

good examples of a thixotropic material. The

paint will flow when applied with a brush or

roller, but without this shear force the paint does

not flow. The shear forces break the weak bonds

between particles so that the viscosity decreases

with even minor shear forces.

Ink tack is a measure of the force or energy

required to split a film of ink. In this regard the

ink is like a contact adhesive. If a high force is

required to split a film of ink, it may cause pick-

ing of the paper. (Think of the Dennison wax

pick test of paper.)

The length of ink refers to the length ink can

be drawn out before breaking. (Hot mozzarella

cheese or taffy behaves like a long ink; on the

other hand, a short ink is said to have a buttery

consistency.) Ink length is a function of the

cohesive forces of the ink and other properties.

An example of the suitable properties of an

ink for a particular application is given by Wil-

liams (1985a) for lithographic inks. (As with

paper, tradeoffs must be made between properties

since many contradict each other.)

The requirements are:

Ink in an open container should not form a

skin at the surface.

Ink should remain a liquid in bulk but dry

quickly when on a substrate (paper).

Ink must be able to absorb (dissolve) a small

amount of water without emulsifying.

Ink must dry with a good gloss while being

subject to many processing operations.

Ink should be compatible with a wide range

of papers and other substrates so that ink

INK AND INK APPLICATION 475

changes are not required and compatibility

problems do not arise.

6. High ink holdout gives better gloss and

decreases the amount required.

Suitable tack for widespread use. Low tack

reduces picking, but high tack gives sharper

detail.

8. Ink color must be permanent and consistent

from batch to batch.

Flexography, gravure, and silk screen require

inks of low viscosity where drying is by vehicle

evaporation.

23.11 PAPER PROPERTIES AND

PRINTING

General considerations

Standard sizes for printing (whether

sheet—fed or web—fed) include the form web

(trimmed to

8V2

in. by 11 in.), mini web (trimmed

to 11 in. by 17 in.), half web (trimmed to 17 in.

by 22 in.), and full web (trimmed to 23 in. by 35

in.).

If the machine direction (MD) is parallel to

the long direction, the paper is said to be grain

long; if the MD is parallel to the short direction

the paper is termed grain short.

Paper properties are important for

runnability

and print quality. Runnability is usually more of

a consideration in offset processes than with the

other processes. For example, a high level of

water—soluble components in paper will require

relatively frequent washing of the blanket. Also,

the use of tacky inks and lightweight magazine

papers in web offset printing requires a consid-

erable tension on the paper to pull it through the

press,

with the potential for web breaks.

It seems many printers learn what paper

works well and what paper works not so well by

trial and error. Once some suitable suppliers are

found, they tend to stick with them. A little extra

cost of paper is not a large factor compared to

jht

les

Fig. 23-10. Improper conditioning may cause

wavy or tight edges.

press costs. (Government institutions, however,

are often forced to look at cost of materials direct-

ly and not the overall cost of using a material.

This is a good example of how total quality man-

agement (TQM), if it were practiced, could in-

crease the efficiency and quality of an operation.)

Some aspects of this section cover material

presented in TIS

108-01.

High paper stiffness is

generally an attribute to printing; stiffness is often

lost in papers with high levels of fillers. The

importance of the surface of the paper to resisting

picking has already been discussed, especially in

regard to inks with a high degree of tack (such as

those used in offset or letterpress gloss printing).

Moisture and dimensional stability

If a stack of paper is of appreciably lower

equilibrium moisture content (EMC) than it would

be in the ambient atmosphere, moisture will be

adsorbed, causing

wavy

edges. On the other hand,

if moisture is given off by the paper, the result is

tight edges (Fig. 23-10).

Dimensional stability is an indication of the

ability to resist strain caused by stress or changes

in moisture content. It should be considered in

both the machine direction and cross direction.

Contact with moisture, heating of the sheet to dry

ink, or high stresses required to handle paper

during printing may cause appreciable changes in

the size of paper. Uneven application of these

factors may cause the paper to cockle. Paper may

be kept in sealed containers prior to use to prevent

some dimensional stability problems.

Curl

Curl has been discussed on page 171. Lack

of curl in paper is important, especially in multiple

printing operations such as four color printing.

Changes in moisture content (between conditioned

EMC and EMC conditions in the press room)

often cause paper to curl {atmospheric curling),

although paper manufactured on twin—wire ma-

chines tends to be less prone to curling. Curl

tends to occur around the axis of a cylinder, and

the direction of curl is defined as the concave side.

On single—wire machines, atmospheric curling

tends to occur around an axis parallel to the

machine direction. The direction is toward the

wire side as water is lost and toward the felt side

as water is gained. Mechanical curl is cause by

476 23. PRINTING AND THE GRAPHIC ARTS

Stress whose origin is not from moisture content

fluctuations.

Paper smoothness

Gravure, because of the low viscosity of ink

used in this process, can work well with reason-

ably rough paper surfaces. Even with this pro-

cess,

however, as the resolution of halftones

increases (more points per inch) paper smoothness

becomes more important so that each halftone dot

can contact the surface of the paper to give uni-

form printing. The rubber blanket of offset

printing can conform to surface imperfections to

some degree. Paper smoothness and other prop-

erties in regard to printing quality are often best

approached by making actual prints and using

standardized techniques to evaluate those prints.

Related to paper smoothness and print quality is

paper compressibility.

Papers with some compressibility tend to give

better prints than paper without compressibility,

especially with letterpress. A very smooth

uncalendered sheet gives better printing results

than the same sheet that has been heavily

supercalendered.

Ink receptivity

Ink receptivity is a measure of the amount of

ink that is transferred from the plate to the paper.

The ink receptivity must be high enough to leave

a clear, even print on the paper. A number of

factors (just as in paper sizing and a few additional

ones such as the rate of ink drying) are important.

Smooth paper usually requires less ink for a given

print quality than rough paper due to a lower

surface area and possible lower degree of ink

migration below the surface. Related to roughness

is paper levelness, which refers to evenness of

caliper on a larger scale, above 0.1 in. (TIS 108-

01).

Paper that is somewhat compressible gives a

more even distribution of ink.

The ink—paper sizing relationship is very

important to ink receptivity. As pointed out in

other areas of this book, sizing of paper must

always be considered in terms of

the

liquid against

which paper is sized. Since the sizing characteris-

tics of paper in terms of ink penetrations are very

important, sizing should be considered in terms of

the components and properties of ink.

Ink holdout refers to the tendency of paper to

resist the penetration of ink inwardly. A high

level of ink holdout means the ink remains on the

surface of the paper. When the vehicle of the ink

(which causes a decrease in paper opacity by

filling air pockets that otherwise increase light

scattering) is absorbed too deeply in the paper

strike—through (soakiness is severe

strike—through) occurs; i.e., the ink is visible

from the other side of the paper. In papers where

the vehicle takes a long time to set,

strike—through may appear several hours after

printing.

Printing with a high degree of ink holdout

usually results in a print with higher gloss in the

printed areas. If the ink holdout or receptivity is

uneven, a mottled (uneven) result may be ob-

tained; this is often caused by uneven binder

migration in coated papers (Engstrom, 1994).

Lithography

and

paper properties

Chalking

occurs in lithographic printing when

the ink does not bind well to a coating. It may be

especially profound in the early stages of drying

the ink where the ink can be rubbed off with mini-

mal effort. Snowflaking occurs when water is

present in the printing nip; small (0.0005 to 0.005

in.) white specks may appear in printed areas.

Tinting occurs when small ink particles

appear on unprinted areas in an (otherwise) prop-

erly operating press. One factor that may cause

this is paper coating ingredients that may alter the

surface tension properties of the printing plate.

Emulsification of ink in the press water may also

cause this. Scumming is the same defect with a

cause traceable to the printing process such as

mechanical or chemical degradation of the plates,

improper preparation of the plates, or improper

ink—water balance during printing.

Water sensitivity refers to the weakening of

paper due to press moisture. This may lead to

picking at the surface or paper curling. The ink-

water balance, therefore, is critical in web offset

(lithographic) printing.

Paper

coating,

binders, and printing

Grades in order of decreasing quality include

ultra—premium, premium, #1, #2, #3, #4, and #5.

The latter two are available in roll form only for

PAPER PROPERTIES AND PRINTING 477

use in catalogs and magazines of short life and

may contain mechanical pulp. The highest quality

grades are available in sheet form only.

Engstrom (1994) discusses mottle as a defect

in offset printing of coated paper; this is a com-

mon problem. The coating is usually applied as a

slurry of 45—60% solids containing 10—15 parts

binder per 100 parts pigment (mostly kaolin clay).

The final dry coat is about 10

give?

(7 /xm thick).

Mottle, nonuniform print density, can be caused

by uneven distribution of

the

coating binder on the

surface of the paper due to binder migration

during the coating and drying operation.

Polyvinyl acetate binder in coated paper is

useful for web offset coatings because it is some-

what porous and imparts stiffness in the paper

(useful for improving the stiffness in the cross

machine direction); these properties decrease

paper blistering during printing. Synthetic binders

often have poorer ink receptivity than starch or

protein binders, but give enhanced ink gloss due to

improved ink holdout.

Miscellaneous considerations

Paper used in books and magazines should be

printed such that the binding edge is parallel to the

machine direction on the paper machine so that

pages turn easily and lie flat. The binder used in

coatings decreases the gloss and brightness, so as

little as possible is used. Gravure and letterpress

put much less stress on the coating adhesive than

offset so paper made for gravure will probably

give picking problems when used for offset.

23.12 SPECIFIC PRODUCTS

Glassman(1985) provides technical informa-

tion on this subject, and the U.S. Dept. of Com-

merce (1992) provides statistical information.

Employment and advertising

In the U.S. in 1990, 1.6 million people were

employed in printing and publishing (compared to

700,000 in paper and allied products), a substan-

tial increase over the 1975 employment of 1.08

million. The value of all printed materials was

$157 billion. In commercial printing operations

(which excludes newspapers, periodicals, and

books),

560,000 people earned $14.3 bilUon and

produced $52.9 billion in shipments. Advertising

expenditures were $32.3 billion in newspapers,

$6.8 billion in magazines, $28.4 billion in televi-

sion, and $23.4 in direct mail.

Of course, letterpress was the dominant

method of printing for virtually all products at one

time,

but this method has been replaced in most

applications.

Newspaper

Most newsprint is printed by web offset

(lithography). The ink is usually carbon black in

mineral or plant oil (soybean oil). (The triglycer-

ides of plant oils are much more easily removed

during deinking of recycled fiber than mineral oils

that are straight chain hydrocarbons.) Offset has

the problem of lint from the paper accumulating

on the blanket. The use of twin—wire formers for

newsprint has greatly decreased this problem. The

introduction of special inks and fountain solutions

have also helped mitigate this problem.

A few newspapers with large circulations,

especially on the west coast of the U.S., use the

flexographic process with water—soluble inks.

This process has the disadvantage that the news-

print is very difficult to recycle. The problem is

that the ink vehicle allows the carbon particles to

disperse easily in water giving a very dark suspen-

sion. This water is difficult to clean or to treat as

effluent.

In the U.S. in 1990, 443,000 people were

paid $10.41 billion to produce $36.6 billion in

newspapers using $8.09 billion of materials. In

1992 there were 11,339 newspapers (of which

1755 were daily with a total circulation of 62

million). Most newspapers are published weekly.

Magazines and periodicals

Magazine papers are often machine coated

with clay and possibly small amounts of calcium

carbonate and titanium dioxide and supercalen-

dered. Increasing amounts of mechanical pulp are

used in these papers. Lightweight coated papers

are being used to larger degrees due to high postal

costs.

Brightness, opacity, blister resistance, and

folding properties are very important in these

papers.

Web offset is widely used for magazine

papers. Gravure accounts for a little under half of

magazine production. It is used for the largest

print runs (like the National Enquirer) or moderate

478

23.

PRINTING AND THE GRAPHIC ARTS

sized jobs where high—quality color reproduction

is desired. In 1994, R.R. Donnelley and Sons,

Inc.

controlled about

45%

of the magazine gravure

market, which accounted for about 20% of maga-

zines printed. Gravure has a long tradition of use

in Europe, but this is changing.

In the U.S. in 1990, 115,000 people were

paid $3.66 billion to produce $20.4 billion in

periodicals using $6.58 billion of materials. In

1992 there were 11,143 periodicals of which 466

were weekly and 4326 were monthly.

Books

Books represent an area where factors outside

printing influence printing methods. (Too, with

periodicals postage costs and regulations play an

important role in how products are printed.)

Many book publishers print short runs because

they do not want large inventories of books on

hand. (This is a trend of

TQM,

to limit inventory,

and, in some cases, inventories are taxed by gov-

ernments.) Most books are printed by offset, but

flexographic printing is commonly used for paper-

back books.

Every year about 40 to 50 thousand new

books or new editions of books are published in

the U.S., not including government publications

and certain other categories. In 1990, the overall

average retail price of a hardcover book was

$39.91.

Mass market paperbacks averaged $4.47,

while trade paperbacks averaged $16.60.

In the U.S. in 1990, 74,000 people were paid

$2.30 billion to produce $15.3 billion in books

using $4.47 billion of materials.

Packaging

Much of the flexographic printing that is

carried out is applied to packaging. It is applied

to bags, milk cartons, and corrugated boxes.

Lithography is used for short press runs requiring

high—quality pictures or print, while gravure is

used in long press runs for the same purpose.

Sheet—fed paper for offset printing

Sheet—fed paper for offset printing is the

most difficult grade of paper to print. The de-

mands on this grade of paper are quite high.

Plain paper copiers

Plain paper refers to the fact that special

coatings are not required as in earlier forms of

office copying methods. The paper for this pro-

cess must be able to withstand the high heating

required to set the toner without curling, which

would otherwise cause paper jamming.

Other papers

Other papers that are printed have special

uses but low levels of production. For example,

consider butter wrappers that must be greaseproof

or soap wrappers that must be alkali resistant.

23.13 COMPUTERS AND PRINTING

With the advent of personal computers, many

people are able to do their own printing by

"desktop" or "micro" publishing. The publishing

industry tends to use Apple computer products

(especially Macintoshes) more than IBM compati-

ble types. The former have been designed for

graphical interfaces from the beginning. Many of

the programs are available for either environment.

Computers are involved in every aspect of

printing from prepress to press control. They

offer the ability to decrease turnaround time from

when the customer submits a job to when the job

is completed. Inventories of printed materials can

be greatly decreased or entirely eliminated in

certain cases. Printing of regional editions of

documents is much more easily accomplished and

new stochastic imaging techniques are now made

possible by computers. The best—selling products

(in 1994) are mentioned as examples.

Most people now use word processing pro-

grams (such as WordPerfect or Microsoft Word)

for routine typing and moderately high level page

layout. (WordPerfect 5.1 was used to produce the

final copy of this book.) Page layout programs

(such as Aldus PageMaker or QuarkXPress)

represent the next step of sophistication for page

production; they are designed to bring text and

graphics (such as those produced on the programs

mentioned below) together on the page(s).

Illustrations are made with programs such as

Adobe Illustrator, Aldus FreeHand, or Corel

Draw. Images (photographs) can be manipulated

with programs such as Adobe Photoshop (about

90%

of the market) or Aldus PhotoStyler. Aldus

Persuasion is used to make slide presentations.

The computer can now take the digitalized

layout and directly make a negative for a plate.

COMPUTERS AND PRINTING 479

This bypasses the tedious steps of making films,

assembling films so that the plate can be made

(stripping), and blue—lining the film proofs. Also

the chance of transcription mistakes is greatly de-

creased. Trapping of a document can be accom-

plished by Island Trapwise or Aldus TrapWise.

Imposition software (Aldus PressWise, Impostrip,

or QuarkXTensions) allows one to lay out pages

from one or more documents to form signatures

(groups of pages to be printed together on a single

sheet as described briefly in the section on bind-

ing).

In the fixture, complex printing plates will

be made directly from the computer.

Possible pitfalls

The use of computers does come with some

potential pitfalls. There is a tendency to over-

design one's product. For example, the wide

choice of fonts occasionally detracts from the

product. Consider the examples in Fig.

23-11.

More information on fonts and types is contained

in this chapter's appendix. The use of numerous

fonts often makes the final work look like the

format used in "ransom notes" (kidnappers some-

times use words removed from a wide variety of

printed matter to "write" ransom notes).

Furthermore, it is easy to design many

special effects on computer screens, but one

should still have some knowledge of printing, or

work with a printer, to produce the final product.

For example, if small text is placed on top of

metallic paint, the text may rub off the final

product because ink does not adhere well to

metallic paint.

Unless one is using an entire system by a

single manufacturer (read proprietary and very

expensive) designed for accurate color reproduc-

tion, the color results one observes on one's

screen will not be the same as the final output.

Each computer monitor is different and subject to

color alignment and calibration. Computer moni-

tors use the RGB color system, and printing uses

the CYMK color system; the sets of colors these

two methods can achieve are different.

PostScript

PostScript is a computer language (as are

Basic, Fortran, C, and Pascal) that is used for

page description to control computer printers. It

is another example of a big company making a big

mistake because they thought "they knew the

market and nobody was interested in this technolo-

gy." A group of people interested in this technol-

ogy defected from Xerox, who did not have

interest in this technology, in 1982 to begin devel-

opment at Adobe Systems. In 1985, the first

printer to use this was commercially available.

Since PostScript is a set of protocols, it can

be run on any printer that supports the protocol.

Its operation becomes transparent to the user; that

is,

one does not need to know anything about it in

order to achieve good results with it. PostScript

files use the file extension filename.eps to desig-

nate their purpose; eps is an acronym for Encap-

sulated PostScript. A printer controller, a raster

image processor (RIP), converts the PostScript file

into the final product, whether a printed piece of

paper from a laser printer or an imagesetter. An

imagesetter is a very high quality printer capable

of 1200—5000 dots per inch. They use inks, not

toner particles as in laser printers. They are

available at prepress service bureaus.

PostScript has the advantages that it provides

high text and graphics quality. Many typeface

choices are available, and it is device (printer)

independent. PostScript uses the CIE color model.

Digital imaging technologies

Digital imaging technology not only increases

the speed of many production steps, it allows

many new capabilities. The data for a print job is

entered into the computer, the data is processed,

and the results are printed to photographic film,

paper, or to a printing plate.

Text data is entered directly from a keyboard

or storage device.

Scanners

are devices that allow

images to be stored in digital form. These images

can be photographs or artwork, for example.

IT IS SMART TO BE

THRIFTY

Fig.

23-11.

The careful use of fonts adds to the

message, the overuse of fonts detracts from it.

480 23. PRINTING AND THE GRAPHIC ARTS

Because of the large amounts of data involved,

storage devices such as compact disks (CDs) are

often used to store the digital information. A

compact disk stores 600 Mbytes (a byte is 8 bits

and a bit is the smallest unit of storage consisting

of a variable that is 0 or 1). An image with 256

shades of color on a 1000 by 800 pixel matrix

(SVGA computer screen) uses 25.6 Mbytes of data

and begins to provide the quality of a small photo-

graph. Photographic CD systems developed by

Kodak use 18 Mbyte images that (using computer

algorithms) compress images to 6 Mbytes in

digital form, allowing about 100 images per CD.

Color images should be scanned with a

resolution of 300—1200 dots per inch, while black

and white material should be scanned at 1000—

1200 dots per inch. The human eye—brain system

gets more of certain types of information from

black and white images than from color images.

For example, night vision is black and white.

Scanners are also used to "read" printed

material so that manual keyboard entry of already

printed text is not required. The digital image is

converted to text data by the use of

optical

charac-

ter recognition (OCR). Various OCR software

programs have various levels of reliability and can

handle certain fonts and font sizes.

Once the data is entered into the computer,

the data is processed. The main categories of data

processing include manipulation of individual

images and page layout. For example, an object

in a photograph can be separated from its back-

ground, put on a new background (or foreground),

and modified to remove imperfections in ways that

were essentially impossible a few years ago.

The results must be printed. It is desirable to

be able to do this to check the layout, color rendi-

tion, and other aspects of the job, but high-quality

color printing still requires an expensive printer.

Examples of good

communication

When Hewlett—Packard was developing and

marketing Inkjet printers, they provided about 20

paper companies (after signing secrecy agree-

ments) samples of their ink in bulk so that compa-

nies could develop papers that would work well in

their printers. This allowed the paper manufactur-

ers to tailor their products to meet this niche. The

result is that paper companies sold more paper and

Hewlett—Packard sold more printers.

Examples of poor

communication

When Perfect Binding was introduced in the

late 1970s, the manufacturer of the binding ma-

chine suggested that print shops leave the glue pot

heated so that binding could be immediately

carried out as the need arose. If only occasional

binding was done, decomposition of the adhesive

occurred and a binding job which did not last long

resulted. After several years, the manufacturer of

the adhesive learned of this problem and indicated

that of course this would happen and one should

not leave the adhesive pot heated unless the bind-

ing machine is being used. Since that time the

overall quality of Perfect Binding has increased.

When many fine—paper mills went to alka-

line papermaking with calcium carbonate fillers,

the characteristics of their papers changed drasti-

cally. For instance, many offset fountain solutions

are considerably acidic and the alkaline paper can

change the carefully balanced chemistry of the

ink—water balance of an offset press. Many

paper vendors did not know or did not care that

their products were suddenly different, and many

printers had serious problems because this change

was not communicated to them ahead of time.

23.14 BEWERY OPERATIONS

Bindery operations include anything that must

be done after printing in order to complete the

printing job. It includes perforation, scoring and

folding (Fig. 23-12), signature formation (Fig. 23-

13),

cutting and trimming, collating, drilling or

punching holes, binding, packing, counting,

storage, and transportation. These operations may

be in—house or out—of—house. Many business

specialize in binding operations.

Scoring

Scoring is the formation of a crease by

folding paper around a rounded edge before the

actual fold. It is carried out when precision

folding is required, when folding stock thicker

than 5 mil, or when folding coated stock.

Perforation

Perforation of straight edges in one direction

can be accomplished off press using a knife that

alternates with sections of sharp edges and blunt

portions. More complicated perforations are

carried out on the press.

BINDERY OPERATIONS 481

4-page

6-page

letter

6-page

accoraian

8-page

parallel

8-page

French

8-page

map

8-page

gate

8-page

accoraian

10-page

accordian

8-page

roll

10-page

parallel

12-page

roll

12-page

broadsheet

16-page

broadsheet

16-page

signature

12'page

signature

Fig. 23-12. Some examples of common folds and their terminology. From Getting It

Printed^

revised edition ®1986, 1993 by Mark Beach. Used by permission of North Light Books.

Signatures

Signatures are groups of pages that are

printed together on a single, flat sheet; they are

assembled together for binding. The signature is

formed by cutting, folding, and trimming opera-

tions.

Signatures of 16 pages are common in book

482 23. PRINTING AND THE GRAPHIC ARTS

publishing, but those of 4, 8, 12, 24, and 32 are

often used too (Fig. 23-13). Signatures can be

assembled in nested signatures or gathered signa-

tures,

depending upon the desired binding method;

Obviously the placement of pages during prepress

operations must take this into account. Nesjted

signatures are used in binding by saddle stitching;

otherwise, it is not common.

Cutting

Cutting of a stack of paper, the

lift,

is done

by a sharp, guillotine blade that may cut through

three inches of paper. It is important for the lift

to be help down tightly while it is cut. Even so,

there is some movement, called draw, that leads to

variation of the cut size.

Binding

A wide variety of bindings are available for

attaching sheets or signatures to form the product

(Beach, 1993). They differ in appearance, dura-

bility, equipment requirements, and cost. (Fig.

23-14 shows a binding test machine that turns a

page back and forth to test its anchoring in the

binding.) The main binding methods are summa-

rized in Fig. 23-15.

Case binding

This is considered to be the most durable and

visually pleasing of the binding methods (Fig. 23-

16).

Case binding may be square back or round

back and uses a hard cover (hardbound). The

paper MD should be parallel to the spline for

optimal results.

Signatures are sewn together (Smythe is the

major manufacturer of the sewing machines),

trimmed on three sides, and placed inside the case

of binder boards covered with paper, cloth, plas-

tic,

or leather.

Mechanical binding

Mechanical binding uses wire or plastic

through a series of small holes to hold pages

together as in spiral notebooks. A plastic comb

(GBC is a trade name) and double wire (Wire—O

is a trade name) are two other examples. They

are commonly used in technical manuals, cook-

books, and in—house publications because the

book stays open when set down and the process

can be done aknost anywhere with simple equipment.

Top

" ei

1 ^^

boLiom

\ ^^

\rl

Nested Signatures Gathered Signatures

Fig. 23-13. A 4 page—signature printed on one

side only (top) and a 16—page signature printed

with 8 pages on each side.

Perfect

binding

Gathered signatures can be bound by perfect

binding. The spine is trimmed so that the edge of

each page is exposed. Adhesive is then applied to

the edges and this is glued to the binding. The re-

maining three edges are trimmed after the adhesive

has set. This method is used in paperback books.

The MD of paper should be parallel to the bind-

ing. Some binders reconmiend against the use of

C2S (coated two side paper) if this type of bind is

to be used.

Traditional binding adhesives for perfect

binding are thermal (hot melt adhesives) or cold

glues (polyurethane resin, PUR). Polyurethane

resin is said to offer the advantages of increased

strength, increased flexibility (so books do not

snap shut), and increased recycling efficiency (the

polyurethane does not break up and is easily

removed when the paper is recycled). PUR is

recommended for

lay

flat perfect binding. Poly-

urethane is moisture resistant and it mitigates

gutter ripple; it requires a 24 hour cure time.

Saddle—stitch binding

This method of binding usually uses a staple

that goes from the top to the bottom of the center

of the open work. It requires at least 8 pages and

is expandable in units of 4 pages. It is a quick

and inexpensive binding commonly used for small

magazines, catalogs, brochures, and pamphlets.

BINDERY OPERATIONS 483

Padded

binding

In padding, the edges of loose sheets are held

together by glue as in note pads.

23.15 ANNOTATED BIBLIOGRAPHY

Beach, M., Getting it

Printed,

Revised Edi-

tion, North Light Books, Cincinnati, 1986,

1993 (199 p.) "How to work with printers

graphic art services to assure quality, stay on

schedule, and control costs." This and other

books by the author are easy to read, well

illustrated, reasonably priced, and highly

recommended by many people in the trade.

Blasche, D.W., Methods of cylinder engrav-

ing for gravure printing, Tappi J.

76(8):

169-

174(1993) (no references).

Engstrom, G., Formation and consolidation

of a coating layer and the effect on offset-

print mottle, Tappi J,

77(4):

160-172(1994),

(63 references).

Glassman, A., Ed., Printing Fundamentals,

Tappi Press, Atlanta, 1985, 388 p. This

book gives much detail about the characteris-

tics of various papers used in printing.

Fig. 23-14. Binding test machine.