FTA (изд-во). Flexography: Principles And Practices. Vol.1-6

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122 FLEXOGRAPHY: PRINCIPLES & PRACTICES

ACKNOWLEDGEMENTS

Author/Editor: Patricia A. Cathcart, Polyfibron Technologies, Inc.

Contributors: Paul McGrath, Flexcon

Gary J. Reich, CT Films

Leighton Derr, AET Films

Steve Chilcote, AET Films

Dan Napralla, REXAM Metallizing

Don Voas, International Paper

SUBSTRATES 123

substrate is a material defined

by Webster’s New World Dic-

tionary as “a medium or a sub-

stance which supports anoth-

er; a foundation.” In printing,

the substrate supports the ink

film that carries the message needed to

describe the internal contents of a package

or give an advertised message.

Substrates for flexography are varied,

depending on the end use of the material.

There is almost no material that cannot be

printed by the flexo process – from tiny

paper toothpick wrappers, to plastic cover-

ings for mattresses, to metal foils. A major

challenge for the flexographer is under-

standing the substrate material to be printed

because each has special requirements.

Primary topics covered in this volume

include: an explanation of the different sub-

strates; how they differ in their production;

printing characteristics; and guidelines on

how they need to be handled.

New substrates are always being added,

while existing ones are constantly improved

upon in response to new needs. Substrates

are divided into five major groups:

• Paper and Paperboard

• Corrugated

• Laminates

• Foils

• Films

Some classes of substrates have gone

through further development, driven by

changes in market demand, and the advent

of recycling.

The flexographer needs to be aware that

the materials are usually produced to meet

end-use requirements and not necessarily

those of the printing process. This is begin-

ning to change with the demand for higher

print quality. In some cases specialized inks

need to be used, or the current inks have to

be altered. Drying ovens are necessary in

some cases. In the past 10 years, the use of

water-based inks has become prevalent on

paper substrates and even on some plastic

films.

The objective of this chapter is to educate

the printer about the properties of various

substrates. Information presented is de-

signed to make it possible and convenient

for the printer to ensure that each material

meets its proper specification before, as well

as after, it is printed.

Common materials are listed under the

five main groups. A brief description of the

material manufacturing process is offered.

Comments about the characteristics and

problems associated with the substrate that

are frequently encountered by the flexogra-

pher are provided.

Introduction

aper is one of the oldest sub-

strates used for printing and has

gone through many changes as

materials and environmental

concerns have influenced pro-

duction. It is believed that man

first invented paper about 200 B.C., but the

earliest known record attributes the develop-

ment and production to the Chinese, begin-

ning early in the second century A.D. This

paper was made using bark, hemp and rags

as the chief ingredients.

The Chinese continued to refine their

paper-making skills and developed starch siz-

ing in the second half of the eighth century.

Starch aids in keeping the fibers bonded

together and holds the ink out at the surface

to prevent blurring the printed image. The

development of paper with sizing was con-

tinued in the Middle East and later in Spain

and in Sicily. Most paper was made by hand

until the 18th century when the Fourdrinier

brothers developed the first practical paper

machine.

The Fourdrinier machine formed a contin-

uous strip of paper instead of the single-sheet

production of the hand-made paper. This

innovation facilitated the further develop-

ment of printing presses. A second milestone

was marked though the use of wood pulp for

paper production. Prior to wood pulp, the

chief ingredient in papermaking was rags.

The new plentiful and renewable ingredient

supported increased large-scale production

to meet the rapidly growing demands for

printed material.

As more people were educated, the

demand for knowledge grew. The rising read-

ership of newspapers and books resulted in

other new developments: advertising and

mass distribution. These in turn necessitated

new methods for wrapping and packaging

merchandise for delivery to consumers.

MANUFACTURING PROCESS

Paper can account for anywhere from 40%

to 60% of the cost of a final printed job, so it

is important to understand the manufacturing

process. The original Fourdrinier invention is

still in use today on most paper machines.

Every piece of equipment can be broken

down into three sections: the wet-end, the

press section and the drying section.

From the wet end, or headbox, a dilute slur-

ry of fiber and additives consisting of about

99% water is deposited onto an endless mov-

ing wire where most of the water is drained

away. Further water is removed by perforated

suction boxes beneath the wire.

The fragile wet web is transferred to the

press section where a supporting wool or

synthetic fabric felt passes the paper through

wringers and suction rolls to the drying sec-

tion. There, heated cylinders reduce mois-

ture to the desired finished level. Paper

caliper and surface smoothness are estab-

lished by passing the web between a calen-

der stack of steel rolls. Finally, the paper is

wound onto a huge reel at the dry end of the

paper machine.

Additional steps might include adding pig-

mented coating(s) to one or both sides of the

web, rewinding to remove defects, slitting the

master reel to the desired roll width and

diameter, or other post-production enhance-

ments. Figure

shows the wet end of the

paper machine.

SUBSTRATES 125

Paper and Paperboard

At the wet end a paper

manufacturing process,

a dilute slurry of fiber

and additives consisting

mostly of water is

deposited onto an

endless moving wire

where most of the water

will be drained away.

126 FLEXOGRAPHY: PRINCIPLES & PRACTICES

The ideal printing paper would be one that

has identical characteristics on both sides.

Paper traditionally has had a characteristic

two-sidedness, or top side of the sheet,

known as the felt side, and the bottom of the

sheet, or the wire side. The difference

between sides could be determined visually

by means of the screen mark left on the wire

or bottom side during sheet forming.

Newer paper machines with twin wires

make the two-sidedness less apparent. The

two-sidedness is most apparent in the differ-

ence in ink receptivity due to the inconsis-

tencies in the concentration of “fines” or

small fibers and fillers. The felt side is more

closed because the fillers are concentrated

on the top of the sheet, while the wire or bot-

tom of the sheet is more open due to the

drainage of water through the fibers forming

on the wire. The use of retention aids and

newer machines have helped to eliminate

some of the top-to-bottom differences in

mechanically produced paper.

Production of Wood Pulp

There are four main types of pulping meth-

ods: mechanical, chemical, semichemical

and thermomechanical.

In the mechanical or groundwood method,

logs are pressed against huge revolving

grindstones to defiber the wood, and the

pulp is flushed from the stones with streams

of water. This pulp is made up of short, stiff

fibers which have little strength properties.

Paper made from this pulp is the least expen-

sive because none of the lignin, resins or

impurities have been removed and as a result

the paper will darken very readily. Newsprint

is a common example of a high groundwood

paper but even this product needs the addi-

tion of longer, chemically treated fibers to

provide sufficient strength for processing in

high-speed printing presses and folders.

Chemical processes for producing wood

pulp provide papers that are stronger and

more impurity free than the groundwood

process. Continuous batch digesters produce

papers that are more permanent. There are

two types of chemical pulping, sulfate (or

kraft) and sulfite. The sulfate process yields a

wider variety of products which are stronger

than those from the sulfite process. Hence,

the sulfate process is more commonly used.

Semichemical pulps are sometimes used in

varying proportions with chemical fibers to

provide bulk or other desirable combinations

at the lowest cost. All chemically separated

fibers are longer, stronger and free from the

resinous contaminates in the wood itself.

Papers with no groundwood fibers are

known as “free sheets” (groundwood free).

Free sheets are used for business papers,

D E F G

A Headbox

B Wire

C Breast Roll

D Tube Rolls

E Foils

F Wet Suction Boxes

G Dry Suction Boxes

H Felt

I Paper

J Couch Roll

K Tension Rolls

forms, envelopes and book grades.

The newest types of pulping are thermo-

mechanical (TMP) and bleached chemi-ther-

momechanical (BCTMP). Mechanical pulp-

ing causes damage to the fibers that results in

fiber bundles and requires the addition of

chemical pulp to provide strength. Thermo-

mechanical pulping produces groundwood

with a better yield and higher strength. This

pulp can be used for newsprint without the

addition of chemical pulp.

After pulping, the fibers are bleached with

a variety of chemicals such as chlorine, chlo-

rine dioxide or sodium hypochlorite. The lat-

est bleaching technology involves the use of

oxygen with the chlorine. Bleaching re-

moves color caused by lignin and other

impurities that can affect the quality of the

paper. Bleaching does reduce the strength of

the fibers. The last step is refining or beating,

which frays the fibers and improves their

ability to bind to one another when a sheet is

formed.

Paper Fibers

Paper can be described as a mat made

from a combination of hardwood and soft-

wood fibers, the blend of which is deter-

mined by the desired finished product

requirements (Figure

). Softwood fibers

are longer and add strength to the paper

while the shorter hardwood fibers fill in the

voids between the long fibers and give

greater smoothness. Depending on whether

strength and economy or appearance and

printability are the criteria, different combi-

nations of fiber blends will be used.

Colored papers are produced by the addi-

tion of dyes to the slurry in the stock prepa-

ration section or headbox (wet end of the

paper machine) prior to the wire. These

papers are expensive and must be made in

large quantities due to the expense of paper

machine changeovers.

Today, due to warehousing costs, the con-

cept of “just-in-time” inventory is popular.

White paper can be inventoried and, as need-

ed, can be tinted on the felt and/or wire side

using flexography in line to produce the

desired quantity of colored paper or board.

Recycled Fiber/Paper

The use of wood fiber made paper produc-

tion inexpensive process. A side effect of the

paper industry’s enormous production capac-

ity was the solid-waste crisis of the late 1980s.

Paper is the most abundant item in landfills.

Although paper is biodegradable, this process

does not happen quickly. The problem is that

existing landfills are closing every day. It was

estimated in the 1980s that 50% of these land-

fills would close by the year 2000. To resolve

this problem, paper is now recycled.

Recycled paper is manufactured according

to United States Environmental Protection

Agency (EPA) guidelines. The guidelines are

not specific for each paper and can include:

• mill broke, which is paper waste gener-

ated in the paper mill prior to the com-

pletion of the paper making process;

• pre-consumer, which includes convert-

ing waste and trimmings prior to fin-

ished product; and

• post-consumer waste (or paper that has

been printed and de-inked before use).

Paper made from recycled fiber does not

SUBSTRATES 127

The magnified view

of paper shows the mat

combination fo hard-

wood and softwood

fibers. This blend

determines the desired

finished product

requirements.

128 FLEXOGRAPHY: PRINCIPLES & PRACTICES

differ very much from that made from virgin

fiber. Some characteristics like formation,

smoothness and opacity can be improved

due to increased pliability of de-inked fibers.

Brightness can suffer, but this can be

improved with the addition of virgin fiber

and optical brighteners. Recycled papers

print comparably to virgin paper with the

added bonus that they tend to curl less and

have greater dimensional stability.

Fillers

Paper contains non-fibrous materials

called fillers. Fillers such as clay, titanium

dioxide or calcium carbonate are added to

modify absorbency, hardness, smoothness,

printability, durability, weight and handling

characteristics of paper. Binders like gum,

methyl cellulose, starch or resins are added

to help hold the fibers together, to increase

stiffness, and to reduce dust and lint. Papers

need fillers to produce higher ink holdout

resulting in less dot gain since, the ink can

be kept on the surface and not be absorbed

into the fiber’s structure.

PAPER PROPERTIES

There are no obvious distinctions in the

definition between paper and paperboard.

The major difference lies in the caliper.

Generally, papers are either coarse or fine.

Coarse are the kraft papers, and fine are the

bleached, smoother papers.

Paper is classified based on its end use

and the term used for this description is

called grade. Each grade is formulated dif-

ferently so its characteristics are appropri-

ate for the ink that will be applied and the

equipment on which it will be run. Paper per-

forms best when used for its intended pur-

pose, but some papers are considered dual

purpose. A good paper is one that prints and

converts successfully. Finished paper prop-

erties can be broken down into several clas-

sifications:

• structural or mechanical;

• surface finish and appearance; and

• chemical.

These properties apply to both paper and

paperboard. However, the method for their

determination may differ. The following is

meant as a brief definition and does not nec-

Table 18

BASIC SIZE REAM AREA BASIS WEIGHT GRAMMAGE TO

PAPER (IN) (FT

) TO GRAMMAGE BASIS WEIGHT

■ Linerboard 1,000 4.883 0.205

■ Writing, Printing,

Computer, Bond 17 x 22 1299 3.760 0.266

■ Cover 20 x 26 1806 2.704 0.370

■ Cardboard 22 x 28 2139 2.283 0.438

■ Bristol, Tag 22.5 x 28.5 2227 2.193 0.456

■ Paperboard, News,

Wrapping, Bag, Tissue 24 x 36 3000 1.628 0.614

■ Book, Text, Offset 25 x 38 3299 1.480 0.676

■ Index

■ Newsboard 26 x 38 3431 1.423 0.703

Note: All values except paperboard based on a 500-sheet ream.

REAM WEIGHT CONVERSION FACTORS

essarily describe the test method or go into

great detail of the method.

See Appendix A for the listing of TAPPI

(Technical Association of the Pulp and

Paper Industry) test methods according to

substrate type: paper, paperboard and corru-

gated board.

Structural or

Mechanical Properties

Basis Weight. Basis weight is the weight in

pounds of a ream (usually 500 sheets) of

paper at a given sheet size (usually the basic

size for a given grade). These 500 sheets also

represent an area of paper. For example, 500

sheets of 25" x 38" is equal to 3,300 square

feet of paper. Therefore, the basis weight can

be converted to a weight per unit area or

pounds per square foot. Today, due to the

International Organization for Standard-

ization (ISO) requirements, the recommend-

ed expression of basis weight is in grammage

(metric unit of weight). In metric measure,

paper size or area is expressed in square

meters and the weight per unit area is

expressed as grams per square meter (g/m

Table 18 lists some common ream sizes and

their conversion factors to grammage or met-

ric units. For example, a 17" x 22", 20# bond

paper is equivalent to 75.2 g/m

(20 x 3.760).

Table 19 lists some useful conversion values

and Table 20 shows the metric “A” and “B”

sizes.

Bulk. Bulk is another way of describing the

thickness of a sheet. Bulk is also expressed

as the number of pages (two pages per sheet

or the number of sheets multiplied by two)

needed to reach one inch of thickness. It is

an important factor where a volume of paper

SUBSTRATES 129

Table 19

KEY:

lb = pound ft = foot

g = gram in = inch

m = meter in

= square inches

cm = centimeter ft

= square feet

= square meter

= square centimeters

1 lb = 453.6 g

1 ft. = 12 in

1 ft

= 144 in

1 m = 100 cm

= 39.27 in

= 3.281 ft

1 m

= 10,000 cm

= 10.76 ft

= 1,550 in

1 gm= 0.002205 lb

1 in = 0.08333 ft

1 in

= 0.006944 ft

1 cm= 0.1 m

1 in = 0.0254 m

1 ft = 0.3048 m

1 cm

= 0.0001 m

1 ft

= 0.0929 m

1 in

= 0.00645 m

CONVERSION VALUES

Table 20

LENGTH WIDTH LENGTH WIDTH

“A” SIZE (MM) (IN)

A0 1,189 841 46.819 33.106

A1 841 595 33.106 23.410

A2 595 420 23.410 16.553

A3 420 297 16.553 11.705

A4 297 210 11.705 8.277

A5 210 149 8.277 5.852

A6 149 105 5.852 4.138

A7 105 74 4.138 2.926

LENGTH WIDTH LENGTH WIDTH

“B” SIZE (MM) (IN)

B0 1,414 1,000 55.669 39.364

B1 1,000 707 39.364 27.835

B2 707 500 27.835 19.682

B3 500 354 19.682 13.917

B4 354 250 13.917 9.841

B5 250 177 9.841 6.959

B6 177 125 6.959 4.921

B7 125 88 4.921 3.479

METRIC “A” AND “B” PAPER SIZES

130 FLEXOGRAPHY: PRINCIPLES & PRACTICES

will be converted into a product that must fit

into a specified container for shipping. This

is important for books, envelopes and busi-

ness forms.

Burst. Burst is a measure of a combination of

properties, like tensile and stretch, up to the

point of rupture. Burst differs from tensile

strength in that the force used for the failure

is in a circular direction, while tensile is in

one direction only. Packaging paper must

meet minimum bursting-strength require-

ments.

Caliper. Caliper is a measurement of the thick-

ness of a single sheet of paper, paperboard or

combined board measured with a micrometer

under a static load for a minimum specified

time. The unit of measurement is thousandths

of an inch, or mils. Caliper is important

because wide variations can cause the final

print impression to be uneven. Caliper and

smoothness are inversely related. Higher

caliper papers tend to be rougher while lower

calipers tend to be smoother. Caliper affects

both stiffness and bulk. Heavier-weight papers

and paperboard have calipers expressed in

points (each point is equal to 0.001".)

Curl. Curl is non-flat paper caused by changes

in moisture content or physical stress and

may take many forms. Due to changing rela-

tive humidity, and ultimately paper moisture,

stresses in the paper may become unbalanced

and a curl will develop. As a general rule,

fibers expand (contract) about three times

more in diameter than in length with

increased (decreased) moisture. A paper’s

wire side, with a higher concentration of fiber,

is more reactive to moisture changes than the

filler-rich felt side. Reel curl may occur near a

roll core with paper wound too tightly and

take on a permanent set in this position.

Density. Density is the value obtained by

dividing basis weight, expressed as mass per

unit area, by the caliper. Paper that is com-

pact and tightly formed will have a higher

density value.

Dimensional Stability. Dimensional stability is

the ability of a paper to hold its original size

or constant dimension in all directions when

exposed to physical stress or variable mois-

ture. This is a very important property espe-

cially where unit-print stations are used and

more moisture is added by water-based ink

at each unit. Papers with poor dimensional

stability will not hold color-to-color register

and may result in a poor, blurred print.

Folding Endurance. Folding endurance is a

paper’s ability to withstand repeated flexing

or folding and bending. The test is usually

run in both the machine direction and cross-

machine direction of the paper. Government

documents like wills and maps need high

folding endurance. Papers have greater

strength in the cross-machine direction. Pa-

perboard uses a different procedure to mea-

sure this property and the result indicates

the suitability of the paperboard for conver-

sion into folding cartons without a scoreline.

Formation. Formation is the uniformity of the

fiber distribution in the paper. There are a

number of instruments that measure forma-

tion. The higher the number, the more uni-

form the sheet. The values are reported as

flocs (hills) and voids (valleys). Flocs are

densified fiber bundles and voids are areas

with less fiber. Calendering can level out the

surface of the paper but the internal struc-

ture that has the compacted fibers of the

flocs will absorb ink less than the adjacent

voids producing a non-uniform, mottled or

blotchy print. Applying more pressure dur-

ing printing cannot overcome the non-uni-

form or blotchy print since the floc structure

is throughout the sheet and will appear

equally on both sides of the paper. In process

work, the print will appear grainy especially

when working with higher line screens.

Grain Direction. Grain direction is essentially

how the fibers lay or align when they are

deposited on the wire in the papermaking

process. “Grain long” refers to the machine

direction with most of the fibers oriented

somewhat parallel to this direction or the

long edge of a web or sheet. “Grain short”

describes paper or paperboard sheets with

fiber orientation parallel to the shortest

dimension. Grain affects many properties

such as tear, stiffness and fold. Paper expands

when exposed to moisture and most often the

effect will be noticed in the cross-machine or

cross-grain direction. Paper will tear most

readily and is stiffest in the machine direc-

tion. Paper folds most easily parallel to the

grain, but fold strength (number of folds

before tearing) is best across the grain.

Internal Bond. Internal bond is another

method for measuring the failure point of

paper. Unlike burst where the force is equal

in all directions, the internal bond is a mea-

sure along the z-axis. It is an indicator of the

force required to delaminate or split apart

the internal fiber structure when the force is

applied perpendicular to the paper surface.

Porosity. Porosity is a measure of the resis-

tance to air flow through the sheet under pres-

sure. Porosity is an indicator of absorbency

(penetration of oil and water) and hence the

amount of ink that penetrates into the surface.

Porosity also relates to the hardness of the

paper surface.

Stiffness. Stiffness is the flexing resistance of

paper, or its ability to resist an applied bend-

ing force. This property is important in con-

verting operations and requires high values

for sorting and folding applications. High

stiffness is also needed where optical char-

acter readers are used and in envelope man-

ufacturing which requires the transport of

the paper through converting machinery.

Less stiffness is necessary for printing

papers, napkins and paper toweling. Stiffness

increases with basis weight and caliper.

Stretch. Stretch is an indicator of the ability of

the paper to elongate under tension and to

conform to a desired contour. Web tension

must be adequate to form a good roll without

distorting the paper. Web tension on the press

must enable the paper surface to travel at the

same surface speed as the plate and impres-

sion cylinders. Paper stretch is determined

during the test for tensile strength. Paper will

stretch a given amount before failure.

Tear. Tear is simply the resistance of a paper

to tear. It is increased by fiber-refining and is

decreased by most fillers. Good tear proper-

ties are essential for papers like tag, cover,

bond, kraft wrapping and bag. Any paper that

will be subject to repeated handling needs to

have a high tear resistance. Papers are most

resistant to tear in the cross-grain direction.

Tensile Energy Absorption. Tensile energy

absorption, or TEA, is the ability of paper

and board to absorb energy and indicates

durability. Papers like multiwall sack are

subject to repetitive strain and stress.

Tensile Strength. Tensile strength is a mea-

sure of the breaking strength of paper (the

force per unit area required to break a spec-

imen). Strength is determined by the fiber

pulping process and not the thickness.

Tensile strength is indicative of the potential

resistance of a web to break during printing.

Tensile strength is higher in the grain long or

machine direction.

Surface Finish and

Appearance Properties

Brightness. Brightness is a commonly used

industry standard for measurement of blue

(457 nm) light reflectance, usually direction-

al. The standard brightness scale is based on

the reflectance of magnesium oxide, which

is rated as 100% on the brightness scale. The

brightness of a paper will determine the

intensity of printed color. Brightness can be

affected by the addition of optical brighten-

ers that will absorb invisible ultraviolet light

and emit it in the violet to blue region of the

spectrum. Brightness is affected by the

fillers and pigments added during manufac-

ture regardless of the paper color. Lower

brightness is desirable where text is printed

because glare will cause eye strain.

Color. The color of paper, as perceived by the

human eye, is dependent on the light that illu-

SUBSTRATES 131

132 FLEXOGRAPHY: PRINCIPLES & PRACTICES

minates the paper. Paper will absorb some

wavelengths and reflect others. If it absorbs

all the wavelengths of white light while reflect-

ing none, then it will be black paper. Most bril-

liant color reproductions are obtained on

papers with high-balanced reflectance.

Friction Resistance. Friction resistance is

sometimes referred to as coefficient of fric-

tion (COF). The coefficient of friction is

expressed in both static and kinetic forms.

The static term is related to the force

required to initiate movement between two

surfaces. The kinetic is the force required to

sustain uniform movement. This is an impor-

tant property for any printing paper and also

for converting operations. Modifiers like

waxes are added to increase the ease with

which papers will move across each other.

Paperboard cartons, file folders and multi-

wall shipping bags must have sufficient skid

resistance to prevent problems during trans-

port. In some cases colloidal silica is added

as an anti-skid treatment.

Gloss. Gloss is the surface quality of the

paper which reflects light like a mirror and

gives it a shiny appearance. It is measured by

an instrument that illuminates a sheet at a

particular angle (usually 75°) and detects

light reflected at the same angle. It is used for

coated and uncoated paper and paperboard.

The smoother a paper surface, the more light

is reflected in this mirror-like manner.

Printed ink gloss is somewhat dependent on

paper gloss. A 20° measurement is preferred

for high gloss, cast coated, lacquered and

highly varnished papers. Neither method is a

measure of image reflecting quality.

Opacity. Opacity is the property of the paper

that obstructs light transmission. Opacity is

influenced by the degree of fiber refining.

Increased refining increases the fiber bond-

ing and decreases the amount of voids in the

paper reducing light transmission. The use

of fillers in the paper also helps to increase

the hiding power or opacity of the paper.

Smoothness. Smoothness is the surface finish

or texture of the paper’s face and is influ-

enced by the fillers, coating, supercalender-

ing and sizing. There are a number of instru-

ments for determining smoothness, so it is

important to understand which method is

being used and reported. In general most of

the instruments are air leak methods and the

lower the number, the smoother the sheet.

Chemical Properties

Fiber Content. Papers are made primarily of

both softwoods (fibers from conifers or pine

trees) and hardwoods (fibers from decidu-

ous trees that lose their leaves). An appro-

priate combination is necessary to obtain

the proper balance between strength and

surface finish for specific paper grades.

Recycled and reclaimed fibers are also used

exclusively or in part for certain grades of

both paper and paperboard.

Moisture. Papers are manufactured to a spec-

ified moisture content. This moisture will

have a direct bearing on how much ink the

paper will absorb during printing. Papers are

made of cellulose fibers that will absorb or

lose moisture very readily. Handling of paper

before printing is critical because paper

picks up ambient moisture from the air. A

very moist sheet will require more ink and

will need many press adjustments to keep

proper registration. Press rooms need to

Excessive moisture will

cause welts and wavy

edges making further

converting difficult.