Xerox DOCUPRINT 155MX, DOCUPRINT 115MX, DOCUPRINT 115, DOCUPRINT 155 User Manual
Helpful Facts
What You Need To Know!
Paper…
About
Xerox Supplies
Helpful Facts About Paper
September 2004
Xerox Corporation
2004 by Xerox Corporation. All rights reserved.
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Changes are periodically made to this document. Changes, technical
inaccuracies, and typographic errors will be corrected in subsequent
editions.
Table of Contents
Table of Contents
Introduction ....................................................................................................................1
Purpose Of This Guide .............................................................................................................................. 1
Xerox Digital Printing Systems .................................................................................................................. 2
Obtaining Optimum Performance.............................................................................................................. 2
Some Notes On Terminology .................................................................................................................... 3
Paper .....................................................................................................................................................................3
High-Volume, Mid-Volume, Office..........................................................................................................................3
A Note On The Information In This Book .................................................................................................. 3
Making Paper.................................................................................................................. 5
Pulp And Paper ......................................................................................................................................... 5
The Papermaking Process ........................................................................................................................ 6
Sizing .....................................................................................................................................................................6
Cutting And Wrapping............................................................................................................................................7
Boxing And Palletizing ........................................................................................................................................... 7
From Pulp To Printer ................................................................................................................................. 7
Paper and Xerox Printers .............................................................................................. 9
Paper Requirements To Ensure Best Performance.................................................................................. 9
Cost Effectiveness................................................................................................................................... 10
A Word About Vendors............................................................................................................................ 10
Paper Properties and Xerox Printers ......................................................................... 11
Weight ..................................................................................................................................................... 11
Grade....................................................................................................................................................... 11
Brightness................................................................................................................................................ 11
Contamination ......................................................................................................................................... 12
Acid vs. Alkaline Papers .......................................................................................................................... 12
Moisture Content ..................................................................................................................................... 12
Curl .......................................................................................................................................................... 13
Moisture And Curl.................................................................................................................................... 13
Curl-controlled Papers............................................................................................................................. 13
Grain........................................................................................................................................................ 14
Stiffness................................................................................................................................................... 15
Abrasiveness ........................................................................................................................................... 15
Smoothness............................................................................................................................................. 15
Formation ................................................................................................................................................ 16
Whiteness (Shade).................................................................................................................................. 16
Gloss Level.............................................................................................................................................. 16
Caliper ..................................................................................................................................................... 16
HELPFUL FACTS ABOUT PAPER i
Table of Contents
Electrical Conductivity/Resistivity.............................................................................................................17
Porosity ....................................................................................................................................................17
Friction......................................................................................................................................................17
Opacity .....................................................................................................................................................17
Cut Quality/Finished-Product Quality .......................................................................................................17
Packaging.................................................................................................................................................18
Preferred Paper Type For Xerox Printers ................................................................................................18
Preparation for Printing ...............................................................................................19
Proper Storage.........................................................................................................................................19
Stacking ............................................................................................................................................................... 19
Temperature ........................................................................................................................................................ 19
Humidity............................................................................................................................................................... 19
Conditioning Paper...................................................................................................................................20
Follow The Arrow (North America Only) .................................................................................................. 21
Determining Curl ......................................................................................................................................21
Built-in Curl .......................................................................................................................................................... 21
Loading The Paper Tray ..........................................................................................................................22
Storage and Conditioning for Specialty Media.........................................................................................22
Preprinted Materials .....................................................................................................23
Pre-Printing: Best Results and Precautions.............................................................................................23
Use the Right Stock .............................................................................................................................................23
Choose Your Printer ............................................................................................................................................ 23
Make a Clean Cut ................................................................................................................................................ 23
Ink Coverage .......................................................................................................................................................23
Pre-printing and Fusing........................................................................................................................................23
Avoid These Inks ................................................................................................................................................. 23
Varnished and Coated: Use Quickly ........................................................................................................24
Press Fountains .......................................................................................................................................24
Powder .....................................................................................................................................................24
Drying and Packaging ..............................................................................................................................24
Special Stocks ..............................................................................................................25
Recycled Papers ......................................................................................................................................25
Colored Papers ........................................................................................................................................ 26
Coated Papers .........................................................................................................................................26
Carbonless Papers...................................................................................................................................26
Xerographic Roll Stock.............................................................................................................................27
Heavyweight Stocks.................................................................................................................................27
Hole-Punched Paper................................................................................................................................27
Main Problems.....................................................................................................................................................27
Edge-Reinforced Punched Paper ........................................................................................................................27
Perforated Papers ....................................................................................................................................28
Potential Problems............................................................................................................................................... 28
ii HELPFUL FACTS ABOUT PAPER
Table of Contents
Parchment Papers................................................................................................................................... 28
Vellums.................................................................................................................................................... 28
Label Stocks ............................................................................................................................................ 29
Synthetic or Durable Products................................................................................................................. 31
Transparencies........................................................................................................................................ 31
Printer Transparency Requirements .................................................................................................................... 31
Usage Hints For Transparencies .........................................................................................................................32
MICR (magnetic ink character recognition)............................................................................................. 32
Paper Requirements For MICR............................................................................................................................32
Security Paper ......................................................................................................................................... 33
Tabs......................................................................................................................................................... 33
Papers That Are Not Recommended ...................................................................................................... 34
Conductive Papers...............................................................................................................................................34
Papers Containing Talc........................................................................................................................................ 34
Papers Containing Stearate, Or Plasticizer.......................................................................................................... 34
Color Printers and Paper............................................................................................. 35
Selecting Paper For A Digital Color Printer............................................................................................. 35
Post-Processing Considerations................................................................................ 37
Post-Process Equipment and Paper ....................................................................................................... 37
Potential Problems .................................................................................................................................. 37
Wavy Edges.........................................................................................................................................................37
Paper Static .........................................................................................................................................................38
Solving Static Problems .......................................................................................................................................38
Grain Direction and Handling Problems...............................................................................................................39
Grain Direction and Interface Problems ............................................................................................................... 39
About Xerox Papers..................................................................................................... 41
Paper Properties and Paper Performance .............................................................................................. 41
Xerox Quality Assurance......................................................................................................................... 41
The Xerox Standard ................................................................................................................................ 42
Quality Paper .......................................................................................................................................................42
The Recommended Paper ...................................................................................................................... 43
Papers by Xerox ...................................................................................................................................... 43
Appendix A: Paper Handling Capabilities.................................................................. 45
Appendix B: Paper Types and Grades....................................................................... 49
Bond Papers............................................................................................................................................ 49
Rag Bonds............................................................................................................................................... 49
Xerographic Bonds .................................................................................................................................. 49
Offset Papers........................................................................................................................................... 50
HELPFUL FACTS ABOUT PAPER iii
Table of Contents
Multipurpose Papers ................................................................................................................................50
Carbonless Papers...................................................................................................................................50
Recycled Papers ......................................................................................................................................50
Digital Coated Papers ..............................................................................................................................51
Appendix C: Paper Weights and Measures................................................................53
Paper Weights..........................................................................................................................................53
Weight Conversion...................................................................................................................................53
Standard Paper Sizes .............................................................................................................................. 55
Appendix D: Troubleshooting Guide .......................................................................... 57
Troubleshooting Hints ..............................................................................................................................58
Photoreceptor Spots ................................................................................................................................63
Fuser Area Condensation ........................................................................................................................64
Appendix E: Ordering Xerox Supplies........................................................................ 65
Index ..............................................................................................................................67
iv HELPFUL FACTS ABOUT PAPER
Introduction
Introduction
Helpful Facts About Paper will help you obtain the best productivity and
output quality from your Xerox Digital printer. Xerox Digital printers are at
work in business, industrial settings, and commercial print environments
throughout the world.
After your choice of a Xerox Digital printing system, the next most
significant decision you will make is the paper or specialty media to be
used in that system. The output quality and the productivity of the system
rest on your paper/specialty media decision. As you will learn in reading
Helpful Facts About Paper, paper may be plain, but it is never simple and
specialty media comes in a great variety of products. The proper matchup of digital print technology, print application, and paper is essential to
achieving the best possible performance.
Purpose Of This Guide
The purpose of this guide is to assist you in understanding the many
facets of paper and specialty media that affect your digital printing
system. Armed with this information, you will be able to choose papers
that enhance the quality of the output from your system, while maximizing
the throughput.
It is this combination of high quality and high productivity that defines
optimal performance.
• Chapter 1 describes the papermaking process, with special emphasis
on those factors that have the greatest impact on the runnability of
paper produced for use in digital printers.
• Chapter 2 discusses how printing conditions affect paper and dictate
the need for papers that meet certain criteria if jams, improper stacking,
degraded image quality, and other problems are to be minimized.
• Chapter 3 examines a variety of paper properties, including weight,
grade, curl, contamination, acidity/alkalinity, moisture, stiffness, grain,
caliper, smoothness, porosity, opacity, and electrical conductivity. You
will learn what effect each of these factors has on a sheet of paper, and
how some of these factors can be controlled, either by setting certain
specifications for the paper you purchase, or by your handling of the
paper after purchase.
• Chapter 4 looks at many aspects of the preparations for digital printing,
from paper storage and moisture control to proper paper tray loading to
minimize paper curl problems.
• Chapter 5 offers information on preprinted forms—forms that have
unchanging information printed on them from another print technology
such as offset print prior to the time they are introduced into a Xerox
Digital monochrome printing system. This chapter discusses factors
that you and your pre-print supplier need to be aware of about the
paper and ink used for these documents.
• Chapter 6 explains specialty media, from labels and transparencies to
recycled papers and vellum that can be used in many Xerox printers.
• Chapter 7 discusses digital color printing, print applications, paper
requirements, and equipment hints and tips.
• Chapter 8 examines the nature of paper after it has been through the
printer, and the effect that process has on post-processing equipment.
HELPFUL FACTS ABOUT PAPER 1
Introduction
• Chapter 9 focuses on Xerox brand papers and specialty media, and
discusses how Xerox Quality requirements and digital optimization will
help improve the performance of your digital printer.
Xerox Digital Printing Systems
Xerox makes digital printing systems in a variety of sizes and with a wide
range of capabilities, thus enabling businesses to accommodate their
varied needs.
Xerox DocuTech and DocuColor printers, are xerographic printers. They
produce an image by placing a positive charge on a photosensitive drum
or belt, then remove the charge from the non-image areas with an
electronically-driven laser beam. The remaining positive charge is then
used to attract negatively-charged dry ink, which is then fused to the
paper through a combination of heat and pressure. This guide uses the
term digital printing for this xerographic process.
For information about the input, output, and throughput capabilities and
machine/paper handling capabilities of the various Xerox digital printing
systems refer to appendix A of this guide.
Obtaining Optimum Performance
Optimum performance is the Xerox goal in building every digital printing
system.
The importance of proper paper selection in obtaining optimum
performance cannot be overemphasized. The digital printing process
involves extremes of heat and pressure that place great demands on a
sheet of paper. This is a very different process and technology than offset
printing. Coupled with the high speeds attained by many of these printers,
even small imperfections can become problems. Even the most
sophisticated digital printer or copier can deliver substandard
performance if a poor quality paper or the wrong type of paper is used.
Using paper that does not meet your digital printer’s requirements as
described in this guide can lead to loss of productivity, decrease in the
quality of the output, increased service calls, and even physical damage
to the printer.
2 HELPFUL FACTS ABOUT PAPER
Introduction
Some Notes On Terminology
Xerox is the largest distributor of digital paper and specialty media under
one brand in the world. Xerox Supplies operates throughout the world.
The paper and specialty media offered in the various regions differ in
some regards; these differences are discussed in this guide where
appropriate.
Paper
Paper weights are given in pounds as well as grams per square
meter ( g/m
world except in the United States and Canada. For a discussion of paper
types and grades, refer to appendix B of this guide; for a chart showing
weights in g/m
appendix C. Although 20-pound paper converts mathematically to 75
g/m2, the functional equivalent of 20-pound paper that is used in Europe
is 80 g/m
High-Volume, Mid-Volume, Office
To improve readability, digital printers and copiers are distinguished in
tables and figures as either high volume, mid volume or office. It is useful
to define mid-to high-volume (35 to 180 pages per minute), and office
(less than 35 pages per minute).
2
). Grams per square metre is in general use throughout the
2
and pounds for each category of paper product, refer to
2
, and is referred to that way throughout this guide.
A Note On The Information In This Book
The information presented in this edition of Helpful Facts About
Paper is current as of the publication date. However, all specifications,
machine-specific information, and other data is subject to change at any
time. Your Xerox Supplies Representative can provide you the latest
available performance, pricing, and product information about Xerox
papers and specialty media. If you have any questions about the
suitability of any particular paper or specialty media for your application,
please consult your sales or service representative.
HELPFUL FACTS ABOUT PAPER 3
Introduction
4 HELPFUL FACTS ABOUT PAPER
Making Paper
Making Paper
Papermaking is a complex chemical and physical process. The product—
a seemingly simple sheet of paper—is a function of many decisions and
variables made at each step of the production process.
Understanding these factors enables you to select papers that produce
the highest quality output while minimizing jams and other problems that
lower productivity.
Pulp And Paper
Paper is made from cellulose fiber. Most of this is derived from trees;
some finer grades of paper are made partially or entirely of cellulose
fibers from cotton or old rags (thus the term “rag papers”).
The characteristics of the finished sheet of paper are determined by
many factors, beginning with the type of trees used in the papermaking
process. Softwood trees (those with needles, rather than leaves) such as
pine produce paper that is strong, but somewhat rougher in finish than
paper produced from hardwoods, which yield a weaker but smoother
paper. Location of the mill is the major determinant in what type of wood
is used to create a given sheet of paper. Economics have historically
dictated that the mills use the tree species closest to their site, however,
global trade flows in pulp are resulting in more variety and flexibility in
pulp utilization.
Most mills use some mixture of soft- and hardwoods, while striving to
produce a uniform sheet with the desired characteristics for the grade.
Papermaking, however, is a high-speed process with inherent
manufacturing variations.
To help comprehend the process described below – it is important to
understand that papermaking is both complex and challenging. For
example, an average modern paper machine that makes multipurpose
xerographic papers averages 300 inches/6-8 metres across and most
operate at 3500 feet/minute / 1000 m/minute.
Also consider that the base material—trees—is itself quite variable. This
places a premium on the mill's ability to monitor and control the quality
and consistency of its papermaking efforts.
HELPFUL FACTS ABOUT PAPER 5
Making Paper
The Papermaking Process
The first stage in processing is the removal of bark from the tree, and the
reduction of the remaining wood to small chips. At this point – the enduse of the product actually determines the way in which these chips are
processed. In papermaking – there are two basic classifications of paper
grades based on the manufacturing process – groundwood or freesheet
(also known as woodfree).
The whitening process is critical in the production of “freesheet or
woodfree” grades. This process is essential as it removes other impurities
from the wood fibers that can affect the overall performance and
appearance of the finished product.
Elemental chlorine-free (ECF) indicates that either chlorine dioxide or
sodium hypochlorite is used to whiten the wood fibers. Total chlorine-free
(TCF) indicates that no chlorine or chlorine-compounds were used in the
process. Both ECF and TCF products are environmentally responsible
and the selection is really a matter of personal preference. While ECF
products are broadly available, products manufactured with TCF pulps
may be more limited.
At the refining stage, refiners work to separate and develop the strength
properties of the fibers. This has a significant effect on the curl, opacity,
porosity and stiffness (discussed in more detail in Chapter 3) of the paper
that will eventually be produced. After this stage fillers and chemicals are
added to the mixture; these additives have an impact on both the
appearance and the physical properties of the paper. They are one of the
major determinants in how bright the paper is, which in turn establishes
the paper’s grade. For more information about paper grades and weights,
refer to appendix B and C in this guide.
The pulp slurry is now ready to go to the paper machine. The pulp slurry
enters the wet end, flowing through a pressurized chamber called the
head box, which distributes the pulp mixture evenly on an endless screen
of very fine mesh.
The pulp slurry is gradually de-watered on this fine mesh by gravity and
suction. When the fibers become capable of supporting their own weight,
they have become paper. Additional water is removed with pressure
before the paper enters the dryer section.
Sizing
The drying stage consists of two sections of steam-heated cylinders that
continually remove water. The mill adds surface sizing after the first
drying section. Surface sizing, which serves to bond the surface fibers
and increase the paper’s surface strength, is a critical factor in the
suitability of a sheet for the xerographic digital printing process. If not
well-sized, loose fibers on the paper surface cause machine
contamination and other problems that result in the need for increased
service calls.
In a second drying section, the paper is brought to its final moisture
content. This is an extremely critical phase, as papers with high moisture
contents tend to cause problems with post fuser curl, while papers with
low moisture contents have a tendency to experience static, which
causes problems with feeding and post-printing operations such as
6 HELPFUL FACTS ABOUT PAPER
Making Paper
stacking. A variation of as little as 1% from the ideal value of 4.5%
moisture content can cause problems.
Cutting And Wrapping
The final product emerges from the machine and is wound temporarily
onto large machine rolls that can weigh more than 30 tons (35 metric
tonnes). These machine rolls accommodate the high-speed papermaking
process. The paper is then slit and rewound onto smaller rolls, and
delivered to a high-speed sheeter in the mills converting operations.
The high-speed sheeter precision-cuts the product to size and wraps the
reams. All Xerox papers are sealed in moisture-proof wrappers that
maintain the moisture content of the paper.
Boxing And Palletizing
In a final step, the reams of paper are inserted into cartons, placed on
wooden pallets, and wrapped with a protective plastic to ensure load
integrity for shipping.
From Pulp To Printer
Knowledge of how paper is made comes in handy when evaluating
papers and paper suppliers. Understanding the many factors that affect
the papermaking process enables you to make a more educated
decision, and to select papers that will increase the productivity of a
printer system.
HELPFUL FACTS ABOUT PAPER 7
Making Paper
8 HELPFUL FACTS ABOUT PAPER
Paper and Xerox Printers
Paper and Xerox Printers
Although it takes only seconds, a piece of paper’s trip through a digital
printing system subjects it to a tremendous number of demands. To
ensure the best quality and productivity a number of requirements must
be met.
Paper Requirements To Ensure Best Performance
While many types and grades of paper can be run in Xerox digital printing
systems, there are a common set of characteristics and quality criteria
that must be built into papers that are optimized for performance in digital
printing systems – either monochrome (black & white) or color.
Digital optimization is the process by which paper and specialty media
products are developed, designed and produced to ensure optimum
performance on digital printing systems. This process includes stringent
product specifications, quality control and assurance criteria, converting
or finishing requirements and supplier training and education.
While some bond and offset sheets may also function, they may not
perform as reliably, or produce the same image quality as papers
specifically designed for use in digital printing systems.
To ensure high quality and performance from Xerox printers, the paper
should be optimized for printing in digital systems and must meet the
following requirements:
• Paper must be as free as possible of the paper dust that can result
from cutting and wrapping operations. If not strictly controlled,
contamination from paper dust eventually causes difficulties, downtime,
and a need for service. Build up of paper dust and loose fibers is one of
the leading causes of service calls and correspondingly lost
productivity.
• The Xerox paper path through the printer demands that the paper
bends in order to pass around drums, feed rollers, and other portions of
the transport mechanism. Paper with excessive curl, due to high
moisture content or other causes, is likely to jam. Paper with excessive
curl is another leading cause of service calls.
• Xerox printing systems use both friction-feed and vacuum-feed
mechanisms to feed the paper from the various trays. Paper must have
the correct frictional properties or misfeeds may result. Additionally, the
sheet must have adequate porosity to ensure reliable performance in
the vacuum mechanism.
• During the image-transfer process, the paper is subjected to
electrostatic charges. If the paper lacks the proper electrical
characteristics, dry ink may not transfer properly or completely, causing
image quality defects or other failures.
• The dry ink is fused to the paper by a combination of heat and
pressure. Paper with an excessively rough surface can cause fusing
failures, preprinted forms with incorrect inks can cause smearing or
offsetting of the preprinted portions of the image, and paper that
contains traces of contaminants can cause spotting of the
photoreceptor (this is where the image is transferred) and poor imaging
of subsequent prints.
Suitable smoothness levels are also required to prevent image
graininess and achieve acceptable toner adhesion results.
HELPFUL FACTS ABOUT PAPER 9
Paper and Xerox Printers
Cost Effectiveness
• The high temperature used for fusing in most printers, combined with
the friction of paper being moved at high speeds through the system
can generate static electricity. This tendency is exacerbated by paper
whose moisture content is too low. Static produces problems with
output operations such as stacking and sorting, as well as difficulties in
a wide variety of post-processing applications.
The cost of a printed document has many components. Paper price is
one of several elements, but is typically not the dominant one.
Runnability—the ability to be processed through a print system without
interruption, while producing a print of acceptable quality—is the primary
consideration in determining cost effectiveness. In printing systems,
especially, high-speed machines, interruptions in production are costly.
These costly interruptions can include, but are not limited to, labor and
machine downtime and missed deadlines.
Paper prices vary widely between different types and brands of paper. To
maximize performance, and achieve maximum cost effectiveness, you
should always purchase high quality paper that is designed to meet your
printer specifications.
Attempts to use “bargain” papers, or papers that are not designed for
Digital printing can cost far more in production problems and increased
service calls than they save in purchase price. Use of the proper paper is
the best investment you can make in securing optimal performance from
your Xerox digital printing system.
A Word About Vendors
Many manufacturers market multipurpose and digital papers to satisfy
what is a very substantial and growing market. A number of these
manufacturers offer products that provide satisfactory performance in
Xerox printing systems.
As you will find in reading Helpful Facts About Paper, there are many
factors that affect how well paper performs. Many of these are difficult, or
impossible, for the end user to determine. Your best assurance of paper
that performs properly is to purchase it from a source that is prepared to
monitor these factors on your behalf, thus ensuring they remain within the
specifications and tolerances set for Xerox printing systems.
While you do not have to use Xerox brand paper to achieve satisfactory
performance, doing so offers you the security of using papers that have
been designed to maximize the performance and image quality of your
Xerox printing systems. You also benefit from the efforts of the most
robust quality assurance program, one that qualifies each mill and each
piece of paper-making equipment individually, and then constantly
monitors the paper produced to see that it meets all the necessary
specifications.
10 HELPFUL FACTS ABOUT PAPER
Paper Properties and Xerox Printers
Paper Properties and Xerox Printers
Paper is both physically and chemically complex. For a paper to perform
properly in your Xerox digital printing systems, its properties must be
within specified limits.
Failure to understand these paper properties, and to assure that the
paper you use is within specified limits for each factor, can result in
problems ranging from misfeeds and jams to poor print quality, excessive
service calls, and damage to printer components.
A sheet of paper is defined by its weight, type, finish, and grade.
Weight
Paper weight is generally expressed as grams per square metre
2
(g/m
), a measure that makes it easy to compare any two pieces of
paper, even if the papers are of different types such as offset and index.
In North America, paper weights are given as the weight in pounds of 500
sheets of a particular size; the size of the basis sheet, however, varies
with the type of paper, thus making it difficult to compare weights
between different types of paper. A 50-pound xerographic bond is not the
same as a 50-pound offset paper, and both are different from a 50-pound
index stock. For a further explanation of paper weights, and a chart that
permits conversion from one weight to the nearest comparable weight of
another type, refer to Appendix C.
For the list of Xerox paper and specialty media suitable for use in your
equipment, consult your digital printer’s Recommended Media List.
(www.xerox.com/supplies)
Grade
Brightness
Paper may be defined in terms of its use. Each grade serves a purpose,
usually suggested by its grade name. Some of the most common
classifications of printing papers are bond, coated, text, cover, book,
offset, index, and label.
Brightness is a measure of the amount of light, of a specific wavelength,
a sheet reflects. The more light it reflects, the higher the brightness.
Brightness, to a large extent, dictates the cost of the sheet, but has no
relationship with functionality. Brightness has no bearing on Performance
but does have a significant impact on image quality. High-brightness
papers give more contrast, allowing colors to stand out; low brightness
papers are easier on the eyes for periods of extended viewing or reading.
Higher brightness papers do not necessarily perform better in your digital
printing system but add value to your print jobs. Adequate paper
brightness enhances the contrast between the paper and the image, thus
improving readability. Brightness is especially important for color printing
to ensure images are vivid.
A further explanation of paper grades is found in Appendix B.
HELPFUL FACTS ABOUT PAPER 11
Paper Properties and Xerox Printers
Contamination
Acid vs. Alkaline Papers
Contamination is usually a direct result of adhesive residue or paper
dust/fibers from paper that has poor cut quality.
Paper dust is a pervasive problem that causes a substantial number of
service calls. The major drivers of paper dust are high filler content and
poor finishing practices. Paper dust causes difficulty by accumulating in
the fuser area creating image quality issues, contaminating components,
and causing a variety of difficult-to diagnose problems.
For best performance, purchase only mill-cut and mill-sealed reams
obtained from a vendor whose quality assurance procedures provide for
strict control of paper dust.
The acidity (or alkalinity) of a paper is determined primarily by the internal
sizing methodology employed in its manufacture. Paper produced using
rosin/alum chemistry is often referred to as acid sized.
Most manufacturers have now converted to synthetic internal sizing,
enabling paper to be produced under slightly alkaline conditions.
Either process can yield a perfectly acceptable product. The major
drawback of the acid sized paper is sheet life. Acid sized sheets age
quicker than their alkaline counterparts, eventually becoming yellow and
brittle.
In North America, the American Society for Testing and Materials (ASTM)
has established standards of permanence for papers. Paper with a pH of
5.5 or higher lasts 50 to 100 years (ASTM Type III). Paper with a pH of
7.5 to 9.5 lasts several hundred years (ASTM Type I). All Xerox paper,
with the exception of 90 and 110 lb. Tabs, is manufactured in an acid free
environment and meets the requirements for ASTM Type I permanence.
In Europe, the International Organisation for Standardisation established
ISO 9706: 1994 for paper permanence. Tearing resistance of papers
above 70 g/m
2
must be at least 350mN in any direction. Alkali reserve
expressed as % calcium carbonate must be 2% minimum. Kappa number
must be less than 5 and pH must be 7.5-10, ie. alkaline.
Moisture Content
Moisture content directly affects reliability and print quality. Too much
moisture can cause excessive curl, jams, and print quality problems.
Moisture levels that are too low may cause static problems, which can
also lead to jams and misfeeds as well as causing difficulties in postprocessing paper handling.
The best performance in Xerox digital printing systems comes with
papers that have nominal moisture content of 4.5%. Offset papers
normally have much higher moisture content than papers designed for
digital printing.
Moisture content must be uniform within the ream. The ream should be
packaged to ensure moisture integrity. Moisture-proof ream wrappers are
essential to maintaining the correct moisture level of the paper.
12 HELPFUL FACTS ABOUT PAPER
Paper Properties and Xerox Printers
Xerox papers are packaged in a moisture-proof ream wrapper, which has
a demonstrated ability to resist the migration of moisture into and out of
the package. These ream wrappers can be a paper-poly-paper, paperpoly, or clear poly constructions.
Refer to Chapter 4, “Preparation for Printing” for suggestions on
controlling moisture in stored reams of paper.
Curl
Excess post fuser curl is one of the most common paper problems in
digital printing, and a very frequent cause of paper jams. Selection of a
low curl paper with proper moisture content will make a significant
difference in your system's productivity.
The best-performing papers exhibit a low amount of curl after being run
through the printer. A trial run quickly demonstrates how much post fuser
curl is likely with any particular paper, and is the best curl test. When
there is too much curl, paper jams can occur within the machine or in
post-processing equipment. For more information on evaluating and
controlling paper curl, refer to Chapter 4, “Preparation for Printing.”
Moisture And Curl
Generally speaking, high moisture content—above 5.3%—and a greater
tendency to curl go hand in hand.
Papers with very low moisture content tend to absorb water when
exposed to the environment for extended periods of time. This can cause
wavy edges that may lead to runnability problems.
While a test run in your equipment is the best means of evaluating paper
curl, successful operation is most likely if you specify a paper that has
been manufactured for digital printing with the correct moisture content
and packaged to maintain that moisture level. Offset papers are
manufactured to a higher moisture content and tend to curl in digital
printers.
Curl-controlled Papers
Some digital papers are manufactured with built-in curl control to
counteract their tendency to curl when exposed to the heat and/or
pressure used in digital printers and copiers. Xerox papers are
manufactured with built-in curl control. These papers work well in all
Xerox digital printers when attention is paid to correct orientation of the
paper during loading.
HELPFUL FACTS ABOUT PAPER 13
Paper Properties and Xerox Printers
Grain
The grain of a paper is the direction in which most of its fibers lie. There
are three methods that can be used to determine grain direction of a
sheet:
• Tear a sheet part way lengthwise; repeat crosswise. Compare the two
tears. Paper always tears straighter with the grain (refer to figure 3-1).
Figure 3-1. Paper tears straighter with the grain
• Fold a sheet lengthwise, then crosswise. Compare the evenness of the
folds. Paper folds smoothly with the grain. Cross-grain folds tend to be
rough and cracked (refer to figure 3-2).
Figure 3-2. Paper folds more easily with the grain
• Moisten two adjacent edges of the sheet. The grain-long direction is
perpendicular to the edge that is wavy (refer to figure 3-3).
Figure 3-3. When moistened, the edge perpendicular to the grain
direction will become wavy
Paper with the grain parallel to the long side of the sheet are said to be
grain long or long grain. Grain-long papers are about twice as stiff in the
long direction (refer to “Stiffness,” in the next section).
Grain-short papers are about twice as stiff in the short direction.
Therefore they do not flex as readily along the long edge as do grain long
papers.
14 HELPFUL FACTS ABOUT PAPER
Paper Properties and Xerox Printers
Grain direction is commonly indicated through the sheet size dimension
on the paper packaging – 11x17 / 297 x 420 mm means long grain and
17x11 / 420 x 297 mm means short grain. Another way to indicate grain
direction is to underline one of the dimensions, 11x17
means long grain and 17
Europe, “SG” for short grain and “LG” for long grain indicate grain
direction.
x11 / 420 x 297 mm means short grain. In
/ 297 x 420 mm
Most 8.5x11/A4 sheets are long grain. Digital color printing and in-line
finishing has required the use of short grain products especially in the
larger sized sheets 17x11/A3 and 18x12/SRA3. Short grain is essential
when full-color printed documents are folded, since grain direction will
minimize toner crack on the fold. Brochure, books and marketing material
are examples of applications where short grain paper would be required.
In certain specialized situations, post-processing equipment impacts the
necessary grain direction of the paper. For further discussion, refer to
Chapter 8, “Post-processing Considerations.”
Stiffness
Stiffness refers to the rigidity, or bending resistance, of paper. Thicker
papers are usually stiffer, and papers are normally stiffer in the grainshort direction. In general, lightweight papers do not have the stiffness of
heavier stock and are more likely to bunch up or wrinkle in the printer,
causing jams. Heavier weight papers, such as cover and index stock,
may have runnability problems as well as print quality defects (skips,
blurs, deletions) due to their reduced ability to bend around rollers and
drums.
Abrasiveness
Smoothness
As a result of coatings and other additives, some papers can be highly
abrasive. Such sheets can cause photoreceptor damage during a jam, or
as a result of particulate contamination. Abrasive papers are not
recommended for use in Xerox digital printing systems.
A paper’s smoothness has a significant impact on image quality. If paper
is too rough, image quality degrades; with increasing roughness, expect a
loss of print quality in solids and halftones resulting in graininess.
Extremely rough paper does not allow toner to fuse properly, which
results in an image that may rub or flake off.
Since surface irregularities must be filled with ink, rough papers require a
higher density setting, and thus more dry ink, to achieve a given level of
image density.
Xerox has conducted extensive image quality testing on digital,
xerographic, bond, and offset papers. The smoother digital, xerographic
and bond grade papers provide the best image quality.
For general monochrome use, xerographic and multi-purpose papers with
a nominal value of 150 on the Sheffield or 180 on the Bendtsen scale
produce the best results. Digital color grades are smoother to meet the
more demanding print quality requirements with coated paper being the
smoothest grade.
HELPFUL FACTS ABOUT PAPER 15
Paper Properties and Xerox Printers
Formation
Whiteness (Shade)
Formation is descriptive of a paper’s fiber structure and uniformity or lack
of it in the distribution of fibers. Good formation is essential in digital
printing to ensure good image quality.
Whiteness is an important property of paper as it relates strongly to the
visual appeal of the printed product. Xerox digital printers and copiers
calibrate their color performance based on the shade of a standard Xerox
paper product.
Whiteness is a measure of the light reflectance of paper across the whole
visible spectrum as opposed to brightness, which is measured at only
one wavelength. In this way it more closely matches the viewers
perception of how white a sheet of paper is. Colors are measured using
different scales. The “L*, a*, b*” scale is the most common. Within this
scale, “L*” measures degree of lightness, “a*” measures red/green, and
“b*” measures blue/yellow. The terms “blue-white” and “yellow-white
come from this scale. Whiteness has no impact on sheet performance but
whiteness and brightness do play an important role in the visual appeal of
the sheet and printed product.
Gloss Level
Caliper
The gloss level of paper is measured as the ratio of reflected to incident
light. It is the reflectance of the surface responsible for its shiny or
lustrous appearance. A higher gloss is achieved by making the surface
more reflective through a combination of calendering (pressing) and/or
coating choices.
Caliper (thickness) of a sheet of paper depends mainly on its weight and
the amount of calendering (pressing) during manufacturing. Thinner
paper is usually smoother than a thicker sheet at a given basis weight.
More calendering makes the sheet thinner, smoother, less stiff, and less
opaque. As a general rule, the higher the caliper, the stiffer the paper.
Thickness is expressed in mils (thousandths of an inch) or microns
(millionths of a meter).
Caliper is important because:
• Low-caliper papers can have low stiffness and opacity. Their relative
lack of rigidity results inwrinkling or bunching up in your copier or
printer increasing jam rates.
• High-caliper papers, in heavier weights, have high stiffness. Their
relative inflexibility can increase jam rates due to an inability to bend
around the photoreceptor, cylinders, inverters, and other portions of the
transport mechanism. Depending on the digital printer or copier
specifications, there can also be print quality problems with these
papers due to their reluctance to conform to the photoreceptor or
image/ pressure cylinders, leading to blurred images and deletions.
• The capacity of paper trays can be altered by using papers of differing
caliper.
16 HELPFUL FACTS ABOUT PAPER
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