improved newsprint

HANDBOOK IN NEWSPAPER PRODUCTION USING
IMPROVED NEWSPRINT
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 03
Improved newsprint . . . . . . . . . . . . . . . . . . 05
Prepress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 06
Pressroom . . . . . . . . . . . . . . . . . . . . . . . . . . . . 08
Mailroom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10 steps towards a successful result . . 12
© TU AND INNVENTIA 2010.
Preface
There is a need to be able to supply free sheets, advertising and newspaper
supplements that are perceived to have a higher quality than normal. This
sense of quality as well as the content value can be heightened by a better
reproduction of colour images, a stiffer paper, less set-off and less printthrough. This is the fundamental reason for using improved newsprint,
characterised particularly by a higher brightness and grammage, and in
certain cases also by a smoother surface.
It has however sometimes been found that the printing of supplements on
improved newsprint gives rise to problems and complaints about colour
reproduction and smearing from page to page. To study these problems,
a user group for supplement printing with a focus on the optimum and
problem-free use of improved newsprint, was formed. Three teams, concentrating respectively on the areas of prepress, pressroom and mailroom,
carried out the tasks within the user group. The aim of the project has been
to develop general guidelines and measures to reduce the set-off when
printing on improved newsprint, to give recommendations on how to adjust
the amount of ink and the ink-water balance and to provide suitable adjustments for the mailroom.
In 2006, the Swedish Media Publishers’ Association (Tidningsutgivarna)
published a “Handbook in Newspaper Printing” for printing on standard
newsprint, which includes standard values and recommendations for the
measurement of viewing conditions, optical density, grey balance and dot
gain in accordance with ISO 12647-3. The present “Handbook in Newspaper Printing using Improved Newsprint” is to be seen as a complement
to the previous handbook, describing what should be modified to create the
conditions for the optimum use of improved newsprint. The measures proposed in this handbook are based on the work carried out by the user group.
A total of eleven test print runs were carried out at three printing houses and
the resulting prints analysed to provide a starting point for the development
of general guidelines and an ICC profile for improved newsprint. The three
printing houses are equipped as follows:
Printing presses: KBA Commander 70 (satellite), KBA Colora (4-high), and
MAN Colorman S (satellite).
Plate manufacture (CTP): AGFA Polaris XTV, CREO Trendsetter and
KRAUSE LS Jet.
Mailroom equipment: Ferag and Müller Martini.
The project involved staff members from DNEX, EKTAB, Flint Group,
Holmen Paper, Innventia, Stora Enso, Sun Chemical, TU and V-TAB.
Stockholm 2010,
Innventia and the Swedish Media Publishers’ Association
03
Improved newsprint
What is improved newsprint?
Improved newsprint (Machine Finished, MF) is a paper with a higher brightness and a greater grammage than standard newsprint. ISO brightness is
higher than or equal to 68 and grammage greater than or equal to 48.8 g/m2.
The increased grammage also makes for a higher opacity.
The composition of the newsprint is not specified and the higher brightness
can be attained in a number of different ways, for example through bleaching or by the addition of fillers. The raw material, the fibres, can be based on
Thermo Mechanical Pulp (TMP), or on recycled De-Inked Pulp (DIP), both
of which make for newsprint with different properties. TMP-based products
often have a high bulk and stiffness while DIP-based products may have
a smoother surface and be less stiff. Unlike standard newsprint, improved
newsprint is not a standardized product.
Definition of
improved newsprint
ISO brightness ≥ 68
Grammage ≥ 48.8 g/m2
91
Opacity
(%)
90
Why improved newsprint?
The advantages of using improved newsprint are many. The greater brightness gives more reproducible colours (a larger colour gamut) and improved
print contrast. In addition, the increased grammage gives a stiffer paper and
also reduces the risk of print-through making for a greater sense of quality.
Improved newsprint can be used with advantage for both advertising and
for supplements in daily newspapers.
89
Grammage
48.8 55
58
60 (g/m2)
Opacity at different grammages.
Printing on improved newsprint
To realize the full potential of improved newsprint, the settings and adjustments in the prepress, pressroom and mailroom need to be suitably adapted.
The set-off can be aggravated, or at least be more visible, on a paper that is
brighter and has a finer surface. With suitably adapted ink density levels and
an ICC profile, great improvements can be achieved compared with printing
on standard newsprint. In addition to these parameters, the choice of paper,
ink and dampening also have a definitive influence on the result.
WFC
Relative price
WFU
MWC
LWC
MFC
SC
MF
News
Relative quality
Mechanical uncoated
News = standard
MF = machine finished (improved)
SC = supercalendered
The advantages of
improved newsprint
- Larger colour gamut
- Greater print contrast
- Higher brightness
- Higher stiffness
- Less print-through
!
Mechanical coated
MFC = machine finished coated
LWC = light weight coated
MWC = medium weight coated
Wood free
WFU = wood free uncoated
WFC = wood free coated
05
Prepress
Print adjustments
Improved Normal density
Standard Normal density
+b*
One of the major advantages of using improved newsprint in a daily newspaper is the larger colour gamut that can be reproduced. On standard
newsprint, the number of colours that can be printed is limited. Thanks
to the brighter paper and the smoother surface of improved newsprint it
is possible to reproduce more colours.
+50
Nevertheless, even though more colours can be reproduced on improved
than on standard newsprint, improved newsprint cannot reproduce all the
colours that we can see on a monitor screen. The original colour gamut
must therefore be reduced, so that it agrees with the printing conditions.
In practice, all the colours outside the colour gamut of the print are recalculated to values within the reproducible area. The ICC profile takes care
of this calculation and conversion while separating from RGB on the monitor
to CMYK on the print.
-a*
+a*
-50
+50
-50
-b*
Chromaticity diagram (CIELAB).
0.03
Set-off
(density)
0.02
Total amount of ink (TIC value)
Improved newsprint is more sensitive to smearing and set-off than standard
newsprint. To reduce the risk of undesired smearing and set-off on the product, the total amount of ink coverage should be reduced from the standard
newsprint value of 220-240 per cent to 195 per cent. For illustrations and
tints (so-called object graphics), the ink tone values should be chosen so
that the Total Ink Coverage (TIC) does not exceed 195 per cent, as in the
example below. For photographic images (so-called pixel graphics), this
is controlled by employing the ICC profile. With lower total ink coverage, a
greater colour gamut is attained than on standard newsprint, but with less
risk of set-off and smearing, as shown in the diagram to the left.
C=40 %
0.01
+
TIC
200 230 260 290 (%)
M=85 %
40.0.0.0
Y=50 %
+
0.85.0.0
K=20 %
+
0.0.50.0
TIC=195 %
=
0.0.0.20
40.85.50.20
Set-off at different TIC levels.
The ICC profile for improved newsprint
06
A new ICC profile adapted for daily newspaper printing on improved newsprint (cold-set web offset) has been developed. This profile is based on
printing trials made at several different printing houses and on a number of
different paper grades. The profile has been optimised from the results of
trials with different profile settings. The full-tone density has been adapted
for printing on improved newsprint. The specifications for the new ICC profile
are shown in the green box on page 7. The profile assumes a lower total
amount of ink than TU’s and IFRA’s ICC profile for standard newsprint. By
using a heavy Grey Component Replacement (GCR) level of 96 per cent, the
total amount of ink is reduced to a level of 195 per cent instead of the normal
220-240 per cent used for standard newsprint. The heavy GCR level results
in a more stable ink balance and reduces the risk of smearing.
The new ICC profile can be downloaded from dagspress.se under
“Annonsmaterial”. There one can also find a description of how the ICC
profile is applied to images to be printed on newsprint. The profile has been
verified on bvdm reference images (Bundesverband Druck und Medien) and
has rendered good results with various image categories such as high key,
low key and mid-tone pictures.
Layout
The cold-set print cannot compete with true heat-set production with
respect to layout. This must therefore be planned or adapted for newspaper
printing in order to reduce the risk of set-off. If possible, large amounts of ink
should be avoided on the first and last pages of the product. It is also best to
avoid printing deep into the gutter and to avoid large empty white spaces in
the layout.
RIP compensation
Printing presses that do not attain the standardised dot-gain value (26 per
cent according to the ISO standard) can be compensated for in the plate
setter’s Raster Image Processor (RIP). This is done with the aid of a compensation curve. For the best results, a curve is needed for each paper grade,
which means that a new compensation curve should also be developed for
improved newsprint.
The compensation curve is calculated by first carrying out a linearization of
the CTP. The CTP is then calibrated so that the complete tone scale from 1
to 99 per cent is included on the plate and that the tone values on the plate
agree with the tone values in the Postscript-file, that is, 40 per cent in the file
is equal to 40 per cent on the plate.
A test printing is then carried out in accordance with the standard, where the
dot gain is checked. In this test printing, it is important that the target densities and grey balance are fulfilled. The dot gain is then measured on the test
prints and an average value for each colour is calculated. If the dot gain in
the various colours does not deviate too much, an average is calculated for
all the colours. Otherwise, each colour is compensated separately in the RIP.
Experience shows that a compromise between the compensation curve for
standard newsprint and that for improved newsprint functions well in both
cases; that is the same compensation curve can then be used for both
paper grades.
Recommendations for
total ink coverage
Total ink coverage (TIC) ≤ 195 %
Specifications for
the ICC profile
Printing process:
Cold-set web offset
Paper:
Improved newsprint
Test chart:
IT8:7-3
Screen resolution:
100-120 lpi (39-47 l/cm)
Total amount of ink:
195 % (whereof 96 % black)
Achromatic repro:
Heavy (96 %)
Density:
CMY=0.85 and K=1.10
Dot gain at 40 %:
26 %
Grey balance:
C=30 %, M=24 % and Y=24 %
Download the ICC profile
for improved newsprint
from dagspress.se!
07
Pressroom
Adjustments in the printing press
When printing on improved newsprint, certain adjustments need to be made
in order to utilise the full potential of the product and to maintain a high print
quality. If the press adaptations, standard values, adjustments and settings
used when printing on standard newsprint are used when printing on improved newsprint, there is a considerable risk that there will be problems with
smearing, set-off and a reduced colour gamut on the product. Any set-off
will also be more visible on the brighter improved newsprint.
Recommended
ink-water balance
As little water as possible
without risking running dry.
Ink-water balance
1.50
To avoid set-off and smearing problems, it is important to keep the ink and
water feed at a minimum level. Improved newsprint does not accept the
same amount of ink-water emulsion as standard newsprint. Using standard
newsprint settings will result in a surplus of this emulsion. To attain the correct ink-water balance, it is recommended printing with an amount of water
only slightly larger than that required to avoid dry running. This amount must
be less than used when printing on standard newsprint.
Density
1.00
0.50
Ink
C
M
Y
K
Recommended density levels.
Recommended
target densities
cyan (c):
0.85 ± 0.05
magenta (m):
yellow (y):
black (k):
0.85 ± 0.05
0.85 ± 0.05
1.10 ± 0.05
08
If the amount of water is too high, more fountain solution is emulsified into
the ink, which is then to all extents diluted. To attain the target density with
the diluted ink, a thicker ink layer is required, and this in turn increases the
risk of set-off and smearing. The rheological properties of the ink are also
changed. A greater amount of emulsified water lowers the tack of the ink,
and this influences how the ink is transported through the ink train, possibly
increases ink splashing in the press. An increase in the amount of water also
increases the dot gain.
Print density
Print density is the parameter used to control the amount of ink in the print.
As mentioned previously, a higher amount of ink increases the risk of set-off
and smearing problems; too much ink also leads to a higher dot gain and
reduced contrast in the dark tones. Much can therefore be gained by reducing the amount of ink, that is, by aiming towards lower target densities.
However, too low a density can give lower print contrast with pale colours
and weak images.
Thanks to the ability of improved newsprint to reproduce more colours, it is
possible to reduce the density. In cyan, magenta and yellow, it is possible to
lower the target density to 0.85 and still print with a larger colour gamut than
is possible on standard newsprint. The black density should be kept at the
same level as when printing on standard newsprint, that is, 1.1. Check the
black density carefully and lower it if it is too high. Do not, however, go below
the recommended value, as this will cause texts to appear too grey.
Impression
An increase in impression in the printing nip leads to an increased ink density
with a given amount of ink. This means that the ink levels can be kept low
and the set-off and smearing can be reduced. Thus, it is recommended that
the impression should, if possible, be increased within the normal working
range. It has also been reported that increased impression may result in less
mottling.
Blanket
Under-packing
Under-packing
Recommendations
for impression
Increase the impression within
the normal work range.
Blanket
C+M+Y K-2%
Paper
Grey balance field with K reference.
Recommendations
for grey balance
Cylinder gap
Plate
Cylinder gap
Impression depth = cylinder gap – under-packing – blanket – plate
or
Impression depth = cylinder gap – 2 x under-packing – 2 x blanket – paper
Grey balance
The grey balance is checked with the help of grey tint patches containing
two fields. One field consists of a screen tone in black and the other of a
screen combination of cyan, magenta and yellow. When both fields look the
same to the eye, the four colours have the correct proportions and the density and balance of the four colours are then under control during printing.
This method of inking level control by utilising the grey balance can also be
used with advantage on improved newsprint. In this case, the black reference should be reduced by 2 per cent units from the current in-house black
reference, as the colour densities have been reduced by 0.05 density units.
The black reference should be
reduced by 2 percentage points
from the current in-house value.
Potential smearing
reduction
-
Lowered density
Correct impression
Good ICC profiles
Ink-water balance
Total
5-10 %
10-15 %
5-10 %
5-10 %
25-45 %
Full-tone shades
The full-tone shades for the various colours differ between improved
newsprint and standard newsprint. However, no standard values have
been developed.
09
Mailroom
Adjustments to mailroom stations
90
Properly adjusted mailroom equipment is more important for the result when
printing on improved newsprint than on standard newsprint. Because of the
higher brightness of the paper, any defects such as markings from grippers,
clamps, tapes and mats as well as smearing and set-off are more clearly visible
than on standard newsprint.
Thickness
(µm)
80
70
Grammage
48.8 55
58
60 (g/m2)
The sheet thickness for various
grammages.
The mailroom consists of many stations that transport and influence the product.
A myriad of adjustment possibilities are available and there is a great potential
for reducing the risk of defects if all these possibilities are utilised. Tests show
that it should be possible to reduce set-off problems caused in the mailroom by
roughly 30 per cent. One recommendation is to use waste copies while adjusting
the equipment. There is little point in running approved copies into the mailroom
while making adjustments. It is also important that all the staff responsible for the
different stations can perform the necessary adjustments. All required instructions
and tools should be readily available.
The measures required in the mailroom constitute a balancing act between attractive products without set-off and smearing marks, and uniform bundles leaving
plant. The target is for the product to retain the same quality when it leaves the
mailroom as when it left the printing press.
0.03
Set-off
(densitet)
The product determines the settings
0.02
0.01
Time
20
300
(s)
Set-off at different times after
leaving the folder.
Different products require different adjustments to achieve an optimum result,
that is, a smooth transport through the mailroom with a minimum of influence
on the product. A product with 56 pages on 45 g/m2 paper can require other
settings than a product with 56 pages on 60 g/m2 paper. The size and grammage (thickness) determine which settings give a good result. Sometimes it
may also be necessary to change the flow through the mailroom in order to
ensure the quality of the product.
Ink setting time
One way of reducing the disturbances is to increase the time from the folding
unit to the first mailroom station. This can be achieved by installing a winding
station. Buffering the products before further treatment in the mailroom
means that the time available for the ink to set is increased. This means that
pressing rollers, tapes and the like in the mailroom equipment can set harder
than if the newspapers go down directly online to the machines. The diagram
to the left shows how the amount of set-off decreases with time after leaving
the folder.
10
Pick-up station
The pick-up station should be adjusted to ensure a correctly aligned product
stream. An unaligned stream in the mailroom increases the risk of ink set-off.
The adjustment of the pick-up station is the responsibility of the pressroom
operators but the result affect the flow in the mailroom. Good communication
between pressroom and mailroom will facilitate the correct adjustment.
Winding station
In the winding station grippers, mats and tapes influence the product. If it
is possible to adjust these, use as low a pressure as possible without compromising the integrity of the reel.
Trimmer
In the trimmer, the in-feed unit, the guides and the rollers influence the
product. If the pressure on these can be adjusted, it should be set as low as
possible. Start off with the lowest possible value and increase as necessary.
If all the adjustments
in the mailroom are
used in an optimum
way it should be
possible to reduce
the set-off in the mailroom by roughly 30 %
!
Quarter folder
Drive tapes and press rollers will cause smearing and set-off if set too tight.
Allways choose the loosest possible settings.
Stacker
Before the stacker it is possible to adjust the alignment jogger, the pressing
roller and the bundle press. After the stacker it is possible to adjust the ejection speed. These should be adjusted as slightly as possible without risking
bundles becoming crooked and unstable.
Strapper
In the strapper station, one can adjust the press beam pressure and the
strap tension. Normally the beam pressure should be as low as possible
without compromising bundle stability. Check bundles after strapping to
see what influence the beam pressure has on product quality.
11
10 steps towards a successful result
1
Reduce the total
amount of ink in
illustrations and
tints to 195 %.
2
3
Adjust RIP compensation
curves for improved
newsprint.
4
12
Adjust photographic
images with an ICC
profile for improved
newsprint.
5
Check ink and dampening
roller settings and reduce
water feed values during
printing to as low as possible
without risking running dry.
Aim towards new target
densities, CMY = 0.85 ± 0.05
and K = 1.10 ± 0.05, when
printing. Use a densitometer
for control measurement.
6
Make sure that you have an optimum
impression setting on the press
thereby keeping inking levels down.
Check the condition of the offset
blankets at the same time.
7
8
Control the ink feed
by checking the grey
balance, making sure to
lower the black reference
value to match the lower
target densities.
Reduce the risk of set-off by
adjusting the folder as lightly
as possible and, if possible,
extending the drying time
between the folder and the
first station in the mailroom.
9
10
Adjust all stations in the mailroom for minimum contact
pressures on the products,
but without risking uneven
or unstable bundles.
Facilitate communication between the
prepress, pressroom and mailroom,
in order together to attain an optimum
result. Discuss with the customer
how you can work together to create
the best conditions for achieving a
successful production result.
13
SOURCES AND INSPIRATION
The results from the user groups project work on supplement printing.
The reports upon which this handbook is based are available at TU and
Innventia. Contact Gunnar Borg at [email protected] or Erik Blohm at
[email protected].
TEXT
Jan Andersson, Holmen Paper
Erik Blohm, Innventia
Gunnar Borg, Swedish Media Publishers’ Association
Christer Hagman, Flint Group
Axel Irestedt, Sun Chemical
Per-Åke Johansson, Innventia
Marianne Klaman, Innventia
Peter Kull, Flint Group
Sofia Thorman, Innventia
Lars Åkesson, Stora Enso
PHOTOGRAPH (p 4)
Matton Images
ILLUSTRATIONS
Linda Johansson
TYPOGRAPHY
Helvetica Neue Light and Helvetica Neue Medium
GRAPHIC DESIGN
Linda Johansson
PAPER
Inlay: 60 g/m2 Holmen Plus 75
Cover: 170 g/m2 Cyclus Offset
14
Printed by EKTAB 2010.
THANKS TO
DNEX
EKTAB
FLINT GROUP
HOLMEN PAPER
STORA ENSO
SUN CHEMICAL
V-TAB