HANDBOOK IN NEWSPAPER PRODUCTION USING IMPROVED NEWSPRINT

Transcription

1 HANDBOOK IN NEWSPAPER PRODUCTION USING IMPROVED NEWSPRINT

2 Contents Preface Improved newsprint Prepress Pressroom Mailroom steps towards a successful result.. 12 TU AND INNVENTIA 2010.

3 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 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

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5 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/m 2. 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. 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. 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. Relative price News MF SC MFC LWC MWC WFU WFC Relative quality Mechanical uncoated News = standard MF = machine finished (improved) SC = supercalendered Mechanical coated MFC = machine finished coated LWC = light weight coated MWC = medium weight coated Wood free WFU = wood free uncoated WFC = wood free coated Definition of improved newsprint ISO brightness 68 Grammage 48.8 g/m 2 Opacity (%) The advantages of improved newsprint - Larger colour gamut - Greater print contrast - Higher brightness - Higher stiffness - Less print-through 05 Grammage (g/m 2 ) Opacity at different grammages.!

6 Prepress Improved - Normal density -a* Standard - Normal density +b* a* Print adjustments 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. 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. -b* Chromaticity diagram (CIELAB) Set-off (density) TIC 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 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 % M=85 % Y=50 % K=20 % TIC=195 % = (%) 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

7 total amount of ink is reduced to a level of 195 per cent instead of the normal 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: 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

8 Pressroom Recommended ink-water balance As little water as possible without risking running dry. Density C M Y K Recommended target densities cyan (c): 0.85 ± 0.05 magenta (m): 0.85 ± 0.05 yellow (y): 0.85 ± 0.05 black (k): 1.10 ± Ink Recommended density levels. 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. Ink-water balance 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. 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.

9 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. Recommendations for impression Increase the impression within the normal work range. Blanket Under-packing Under-packing Paper Blanket C + M + Y K - 2 % 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 The black reference should be reduced by 2 percentage points from the current in-house value. 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. 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. Potential smearing reduction - Lowered density 5-10 % - Correct impression % - Good ICC profiles 5-10 % - Ink-water balance 5-10 % Total % 09

10 Mailroom Thickness (µm) Set-off (densitet) Grammage (g/m 2 ) The sheet thickness for various grammages. Time (s) Set-off at different times after leaving the folder. Adjustments to mailroom stations 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. 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. The product determines the settings 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/m 2 paper can require other settings than a product with 56 pages on 60 g/m 2 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

11 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

12 10 steps towards a successful result 1 Reduce the total amount of ink in illustrations and tints to 195 %. 2 Adjust photographic images with an ICC profile for improved newsprint. 3 Adjust RIP compensation curves for improved newsprint. 4 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.

13 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 Control the ink feed by checking the grey balance, making sure to lower the black reference value to match the lower target densities. 8 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 Adjust all stations in the mailroom for minimum contact pressures on the products, but without risking uneven or unstable bundles. 10 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

14 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 or Erik Blohm at 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/m 2 Holmen Plus 75 Cover: 170 g/m 2 Cyclus Offset 14 Printed by EKTAB 2010.

15 THANKS TO DNEX EKTAB FLINT GROUP HOLMEN PAPER STORA ENSO SUN CHEMICAL V-TAB

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