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Sappi presentation climate and paper

May 15, 2015

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  • 1. Cover HannoArt Gloss 250 g/m2, text HannoArt Gloss 150 g/m2, 2004, Sappi Europe SA, communications@eu.sappi.comClimate and Paper is one of Sappis technical brochures. Sappi brought together this paper related knowledge to inspire ourcustomers to be the best they can be.Climate and PaperThe interaction between climateand the processing of coated papersin printing and finishing Water Interference Mottling Adhesive Techniques Processing Matt Paper Verarbeitung von Mattpapier Is water an interference factor Developments in the Why do matt papersWarum verdienen Mattpapiere in offset printing? printing and paper making industriesrequire special attention? and their effect on adhesive techniquesbesondere Beachtung? in the bookbinding trade sappi Folding and CreasingThe Paper Making ProcessThe Printing Process Finishing of Coated Papers afterFrom wood to coated paper Sheetfed and heatset web offset Sheetfed Offset Printingprinting technology www.sappi.com sappi sappi sappi Sappi Fine Paper Europe Sappi Europe SA 154 Chausse de la Hulpe B-1170 Brussels Tel. + 32 2 676 97 36 Fax + 32 2 676 96 65sappi ideaexchange This one and the other technical brochures are freely available at our knowledge bank: sappisappi www.ideaexchange.sappi.com/knowledgebank The word for fine paper

2. Climate and Paper, the seventh technical brochure from Sappi Idea ExchangeElectronic measuring equipment lX Concluding remarksNowadays, electronic gauges with digital displays have The contents of this brochure are the resultbecome widely-used tools for measuring air humidity. These of practical experience and close collaborationmodern gauges combine very fast response times with ease with FOGRA, an organisation which has beenof use and calibration. Common humidity gauges all use very helpful in many ways.one of two possible methods of measurement conductivitymeasurement or capacitive measurement.Conductivity measurement uses the changes in conductivityof hygroscopic electrolytes under the influence of vapourFOGRAsappi ideaexchangeabsorption as the basic input for measurements. Capacitivehygrometers measure the capacitive changes of dielectricsubstances non-conductors under the influence of Forschungsgesellschaft Druck e. V., Mnchen www.fogra.orgvapour absorption. In both cases, these changes occur as aresult of changes in air humidity. Numerous instruments of We would like to thank FOGRA for making textsdifferent design are available for these measurements available to us from FOGRA Praxis Report 50,sword gauges for measuring humidity in stacks of paper,"Klima, Papier und Druck" bysurface gauges for measuring sheets and reels of paper. Sword gauge Dipl.-Ing. (FH) Karl-Adolf Falter, 1998There are also sensors for measurements of air humiditywhich are consequently used to control moisturising andconditioning installations. Most of these instruments comewith a set of tools for easy calibration. To carry out thiscalibration process, the measuring cell at the tip of the instru-ment is sealed air-tight. Next, a saline solution is introducedin the very small space directly under the measuring cell inorder to set the air humidity. The values indicated by the toolare then compared to the values derived from the salinesolution, which must always be kept at an exact, prescribedtemperature. For the illustrations used in this brochure, we thank: Rotronic Messgerte GmbH, Ettlingen www.rotronic.de MAN Roland Druckmaschinen AG, Augsburg www.man-roland.com Wilh. Lambrecht GmbH, Gttingen www.lambrecht.net DRAABE Industrietechnik GmbH, Hamburg www.draabe.deSappi is committed to helping printers and graphic designers use paper in the best possible way. So we share our knowledgewith customers, providing them with samples, specifications, ideas, technical information and a complete range of brochuresthrough the Sappi Idea Exchange. Find out more on our unique web site.Surface gaugewww.ideaexchange.sappi.com1718 3. Climate and PaperThe interaction between climateand the processing of coated papersin printing and finishing Table of contents V Circumstances within the printers power to control I Introduction Circumstances in the workshop 10 Paper handling10 The situation in paper production2 and printing industry The situation in printing3 VI Special issues in 11 and finishing industryweb offset printingII Definition of termsVII Problems in web offset printing Weather, weather situation and climate,4 Blistering12 interior climate and surrounding climate Breaking in the fold13 Air temperature and air humidity, absolute 5 Fluting 14 moisture content, condensation point Expanding 15 temperature and relative humidity Humidity of materials, absolute moisture 6 content and humidity balance VIII Measuring temperature and humidityIII The influence of interior Measuring interior temperature16climate on paper flatnessand room humidity Measuring the moisture content of paper 16 The influence of air humidity7 Measuring the humidity balance of paper 16 Wavy edges and tight edges Electronic measuring equipment17 The influence of interior temperature8 The influence of humidity8 on curling tendencylX Concluding remarks18 The influence of stack humidity8 and temperature on ink dryingIV The relation between climate and technical printing problems Dimension variations 9 Static charge91 Obtain a printed version of this brochure from the Idea Exchange at www.sappi.com 4. l Introduction optimal condition for the subsequent printing process, it is wrapped in special packaging material that protects it fromThe situation in paper productionclimate changes in the environment. How the paper or, moreand printing industryspecifically, the fibre will react to climate circumstances at the printers or binders facilities or at the location of the endDiscussions about the effect of climatic influences during storage consumer, however, is a matter beyond the control of theand transport and in the process of printing and finishing, are as paper manufacturer.old as the industrial production of paper itself. Generations ofexperts have had to deal with the more pronounced negative As a global supplier of quality papers, Sappi has a market shareeffects and there are numerous publications in the field ofof 25% in coated woodfree papers for the Western world.specialist literature on measuring temperature and humidity. SoSappi Fine Paper Europe manufactures coated papers init is not as if experience is lacking on the subject. Still, many of seven different mills across Europe, using state-of-the-artthe relations have not yet been sufficiently explained. And in technology for the production of, mostly, woodfree coatedsome cases, cause and effect remain completely obscure. In papers for the printing industry. Innovation and continuousthe practice of paper processing, many delusions and misunder- development are among our key priorities.standings still exist, particularly with respect to the interactionbetween climate, paper and printing. Gratkorn mill houses the worlds largest and most advanced paper machine for woodfree coated paper. All seven of ourIn modern production facilities, paper intended for sheet offset production facilities can look back on a long tradition of paperprinting is prepared at a relative humidity of 50%, with a deviation manufacturing and several of our paper mills with integratedtolerance of 5%. Papers intended for web offset printing havepulp production have led the way in new technologies for thesimilar or slightly lower humidity values, depending on quality. paper industry.These humidity properties are continuously monitored in all stagesof the production process. And in order to keep the paper inSappi Ehingen2Obtain a printed version of this brochure from the Idea Exchange at www.sappi.com 5. The situation in printingand finishing industryNormally speaking, there are few climate related problems inprinting and finishing. As a result, climate only becomes anissue when printing problems, such as dot doubling, mis-registering, creasing or curling, do occur. Obviously, the likeli-hood of this happening, is more pronounced in seasonswith extreme weather conditions hot summers and coldwinters. In these periods, improper handling prematurelyunwrapping the paper, use of paper that is too cold orunfavourable conditions in the printers or binders facilities,can have disastrous consequences for the flatness andrunnability of the paper.This publication is intended to help clarify some of the moreserious negative effects of climate circumstances. It offersguidelines for correct handling of coated papers, one of thepre-conditions for optimal control during the actual processof printing.3Obtain a printed version of this brochure from the Idea Exchange at www.sappi.com 6. ll Definition of terms In conditioned locations, heated during the winter months, but not air-conditioned, relative air humidity is the reverse ofWhen we use the term weather, what we actually mean areoutside air humidity. When the heating is on, during winter,the atmospheric conditions at a certain location at a specific inside air humidity is at a minimum. During summer, it reachespoint in time. When we refer to the weather during a longermaximum levels.period of time, we talk of the weather situation. Finally, there are the climate conditions in the immediate vicinityThe concept climate is slightly more complex. It refers to the of an object, in our case a reel of paper or a stack of sheets.long-term weather conditions or weather situation in a certain Here, the term surrounding climate is sometimes used.region in terms of temperature, air humidity, air pressure,precipitation, wind direction and wind-force, cloudiness andsun hours.Interior climate is a term used for the air condition in roomspartially or completely shutting off people and equipmentfrom the influence of outside climate conditions. The interiorclimate, in other words, the climate condition of the imme-dia