The Munken Guide to Uncoated Paper

The Munken Guide to Uncoated Paper

MUNKEN PURE ROUGH 120g/m² The Munken Guide to Uncoated Paper A workshop of common understanding for better results At the mill in Munkedal, we believe every part of the production process is equally important for achieving a quality result. And while we all know the definition of quality may vary from one person to the next, the way we see it, clear communication is key to achieving a common goal. This guide contains detailed information that will help you avoid taking chances when it comes to producing printed matter on uncoated paper. By having a single reference document, there can be better communication in each step of the process, ensuring all parties have the same expectations on the final artwork. The guide is divided into four workshop sessions. While some of you may know the contents inside out, others may be understanding it for the first time. The aim is that by using this guide, all the questions such as, Am I using the right ICC profiles?, Is the image adjusted for uncoated paper?, Does the printer need additional information? may be better answered to obtain the desired results. So, equip yourself with the knowledge provided in this guide, and use it to enhance your next project. Because, as you probably agree, when it comes to producing great artwork, the common language we should all be speaking is quality.

MUNKEN PURE ROUGH 120g/m² Table of contents Art Workshop Session 1 The paper Session 1:1 The make-up of paper Pulp Fillers Water & moisture content Chemicals Session 2 The repro Session 2:1 Main paper issues in repro p. 34 How does the repro affect the result? p. 34 Screen/Raster p. 36 Dot gain p. 36 Total ink coverage Session 1:2 Production p. 11 Production Session 1:3 Paper properties p. 12 Wood-containing & woodfree paper p. 12 Grammage, thickness & bulk p. 13 Roughness p. 13 Brightness & shade p. 14 Opacity p. 14 Porosity & absorption Session 1:4 Fibre direction & format p. 16 Fibre direction p. 16 Format p. 16 Reel formats p. 16 Sheet formats & sizes Session 1:5 How to choose paper p. 22 The paper choice p. 22 The choice of shade p. 22 Opacity in your printed matter p. 22 The paper feeling p. 23 Images on different paper p. 23 Text on paper p. 23 Lifespan p. 24 The environment & recycling Session 1:6 Storage handling & conditioning p. 25 Temperature & humidity Session 2:2 Image p. 40 Image types p. 40 Image format & quality p. 40 Image resolution & pixels p. 41 RGB & CMYK p. 41 File types p. 42 Paper & colour space p. 43 Spot coloured areas & images p. 43 Black & white images p. 43 Six-colour separation p. 43 Image preparation p. 43 Short summary Session 2:3 ICC profiles p. 46 Overview p. 46 Calibration p. 46 Characterisation p. 46 Conversion p. 46 Paper perspective when creating an ICC profile p. 48 A paper ICC profile p. 48 Different types of ICC profiles p. 49 Basic & special ICC setting Session 2:4 Production flow p. 50 Production flow & colour management p. 50 CTP & paper types p. 51 ISO Standard p. 53 Image references p. 54 Image optimization p. 56 ICC uncoated profile p. 58 ICC coated profile p. 60 Colour separation p. 66 Screens p. 68 Black & white/ duplex/ triplex p. 70 Ink drying 2 Art Workshop Table of contents

MUNKEN PURE ROUGH 120g/m² Table of contents Art Workshop Session 3 The printing Session 3:1 Printing methods p. 80 Offset p. 80 Sheet offset p. 80 UV sheet offset p. 82 Web offset heatset & coldset p. 82 Flexographic printing p. 82 Digital printing p. 83 Inkjet, digital printing with ink p. 83 Digital printing with toner/xerography & laser p. 83 Pre-print in a conventional press Session 3:2 Offset printing & uncoated paper p. 90 The offset principals p. 90 Water, ink & paper interaction p. 90 Different inks p. 91 Ink density & uncoated paper p. 92 Back pressure p. 92 Print powder & after print stocking p. 92 Ink drying & paper p. 93 Press varnish p. 93 Print quality on paper Session 4 The post production Session 4:1 Effect enhancing & post production p. 100 Foil blocking p. 100 Embossing p. 100 Varnishing p. 100 Relief printing p. 101 Laminating p. 101 Die cutting p. 101 Hole punching p. 101 Perforation Session 4:2 Binding p. 102 Bookbinding p. 102 Folding & scoring p. 102 Binding p. 102 Trimming Summary Bear in mind p. 114 Key points p. 115 Summary charts p. 116 Your own keypoints p. 126 Munken Design Range Table of contents Art Workshop 3

4 Art Workshop Session 1 The paper

Session 1 The paper Paper is an extremely broad concept. The variations are almost limitless, and it is not only the visual impression but also the tactile qualities that make each paper unique. This is why paper is far more than just a surface. Paper can convey feeling and add an extra dimension to your printed message. Our aim is to give you the knowledge to be able to distinguish one paper from another, but with particular reference to uncoated paper. Uncoated simply means that the paper has no added layer on the surface and is completely natural. We hope this knowledge will help you select the best paper for your particular end use by being able to recognise the individual qualities and properties of the paper you see. Session 1 The paper Art Workshop 5

MUNKEN PURE ROUGH 120g/m² 6 Art Workshop Session 1 The paper

MUNKEN PURE ROUGH 120g/m² The paper master Leif Lundgren A great mill is nothing without its paper machines. And the paper machines are nothing without the skilled craftsmen running them. Leif Lundgren is a paper master at the mill in Munkedal. The 80-metre-long paper machine he is in charge of during his shift produces some 50 000 metres of paper every hour. Being a bit of a control person, Leif and his team hang up a huge sheet of paper on the lightbox every twenty minutes and slowly search the surface to make sure the paper is up to Munken s high standards. Session 1 The paper Art Workshop 7

MUNKEN PURE ROUGH 120g/m² 8 Art Workshop Session 1 The paper

MUNKEN PURE ROUGH 120g/m² Session 1 The paper Art Workshop 9

MUNKEN PURE ROUGH 120g/m² Session 1:1 The make up of paper In simple terms, paper consists of pulp, filler, water and chemicals. The ingredients are combined according to the unique recipe for each particular paper, and the grades are then produced in a way that ensures they have the desired properties. Pulp In school, we used to learn that paper comes from trees. This is of course true, but also an extreme simplification. It would be more correct to say that pulp consists of cellulose fibres that usually come from pulp wood which in turn comes from trees. Cellulose can also be extracted from cotton or grass, but here we will be focusing on pulp made from wood. The most common wood types used for pulp are hardwood as aspen, eucalyptus and birch, and softwood as pine and spruce. Different types of wood are used because the properties of the fibres vary. For example, hardwood fibres are shorter and give the paper good opacity and formation, while fibres from softwood trees are longer and make for a strong paper. There are two main ways of producing cellulose fibres from wood: a chemical method and a mechanical method. With the chemical method, which produces chemical pulp, cellulose fibres are released from the other constituents in the tree trunk by first being ground into chips and then digested using chemical additives. This method produces strong, almost pure cellulose fibres which are highly resistant to ageing. Since this method almost exclusively uses the tree s cellulose around 50-55% of the tree s volume the resulting product is often called woodfree pulp. The other constituents in the tree are instead used as many different kind of raw materials or energy, which also means that many modern pulp mills are more than self-sufficient in terms of energy. The production of mechanical pulp, on the other hand, involves grinding the tree in a mill or between grindstones until the cellulose fibres have been separated. Thus the name mechanical pulp as the fibres are extracted using a mechanical method. Moreover, unlike the chemical method, mechanical pulp production also utilises other parts of the tree such as lignin and resins so that almost 95% of the tree s volume is exploited. Mechanical pulp is therefore often called wood-containing pulp, as all the wood-containing substances are still there. There are several different variations of chemical and mechanical pulp. Also, combinations of the two methods are used to produce a third type of pulp, semi-chemical pulp, one example being Chemo Thermo-mechanical pulp, known as CTMP. In CTMP production, the tree is turned into chipwood in the same way as in the chemical method, and the chips are then partially treated with heat and chemicals before the fibres is separated mechanically. Fillers Pulp made of fibres therefore represents the most important ingredient in paper, although it alone is not enough. Additives are also required, one being filler. As the name suggests, the task of the filler is to fill in the gaps in the complex fibre network. A paper made with filler is softer and more even. It has better formation, higher opacity, better inksetting properties, a smoother and more flexible surface all of which make for better printing characteristics. There are various types of fillers, the most common being calcium carbonate, e.g., limestone, and clay, e.g., kaolin or china clay. The choice of filler depends both on the desired paper parameters and on the type of production system. The filler will affect certain paper parameters like shade, opacity, porosity, stiffness, etc. For this reason, different types of calcium carbonate are also used. They vary depending on how they are ground, original brightness and if they are treated in different ways. Some common names are GCC and PCC. Each mill has a very sensitive production system with process water, and this can be acid or alkali/ neutral. Calcium carbonate is only used in a alkali /neutral system and results in a paper with a high ph value, i.e., an alkali/neutral paper. Kaolin filler is normally used in an acid system and produces a paper with a low ph, i.e., an acid paper. A paper s life span partly depends on whether it is manufactured in a basic/neutral or an acid system; if it s acid-free or not. This is because a paper made in an acid system is broken down from within by the low ph value, while the opposite applies for a basic /neutral paper: the high ph value helps the paper better withstand external acid stress. This is a requirement for an age-resistant paper. Water & moisture content Paper also contains some moisture in the form of water, commonly between 3 7% of its weight. The moisture level depends on the application and printing process the paper is intended to be used in. The water content of paper is expressed in two measurements: absolute humidity (AH) or relative humidity (RH). Absolute moisture refers to water content as a proportion of the paper s weight, for example 5.5% of the total paper weight. Relative moisture is a quota figure that defines existing water and the paper s (water) saturation at one and the same temperature, e.g., 50 55% at 20 C. If the temperature or air humidity in the paper s surroundings change, the paper will either release or absorb moisture. This in turn means that the paper may change format or become wavy during exposure resulting in poorer printing properties. It is therefore essential to handle and store paper in the correct way. This is discussed later in this session. Chemicals Paper production also requires other chemicals in addition to fillers. These are necessary primarily for the paper to be made, but also to ensure that the finished product has the desired properties, such as extra strength, better water resistance and the right shade. For instance, stock-sizing is used to stop the paper absorbing too much moisture, while the manufacturing of surface-sized fine paper also uses a starch additive to make the paper more print-friendly and durable. Furthermore, shading dyes are also usually required so that the paper maintains a consistent colour from one production run to the next, as the shade of the pulp frequently varies. In order to achieve higher brightness, an OBA, or Optical Brightening Agent, is also used. The OBA and dying inks will also interact to gain a final perfect shade. Production chemicals will always be necessary to obtain a stable chemistry in the production process, and then a stable product quality. Paper is almost a 100% natural product, but as always when chemicals are used, it is essential to use the right type of chemicals to avoid environmental impact and also get a final product that is harmless. For this reason there are very strict controls today both by local authorities and the EU via the REACH system. Paper grades can also be tested for compliancy with food contact as well as for safety of toys, and these should be the best guarantees for a safe paper choice. 10 Art Workshop Session 1 The paper

MUNKEN PURE ROUGH 120g/m² Session 1:2 Production Once the pulp has been produced, paper is manufactured in two stages: stock preparation and on the paper machine. Production In stock preparation, the fibres in the pulp are beaten to give the paper special properties, such as optimum strength and fibre binding. In addition to pulp, the stock ingredients usually comprise of stock size, calcium carbonate, shading dye, and 99% water. Paper production begins with the stock mixture being fed into the head box, which is the starting point of the paper machine, and sprayed onto what is called the wire. The wire section is basically the paper machine s first dewatering process. Using one or two wires or straining cloths, the water in the stock is removed with dewatering elements and vacuum, and the moisture content of the mixture decreases considerably. It is also in the wire section that the paper begins forming, and the fibres orientate themselves mainly in the direction of the fast moving paper web. From the wire, the still wet pulp moves on to the press section, where it is dewatered further using pressure between cylinders and felts. The pressure in the press section also influences the finished paper s bulk, stiffness, opacity, strength and roughness. The next stage is the drying section, where the paper passes over a number of steam-heated cylinders, and the majority of the remaining water is removed. Only now, after the drying section in which almost all the moisture has been removed, can the word paper be used in its true sense. As the paper comes out of the pre-dryer, it is often surface sized. Surface sizing means that a thin film of a sizing agent, most often starch, is applied to the surface for extra strength and printability. The paper then goes on to the after-dryer still at the same high speed, where it is dried after starch has been added. This stage is omitted if the paper is an unsized quality. Before the paper is completely ready and wound onto a large reel called a tambour reel, it is often calendared, pressed between cylinders, were pressure and friction are applied to reach the desired surface smoothness and the final thickness. In the final stage of the process, the finished paper is wound onto large tambour reels, and then cut down into smaller reels or sheets. The entire process in the paper machine takes very little time, between 10 and 30 seconds from stock to finished paper. During this brief sequence of events, the stock is dewatered and becomes paper. The paper machine is therefore, quite simply, a large dewatering machine. WIRE SECTION PRESS SECTION DRYING SECTION Head box Upper wire Pre-dryer Surface sizing After-dryer Calendering/smoothing Tambour reel Lower wire Session 1 The paper Art Workshop 11

MUNKEN PURE ROUGH 120g/m² Session 1:3 Paper properties All papers are unique and have different properties properties that are crucial to the final result of a piece of printed material, how it is perceived and the feeling it conveys. Choosing the right paper is therefore important, and requires some knowledge. Quite simply, you have to understand the preconditions and properties of the paper in order to make the correct choice. Wood-containing & woodfree paper Earlier in the section, we explained the two principal ways of manufacturing pulp, the chemical method and the mechanical method. The chemical method removes practically all wood-containing substances from the wood, apart from the cellulose. This is why paper that contains woodfree pulp, i.e., chemical pulp, is called woodfree. Woodfree paper properties include high strength and good performance. A woodfree paper can fulfil the requirements of permanent paper, the ISO 9706, if certain parameters are fulfilled. The parameters are maximum permitted lignin content, an alkaline buffer of calcium carbonate and high enough strength. The production of mechanical pulp exploits the majority of the tree volume, which means that parts other than the pure cellulose are added to the pulp mixture. A paper with mechanical pulp is therefore called wood-containing paper. The properties of a wood-containing paper include good strength, high opacity and a natural feel. Paper grades, which mainly comprise of semichemical pulp (CTMP), change the traditional distribution of woodfree and wood-containing paper because benefits are gained from both types of pulp. By definition, these are often referred to as wood-containing paper, although they are often more similar to woodfree grades, depending on the desired function. when choosing a paper, although it is often used somewhat carelessly to refer to a paper s thickness, which is misleading as thickness actually depends on the paper s bulk. Thickness=grammage x bulk A paper s thickness is measured in micrometres (µm) thousandths of a millimetre and is the distance between the paper s two surfaces. Thickness is in many ways an important consideration in paper selection, as it affects the stiffness, stability, feel and of course thickness of the final printed product. This is particularly true in books, which can contain hundreds of pages of sheets. Bulk=thickness / grammage As the above formula shows, bulk defines the relationship between a paper s thickness and its grammage. The dimension refers to the volume or compactness of a paper which is then cm3/g. The correct definition of bulk is in fact the reciprocal value of density, (g/cm3). These formulas show that the bulk is actually the volume divided by the weight and not the thickness divided by the grammage. However, when the weight and the volume of the paper are both per m², the calculation will give the same result. A paper with a low bulk is more compact than one with a high bulk, and contains less air. A low-bulk paper is therefore thin and heavy, while a highbulk paper is light, airy and thick. bulkier paper dramatically increases stiffness and rigidity. When comparing an uncoated paper with a coated, the coated is, in general, more floppy than its uncoated equivalent in grammage. The definitions of woodfree and wood-containing paper differ between standards, but the most common is that woodfree paper can consist of up to maximum 10% mechanical fibres. Paper made to meet the requirements of the various standards for age-resistant paper (such as ISO 9706) can, in principle, not contain any mechanical fibres at all. Grammage, thickness & bulk Grammage, thickness and bulk are three important and common paper properties. The three are often mentioned in the same breath, for the simple reason that they are mathematically linked. Thickness and grammage are defined independently of one another, while bulk, sometimes also referred to as volume, is the relationship between grammage and thickness. This section defines each term more closely. Grammage=thickness / bulk Grammage is the most common measure of a paper s weight, and is given as weight per square metre, e.g., 130 g/m². The concept is fundamental Compare bulk 1.4 and 1.13 on pages 16 17 Bulk is a very important factor when producing books, and is crucial to how the final result is perceived. If the aim is to convey an impression of a thick book rich in content, a high-bulk paper should be used. If the idea is to fit in a lot of text but still keep the book thin, a low-bulk paper is more appropriate. Bulk can also, in many cases, be a question of saving costs. For example, when setting up a mail campaign and using a paper with a slightly higher bulk, a lower grammage can usually be used without detracting from the feeling. This could save a lot of money in distribution costs. We often talk about what yield we get per m² and the result is that you get a higher number of printed books, brochures, DMs, etc. with same weight of paper, a better yield of paper and money. We recommend that you compare different papers according to the image and see for yourself that a This sheet has a high bulk it is airy, light and thick. Bulk 1.8 x grammage 130 g/m² gives a thickness of 234 micrometres. This sheet below has a low bulk it is thin and heavy. Bulk 1.1 x grammage 130 g/m² gives a thickness of 143 micrometres. 12 Art Workshop Session 1 The paper

MUNKEN PURE ROUGH 120g/m² Session 1:3 Paper properties Roughness In some way, the surface of a sheet of paper is like the topography of a landscape, with peaks, troughs and minor bumps. The term used to define a paper s deviation from an absolutely smooth surface is roughness. Roughness is expressed in ml/min, referring to the volume of air that passes between the paper and the flat surface of a measuring device in one minute. This measurement is called the Bendtsen value. In general, uncoated paper has a higher roughness more peaks and troughs on the surface than coated paper. In order to reduce roughness, the paper is compressed and smoothed in a calendar. This makes for a certain link between bulk and roughness, as a smooth, compressed paper will have a lower bulk. So to achieve a higher bulk, the evenness of the paper surface will have to be compromised to some degree, and the paper will be rougher. And this is, of course, significant to the final result. In some cases the aim is a nice, even surface, while in others the printed matter is intended to convey more of a coarse, robust impression. Surface roughness also affects the printing process, especially in high-roughness papers where irregularities can affect the graphics. There are also other standards with similar methods to measure the paper surface roughness as Bekk, Sheffield and Parker Print, etc., and when measuring coated paper the smoothness is normally defined according to Parker Print Smoothness PPS. Brightness & shade Just like the Innuits have many different words for the colour and consistency of snow, so paper has a broad spectrum of brightness and shades. All with one thing in common: they enhance the impression of the finished printed product. Because as we know, there is a great difference between white, natural and coloured paper. However, all pulp of the same type, basically has a similar brightness and shade. For this reason, different chemicals and dye colours are added to distinguish the finished papers brightness and shade. Adding OBAs (Optical Brightening Agents) to the mixture also increases the final brightness of the paper. OBA works by converting reflected invisible UV light into a visible blue white light, which makes the paper look brighter than it actually is. This effect can easily be verified by using a UV-lamp. optical parameters are with the CIE whiteness, ISO brightness and the shade. Although whiteness, brightness and shade are visual properties that may seem hard to distinguish at first sight, they do in fact describe different things. Brightness is expressed as a percentage of how much light of one particular wavelength, in the blue area of the daylight spectra, the 457nm, that is reflected from the paper. Whiteness is a related parameter, although this is gauged over several wavelengths, also in the blue area, it gives a value closer to what the eye actually perceives. The fact that these two most common parameters more or less express the different levels of blueness in the paper, we often need some supporting information when papers differ in other colours. In fact, two papers with the same whiteness or brightness can have differences in yellow, red or green. Shading dyes are also added to most papers. For example, a blue shade is often added to a paper when the aim is to give a whiter impression, while a touch of yellow will make the paper appear more natural. Therefore, it is common to describe the shades of the paper in words such as white, natural white, bluish white or cream. The shade of a paper can actually be well-described in a common colour model called CIE Lab, which gives the level of the blue, yellow, red and green shades and also the lightness. This is often used when controlling quality during production, but is not as common for explaining paper parameters. As you have already understood, the colour of paper is a science in itself. However, the information provided in technical specifications is very helpful. But two fundamental things are needed to make a good visual comparison between paper shades: samples and the right lighting conditions. Samples with different shade levels and references are normally needed when visually determining the paper s optical parameters. Without comparing references, it is very hard to do a proper evaluation. When evaluating shades, you should also use the correct lighting conditions. In the paper industry, we use D65 as an illuminant, while in the evaluation of printed colours D50 should be used. In most cases, these specific lights are not available at hand, and then the best practice would be to use and compare the samples with several different light sources. Compare paper shades on pages 96 97 The most common way to describe a paper s Session 1 The paper Art Workshop 13

MUNKEN PURE ROUGH 120g/m² Session 1:3 Paper properties Opacity Another word for opacity is non-transparency. Therefore, the higher a paper s opacity, the less translucent it is. A paper with 100% opacity is therefore completely non-transparent, while one with a low opacity, such as greaseproof paper or tracing paper, lets a much higher proportion of light through. Opacity depends on how well the paper surface can scatter and absorb light. The perceived opacity is altered during printing, after which we refer to print opacity. This is an important factor to consider, as printing ink penetrates the paper and reduces its opacity, which could result in the print being visible through the sheet. This is especially important in double-sided printing, particularly on low-grammage paper, when images or text on one side can disturb the other. It is therefore important to think about where on the page the text and graphics should go Porosity & absorption Porosity and absorption are two important factors where coated and uncoated paper differ. These two parameters have a major influence in the way paper absorbs the printing ink, and we would therefore like to spend some time reflecting on these. Porosity and absorption are not normally considered when choosing a fine paper, and therefore these parameters will seldom be found in technical specifications. They are more related to the way ink is absorbed and how images will turn out on the paper. It is not easy to imagine that a paper, which is based on cellulose fibre, is a porous material of which 70% of the volume could be air. As we explained earlier, the cellulose fibres form a web with gaps and pores in between. Even if the gaps are filled with fillers, the paper will still be a porous material, where air can pass through and liquids can be absorbed. The way paper absorbs liquids is due to the porosity, but also the way the paper is surface sized and the surface is treated. On uncoated paper, the actual fibres absorb liquids as well. This is often called the micro porosity, which affects the way liquids are absorbed into the paper. The total absorption on uncoated paper occurs both in the paper and on the surface, creating a bleeding effect in all directions. On coated paper, the surface coating will cause a totally different absorption behaviour. The coating layer consists of pure minerals like calcium carbonate and/or china clay with a certain amount of binders. This layer is much more compact than the fibre network, but this layer is also highly porous on a fine micro porosity level. This porosity is created by the gaps between the mineral particles, which are very small. The coating layer is developed to interact with the offset printing inks. It will have a kind of filtering effect that keeps the colour pigment, together with some amount of ink binders, on top of the surface. But the main part of the solvent and liquids will be absorbed into the coating layer. The colour pigment particles should be bigger than the micro-porosity gaps to be kept on the surface. The absorbtion of liquids is very quick with the main part soaking into the surface with a minimal bleeding effect. To summarise the absorption of ink; on uncoated paper, both the solvents and pigments will be absorbed into the paper s surface. This will also cause the ink dots to grow and more colour pigments to be absorbed into the paper, resulting in a lower ink gloss. The coated paper will, instead, very quickly absorb the ink straight into the coating layer, keeping the pigment more or less on top of the surface, providing a high ink gloss. Uncoated and coated surfaces are fundamentally different. The surface of uncoated paper is made of pure fibres, and the porosity and absorption are caused by the gap between fibres and the fibres own absorption. The coated paper has a surface of mineral coating on top of the base paper, and absorption is caused by the micro porosity in this coating layer. 14 Art Workshop Session 1 The paper

MUNKEN PURE ROUGH 120g/m² Session 1 The paper Art Workshop 15

MUNKEN PURE ROUGH 120g/m² Session 1:4 Fibre direction & format In much the same way as fish in a school orientate themselves to swim in the same direction, most fibres point in the same direction as the paper web during production. The fibre direction is a crucial parameter in the printing and in post production but most of all important in printed matter. A book or brochure with the wrong fibre direction will immediately give a feeling that something is wrong, therefore getting the fibre direction right, is one of the first things that needs to be learned when working with paper. Fibre direction The direction the fibres orient to during paper production is simply called the paper s fibre direction and sometimes the machine direction (MD), the opposite direction is called the cross direction (CD). In the fibre direction, the paper will be stiffer and thereby harder to bend across. This has implications in the feeling of a printed matter. For example, a brochure with the wrong fibre direction feels less stable, and in a book, the pages feel stiff and are harder to open. It is easy to find out in which direction a paper s fibres run by laying a sheet over the edge of a table. Across the fibre direction, the paper will be stiffer and harder to bend and fold. Another way is to drag hard with your thumbnail and index finger along the paper s edges. The edge that distorts most runs across the direction of the fibres. The paper supplier s size information also reveal the fibre direction, as the figure given first (e.g., the 210 in 210 x 297) refers to the length of the side running across the fibre direction. There are several other ways to note fibre directions, as for example, noting the fibre directions size in bold or adding a terms like long grain when a paper sheet is longer in the fibre direction or short grain when it is shorter in the fibre direction. Format As the paper comes off the paper machine, it is wound onto a large reel called a tambour reel. If the paper is to be used in a web offset press it is cut down into smaller reels, otherwise it is cut Fibre direction. Sheets can be cut so that the fibre direction runs along the short or long edge of the paper, thus influencing the way the size figures are given. into the required sheet sizes. Sheets and reels are the main paper formats, but there are a great many different formats within each primary group that are either standard or customised depending on the customer and intended use. A paper buyer can be relatively certain that standard formats are in stock with the supplier. However, if a customised format is required there may be a slightly longer delivery time, as it first has to be ordered and then produced at the mill. Reel formats Like sheets, reels are cut into the diameters and widths ordered by the customer, and also according to weight and length. However, standard formats are less common in reels, although they do exist. All paper reels also have a core in the centre so that they can be brought into the printing press. Common standard core diameters are 70, 76 and 153 mm. Sheet formats & sizes The sheeting machine cuts the paper into sheets according to the customer s ordered dimensions or a standard format, and the paper is then either delivered on pallets usually in a bulk pack where all the sheets are stacked up or in smaller packs, where sheets are wrapped in reams of 500, for example. As we mentioned before, the sheet dimensions are given depending on fibre direction. The first figure is the length of the side that runs across the direction of the fibres. There is also a wide assortment of formats in standard use in different countries. Suppliers normally offer these as standard stock at a fixed number of sheets per pallet. Two common standards are the A series and the B series, and below you can see the similarities and differences. There are also versions of these standard sizes that are adapted for local demands or for special applications. 1414 353 176 88 707 297 148 74 62 B7 B8 B5 52 A7 A8 A5 125 B6 B3 105 A6 A3 250 B4 1000 B1 210 A4 841 500 B2 420 A2 Direction through paper machine 1189 594 A1 297x210 210x297 16 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² Session 1 The paper Art Workshop 17

MUNKEN LYNX 150g/m² 18 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² The selector Örjan Öhman Most printers have their house paper. Still, keeping updated and informed about what paper can do is what every successful printer continuously needs to do. Örjan is a classic jack-of-all-trades character. With eleven years in the craft, he is involved in processes spanning from paper purchasing to overseeing the post production work. This holistic view on the production and the in-depth understanding of all stages is invaluable when choosing and purchasing paper to the printing house. Being a keen golfer, he also understands the virtues of keeping up quality every single step of the way. Session 1 The paper Art Workshop 19

MUNKEN LYNX 150g/m² 20 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² Session 1 The paper Art Workshop 21

MUNKEN LYNX 150g/m² Session 1:5 How to choose paper In some cases, the paper is only a means of carrying information, and very little attention is given to the paper itself. So the standard house paper will be the obvious choice. But often, the ambition of the total impact of printed matter is higher. The paper then becomes a key part of the whole message the feeling, shade, environmental aspects and the way images are reproduced need to interact. The paper choice Deciding whether printed material actually is needed is not as obvious today as it was in the past. These days, there are many alternative ways of spreading information and reaching the target group. However, the decision to use paper as the material is often an easy choice, due to many obvious reasons. The actual choice of a specific paper grade will affect the impact of the printed material in many ways, and therefore needs to be very carefully considered. If chosen correctly, the paper can boost the impact, but interpreting different technical paper parameters into the effect in your own printed matter requires some reflection and knowledge. If the paper choice is not well made, the whole concept can be lost. On the other hand, the perfect choice of paper can support the purpose of the content and the total sum may be greater than the sum of each individual part. When choosing paper for a graphical production, there are two main perspectives to consider; the technical criteria required for functionality and, the more subjective, how the paper suits the idea of the end product. There are, of course, other perspectives, such as price and availability, etc., but the aim of this guide is to focus on the paper itself. Earlier, we explained the technical parameters of paper. In this part of the session, we will aim to link them to a more subjective perspective in the paper choice. If we, from a subjective perspective, were to divide the paper choice, we would start with visual appearance in shade, the tactile paper feeling, how paper can reproduce images, readability in text and finally the lifespan of the paper. When you have obtained the basic knowledge on how paper can be perceived, your experience of how paper characteristics can be used will add to this knowledge for many years to come. So don t hesitate on exchanging experiences with others. The choice of shade For some paper grades, standard shades has been developed, as for example, standard offset grades or A4. But for some grades a unique shade is developed so that the paper will stand out. Therefore, the first decision is whether to choose a unique shade or not. Whites and creams are very common paper shades. But the most common papers today are white, which normally have different levels of a slightly bluish tone. The blue tone in white paper will often give a slightly colder impression than a cream shade paper, which has a warmer, yellow tone. White paper will give more contrast in images. Whereas a cream shade paper is recognised as friendlier to read on, and that s why most novels are printed on a cream shade. The paper shade we see is actually a reflection of the surrounding light on the paper. This means that the lighting conditions will heavily affect the shade we perceive. So, it s always a good idea to consider where the printed matter will be used and to test the paper in different lighting conditions, for example, daylight, tube light and bulb light. You will notice a big difference when changing the light. Note that the paper shade measurements, such as ISO brightness and CIE whiteness, will not cover all the colour aspects of a paper and therefore the visual comparison between paper should support your final decision. Opacity in your printed matter Another obvious visual effect when something is printed on paper is the opacity. Remember that on a computer screen, there is no disturbance from the backside, however on paper, the text and images on one side of the sheet may show through, creating unwanted effects on the other side. Therefore, it s important to choose a paper with an opacity level that s high enough for your needs. The opacity level is influenced by the grammage the higher the grammage, the higher the opacity. Therefore, sometimes there needs to be a compromise between the grammage and opacity you choose. However, the measured paper opacity is only part of the visual opacity in printed matter. How ink-heavy the images are and how the layout is structured both play large parts in the final, so called, print opacity. So we strongly recommend that you consider the layout and image types, and the show-through effect they will have, and select the grammage and opacity level based on these. The paper feeling One of the most important and talked about aspects of paper is the physical feeling. The paper feeling can, of course, mean different things to different people. But in simple terms, it is the way paper feels when you touch and hold it. It can be warm or cold, smooth or rough tactile, soft or stiff, thick or thin. The first thing you will react on when touching a paper is whether it s warm or cold. This is an unconscious, physical reaction to how different paper surfaces draw heat away from your fingertips and although obvious, is not often considered. Uncoated paper is a wood fibre material, and will therefore feel warmer. Whereas a coated paper, which has a surface of minerals, will feel colder. Natural feeling, tactile, robust and abrasive are words we use to describe the feel of paper. However, it s the paper roughness that we usually try and put words to. A smooth surface is often considered to give a more exclusive touch, whereas a rougher surface has a more tactile and natural feeling. The surface roughness will also, to some extent, affect printed images and it will be slightly harder to get the best result on a really rough paper. However, a rough surface will often give the image a very special character. Stability, stiffness and the perceived thickness will all come from the actual paper thickness. Papers containing the same grammages can be produced in different thicknesses, and this is defined as bulk levels. A bulkier paper has a higher thickness, at a given grammage, and will feel more stable and robust than a low bulk paper. The thickness of a paper will also give a different impression on how solid the printed matter feels. If the thickness is too low, it will give a floppy and sub-standard impression. If it is too high, it can have an unpleasant feel and can result in pages in a book or brochure not opening in a nice way. Very often, the format of the printed matter, in terms of height and width, is well defined. However, the thickness also greatly affects our initial impression. A thick, heavy brochure or a thin light one will communicate different things. There are great opportunities to make the best first impression by choosing the right grammage, thickness and bulk. 22 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² Session 1:5 How to choose paper Images on different paper So how will images turn out on different paper? This is a wise question to consider at an early stage. And you will get the best answers by looking at good printed references for the specific grade. These should be confirmed as having top quality in the repro and print, otherwise you might get the wrong impression of the possibilities. When you are searching for the paper feeling you want, it s important to know how different papers will affect the printed images. For example, coated and uncoated papers will show colours in very different ways. This will be explained in more depth later in this guide. Another factor that will affect images is the paper shade. The base shade of the paper will give a certain tone to the image. For example, a yellow toned paper will give a slightly warmer feeling, and a blue tone a slightly colder one. At the same time, the blue will increase the feeling of white and often give a higher contrast. Text on paper We already mentioned that cream shade paper is considered to be more reader friendly. Several studies have shown this to be true, and black text with good contrast on cream shade paper enables you to keep concentration levels up for a longer period of time with your eyes becoming less tired. Specular reflections from paper cause major disturbances when reading text. Coated paper has a certain gloss level, which you will find in the technical specifications. This value gives information about the actual reflection at a specific angle the higher the value, the higher the reflection. Uncoated paper tends not to reflect directly due to the light being scattered so much. The absence of reflections enhances readability to a greater extent. In most printed material, there is a combination of text and images. Therefore, you should consider if the importance of the text is greater than that of the images, and if it is, then readability is a vital parameter. Lifespan Is the lifespan in a paper a subjective parameter? We would say yes, because a paper will not just break or die of old age after a certain point. However, all paper will age over time, and this will become obvious from two main aspects, yellowing and decreased strength. The effect of this will be that at some point, you will think the printed matter is not as fresh as you would like it to be. In your planning of a production, you should normally consider the time the paper is required to stay fresh. For example, a direct mail just needs a few days, but an advertising brochure may need a year or two. Whereas a schoolbook, a cookbook or a novel should be able to be passed on to future generations. Yellowing is an aspect that usually needs to be considered when selecting a wood-containing paper. However, all paper will change colour to some extent. For example, the OBA in white paper will fade somewhat, and even woodfree paper will become slightly more yellow over time. Whereas, while the effect on wood-containing paper can start after just a few days, depending on what lighting conditions it is exposed to, with woodfree we re talking decades or even several hundreds of years. Regarding strength in the paper, there are two issues to consider: the binding and how the paper will withstand the handling it is supposed to endure. In the binding, the paper strength plays a great part actually keeping it all together. A few basic rules can be applied: woodfree paper is stronger than a wood-containing one, higher grammages are stronger than lower grammages and uncoated paper will be stronger than a coated one at the same grammage. There is, however, an additional strength aspect how the paper changes when it is exposed to moisture. Paper can remain strong in wet conditions from different sizing and surface treatments. Therefore, it s important to consider whether the paper will be exposed to humidity in some way. Finally, it can be interesting to reflect over the lifespan of your information when choosing a long life paper. You probably no longer use the content of a floppy disk created 15 years ago, but you can still read a book published then. Do you think you will be able to read the information you store digitally today in 30 50 years? Perhaps, but today there is still no future-safe digital media. By choosing the right paper, however, you can ensure your information lasts several hundreds of years. Session 1 The paper Art Workshop 23

MUNKEN LYNX 150g/m² Session 1:5 How to choose paper The environment & recycling Caring for the environment has become a natural part of our everyday life. An increased number of reports about global warming, waste mountains and polluted waters has made us more and more environmentally conscious. We are faced daily with large and small environmental choices and as a producer of printed matter, the paper choice is one of them. Essentially, paper is a product with many environmental benefits and to use paper as a media carrier is, most of the time, the obvious and most environmentally friendly choice. Paper is a renewable, recyclable and biodegradable material. What makes paper so unique from an environmental perspective is that it is produced from cellulose fibre. The cellulose fibre used in paper has a life cycle in balance with nature and it is an amazing material for many reasons. First of all, it is chemically built up by carbon, which the trees, as they grow, take up from the atmosphere in the form of carbon dioxide. In return for the carbon dioxide the trees give back oxygen, which is essential for all life on earth. The fact that the trees take up carbon dioxide makes the cellulose fibre a carbon-neutral raw material and this is one of the main reasons why the carbon footprint of paper and printed matter is very low. One other advantage with the cellulose fibre used in paper is that it can be recycled and re-used many times. These days, paper can be almost 100% recycled, and to minimise the paper industry s impact on the environment, it is essential that the fibres are recycled to the greatest extent possible. In the paper manufacturing process, the paper waste from quality changes and trimming is efficiently taken care of by recycling it directly back into the process. This is possible because this paper is clean which is to say that it has no printing ink on it it is ground down, added to the pulp stock and used again. This type of re-used surplus paper is called broke, and it ensures that everything in the process is exploited to the maximum. But maybe the greatest gain in terms of reduced environmental impact is the collection and recycling of all sorts of printed matter and packaging paper in our community. Paper that has been printed on or used in some other way nearly always contains impurities that a normal paper mill cannot deal with. In this case, it is sent to a special recycled-paper mill that has the necessary cleaning systems. The paper undergoes several stages of cleaning before being used to make new paper. Recycled paper is primarily used for newsprint or cardboard, but is also found in some other grades of paper. quality and each time the fibre is recycled, to use it in paper grades with lower quality requirements. In this way, the fibre will be used to its maximum potential with minimal input of chemicals and energy for the recycling process. So, for high quality printed matter it is a good environmental choice to use paper made of virgin fibre when it is used and recycled, it will be a necessary input of fresh fibre into the paper recycling system and can be re-used for production of new paper. Even this guide, which has been made from virgin fibres and broke, is on its way into an eco-cycle. It may be recycled and become a newspaper in just a few years time, when you think you know everything about paper and printing. But what we really want is for you to keep it for many years to come, which is why we have made it from woodfree grades. If you do choose to keep it, it can last for several hundred years. Everything has an end and so does the life cycle of the cellulose fibre. Even though it can be recycled many times, it will eventually reach its end-of-life phase. But here the benefits of being a natural material are also evident. Paper can be incinerated to generate electricity or central heating for houses. The carbon in the cellulose fibre is then released and goes back into being the carbon dioxide it once was before taken up by the growing trees. If the paper by accident ends up in nature, the same thing will happen as the cellulose fibre degrades naturally that is the advantage of a biodegradable material. Indeed, paper is essentially an environmentally friendly material, but to make the best paper choice from environmental perspective there are a number of aspects to consider. What are the impacts on water from the paper production? What is the carbon footprint of the paper? Does the wood raw material originate from sustainable forestry? What environmental certifications does the paper have? All of these are relevant questions to ask. To analyse and compare in detail all different environmental parameters is however a complex task and it does not always give an easy answer. One paper grade can be better from one perspective a second paper grade from another perspective. Therefore it could be a good recommendation to focus on a limited number of environmental aspects or certifications, the ones which feel most important and relevant for you, and make the comparisons and choices based on those. So, what are the most common environmental aspects and certifications for paper? We can recommend looking for the following: environmental criteria from a life cycle perspective and with a wide range of environmental aspects taken into account. TCF and ECF means that the paper has not been bleached with chlorine gas. The bleaching actually takes place during the pulp production and nowadays most pulp mills have stopped using chlorine gas for bleaching. Instead oxygen, ozone, hydrogen peroxide or chlorine oxides are common methods. TCF stands for Total Chlorine Free and means that the pulp has been bleached without any chlorine compounds. ECF stands for Elemental Chlorine Free and means that the pulp is bleached without chlorine gas but that chlorine oxide is used in combination with, for instance, oxygen and hydrogen peroxide. ISO 14001 and EMAS these are Environmental Management Systems (EMS) which many mills have in place in order to work with environmental issues in a structured way. One important principle in such work is to set and follow up environmental targets in order to continuously improve the environmental performance. Paper Profile this is an environmental product declaration (EPD) for paper where the most important environmental parameters are given, such as emissions to air and water, waste to landfill and purchased electricity. Declarations according to Paper Profile follow a well-defined method in order to provide comparability of the data. So there are many certifications and tools to help you find the most environmentally friendly paper. For us, as a paper producer, the most important thing is probably to have an open approach in the contact with our customers; it is through continuous dialogue and openness around environmental issues that you can feel confident that you have made the right paper choice from an environmental perspective. Since the cellulose fibres are processed and circulated several times, they eventually wear out. This is why new or virgin fibres will always be necessary in the paper industry. From an environmental perspective, it makes most sense to use the virgin fibres in paper grades of highest FSC or PEFC certification certifications that guarantees that the forests have been managed in a responsible way. Nordic Ecolabel (Svanen) or EU Ecolabel paper which is certified or approved according to these environmental labels meets strict 24 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² Session 1:6 Storage, handling & conditioning Like almost all other materials, paper will change due to ageing and the surrounding environment. Paper is a natural living material that creates the final artwork. The understanding of these fundamental changeable parameters is vital both during production and in the final printed product. Temperature & humidity All paper contains a small amount of moisture, and is highly sensitive to changes in temperature and humidity in the surrounding air. In humid environments, the paper s fibres expand and make the sheet swell. If on the other hand the environment is dry, the opposite occurs and the paper releases moisture. These phenomena can cause dimensional changes and waviness, which in turn can lead to printing problems. In order to reduce this external influence, and to protect the paper against dirt, damage and other wear before it reaches the customer, the paper is wrapped. However, the wrapping should be kept on even after the paper reaches the customer, as it will begin to interact with the surrounding humidity level as soon as the wrapping is opened. If the premises do not have the right temperature and humidity, this can lead to the problems mentioned above. maintains the existing moisture level while keeping water out. Corrugated board end-discs are used to cover the ends of the reels. There are also several types of plastic packaging. One of these is stretch film, whereby thin plastic wrap is wound several times around a pallet or reel to ensure a stable parcel. The film also provides protection. Another plastic wrapping is shrink film. The pallet is wrapped in plastic polythene which then shrinks after passing through an oven. Finally, any air is removed by compression. Following this process, the pallet is practically vacuum-packed and very steadily supported and well protected. Below are suggested conditioning times, in hours, of original wrapped paper depending on temperature differences between paper and environment. To reduce the risk of dimensional change, the paper should be stored in the same environment as it will be used in, to make sure it adapts to the right temperature. This is of course especially important if the paper has been transported over a long distance or has previously been stored in a cooled warehouse or over the winter. Temperature differences between paper and environment Volume of paper (m3) 0,2 0,4 0,6 1,0 2,0 Humidity, after temperature, is the second major factor which influences the behaviour of paper. The suggested maximum difference between the relative humidity of paper and the printing hall, shouldn t exceed 10%. Otherwise, paper processing problems might occur. In the case of standard offset paper, the suggested humidity of the printing house environment should be in the 40 60% range at a temperature of 22 23 C. Also bear in mind, that once the dimensional changes caused by excessive humidity differences have occurred, the paper will never return to its original shape, even if the correct air humidity level is restored. There are several different kinds of wrapping, the most common being paper and plastic. Paper wrapping usually consists of a special type of kraft paper with a thin embedded plastic film, and this is wrapped around the reel of paper. This 5 C 6 8 10 11 12 6 C 7 9 11 12 13 7 C 8 10 12 13 14 8 C 9 11 13 14 15 9 C 10 14 17 18 21 10 C 11 15 20 22 24 15 C 16 23 28 32 36 20 C 22 33 45 52 60 25 C 27 43 64 77 100 Conditioning time (h) Session 1 The paper Art Workshop 25

MUNKEN LYNX 150g/m² 26 Art Workshop Session 1 The paper

MUNKEN LYNX 150g/m² Session 1 The paper Art Workshop 27

28 Art Workshop Session 2 The repro

Session 2 The repro Not so many years ago, the graphical reproduction of images, as we normally just refer to as the repro, was a manual craft. The repro was very complex work that needed years of experience and very special equipment. Today, the complex part of the work is done under the hood of any modern computer with the right software. The repro is today possible for anyone to do. However, to reach the level of quality that is needed in a high quality production, craftsmanship and skilled art workers are needed more than ever. A well done repro and a repro adapted to the paper will enhance the images and will use the full capacity of each paper grade. This session covers the most general aspects that occur in prepress from a paper perspective and particularly for sheet fed offset. The topics explained evidently occur in all printing techniques, but to a different extent. The recommendations given are mainly for sheetfed offset in order to achieve the highest quality. Session 2 The repro Art Workshop 29

MUNKEN LYNX 150g/m² 30 Art Workshop Session 2 The repro

MUNKEN LYNX 150g/m² The magician Hans-Olof Axgren Understanding how a specific paper behaves in a printing machine and how different inks act in the same process is key to successful retouching and repro. Having an interest in photography helps Hasse to do a better job as a retoucher. But retouching for printing is something completely different from improving your personal images in Photoshop. In printing, the magic lies in meeting the attributes of the chosen paper, the printing press and inks. Still, the most important aspect of Hasse s job is to be accurate and never, ever cut corners. And the biggest reward? A great result, of course. Session 2 The repro Art Workshop 31

MUNKEN LYNX 150g/m² 32 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2 The repro Art Workshop 33

MUNKEN LYNX ROUGH 120g/m² Session 2:1 Main paper issues in repro Often the smallest changes have the greatest impact. The essence of years of experience with uncoated paper could be condensed into a few main issues. The handling of these main issues; dot gain, total ink coverage and screen can be the difference between a true artwork and a disappointment. Of course, other parts in the process are also important, but they might not differ between paper types. How does the repro affect the result? The aim of a good repro is to reproduce an image, most often printed on a paper, in the best possible way. The repro should handle the most important parameters that will affect the final result. Keep in mind that it is the actual repro that sets the main quality level on the end result, not the actual printing. The repro will affect two important things: the printability and the runability. The printability, or as we normally say, the print quality, is the actual visual quality of the image. To some extent, this is a subjective term whether it s visually similar to the original image, or it s a certain desired effect in print. But it is also measurable on certain parameters, such as dot gain, density, misregistration, etc. When the repro is done incorrectly for uncoated paper, what you often see is that images are darker then expected. Dark areas can also lose details and contrast. Another common effect is that colours are not as clean and bright as they could be. The main impact on print quality in connection with uncoated paper and repro is due to dot gain, and the chosen screen ruling and screen type. This will be described in more detail later in this session. Runability is when we talk about the actual production in the press, which involves stability in the press, ink drying time and problems like smearing and set off. It also consists of problems in post production, like binding. Different papers absorb ink very differently, meaning the possible amount of ink that can be applied is different. If a paper is over inked, it may cause several problems, such as prolonged drying, smearing and set off, both in press and in binding. The biggest impact the repro has on the runability is in the Total Ink Coverage (TIC), the density value for each process colour and the balance between the TIC and density. A few small changes in the repro will have a huge effect on the entire production and end result, and will also be the difference between a true artwork and a disappointment. It is not more difficult to perform a correct repro, but to understand cause and effect might require some study and experience. Therefore, we recommend that anyone working with production of printed matter tries to understand the basics, so that each person knows what is important to communicate and when. used terms in the graphic design and printing industry, although, these days, we tend to refer to the screen, screening, screen ruling and screen density of a digitally processed image. The word raster comes from the Latin word rastrum, meaning to divide. A normal, classic photograph consists of continuous tones or gradients of colour. However, these tones cannot be reproduced in print quite simply, a printing press cannot handle the task. In order to make the images printable, they are therefore screened, i.e., divided into a multitude of microscopically small dots. The dots in a screened image therefore give the eye the illusion of a single continuous image, with tone values of differing strengths, just like a normal image. Screen dots are created in a computer called Raster Image Processor (RIP), and then exposed to the printing plate in the CTP, which will be further explained later in this session. The size of conventional screen dots ranges from 1 to 100%, creating a perception of half tones. Tones of colour can be obtained by changing the size of the dots. A 5% dot is just a very small dot giving a very light hint of colour on the paper. 50% dots cover half of the paper surface and then give a mid tone of colour. When the dots are at 100%, for instance, they have completely run over into each other to produce a fully covered surface, which is called a full tone area. A full tone area will not show any details, because it s only when there is space between the dots, the screen is open and it s possible to show details. Offset inks are transparent, so the paper always acts as the fifth colour. But it s when a screen is open that the paper surface and colour will really give brightness and detail to the image, between the printed ink dots. On a conventional screen, also called AM screen, the screen dots are arranged in lines or rows. The density of these lines is called the screen ruling or screen density, and is normally measured in lpi (lines per inch) or l/cm (lines per centimeter). The denser the screen ruling, the harder it is to distinguish between the dots and the detail of the image improves. When the ink dots representing each colour are printed on paper, they jointly make up the final image. In order to avoid unwanted pattern distortion the Moiré effect the dots need to be placed at specific screen angles. with different frequencies in darker and lighter areas. A dark area means that a lot of dots are added and in light areas just a few. The benefit of stochastic screen is that it can reproduce very fine detail and eliminate the Moiré effect. Screen/Raster Raster dots and raster density are traditionally In a stochastic screen, also called FM screen, the dots are all the same size. They are very small, 10 30 microns, and they are placed randomly and 34 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2:1 Main paper issues in repro When talking about screen dots, resolution must also be mentioned. This is because screen dots are represented by the small pixel dots in the digital file, whose proportional size define the printout resolution. This is usually measured in dpi (dots per inch), or ppi (pixels per inch) Producing a high screen density will also require a high printout resolution. This will be further explained later on but it should be mentioned here that the higher the screen ruling, the higher the number of pixels needs to be, and stochastic screen normally demands much higher resolutions due to the very small dots in the raster. Today, a new type of screen, called a hybrid screen is becoming more commonly used. The hybrid screen combines the conventional AM screen and the stochastic FM screen into one. Normally, the stochastic FM screen is used for lighter tones and the conventional AM is preferred for darker tones. This enables a higher screen resolution and finer reproduction of details in print, all of which enhance the overall print image quality. When printing four colours, four different screens are printed on top of each other. Therefore, to ensure each of the four screens is positioned correctly, there are several control lines or crosshairs of each process colour in the edges of the printed sheet. These lines should perfectly fit over each other, otherwise there will be a certain degree of misregistration and the image will appear to be slightly blurry. Conventional screen Stochastic screen A screen rose. In a conventional screen the lines are placed at different screen angles, one for each process colour. The colour tones are varied by varying the size of the dots. When the dots are laid overlapping one another, a new colour is created. The illusion of different colours is also created when the screen dots are close to each other. Compare different screens on pages 66 67 Session 2 The repro Art Workshop 35

MUNKEN LYNX ROUGH 120g/m² Session 2:1 Main paper issues in repro Dot gain Dot gain, or dot expansion, is a necessary concept to know about in printing on any paper, but especially on uncoated. Dot gain occurs in all printing, but is greater on uncoated than coated grades, due to the rougher surface on uncoated paper and its ability to absorb ink. The phenomenon occurs in the various stages of the printing process. First of all, digital information is converted into dots on the actual printing plate. The plate picks up ink which is transferred onto a rubber blanket, and finally onto paper. At each stage, the diameter of the dots increases slightly, and as a result the dots and therefore the colours bleed out and the images lose both coverage, particularly in the dark areas, and detail definition. In practice, the images often come out too dark and drab, and this must be taken into consideration during the repro. In the past, dot compensation was relatively complicated to handle and it was often very imprecise. Today, it can be very exact, but the challenge is to add the right correction for the specific paper grade. The dot gain will vary greatly depending on the paper grade, but also on screen type, screen ruling, press, ink and several other aspects that can be hard to grasp. To handle each step separately would be very tedious. Therefore the way to handle the total dot gain is by doing a test print in each different environment with all parameters well considered. Then a total dot gain will be defined in what is called a dot gain compensation curve. The test is done by printing bars in each percentage of the entire half tone range, from 1 to 100% dot size, and also one set of bars for each of the process colours. The unavoidable dot gain will show in the form of a difference from the original size of each dot. The dot gain will not be the same over the whole range; there will be no dot gain at all, in 0% or in 100% dots due to obvious reasons. It will be less in lower half tone areas, increase in the middle part and the decrease again in the higher range of the halftone area. The result is a curve, with a certain percentage difference in each percentage of the halftone range, from 1 to 100%. These dot gain curves can be used in different ways, but should be implemented in some way during the process. We have not explained all parts of this process yet, but we will give a short introduction anyway. We will also explain further about ISO-standard paper curves that are a set of standard dot gain curves, which normally are used in the CTP. The compensation curves that come from test prints on specific paper grades can also be embedded in the ICC profiles or used in different ways in the process. In some cases, the ISO standard curves or similar standard curves can be used to compensate the print process and additional curves for each paper can be used. It is then important that these interact correctly. If the print processes are kept stable and calibrated, the main variations in print production will be due to different paper. This will also be very obvious in dark and blurry images if the wrong compensation is used. Therefore, we strongly recommend that you ensure both that the correct ICC profile is used but also that the correct compensation curves in the CTP are used, and that these all work well together. Compare the effect of dot gain between uncoated and coated repro on pages 58 59 Total ink coverage For a digital RGB image to be printed, it needs to be transformed into four process colours, which, when mixed correctly, can recreate all printable colours. The four colours are called CMYK (Cyan, Magenta, Yellow and Key-colour, i.e., Black), and these days you can generally choose at the scanning stage to separate a digital image into CMYK straight away, or keep it in RGB throughout the process and separate it in the final phase. When the image is separated, it is divided into the four constituent colours, and reproduced again as an image on the printed paper, with all the colours and shades of the original. Each of the CMYK colours is transparent, and the various shades are blended to form a colour image, as the dots are printed directly on top of each other, ink on ink. In screen-dot printing, dots of different colours side-by-side also create an illusion of a new colour. However, this stage demands thought and care. Because the four colours are printed onto one another, in extreme cases this may mean you are using 100% ink in each layer, giving a tota++l ink coverage of 400%. The total percentage of ink that will add up on the paper is called the Total Ink Coverage (TIC). As the quantity of ink is also increased when printing on uncoated paper, the result will be far too much ink to produce a satisfactory printing result. Had the material been printed anyway, the result would very likely have been a worse image with bleeding, reducing coverage in dark segments. Also, the ink would have smeared and the drying time would be far too long. Therefore, in order not to over-ink the paper, a maximum limit for total ink coverage in the image needs to be set when separating the image. Assuming the printing equipment is precisely calibrated and the repro and plate have been prepared to perfection, the ink coverage on uncoated paper can be a maximum of 280%. However, a general guide limit is 260%, as the results are rarely improved if the quantity is increased. Instead, there will be problems with ink drying, set-off and smearing, and the detail definition in the image will certainly be compromised. The values given above refer to the total ink coverage percentage obtained on plate and transferred to the paper. This is important, as it can affect the final total ink coverage percentage, depending on how dot gain is compensated for and how the image is processed. So what can you do to reduce the total ink coverage without detracting from the image s quality? A common solution is Under Colour Removal (UCR) or Grey Component Replacement (GCR). And how do you do that? Tradition has taught us that equal parts of cyan, magenta and yellow will create grey, which means that there is always a common grey component in all shades that use all three colours. Let s look at an example: if you have a shade that requires 70% cyan, 50% magenta and 50% yellow, the three 50% proportions actually only create the grey shade in the colour. You can therefore replace 3 x 50% with 50% black/ grey. Add the remaining 20% cyan and you obtain the desired colour. The difference is that the overall colour saturation decreases by 100 percentage points. Of course, all parts of an image never require high ink coverage, but in most cases, there are one or more dark shaded areas. UCR/GCR therefore allows you to keep the total ink coverage below the recommended 260% limit for uncoated paper, while at the same time, you achieve a more even degree of inking and avoid problems with long drying times, set-off and smearing. Compare the effect of four-colour separation with a total ink coverage of 260% and 320% on pages 62 63 36 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2:1 Main paper issues in repro Dot gain The illustration shows dots in three different halftone areas, ranging from 0 to 100 % in a digital version, on the printing plate and finally on the paper. Digital The first halftone area shows blue and yellow marked dots at the original and intended sizes in the light, medium and dark areas of the digital image. Plate The second halftone shows two alternative dot sizes on the printing plate, the yellow dots are without any dot gain compensation and the blue dots have been made smaller by the dot gain compensation for the specific paper. 100% 50% 0% Digital Paper The third halftone shows the two alternative dot sizes and the effect of the dots on the paper. The yellow dots have expanded much more than the original values. This means that in light and medium areas, the colour tones will become much darker. In the area above a certain point, 85 90%, the dots have merged into a full tone area, meaning that all details have been lost. The blue dots that represent the compensated dots however, have regained their intended size and will reproduce a perfect colour tone without any loss of detail in the dark areas. Plate Paper 100% 50% 0% The dot gain is not adjusted for uncoated paper and the dots are greater than intended. The dot gain is adjusted for uncoated paper and the dots have the correct size. The dot gain is adjusted for coated paper and the dots have the correct size. On the uncoated surface, the ink dots are absorbed slowly into the paper surface and dots expands in size. This makes the dots less sharp and colours slightly dull. Compensating for dot changes is important, otherwise the ink dots will not give the intended colour. The coated surface quickly absorbs the ink dots. The ink pigment mainly stays on top of the coating but the ink solvents are absorbed into the coating layer with less dot gain. Therefore, the dots get sharper and the ink pigment adds a certain gloss to the colours, however, the right compensation is still important. Session 2 The repro Art Workshop 37

MUNKEN LYNX ROUGH 120g/m² Ever considered the maximum percent of ink coverage you should use on uncoated paper? Find out on page 36! 38 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2 The repro Art Workshop 39

MUNKEN LYNX ROUGH 120g/m² Session 2:2 Image A picture speaks a thousand words, as the cliché goes. But is it true? Well, true or not, few would dispute the fact that images are an extremely important and central part of the graphic production process. In other words, the choice of images is important and should not be taken lightly. Images in combination with the paper quality are very much the first impression of a printed product. Image types What is a good image and what is a high quality image? These may partly be in the beholder s eye, but also very much depend on your knowledge in the art form of photography. We will not go into this art form in such, but will, from a paper perspective, give some thoughts and recommendations. When it comes to image reproduction, one will have to answer a fundamental question: is photorealistic reproduction really needed? In many cases, perfect realism is not needed, or even wanted. It s true that coated paper was originally invented for photorealistic reproduction. However, coated grades are often considered to have a plastic-like feeling, and lack many of the tactile qualities of uncoated grades. In the past, when repro was done by hand, it was difficult to achieve nice results on uncoated paper. However, as we intend to demonstrate in this guide, a few simple clicks and the settings will steer the process in the right direction. For every art worker and creative artist, it s essential to have basic knowledge about the material you work with. The original image is actually only one part of the final image since the material it is printed on will add another dimension not just visually, but the tactile feeling. Everyone will be able to touch and feel the image. Therefore, it is important to consider, when shooting or selecting images, how the final images will turn out when printed on uncoated paper. Print references of high quality images will be good tools to be able to fully understand what the end result will be. By selecting images with knowledge of how they will turn out on different paper, it can help to make the best choices, and allow you to use the paper s own characteristics to enhance the desired effect. Knowledge and experience are often the most important factors when selecting images for a certain paper, but a good image classification is also very helpful. From a paper perspective, you could use the following categorisation as a starting point: Dark and heavy with a large part close to full coverage Mid tone with the majority of colours in mid tone Light and bright with minimal colour coverage Colourful images with clean colours Less colourful images with less clean colours High contrast and definition or low contrast and definition High degree of fine details or less or no details Bright and shiny metal, chrome, gold, etc. While most images are a blend of two or more of the above, considering the different categories makes it easier to prepare for and prevent surprises, so that difficulties can be overcome whether it s the whole image or just one part that needs special attention. Uncoated papers absorb ink very differently to coated papers. The effect is less ink gloss, ink density and contrast. On the other hand, uncoated paper creates a much more natural image and tactile feeling. You could say that when printing on uncoated paper, you are actually colouring a natural material, therefore, the image and paper merge into one common expression. The first and most obvious effect on uncoated paper is that the colours appear more matt and dull. In some cases, this is seen as a negative. While, sometimes achieving the true uncoated effect with matt colours and less contrast is the aim. But often, great colourful images are desired. In those cases, we recommended using extra colourful images with higher definition and contrast. This will enhance the contrast between the uncoated paper surface and the image, and a more colourful result will be easier to achieve. Dark and heavy images can have a tendency to lose details. Therefore it is important to consider the end result more carefully and see to it that the repro is prepared with extra care. Image format & quality Today, most images are taken by digital cameras, even if analogue film cameras are still used. Nevertheless, if the image should be printed, sooner or later it needs to be converted to a digital form, and later also into a printable form. When printing on uncoated paper, maintaining high quality standards throughout the whole process is important. A camera can capture millions of colours. However, the challenge of retaining as many of those colours as possible starts when the image is stored on a device. When images are handled, stored and compressed, there is a risk of losing essential colour information. Image resolution & pixels There are two types of images: vector based and pixel based. Vector-based images, also called vectorgraphics or linework, are based on simple geometric shapes, or vectors, in two dimensions. These are normally used for lines, text, drawings, CAD images, etc. Pixel-based images comprise of pixels, which stand for picture elements. These are the smallest parts of an image and are a numeric mapping of colours and lightness arranged in a matrix, where each single cell, the pixel, contains the necessary information. This enables an image to be digitally stored and displayed on digital equipment, such as a computer screen, as dots of colour. The resolution of an image represents the number of pixels per unit of length one inch. For example, an image consisting of 300 pixels per inch (ppi) would have a resolution of 300 ppi. The number of pixels within a defined area is normally counted in megapixels (MP), i.e., millions of pixels. This is obtained by multiplying the image size in both directions (height and width) by the ppi. For example, an image on an A4 (210 X 297mm) with a resolution of 300 ppi will have 2480 pixels in the width direction (210mm) and 3504 pixels in the height direction (297mm). So if we multiply 2480 by 3504, we see that the image has a total of 8.7 MP. When an image is enlarged, its pixels will also scale accordingly; and the larger the pixels, the less of them can fit into one inch, resulting in a lower resolution. Therefore to keep a resolution of 300 ppi on a larger image, the total amount of MP needed will increase. On a computer screen, the demand for ppi is quite low. For example, an image with a resolution of 72 ppi will display well and image sizes are often reduced to minimize the file size. Print on paper, 40 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2:2 Image however, needs a resolution of around 4 5 times higher. The reason is that print screen dots are normally created from 2x2 pixels (4 pixels). A basic recommendation then is to have at least double the screen ruling. For example, 2x150 lpi screen ruling gives 300 ppi. Also note that the dots in stochastic screens require a higher value because they are much smaller than in conventional screens. The recommendation is to compare with at least 175 lpi of conventional raster. From a paper perspective, this is important because if an image is prepared for one type of paper, it may not work on another type.for example, in newsprint, where a screen ruling of 80 lpi is sufficient, an image may be saved in 160 ppi. This image will then not work if printed on a higher quality paper that can handle 150 lpi or more. Therefore, we recommend keeping images, whenever possible, in a resolution high enough to handle all paper types, and in turn the highest screen rulings. RGB & CMYK The pixel numeric data contains the colour information for each pixel whether it s described in RGB or CMYK. In the graphics industry, RGB and CMYK are the two main colour models used to handle the colours in images. is important that the camera is set to the RGB mode that will give the largest possible colour space. Otherwise, the number of possible colours will be lower from the beginning. A common RGB mode for computers and screens is srgb. This has a smaller colour space than newer versions. For example, AdobeRGB has a larger colour space and is more suitable for images used in graphical production. There are also other modes that can be used, but a recommendation is to use the mode with the largest possible colour space. File types When it comes to storing RGB or CMYK images, it can be done in a variety of file types. The different file types are developed to compress an image and make it possible for the image to be handled by different software. When it comes to image quality, it is important to Colours on the screen means that coloured light is transmitted from the computer screen. This means that if the screen is not calibrated correctly, the wrong colours can be shown. distinguish between destructive and nondestructive file formats (also called lossy and lossless). The destructive format will cut data and colours, and non-destructive will keep data and colours. In the graphical industry, it is best to save images in non-destructive formats. Common nondestructive formats include TIFF and RAW, and a common destructive format is JPEG. Some formats are specially developed for use on computer screens, such as GIF and BMP, and should not be used in graphical productions. Today, most of the work on images and text is done in software such as Adobe Photoshop and InDesign, but usually, final artwork is saved and delivered in PDF (portable document format) that embeds all content into a single document. PDF has become a world standard for saving and distributing documents. PDF/X is a describing standard protocol that is good to follow when creating a PDF, securing that the PDF delivered to the printer fulfils the needs for printing. RGB is often called the additive colour model because it uses different proportions of Red, Green and Blue colours light from, for example, a computer screen, to visualise all the other colours. No light gives black and all three in full gives white. CMYK is often called the subtractive colour model because a colour on a material means the material is only reflecting part of the incoming light and cancelling the rest. In the same way, printed ink filters the incoming light and visualises a colour by reflecting only that part of the spectrum. If it reflects the entire spectrum, you see white, and if no colours are reflected, you see black. The colours used when printing in CMYK are often called the process colours. Devices that emit light, like a computer screen, will always show images in RGB, and ink is printed in CMYK. The RGB colour model is the regular and best way to store digital images, because it contains a higher amount of possible colours than CMYK. The total amount of possible colours in images can be presented in a colour space and shown on a chart. There are several RGB standards and types, and these will provide different possibilities to handle the total colour space the actual amount of colours shown. Therefore, when taking pictures, it Colours printed on paper means that CMYK ink reflects the incoming light as colours from the paper surface. Therefore, the type of light source is important as it will affect the appearance of colours. Session 2 The repro Art Workshop 41

MUNKEN LYNX ROUGH 120g/m² Session 2:2 Image Paper & colour space In pure physics a colour is defined as light from a mixture of wavelengths within the visible light spectrum. Humans don t see wavelengths as such; humans actually only see red, green and blue with the cones on the retina and black and white with other receptors called the rods. The human eye is extremely sensitive and can distinguish between a huge amount of colours. This was studied in an experiment called Standard Observer Experiment, done in 1931 by the International Commission on Illumination (in French, Commission Internationale de l Eclarage, CIE). From this experiment, colour models were derived to be able to describe the colours we can see and approximate the perception of the human eye. The basic colour model is the CIE Lab colour space, a mathematical model containing all visible colours that can be seen by humans, showing colours in three dimensions L Lightness from total white to total black, a axis from yellow to blue and b axis from red to green. This is the Cartesian definition like in a graph. The alternative way is to describe a color with so called polar coordinates i.e. the Hue [the angle measured counter clockwise starting at red], the saturation or Chroma [the distance from the center of the space] and the Lightness range. This is also defined in the CIE Lab system as Lch. One specific colour is referenced in the colour space by one set of coordinates, Lab or Lch. The standard unit between two colours in the CIE Lab colour space which can be distinguished by the human eye, has been set to equal 1. The boundaries are set to 100 units for each axis (L, a and b), giving 100³ possibilities and distinguishable colours. This has been shown to work pretty well in practice. However, it is still an approximation for the human eye, so it s hard to say exactly how many colours we actually can see. The mathematical model in itself can be divided in an endless numbers of colours, but humans will not be able to distinguish between all of these. In a digital file, the amount of colours can be calculated. For example, in an 8-bit colour file, 16.7 million colours can be defined. All of these colours can, in principle, be shown by a modern computer screen, but are not all visible for the human eye. Printing on paper will decrease this number down to 4000 6000 colours. The reason is that print on paper cannot reproduce the colour tones precisely enough to be able to distinguish between them. Also, the rougher the paper is, the higher the dot gain is and the more imprecise it will be, so it is even harder to show a large amount of tones. there are three ways to do this. One is by simply cutting off the colours and not actually handling them at all, this is called the relative way. Another is to recalculate the closest visual colour and replace the non-possible colours with the closest possible ones, or the perceptual way. One of the more common ways today is to actually use a version of the relative way and to cut the colour off, but also compensate the colour tone with more or less black, also known as relative with black point compensation. Different papers will have different colour spaces and different ways to calculate CMYK. Therefore, we recommend keeping an image in RGB mode for as long a possible, preferably in AdobeRGB. If the colour separation is done as late as possible, you will be able to obtain the best possible colours regardless of paper choice. The CIE Lab colour space is illustrated below in two dimensions with the coordinates of a and b and the range from 0 to ±100. All colours will have a position in these coordinates. If the third coordinate L (lightness) is added, the three dimensions will cover all the colours you can imagine. This means that all colours can be given a numeric value in Lab coordinates that can be used in technical devices. As an example, the yellow in the printed colour strip in the image part has an approx. value of L=86, a=4, b=68. Try to find the a and b position in the chart. In practice colour devices like cameras, scanners, printers etc are not able to handle all CIE Lab colours. Instead these devices and techniques use srgb, AdobeRGB color models or for printing inks CMYK. When converting colours between different devices or from RGB to CMYK, the CIE Lab colour space is often used in an intermediate step because its device independent. The aim when converting is also to maintain as large a colour space as possible throughout the whole process to be able to reproduce a wider range of colours in the end as there can be a risk that some colours are lost. The total number of possible colours for one medium is called the Gamut of, for example, a paper grade printed in CMYK. When measuring the total amount of colours for different papers, it becomes obvious that the biggest differences are mainly between coated and uncoated grades. When separating an image from RGB to 4 colours, the colours will be recalculated to the possible CMYK colour per each paper grade. And because each grade has its limitation, and CMYK can handle fewer colours from the beginning, colours will inevitably be lost. One of the tasks done in recalculations is handling the colour tones that don t fit into the CMYK colour space. In principle, This diagram illustrates the range of colours that various medias can distinguish between. CIE Lab / Human eye Computer monitor, RGB Paper in CMYK 42 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2:2 Image Spot coloured areas & images If an image, or drawing needs to be in an exact or very unique shade, it can be hard to reproduce in regular CMYK. For example, logos often need to be in a very precise colour. Then a ready-made spot or index colour can be the solution. Indexed colours are specially pre-blended colours available in a host of different shades. The most common colour system is the Pantone Matching System (PMS), but silver, gold and other metallic colours are also indexed colours. When selecting and checking PMS colours, it is important to check against the right sample charts a chart for uncoated paper to ensure the correct colour and shade reproduction. When printing gold or silver on uncoated paper, apply a suitable base colour first to make a good foundation for enhancing the gold and silver. Black & white images Not all images will be printed in four colour As we know, beautiful, well-reproduced black & white images are aesthetically effective. However, it is essential that they are reproduced and printed in the right way. This can be a problem, as it is sometimes difficult to reproduce fine details, blackness and depth by using only various shades of black ink. In order to produce a softer result, with a broader spectrum of fine details, one option is to use duplex or triplex i.e. tinted grey-scale images. Indeed, the fact is that four-colour printing is also often used even for black & white images as we explained earlier, the same amount of each colour gives a grey or black shade. As the name suggests, duplex involves using two printing inks rather than one, often black in combination with another colour or a index/pms colour. With triplex a further colour and ink is used, and usually one or two blacks are mixed with one or two index/pms or process colours. Both duplex and triplex are suitable for uncoated paper, as it can otherwise be difficult to achieve enough black in the dark areas. They also improve detail definition, and the image can be given that black feel which the aim is probably. One tip to increase the blackness in for example a headline is to add 40 60% cyan or another process colour. Compare the different black & white images on pages 68 69 Six-colour separation There are also a number of more advanced colour separations that will increase the colour range compared to the normal four-colour one. For example, Hexachrome with six colours by adding orange and green or using different Hexachrome colours. The art form of photography has entered into a digital era. In earlier days, the repro was more or less a straightforward task of showing an image as close to the original as possible. Today, a large part of the art form is more and more moving into the computer, and most of the work takes place after the picture is shot. This means that the photographer will often change and adapt the image to obtain a certain artistic look and feel before delivering to the repro. This however, creates new challenges for the repro work and the printers, because the changes and effects may be hard to handle or print. Therefore, it s extremely important that photographers are aware about which effects are best to be shown on screen and which print well on paper. Image preparation The image preparation for print should be done to ensure the best possible image reproduction on each type of paper, not to show a unique effect on screen or in digital proof that can never be recreated on paper. There is no digital proof that can fully render an image exactly the same way it will appear printed on uncoated paper. Therefore, it s essential to have a clear understanding on how you want the image to be perceived in a printed form. When preparing an image for print, the main choices to consider are if the image should be kept as original as possible, be altered to show a certain effect, or be altered to improve the final result on paper. Image preparation is usually done in several stages, and involves many different tasks, such as adjusting the colour balance, saturation, contrast, brightness and a huge amount of possibilities to manipulate and improve the image. In the past, this was often done in the CMYK mode, but today it is normally done in RGB. As described earlier, there are some basic parameters that will affect the image when it s printed on an uncoated grade. Our recommendation should then be to compensate the parameters that are affected by paper to minimise the negative effects and enhance the positive. This often means increasing the saturations on basic colours to keep them cleaner. Increasing the contrast slightly will also often improve the final results as some of the contrast and definition will be lost on uncoated paper. Increasing brightness should also be considered to compensate for the risk images becoming slightly darker. These adjustments will give the illusion of more colourful images, a larger colour space and higher contrast on the printed image. These tasks can be done in, for example, Photoshop in RGB or CMYK, and actually involve altering part of the colour space to achieve a better perception on paper. Short summary Printing on paper will reduce the colour space in an image to a great degree, but if it is as large as possible in the source file, it will increase the final possible printed colour space. Keeping the resolution in ppi at 2x the screen ruling is recommended. RGB or CMYK? It s normally best to keep an image in RGB mode as long as possible, then convert to CMYK in the final step of the process. File format will to some extent depend on the software used, but we recommend using a nondestructive file format as much as possible. Size of the final printed image if an image is enlarged, make sure a high ppi is maintained. Compare the different image adjustments on pages 54 55 Session 2 The repro Art Workshop 43

MUNKEN LYNX ROUGH 120g/m² 44 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Ever wanted to know what difference ICC profiles can make? Find out on pages 48 49 and 58 59! Session 2 The repro Art Workshop 45

MUNKEN LYNX ROUGH 120g/m² Session 2:3 ICC profiles An ICC profile is making something extremely complicated very simple. It will show your pictures with the same colours in any device or media you choose to use; the screen, the proofing or finally on paper. Most of the time, you don t even know it is used, for example on your screen,tv or camera. In this session, we focus on the output paper profile that, when correctly handled adjusts the image to the specific paper characteristics. Overview It all started in 1993; the ICC (International Colour Consortium) brought together a handful of companies with a view to simplifying the exchange of colour data in the graphics chain. This means that ICC knowledge and use of ICC profiles is mature and even papermakers are well aware of its importance in enhancing the quality of the end-product on paper. To make this possible, there are three principals that need to be understood and handled in a correct way by everyone involved in the production flow. From the scanner or digital camera to the screen; from the screen to the proof; then from the proofing to the offset press the colours must be respected and managed correctly. Regardless of where you are in the graphics chain, there are a number of steps that needs to be taken into consideration. These steps are: Calibration Characterisation Conversion (Separation) Calibration Calibration actually means to set the systems to the correct and ideal setting. If your screen is not properly calibrated, it will not show colours correctly. What s worse is that if you make colour adjustments in the image, they will most likely be the wrong ones. Calibrating equipment in the graphics chain means taking it to a chosen operating state and ensuring that it remains in this state. For example, calibrating a screen consists of using software and the correct measuring equipment (called a colorimeter) to set the screen s physical parameters; the white point, the contrast and the brightness. Calibrating an offset press consists of choosing precise parameters, for example, the dot gain, colour readings and greyscale, etc. These should then be monitored during printing to ensure they remain within an acceptable range. This is often done today by reaching the ISO 12647 standard. We strongly recommend that calibrations on screen and presses are done on regular basis to be able to maintain a stable quality. Characterisation You can actually create an ICC profile by testing how your media (the screen or the paper) will change colours, by comparing the colours in your media with a standard reference. This is called the characterisation of a media. In offset printing, this means printing a test chart in one specific press on one specific paper. This test chart consists of several hundreds of colour bars that will be measured by a photo-spectrometer and analysed by specific ICC profile-generating software. This process will determine how your equipment reproduces and presents colours under the current settings. The result of this characterisation is the actual ICC profile. The ICC profile is a translation table that allows the digital values in your image file to be transferred into correct ones. On a paper ICC profile, this translation table will be used when the RGB image is converted to a CMYK image. We recommend that you test and secure which ICC profiles will work for your chosen paper and if there is a need for creating new ones. This should be done before the actual production starts. Conversion Conversion means applying the actual corrections of the ICC profile from your image file to the fourcolour separation (CMYK). Whether it s done in Photoshop, with an image-by-image approach or as a batch in a more developed workflow, it means that the colour values from your document are translated. The values from the workspace in which the documents were created are translated into values that allow the right colours to be obtained with the selected printing system and paper. Each conversion is a mathematical transformation of the files and the values that are changed or lost can no longer be recovered by reversing the process. A conversion is done every time a file is transferred and processed from one type of equipment to another; e.g., while being transferred from the scanner or camera to your computer. However, when you open an image on your screen, a virtual conversion is carried out as a background task and doesn t change the file. If you use a software like Photoshop, you can decide to convert your files yourself from RGB to CMYK, and the full separation is done with all the consequences of this. Our most important recommendation is that you ensure the correct ICC profile is used and also in which stage it should be applied. If a separation is done, the following person in the production flow needs to have this information. Otherwise, they will have no knowledge of any changes that have been made before, with the risk of doing the compensation twice. Paper perspective when creating an ICC profile As mentioned earlier, the creation of a profile is called the characterisation on a media. When a perfect ICC profile is used, it should, in principle, make it possible to print a perfect image. However, this isn t entirely true. There will always be variations in the process and mainly in the printing press, due to different paper types. To limit these variations, a paper ICC profile comes with a set of certain added repro functions to handle different paper parameters. These are extremely important to be aware of, because they are actually a very big part of what in the past has been the actual repro work, and these are today handled by the ICC profile automatically. Below is a set of decisions and repro settings that, due to paper type and paper quality, need to be considered both before the ICC profiles are created and also when they are used. It is of greatest importance that these are chosen correctly, mainly when using different paper types, such as uncoated and coated. These settings are just as important when you create an ICC profile as when you are using it. If the choices, for example, differ in screen rulings or density values between the creation and use, they will not give the expected result. From a paper perspective, the most critical choices are: The screen ruling and screen type Density value Total ink coverage Which CTP curves that should be used If these choices are not handled with care and also communicated, it will be hard to reach the desired quality and levels. A typical example of a critical situation is when different people in the process comment on the actual printing, and have a strong opinion about how strong or dense the colours should be. If the profiles are set to a certain density value, it might create problems if these differ from the actual ideal profile values. Our recommendation is to clearly communicate which settings should be correct and have this as a starting point when printing starts. It is, of course, perfectly okay if all stakeholders agree to deviate from these settings, as long as everyone knows the consequences of it. We have explained these critical main paper issues in repro and the consequences of them in more detail earlier in this session. 46 Art Workshop Session 2 The repro

MUNKEN LYNX ROUGH 120g/m² Session 2 The repro Art Workshop 47

MUNKEN LYNX ROUGH 120g/m² Session 2:3 ICC profiles A paper ICC profile A major part of this guide focuses on the ICC profiles. This is due to a very important reason the main parts of the repro adjustment have been moved into the paper ICC profiles. Even if ICC profiles should be standardised, the main issues and core settings to handle dot gain and total ink coverage, etc., are open to anyone who creates the actual profile. This means there will be a number of profiles for the same paper that will be more or less specific to a paper and more or less adapted to different types of printing processes. First of all, there are different kinds of ICC profiles, such as input profiles from the cameras or scanners, display profiles for computer screens, and output profiles for printing and proofing. We will focus on the output paper profiles. The output ICC profiles are unique per paper type and therefore, there is a need to understand the basic variables that can be set on available paper ICC profiles. Different types of ICC profiles A very important perspective on a paper ICC profile is how specific it is set to be. In simple terms, we could say that a general profile will adjust for any press and any paper type. A specific profile will adjust for one unique press and one specific paper quality. Every profile will have a level of generalisation, and it s crucial to know to what extent. Just because a profile is used, doesn t mean that everything will be correct. A paper ICC profile is actually set exactly to the environment it was developed in. Every deviation from this will make the compensation less exact, and you cannot predict the result to 100%. Profiles will be more specific or general according to: Paper type, e.g., coated, uncoated, LWC, paper quality, grammage, etc. The print process and calibration, CTP condition, settings and plates press setting, blankets, ink, etc. An important part of this is also agreeing to what degree a chosen profile handles the chosen print environment. This is most crucial when profiles are added outside the control of the printer and when the printer receives a print-ready document in CMYK. There is no defined categorisation of paper ICC profiles, but if we were to roughly categorise the levels, they would be as follows: General General press and general paper type general profiles that will handle a general offset press and defined paper type. If the profiles are developed in an ISO certified environment, it will be a more well-defined process. Part specific Press and specific paper quality general profiles that will handle a general offset press but a specific paper quality. If the profiles are developed in an ISO certified environment it will be a more well-defined process. Specific press and general paper type general profiles that will handle a specific offset press and a defined paper type. Specific A truly specific profile that will handle a specific offset press and a specific paper quality. Specific press and specific paper quality plus project adaption in addition to being truly specific, it is also adapted to, for example, a special request or a specific image. The more specific a profile is, the more exact it will correct for deviations. This means that the more general the profile is, the greater the need will be to secure it by other means. This can be done by, for example, a real on-press proof printing or through experience from previous print jobs. Note that a soft proof on screen will not help, because it doesn t take into consideration the process steps after the image leaves your computer. specific paper. Compare the printing result between two uncoated ICC profiles on pages 56 57 These parameters are roughly the parameters that the ISO 12647 is meant to secure, but these will vary even if they are strictly secured and monitored. In every production and also in the graphical business, there is a set of tolerances that should be acceptable and this is also defined by the ISO standard. The basis of understanding normal variations, to a degree, also depends on the experience in working with printed matters. Therefore, it is very important that everyone agrees at an early stage on what quality level is required, and which deviations from an agreed proof should be accepted. So our recommendation is to use as specific profiles as possible, and when more general profiles are used, test them to ensure how they will work and if they are able to reach your ambitions on quality. It s important to remember that using a general profile doesn t mean that the results are always of less quality, but just that they will be harder to predict. We would also recommend that the printer has final control of what profiles should be used because the aim of the profile is to correct for the print environment in combination with a 48 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Session 2:3 ICC profiles Basic & special ICC setting ICC profiles are developed for, and used in different situations. So there are several choices that can be made, both when creating the profile and also when using the profile. When a profile is created, there are a number of on-press and CTP test chart choices: Screen ruling Back pressure Density value CTP paper type compensation When creating the profile in the actual profilecreating software, there are more choices: Total ink coverage (TIC) in percentage and also how it achieved with GCR/UCR, and if this setting is light, medium or heavy OBA compensation How to handle neutral grey If perceptual or relative mode should be default The number of bits used to build the profile These choices should be made carefully, because they will be a part of the actual repro to adapt for certain paper characteristics. Later when the profiles are used to make the actual CMYK separations from RGB, there is an option how to finally handle colours outside the CMYK colour space: Perceptual Relative Relative with black point compensation We will not go into each setting and explain the pros and cons when using the actual profile. This would be going too far for a paper company. However, we need to mention that these are important and will affect the final end result on paper, and that variations in the results are often influenced by the different choices made at this stage. Colour proofs When an ICC profile is chosen, always output a colour proof before the printer starts up the presses, to make sure everything looks right. Proofing is normally done with some kind of digital proofing equipment that can usually be adjusted to obtain the final end result on the chosen paper. In most cases, a soft proof (on-screen) is also possible. However, a word of warning: colour proofs on uncoated paper can be quite misleading, as the repro adjustments for dot gain, paper, shade, definition, screen ruling, etc. may be impossible to reproduce on a colour proof. This is especially true if the proof is made on a medium with a very smooth or coated surface. Then the colours and the image will be perceived in a completely different way compared to the actual end result. The best solution is to run the test in the actual press that will be used, using the same paper grade. Then you ll have an ideal basis for making any final repro adjustments, to ensure the end result is completely in line with your expectations. This may seem like quite a costly affair at first sight, but in the long run and in high-volume productions, it often ends up being the most costeffective option. It does not only reduce the risk of errors, but also eliminates any misunderstandings that can so easily occur when checking and approving proof outputs by other methods. After all, always going for the cheap option can sometimes end up being very expensive. IMAGE INPUT IMAGE ADJUSTMENT CONVERTING FOR OUTPUT MEDIA PRINT RGB SOURCE PROFILE MONITOR PROFILE SEPARATION BY OUTPUT PAPER ICC PROFILES PAPER COMPENSATION CURVES PRINTING ACCORDING TO RECOMMENDATIONS Session 2 The repro Art Workshop 49

MUNKEN POLAR 150g/m² Session 2:4 Production flow The lead time in graphical production is extremely short. This is made possible by new work processes and production flow systems. They bring a whole new challenge, of steering and controlling the process, but also to secure the best possible input quality. It is very important that the knowledge about each single task is not lost in the process based work flow, as well as to which degree the paper itself will affect the result. Production flow & colour management From a paper perspective, there are a few very good tools that ensure paper types and paper qualities can be embedded in the production flow. However, they come with some principals and steps that needs to be understood and handled ISO 12647 print standard, ICC profiles and the CTP are the most important to understand. Throughout the production process, there are many stages where the material is handed over from one step to the next. Therefore, clear definitions of the requirements of these steps are the most crucial and to be communicated. There are different kinds of production flow systems developed to create the actual documents at repro companies and printers. These systems can be stand-alone or integrated and linked to external parts in the production chain from idea to final printed product, even to the actual end user. It is important to understand and define the requirements for each next step in order to obtain the final desired quality. This part of the session will mainly cover the internal processes in repro and printing, but the incoming requirements of material such as documents and images is, of course, extremely important to communicate to everyone. Colour management in a production flow will mean standardizing to as high a level as possible, but also managing parameters that vary between different productions. Two very important parameters that will vary to a great extent are the type of image and the type of paper used. The question is, where in the process will this be handled and how? flow, but will define how colours are visualised and presented on different media and also give the possibility to adjust colours for each media. This makes it a good tool for adjusting images for each paper type and grade. Today, most printers also use specific production flow systems. The purpose of these systems is to make the process as smooth as possible. The production flows can also incorporate the ISO 12647 and ICC profiles, but will differ from printer to printer. CTP & paper types When a document is ready, approved and the page layout is completed, it can be prepared for printing. It can be digitally printed in either a laser or inkjet printer, but if it is going to be printed in offset, it is in the CTP (Computer to Plate) the digital life of an images ends. The CTP consists of a RIP (Raster Image Processing) unit and a platesetter. The RIP unit converts the digital information so it can be used by the Platesetter. As mentioned before, an image can be saved in two different colour models: RGB or CMYK. This can be handled in several different stages in the process. But in the CTP it will finally be converted to CMYK. The platesetter will use laser beams or UV light to print out the whole document onto four aluminium plates. These are the actual printing plates used in the offset printing press, one for each process colour. It is in the CTP workflow that the final repro compensation to the image is done, and no changes can be made on the actual plate later on. The images are fixed and the only way to change them is to replace them with new ones. ICC profiles perform the final compensation for the differences between the specific paper quality versus the ISO standard paper. Our recommendation is to check what kind of repro compensation will be done, and where and how this will affect the CTP. If the repro compensation is done in earlier stages, for example, on images embedded in a PDF, check what parameters will be affected by the paper type setting in the CTP. The main parts in a production flow and colour management are: A well defined production process such as, for example, the ISO 12647 Colour management tools like compensation curves or ICC profiles A production flow system or process, whether it s a single system or a set defined work process The two most important developments, besides the development of computers and software, has been the development of the industrial printing standard, ISO 12647, and the development of a common colour space as CIE Lab, which is handled by ICC profiles. ISO 12647 defines the main part of the colour management flow, but limits the adjustment to five predefined paper grades and doesn t provide any details about the actual colour management itself. ICC profiles don t define the process or work All image and repro adjustments should be made before the CTP, or left to be defined partly or totally in the CTP itself. The most common compensation in the CTP is dot gain compensation. It s important to note that today, almost all CTPs have a set of, so called, compensation curves or paper types settings, that will compensate the image to one of five ISO standard paper types. It is also possible to develop dot compensation curves that are unique for the specific printer instead. If nothing else is selected, all images will normally go through this paper type compensation automatically. Together with an ICC profile, the paper type setting is fundamental to the whole process of repro. This means that the paper type should be known before the repro is started. One increasingly common way is to have the CTP compensation curves do the compensation for the print process and leave out the dot compensation in the ICC profiles. Or just do the paper specific compensation for the ISO paper type. Then the 50 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Session 2:4 Production flow ISO standard Today, standards are increasingly being used in every business to secure and stabilise production and quality. Standards also play a key role in the on-going development of the graphical industry. The ISO standard 12647 is defined as Graphical technology-processes control for the manufacturing of halftone colour separation, proof and production, where part 2 covers the offset process. The ISO 12647 is a printing standard that is meant to guarantee a stable and predictable quality in print. Today, most printers are able to obtain this standard and more and more printing companies are actually taking the step to be certified according to the standard. For the end customer, it is a guarantee that an even and good standard is reached. But it doesn t always mean the optimal quality is reached. The main goal is stable and predictable printing. However, most often, it s also useful to have when a special requirement is demanded. In principle, it should not make any difference in print quality whether an image is printed in one print shop or another. use the default paper type anyway, normally resulting in a compensation for coated paper. In that case, when printing on uncoated paper, the repro will be set for the wrong paper. We would strongly recommend that all printing processes are as well-calibrated and controlled as possible, and this can, of course, be performed by other means than the full certifications on ISO 12647. However, when processes are automated, it becomes more important to have an identical reference base for communication. The purpose of the standard is to define and explain a set of primary process parameters that have an effect on the process and final result, and suggest targets and values that should be reached. It covers the whole process, from the digital material received, your screen, proofs and print forms, to print process and quality control. It also takes into consideration the colour temperature of the observer light used when analysing images. It defines what targets should be acquired and what differences will have an impact when trying to reach a certain end result. One of the parameters is the paper primarily the paper types, the colour or optical parameters and the surface of the paper. The five standard paper types defined in ISO 12647 are: 1 Gloss-coated woodfree paper 2 Matt-coated woodfree paper 3 Gloss-coated web 4 Uncoated white 5 Uncoated yellowish Note that two types are for uncoated paper, i.e., 4 or 5. These paper types are normally handled in the process by the CTP. However, in some cases, printers may decide to make the whole compensation through an ICC profile, regardless of paper type, and then use the default paper type settings. If no paper choice has been made, the CTP will Session 2 The repro Art Workshop 51

MUNKEN POLAR 150g/m² 52 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Image references Compare the results of different prepress techniques Image optimization p. 54 close to the original p. 55 higher saturation and contrast ICC uncoated profile p. 56 with a Munken Polar profile p. 57 with an uncoated ISO ICC profile ICC coated profile p. 58 with a Munken Polar profile p. 59 with a coated ISO ICC profile Colour separation p. 60, 62 with a total ink coverage of 260% p. 61, 63 with a total ink coverage of 320% Screens p. 66 conventional and hybrid screens p. 67 conventional and stochastic screens Black & white/ duplex/ triplex p. 68 black & white in CMYK p. 69 grey scale, duplex and triplex Ink drying p. 70 UV inks in a H-UV press p. 71 normal oxidation ink in a conventional press Session 2 The repro Art Workshop 53

MUNKEN POLAR 150g/m² Image has been adjusted to match the original as closely as possible. Screen: 150 lpi. Total ink coverage: 260%. No adjustment in RGB image. For more info see page 43. 54 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Image has been prepared to lend the image new qualities such as higher colour saturation and contrast. Screen: 150 lpi. Total ink coverage: 260%. Increased contrast with XX%. Increased saturation 10%. For more info see page 43. Session 2 The repro Art Workshop 55

MUNKEN POLAR 150g/m² Image is separated to CMYK with a specifically developed ICC profile for Munken Polar. Screen: 150 lpi. Total ink coverage: 260%. For more info see page 48. 56 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Image is separated to CMYK with an ISO ICC uncoated V2 profile. Screen: 150 lpi. Total ink coverage: 300%. For more info see page 48. Session 2 The repro Art Workshop 57

MUNKEN POLAR 150g/m² Image is separated to CMYK with a specifically developed ICC profile for Munken Polar. Screen: 150 lpi. Total ink coverage: 260%. For more info see page 48. 58 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Image is separated to CMYK with an ISO ICC profile for coated paper. Screen: 150 lpi. Total ink coverage: 320%. For more info see page 48. Session 2 The repro Art Workshop 59

MUNKEN POLAR 150g/m² These four images show a four-colour separation with medium GCR and a total ink coverage of 260%. For more info see page 36. 60 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² These four images show a four-colour separation with medium GCR and a total ink coverage of 320%. For more info see page 36. Session 2 The repro Art Workshop 61

MUNKEN POLAR 150g/m² Image is the result of the four-colour separation with a total ink coverage of 260%, Medium GCR (TIC) 260%. For more info see pages 36 and 60. 62 Art Workshop Session 2 The repro

MUNKEN POLAR 150g/m² Image is the result of the four-colour separation with a total ink coverage of 320%. Medium GCR (TIC) 320%. For more info see pages 36 and 61. Session 2 The repro Art Workshop 63

MUNKEN POLAR 150g/m² 64 Art Workshop Session 2 The repro

MUNKEN POLAR 170g/m² Want to see the effects of different screen types on uncoated paper? Go to pages 66 67! Session 2 The repro Art Workshop 65

MUNKEN POLAR 170g/m² Conventional screen 100 lpi. Conventional screen 133 lpi. These three images show one image with three different screens. Images on the opposite page show one image with four different screens. For more info about different screens see pages 34 35. Hybrid screen. 66 Art Workshop Session 2 The repro

MUNKEN POLAR 170g/m² Conventional screen 150 lpi. Stochastic screen 30 µ. Conventional screen 175 lpi. Stochastic screen 20 µ. Session 2 The repro Art Workshop 67

MUNKEN POLAR 170g/m² Black & white in CMYK. 68 Art Workshop Session 2 The repro

MUNKEN POLAR 170g/m² Black & white in greyscale. Black & white as duplex (black + Pantone 430). Black & white as triplex (black + black + Pantone 430). Session 2 The repro Art Workshop 69

MUNKEN POLAR 170g/m² Image is printed with UV inks in a H-UV press. Total ink coverage 320%. For more info see page 80. 70 Art Workshop Session 2 The repro

MUNKEN POLAR 170g/m² Image is printed with normal oxidation/setting ink in a conventional press. Total ink coverage 260%. Session 2 The repro Art Workshop 71

MUNKEN POLAR 170g/m² Can you tell the difference between a correctly reproadjusted image for uncoated paper and one that is not? Find out on pages 58 59! 72 Art Workshop Session 2 The repro

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74 Art Workshop Session 3 The printing

Session 3 The printing We are now rapidly approaching an important milestone in the production of a printed product the printing itself. The image adjustment has been done, the right ICC profile been selected and tested, via soft proof on screen or a digital colour proof. So it s time to make an imposition i.e., arrange the pages so they are printed in the right order and produce the plate by using Computer to Plate (CTP) to make flexo stereotypes or print directly in a digital press. Since this guide is about printing on uncoated paper, the focus will be on adjustments that are particularly important when working with uncoated paper grades. Session 3 The printing Art Workshop 75

MUNKEN POLAR 170g/m² 76 Art Workshop Session 3 The printing

MUNKEN POLAR 170g/m² The purist Katja Viklund A great printing result often comes down to something as abstract as perfect flow. A flow between paper, inks, printing machine and the person running it. Katja Viklund has been running the Komori Lithrone S40 for many years now, and she knows what it feels like to be in the flow. She also knows that it takes confidence and experience to control a printing press, which over Katja s shift can print 100 000 sheets in four colours on both sides in one go. To maintain her flow at work, Katja uses her spare time to work out, often many times a week. Session 3 The printing Art Workshop 77

MUNKEN POLAR 170g/m² 78 Art Workshop Session 3 The printing

MUNKEN POLAR 170g/m² Session 3 The printing Art Workshop 79

MUNKEN POLAR 170g/m² Session 3:1 Printing methods Regardless of which printing method you choose, your material and images will now end up on paper. The choice between different printing methods is determined by the quantity that should be printed, the cost, the type of post-production and the quality demanded. In this session, we cover some common printing methods. And we have highlighted some of the most important factors to consider when printing on uncoated paper. Offset Offset is the predominant printing technique in use today, and there are several variations of the method. Whatever the variation though, all offset is based on the lithographic principle. This principle, in turn, is based on the opposition or seen from another perspective, the interplay between water and ink. The method is therefore also sometimes called wet or water offset. The process basically works as follows: ink is transferred onto the paper via a rubber blanket, which picks up the ink from a printing plate. However, the printing plate has first been exposed to light to make certain areas repel water but absorb ink, and other areas to do the opposite. The ink attaches to the dots, and is transferred onto the rubber blanket and then onto the paper. The basic offset principles are the same, regardless of the type of press or specific techniques that are used, but the major differences are in speed, finishing and quality levels. We will cover these basic implications and shortly explain this principles and how they interact with paper. However, it is very important to first understand the main types of offset techniques: Sheet offset Web Heatset Web Coldset Offset is used for both mono-colour and fourcolour printing (using one or four colour units). In offset, one ink unit per colour is needed, but it is also possible to add extra colours and varnish, increasing the possibilities of offset a great deal. These principles will be explained in more detail in the next session. Sheet offset Sheet offset is, together with web offset, the most common printing method, and it is used with all kinds of paper grades in today s industry. Sheet printing can be run in everything from small to very large volumes, and always with the possibility of reaching the highest results. Sheet printing is therefore popular for various kinds of advertising, posters and books, especially as the technique allows advanced post production. Briefly and in greatly simplified terms, sheet offset involves placing a pallet of sheets at one end of a printing press, feeding them into the machine, and collecting the printed sheets at the other end. Of course, all kinds of things happen in the process. The suction nozzle picks up one sheet at a time and feeds it into the press. The sheet then passes through one or more printing units. As mentioned, one colour or ink unit is needed per colour and the number of printing units varies, but in four-colour printing there are, of course, four units needed to create a four-colour image. However even if only four colours actually are needed to create an image, presses have today often more print units. 5, 6, 8 colour, 10 colour or even 12 colour presses are common. Some of these presses will be able to print both sides of the sheet at once. This is done by printing the first four colours and then, with a turning drum in the middle of the press, turning the sheet and printing the next four. These presses are often called perfector presses. It is also possible to add, for example, varnish and/or index and PMS colours at the same time. This means that very advanced and complex print jobs can be done in one press in one run. The possibilities of controlling and adjusting the print in a feed press are also great, meaning a very high quality can be reached. The printing units are set to determine how much ink should be transferred to the printing plate, then to give a certain density value, per colour. The back pressure is also adjusted, i.e., the pressure between the two cylinders the paper passes through. powder, otherwise the fine granules can get stuck in the rough structure of the uncoated paper this eliminates the air column while also potentially producing a dull image. When the printed sheets are moved onto pallets to dry, there is a risk of ink setting off if the sheets are piled too high. It is therefore vital to keep the pallets as low as possible until the ink has completely dried. UV sheet offset There are also sheet feed presses with UV drying that dries, or actually cures, the ink instantly. Thus avoiding all normal drying problems and set off risk. These UV presses have been rather rare because of difficulties with handling the ink and heat in the press. But new UV techniques being developed that minimize the problems, and this can have a great impact on sheet feed printing in the future. These new techniques are so rapidly developing, it will mean a lot of progress in print and print quality and could, in fact, make several parts of this guide unnecessary. The UV ink is cured directly meaning that the dot gain is far less and no drying problems will occur. These two are the main problems with sheet feed offset with the current process and inks. Compare conventional sheet fed offset to UV sheet fed offset on pages 70 71 The ink used in sheet feed offset normally needs to dry over a certain period of time by setting and oxidation. As the sheets leave a normal sheet feed press one by one, they each have to dry one by one, but on the pallet. And since the drying time can vary by up to 24 hours or more, some precautions need to be considered. In order to avoid set-off, spray powder is sprayed onto the sheets to ensure they do not come into contact with each other. This also creates an air column between the sheets, which helps the ink dry. It is important to use quite a coarse-grain 80 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3 The printing Art Workshop 81

MUNKEN PURE ROUGH 120g/m² Session 3:1 Printing methods Web offset heatset & coldset For high-volume printing, such as brochures, daily newspapers and weekly magazines, web offset is the most common printing method. However, printing from the reel does not really produce the same high-quality results as sheet offset, and lower grammages are often used. Moreover, web offset does not offer the same opportunities for advanced post production. The main advantage is that the unit cost for large volumes is far lower than sheet printing. In web offset, a large reel of paper is fed into the press in a long web, and it runs through the entire printing press at very high speed. It is common that printing and often the post production such as folding, cutting and stitching are done in the press in one process. There are two main types of web offset presses: heatset and coldset. The main differences between the two types are the way the ink is dried and to some extent the quality required. The speed of the web process places great demands on short drying times so that the ink doesn t set-off. A heatset press therefore uses a heat-dryer or infrared light to dry the ink. The results are of a high quality and there is no problem printing on uncoated grades. There are also web presses that use the special UV-inks that don t dry under normal conditions, but are instead cured by ultraviolet light in less then a second, with no risk of set-off or other ink drying problems. The coldset method uses a different ink setting process drying by absorption. Coldset uses a very fast-setting ink, and it is essential to check that the chosen paper is compatible with the ink and allows it to set quickly. Due to the type of fastsetting ink, the print quality is also most often lower than in heatset and the most common application is newsprint or mono-colour book production. In web offset, both sides of the paper are usually printed simultaneously in a perfector press, by blanket to blanket. With this method, the opposing printing unit s rubber blanket is used to provide back pressure, so you can t set the back pressure for each side individually. This differs from a sheeted perfector, where each side is printed separately. As with sheet printing, the ink density should be kept rather high when printing on uncoated paper. Flexographic printing Flexographic printing works in much the same way as a stamp, i.e., with raised areas and depressions between the parts that print and those that don t. Plastic or rubber stereotypes with different level variations attached to a cylinder or a belt are used. Flexography is a typographic printing method. The flexographic method is used for reel formats and prints at very high speeds. It can print on most materials and is therefore often used in the packaging industry and book production. Flexographic printing is also an excellent method for uncoated paper. Digital printing Digital printing is the collective name for a range of printing methods, where text and graphics are transferred directly from computer to paper without any interim media, such as printing plates. Moreover, information is freshly transferred for each individual print, which means that sections of text and images can be replaced each time without compromising the printing speed. The altered information is called variable data, and used correctly, dramatically increases the value of printed matter. There are two main types of digital printing methods laser (xerography), which uses dry toner distributed by electrical charges to generate and transfer the print, and inkjet, where drops of a very fine liquid ink are sprayed onto the paper surface. There are also special techniques, which, in one way or another differ, from these two main types of digital print. HP Indigo is one such example. Even though the digital printing methods have distinct differences, which put unique demands on the paper compared to the traditional printing methods like offset and flexo, the technical development of both the digital printing machines and paper grades has gone in the direction of multi-functionality. Most new digital printing presses can handle a wide range of papers, and many papers are, in addition to the traditional printing methods, also compatible with one or several digital printing methods. One of the benefits with digital printing is the low start up costs. In principle, the cost per copy is the same, regardless if you print an edition of ten, a hundred or a thousand copies. In traditional offset printing, the start-up cost is high, due to the cost of the plates and long startup time. This means that the price per copy is initially high, but decreases when the number of copies increases. In the past and still, to some extent, today digital printing has mainly been used for low volumes, but as technology and quality has improved, so have the opportunities. The breaking point, where digital printing is less expensive than offset, has, however, moved higher and higher due to a growing capacity and lower print costs of the digital presses. Within inkjet printing especially, the development in recent years has been focused on increased printing speed, and today, the capacity of an inkjet press is comparable with sheet fed offset. Digital printing has also opened it up for totally new business models. One example is the possibility to use variable data, which allows a more efficient use of printed media. Instead of mass production and mass distribution of, for example, direct marketing material, selected messages adapted for each specific receiver or group of receivers can be printed. In this way, the total volume of material can significantly be reduced and, at the same time, a higher response rate reached. Another opportunity with digital print is what is commonly known as on-demand production, which means that instead of producing a high number of copies of, for instance, a book in one go, the initial production can be smaller and complemented with additional print productions, depending on the demand at a given time. In this way, the cost for stock keeping will be lower, and the risk of ending up with a high number of unsold copies is eliminated. In its extreme, on-demand production can mean the production and distribution of single copies of a book after it has been purchased in a web shop by the consumer. Digital printing has also its given place in the office environment. Whether it is in the form of small desktop printers or larger central printers, most of us, more or less daily, take advantage of the digital printing techniques to print out documents. Here, we describe the two main types of digital printing using toner in xerographic and laser printing, and using ink in inkjet printing and clarify the issues that are particularly important to consider when printing on uncoated paper. Another technique we outline here is pre-print, a combination of digital and conventional printing. 82 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3:1 Printing methods Inkjet, digital printing with ink As the name implies, inkjet printing involves spraying liquid ink onto the paper in drops, and this forms dots in roughly the same way as in offset printing. Today, there are two main types of inkjet printers. One is called Continuous inkjet, whereby high pressure is used to form drops and electrical charges are used to guide them. The other is called Drop on Demand, where the drops are added one by one. The latter method is most common in office and text printers, while continuous inkjet is more suitable for faster, more advanced productions. Inkjet technology is developing rapidly, and there are many different machines on the market today from inexpensive home printers to very high-quality large-format printers and extremely high output machines. But progress is not likely to stop there. Most uncoated grades are suitable for the various inkjet methods. Since ink is a liquid and relatively thin, it has to be absorbed soaked up and set on the paper in the right way. A normal uncoated paper has quite a high absorbency level, but because the drops flow out, there is roughly the same effect as dot gain in offset printing. In order to achieve truly fine results, the paper surface should therefore be treated in a special way to allow it to quickly absorb and set the ink. Digital printing with toner/ xerography & laser Digital printing methods based on xerography are often used in laser printers and photocopiers. They involve using a dry toner, i.e., a powder of the colour to be printed. The number of colours in the press varies, some using only black (or monochrome ) and others using several colours. The xerographic process begins with the toner being electrically charged. When, for instance, an image is being printed, the areas on the paper that are to be printed are also given an opposite charge to the toner s, so that the powder particles are electrically attracted and attach to the charged areas on the paper. Once the powder is in place it is fixed onto the paper, heat is applied, which melts it onto the paper surface. Toner powder rests on the surface of a paper rather than being absorbed, and you can actually feel it if you run your finger across the surface of a printed material. Because heat is a central factor in the process, the moisture content of the paper is very important. Too much moisture in the paper means a lot of it will leave the surface in the fusing process, resulting in a warped, curled paper. Too dry a paper, on the other hand, can cause problems with static electricity. The paper s conductivity is also very important. If the conductivity is wrong, the toner will not attach to the paper. Conductivity is also influenced, to a certain degree, by the paper s moisture content. Bear in mind that the printing temperatures can vary widely between the different types and makes of machine, and that some presses use heat in direct contact with the paper while others do not. This means that the effects of incorrect moisture levels can vary according to the machine being used. In order to retain the proper moisture level i.e., the level to which the paper has acclimatised at the mill or with the supplier it is extremely important to reseal the packaging and to maintain a controlled humidity level in the print house. Also, make sure that the paper s moisture content is compatible with the type of machine being used. Sometimes there are even script files for each paper grade, which ensure the press has the correct settings. Also bear in mind that this type of digital printing method dries the paper out slightly, and this should be taken into account before post production. Digital methods based on dry toner are ideal for uncoated paper, as the toner powder is not absorbed into the paper so dot gain is not an issue. It is also possible to print with a higher ink coverage than in, say, offset printing, which can produce better image reproduction. However, it is not a good idea to use uncoated paper grades that are too rough, especially not in colour printing, as with current technology, it is difficult to achieve an even layer of toner on very rough surfaces. There are also digital methods that use wet toner, i.e., liquid ink as the HP indigo press. The process is however much the same as with dry toner the liquid ink is transferred by electrical charges, but first to a rubber blanket and then onto the paper. Pre-print in a conventional press You are probably familiar with balance statements and invoices, etc., that contain variable data, i.e., text and figures customised for your particular message. These documents are usually produced in a monochrome digital press, where the black text and figures are printed on sheets or reels which are pre-printed with colour usually logos or similar in a conventional printing press. This method is called pre-print. Remember, that when using pre-print, it is extremely important to choose an uncoated paper that can deal with both printing methods. The ink must also be compatible with both methods and often a longer drying time of the offset inks is recommended. As with several other digital techniques, the moisture content of the paper is important. Pre-printing in offset adds a damping solution and ink to the paper, thereby increasing its moisture content. Therefore, if the original moisture content of the paper is high before the damping solution is added this can cause problems in the next stage, i.e., digital printing. Therefore, we recommend that the proportion of the damping solution in the initial offset run be kept to a minimum, even if the paper is designed for pre-print. Find out more about digital print on Munken Design Range at www.arcticpaper.com/digitalprint Session 3 The printing Art Workshop 83

MUNKEN PURE ROUGH 120g/m² 84 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3 The printing Art Workshop 85

MUNKEN PURE ROUGH 120g/m² Curious to know what ink density level is best for uncoated paper? Find out on page 91! 86 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3 The printing Art Workshop 87

MUNKEN PURE ROUGH 120g/m² 88 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3 The printing Art Workshop 89

MUNKEN PURE ROUGH 120g/m² Session 3:2 Offset printing & uncoated paper Every printer is their own art worker, but knowledge and experience always differs. Some printers say it s hard to print on uncoated paper and some say it s easy. Actually, printing on uncoated paper is not more difficult than printing on coated. It just needs some different basic settings. The offset principals As an introduction to printing on uncoated paper in sheet feed offset, it is a good idea to have a closer look at the actual principle of offset. Covering the background in earlier sessions, about uncoated paper and the main issues in repro, will make the following recommendations a lot easier to understand. The main and basic principle of offset is that oilbased ink and water don t blend, which means that ink will separate from water. The printing plate consists of two different layers, one that attracts oil and one that attracts water, with both layers repelling their opposites. In the CTP, one of the layers of the printing plate is burnt off. The effect is that the exposed print plate has two different surfaces one picks up ink where the image should be and the other picks up water where no print should appear. This ensures that ink hits the paper at exactly the right areas while the other areas remain blank. Offset is an indirect printing method, meaning that the printing plate will not transfer the ink directly onto the paper, but instead onto an intermediate rubber blanket. The rubber blanket will set off the ink onto the paper. Also, the soft surface of the blanket enables it to follow an uneven paper surface in the best way. This indirect technical or offset technique is why this printing method is named offset. In order to maintain the delicate ink-water balance, an offset press has a set of rollers for each that will cover the printing plate with water and ink in a very exact and controlled way. The top cylinder has a printing plate, which takes up the damping solution and printing ink (A). The ink is set off onto the rubber blanket on the cylinder in the middle (B), which in turn transfers the ink onto the paper. At the bottom is a back pressure cylinder (C). A B C An important part is also the impression pressure, or back pressure. The paper sheet will pass through the rubber blankets and a counter press cylinder, sometime called the back pressure cylinder. In sheet feed, this is normally a steel cylinder. But in web offset, this is often the rubber blanket from the print unit on the other side. The colours used in the offset process are the four CMYK colours (cyan, magenta, yellow and black), often called the process colours. These process colours are transparent and are laid on top of each other in layers, so that each layer shows through the others to jointly form the different shades in the image. Water, ink & paper interaction Paper, ink and water all meet in the press, meaning they will interact in several ways. As mentioned earlier, the principles of offset are built on the physics that oil and water don t blend. To make the balance work, the water needs to have certain characteristics controlled precisely. Pure tap water will not work, it needs to be treated and have certain chemicals added to it. The chemicals will control the viscosity, ph, hardness and conductivity. If these are not correct, the inkwater balance will not work. The treated water is called fount water. We have also explained that ink and water shouldn t blend, but, to an extent, some mixing will always occur anyway. Even small variations in the water balance can cause the water and ink to start mixing too much this is often called emulgation. This can cause a number of problems, such as low print quality and long drying time. Incorrectly set water could also begin dissolving the paper surface and could cause paper picking and set off. The paper also needs to interact well with water and ink. The paper needs to pick up some degree of the water to keep a good balance of ink and water, and also to keep the blankets clean in the non-printing areas. It is important to find the right mix of water and ink for each paper type and quality. Damping/fount solution plays the most vital role in the lithographic printing process. Most print problems in offset are caused by an imbalance in the water and ink chemistry. Therefore, we recommend that the fount water is carefully monitored; this will secure stable and problemfree printing. Both the incoming water and the final blended mix are very important. Often, there are variations in the water quality that can change the printing conditions on very short terms, even if the added fount solution is kept constant. One tip is to check the water if the fount solution suddenly interacts badly with the ink and paper. An alternative method to wet offset is dry or waterless offset, where the damping solution is replaced with chemical substances on the printing plate s surface. However, this technique is not widely spread today. Different inks If you want to repaint your house or paint a painting, there is a huge number of different colours and inks to choose from. However, for the printer, choosing the type of ink is actually more important than the actual colour itself. The ink area is an entire science and would need a whole book for itself, so we will only give you a short introduction from a paper perspective. While there are many different types of inks, when printing on paper, the process is based on the four process colours CMYK. It stands for Cyan, Magenta, Yellow and Key colour, which normally is black. These process inks are transparent, which means that when they are printed on top each other in various dot sizes, they will optically mix and create a huge amount of different colours. Each printing method also has its special ink type. But also within each print method, there are special inks depending on specific processes for the drying and on which material the print would be on. The colour itself in the ink is made up of small particles of solid pigments. The offset printing inks are pigment based, but the big differences are in the solvents and chemical contents used, depending on print techniques and other requirements. The main part of the ink is the solvent a blend of mineral oil and vegetable oil. The inks also consist of other ingredients, like resin, wax, etc. To control the drying properties, chemicals such as cobalt and manganese are also used. The printing mechanism in offset is quite fascinating. The ink has to be able to withstand contact with water while keeping the pigment bound to the oil. As we want the ink to dry as quickly as possible, the pigment concentration in the ink has to be as high as possible, in order to keep the ink film very thin. Offset ink usually contains ±25% of pigment, while flexo ink only contains 10 12%. The moment the ink touches the paper, the ink splits into two parts. The thinner (mostly mineral oil) then rapidly penetrates the paper, reducing the volume of ink that stays on top. This process is called the ink setting. The pigment that is bound to the resin and vegetable oil remains on the surface to dry, mostly by oxidation (hence the importance of air between the printed sheets). Oxidation of oils is a slow process that 90 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3:2 Offset printing & uncoated paper takes many hours and depends on the temperature. Slow or fast setting inks are chosen depending on the substrate a very open surface like an uncoated paper requires a slower setting (less thinner or mineral oil), and a synthetic paper, which allows for no setting at all, requires an ink that dries exclusively by oxidation. Each ink has a unique formulation to suit the printing technique, the type of substrate and any special requirements, such as drying and setting time, tackiness, gloss, rub-resistance and colour intensity. Ink suppliers offer a large number of different inks to suit the process, but also to meet the demands of certain end results. What s interesting is the current development of higher pigment content, which can boost the colours in a nice way. Ink density & uncoated paper The human eye is very sensitive and it can easily tell whether one colour is denser than another. As mentioned, the density values decide the actual colour density. There are often strong opinions about the levels, because even the slightest shift will become very obvious. Therefore, this is one of the most crucial factors to consider when evaluating a print result. Ink density is the measurement of the thickness of an ink layer on the paper. The thicker the ink layer, the denser the colours. The ink density is actually an indirect way of measuring the actual ink thickness that you put on paper. It is measured with special equipment, like a densitometer or a photo spectrometer. These devices measure the differences in colour density between the paper you print on and each of the four CMYK colours. For this reason, there is always a set of process colour bars, the colour strip, on the edge of each printed sheet. The density range in offset printing goes from 0.0 up to over 2.0, this is far less than in analogue photographs where densities can be up to 4.0. There are different recommendations given in the ISO standard and printers often have their own targets set. For each ICC profile created, there should also be a target set. Note that the ink density will decrease as the ink dries, so measuring directly at the press when the ink is still wet will result in a higher value than the final printed matter would. On coated paper, the pigment layer stays on top of the coated surface, so a high density is very easy to reach even with a rather small amount of ink. On uncoated paper, however, the ink pigment soaks into the paper. To reach the same ink density values, more ink is needed. Very often, the density level recommendations for uncoated paper are rather low, because there is a risk of over-inking the paper. When a paper is over-inked, it cannot absorb more ink, and the drying time can be very long, meaning a greater risk for set offs. However, if the repro is properly done and the total ink coverage (TIC) is set low, this will limit the layer-on-layer effect and the actual amount of ink in the risk areas. Then the paper can better absorb all the ink in each remaining layer, and it s possible to reach a relatively high density on uncoated paper without the risk over-inking. This means there is a very strong link between the total ink coverage (TIC) and the ink density, and that the solution to over-inking is not in the press but in the repro. The over-inking problems will normally only occur in four-colour print, because the four colours will be printed on top of each other. We recommend keeping the total ink coverage relatively low and the density relatively high. If ink coverage is kept at 250 260%, it will enable an increase in density to 0.2-0.3 units or more per colour from the ISO standard targets.this will provide more colourful images, but also better flexibility for increasing the density in the press, if needed. In recent years, we have seen numerous developments in colour matching and process control. The common approach of measuring density values of the process colours is less accurate than direct Lab measurement. Spectrometers, measuring Lab values continuously and feeding this data into automated press control systems, have become affordable. Hence, CIE Lab measurement has become an alternative way of controlling the amount of ink on paper during printing instead of the density value. The ISO 12647 standard itself is defined in CIE Lab, not density. In the years to come, we will see a major shift towards CIE Lab colour matching, simply because it is closer to the human perception. Below shows a typical colour bar that is used to check the density value. The colour bars contain all the colours used in the process, as the CMYK and/or PMS colours, and often also show screen in a mid tone as 40 50% and in an upper tone as 75 80%. Session 3 The printing Art Workshop 91

MUNKEN PURE ROUGH 120g/m² Session 3:2 Offset printing & uncoated paper Back pressure Back pressure refers to the pressure between the rubber blanket and the impression cylinder between which the paper passes in the press. Reducing the distance between the two increases the pressure; pushing the ink into the irregular surface of the paper. In a modern press, there is normally a default set pressure that makes the gap between these cylinders slightly less than the actual paper thickness setting. Because the rubber blankets are made from soft rubber, this creates pressure on the paper, making the ink cover every small irregularity in the paper surface evenly. On uncoated paper, the irregularities in the surface are much higher than on coated paper. The default settings in the press is for coated paper. This means that the rubber blankets will not be able to push the ink into the deepest irregularities of the surface, resulting in dropped out dots and a mottling effect. It is very important to increase this pressure to a level where the whole paper structure will be covered in a good way. When the back pressure is increased, ink is also pressed into the paper better, improving the drying capabilities. The default setting in a press is often set to be 10 microns less than the paper thickness. The back pressure can be altered by increasing the actual back pressure value. In some cases, it can be easier to just enter a lower paper thickness in the press. Depending on how rough the paper is, the needed value can differ, but a recommendation is to have the back pressure increase with 20 30 microns as a starting point. In some cases, more is Example A: the back pressure is low and the ink does not cover the whole paper surface structure. needed, and in others less. However, if you see a solid area that is not even enough and showing a mottling effect, it is a good idea to increase the pressure. There is one risk with increasing the pressure too much and that is that dot gain slightly increases at some point. Print powder & after print stocking As the sheets leave the press one by one, they have to dry. And since the drying time can vary by up to 24 hours or more and in order to avoid set off print powder should be sprayed onto the sheets to ensure they do not come into contact with each other. This also creates an air column between the sheets, which helps the ink to dry by oxidation. It is important to use quite a coarse-grain powder, otherwise the fine granules can get stuck in the rough structure of the uncoated paper eliminating the air column while also potentially producing a dull image. When the printed sheets are placed onto the pallets to dry, there is a risk of the ink setting off if the sheets are piled too high. This is due the pressure created in the lower end of the pallets. It is therefore vital to keep the pallets as low as possible until the ink has completely dried. Also note that there are two environmental aspects that will influence the drying time: temperature and moisture. A lower temperature and higher relative humidity will increase the drying time. Therefore, it s important that printed material is kept in an ideal environment during the drying time. Ink drying & paper In offset printing, there are, as we explained, three main different offset techniques that have very different ways of drying the ink. In addition to this, there are also UV-inks that are cured instantly with UV light. In web offset the drying is a minor issue due the special solutions that dry the ink at once. There are, of course, other important aspects to consider, but for uncoated paper, the main challenge is with sheet feed offset. In sheet offset, the drying is an essential aspect because the ink will dry over a certain time after the printing, and the capacity to dry is actually in the ink, in combination with paper. The repro plays a large part in the way ink is applied on the paper and then also how the ink dries. But as long as the repro is correct, the different ink will have the main impact on drying on uncoated paper. Ink in sheet offset will dry in two steps: setting and oxidation. Setting means that the ink solvents are absorbed into the paper and then leaving the pigment and binders more or less dry on the top. Oxidation of the solvent means that the solvents (oils) will be oxidised into a dry condition due to a reaction with oxygen. The different inks for sheet offset could be categorised in levels, depending on how large a part of the drying will be done by the setting and the oxidation. The non-oxidation inks, sometimes called over night inks or duct fresh inks, are meant to not dry in the press or in the can. The benefit of this is in the starting and stopping time for the press. Partly-oxidising inks are called semi overnight or semi duct fresh inks. The benefit of these are that they are meant to dry, to some extent, by oxidation, but still do not dry in the press or can too quickly. Example B: the pressure is higher and the flexible rubber blanket follows the rough uncoated paper surface. The ink covers the whole surface and also presses the ink more into the paper. The illustration shows two sizes of spray powder. The above is too small and does not create the needed space between the printed sheets. The below shows a coarser grain that create a sufficient space to eliminate the risk for ink set offs and creates an air column that enables the ink to dry well by oxidation. Oxidation inks that mainly or completely dry by oxidation are often just called oxidation drying inks or quick drying inks. Choosing an ink often means a compromise on different aspects, such as the drying time, cleaning in the press and the functionality and impression on paper. On uncoated paper, we strongly recommend that duct fresh inks are not used. The reason is that on uncoated paper, the oxidation is the most important drying step. As the non-oxidation ink normally needs the coating layer to set in a proper way, there is a large risk that part of the ink will not set fully on uncoated and the wet ink will remain on the surface and if no oxidation drying 92 Art Workshop Session 3 The printing

MUNKEN PURE ROUGH 120g/m² Session 3:2 Offset printing & uncoated paper occurs, the ink can stay wet for a very long time. Press varnish A very common way of protecting a printed sheet, both as a final product and for the upcoming post production is press varnish. On uncoated paper, the visual effect is almost none, but is often used as protection. The press varnish can be either oil based or water based. Press varnish means covering the whole printed sheet with varnish, which can be dried in the press by infrared light or in the same way as normal ink. This then dries on top of the ink and protect the ink during post production. It will also protect the paper surface in the ready printed material. It is important to remember that while on uncoated paper, the effect will only be protective, it can also, to some extent, change the shade of the paper slightly in the unprinted areas. image details will always be lost to some extent, but a well-handled dot gain will minimise that. F Fine details these will be harder to reproduce on uncoated paper, but is it possible to see the fine details or are the details lost and the contrast low? G Highlights if dot gain is to high, supporting dots can be increased to such a level that bright areas are not longer bright. H Full tones are they even without mottling? Print quality on paper Evaluating the print quality on paper is not easy and is quite subjective. However, it is also a matter of perspective and profession. A printer will look at print in one way, a graphical designer in their own way and an end user or a consumer in another. The important aspect is that each party is satisfied with the final result. And that s why a common understanding on what will be achieved is crucial. Therefore, some kind of colour proof is very good to have as a reference at an early stage of the process. Below is a test sheet used by Arctic Paper. H C A B A D There are also some good tips to bear in mind when actually looking at print quality. The whole repro and print aims to handle a number of parameters, and if everything is well-handled, focusing on these will enable you to evaluate print on uncoated paper: D G F E A Colour similarities to real life skin tones, fruits, trees, skies, etc., are easy to recognise and these should look as close to normal as possible, if realism is the aim. B Clear and bright colours if dot gain is not treated well, bright colours could feel slightly dirty. C The colour strip is the density correct and high enough? D Neutral grey tones areas that should be grey can easily show a hint of red, blue or yellow, and checking the grey areas in images is a good way to know if the colour balance has been handled well. E Details in dark areas are details lost in the very darkest areas? On uncoated paper, Session 3 The printing Art Workshop 93

94 Art Workshop Session 4 The post production

Session 4 The post production A printed product is not finished just because it has come off the presses. There is still post production, a collective term for several different stages and processes that take place after printing. Although post production comes last in the printing process it has to be decided at an early stage, as the choice of post production methods often governs other factors, such as choice of paper. It is therefore a good idea to have post production in mind early on. We are now going to take a closer look at the most common post production methods for uncoated paper. Session 4 The post production Art Workshop 95

MUNKEN PURE ROUGH 120g/m² 96 Art Workshop Session 4 The post production

MUNKEN POLAR 150g/m² The wrapper Dennis Johansson The finishing touches and the bookbinding are keys to excellent results. And however odd it may sound, if the post production isn t immaculate, it can ruin the whole impression of a printed product. Dennis has been working with paper for all of his life. He has always enjoyed his job and is happy to see that papers are actually evolving and becoming better. The quality of paper plays a central role when varnishes are applied, scoring is performed and the cutting is done at the post production workstations. Having been a sports fan since childhood, Dennis recognises the value of a strong team both in athletic arenas, but also on the printing floor. Session 4 The post production Art Workshop 97

MUNKEN POLAR 150g/m² 98 Art Workshop Session 4 The post production

MUNKEN POLAR 150g/m² Session 4 The post production Art Workshop 99

MUNKEN POLAR 150g/m² Session 4:1 Effect enhancing & post production In the total design, it must not be forgotten that there are several ways to finally enhance and make printed matter really stand out by adding foils, embossing and cutting the paper into unique shapes. All of this is done after the print, however, it needs to be planned in advance and knowledge about what is possible is crucial. Here is a short introduction to the world of paper creativity. Foil blocking Foil blocking involves adding a thin layer of foil to the paper with the aid of heat and pressure. The plastic foil is usually metalized with gold or silver, although there are also other shades, mother-ofpearl and structured versions. If more than one foil is being used, they should not overlap, and the ink must have dried properly before foil blocking begins, otherwise the print will not adhere correctly. One tip is to also avoid using too much spray powder when printing. This also applies in other cases of post production, like offline varnishing or laminating. Sometimes it is necessary to remove the spray powder by passing it through a printing press without ink or water. The powder is then picked up by the rubber blankets. In the context of foil blocking, another term sometimes heard is foil embossing i.e., embossing the paper at the same time as foil blocking. There is also a type of foil blocking where different amounts of pigment are used, called tint foil blocking. Embossing The process of creating differences in the level of the paper s surface known as reliefs with depressed and raised areas is called embossing. The pattern is created in an embossing machine using stereotypes or embossing plates. There are basically two different kinds of embossing: positive and negative. Positive embossing involves raising a section up out of the paper, while negative entails depressing a section. Moreover, sculpted embossing can be used to create several different levels. This method is the most advanced, and can only be achieved using embossing plates. When ordering embossing plates, it is particularly important that the paper has been selected and to be extremely clear about the desired effects. Paper grade is a vital factor in embossing. As a general rule, the thicker and softer the paper the better the results. The strength of the paper is also significant, and woodfree grades are generally recommended as they have better bursting resistance. To avoid bursting, it is also important to use the right pressure when embossing. Careful testing on the right paper is essential when embossing, and a good working relationship should be established with the engraver and printer before the actual embossing phase. Also note that embossing on coated paper is more difficult due to the less flexible surface. Recently, a new embossing technique has been introduced based on laser cutting. Instead of completely cutting through the paper, the laser only cuts half way through it, creating a bas relief. Varnishing Together with laminating, varnishing is the most common method of surface-treating a paper. There are several varnishing methods, the most common being spot UV varnishing in a screen press, full varnishing and protective varnishing direct in the printing press. There are two categories in varnishing: protective varnishing and embellishment. The first should not produce any visual effect, but create a sealing effect, avoiding rub off and allowing quick finishing and folding. The second type aims for a strong visual effect, but other effects like odour/ perfumes, heat sensitive or pearlescent varnishes are common. Varnishes can be applied in several ways, the most simple technique is to use a printing unit with varnish (i.e., colourless ink). Varnish layers can be printed just like any other image, but the varnish layers are usually thin (max 3 g/m²) and the visual effect not very strong. But the technique works well for protective varnish. In this case the difficulty is to produce a specific varnish thickness constantly, because there is no easy way to determine the varnish thickness like, for instance, with a densitometer. Nowadays, varnishing is often done in a dedicated inline varnishing unit, which does not work like an offset printing unit but, in fact, uses the flexo technique. The varnish can be a water based emulsion (acrylic dispersion) that is cured with hot air knife, which provides instant drying. This technique gives a very even varnish layer because of the anilox roll, which provides a constant flow in the system. But even here, the visual effect is not very strong and the varnish layer is of a medium thickness (max 10 g/m² wet, equals max 6 g/m² dry). Water-based varnishes give a flexible, medium gloss result, causing no problem in folding or binding afterwards. Screen print varnishing can be done on any substrate in very thick layers. The varnish can be water-based, solvent-based or UV cured. UV curing provides instant drying, but also a very hard varnish layer which could crack when folded. UV varnishing often requires a primer be applied on the uncoated paper, this (water based) primer is often applied in an inline flexo varnish unit, as described above. All techniques allow spot varnishing, but in flexo it is more expensive because of the 3D flexographic plates that are required. Uncoated paper grades can be UV varnished for an extra effect, although it is important to bear in mind that the effects are different to those seen on coated paper. The porosity of uncoated paper enhances the penetration of varnish into the paper, destroying the visual effect. Therefore, multiple layers are needed. The first layer (primer) provides a barrier, and the top layer will be the actual varnish. Since fully varnishing a sheet is rarely a complete success, spot UV varnishing is preferred. This entails varnishing selected parts of the paper, such as an image or logo. Very special, exciting results can be created using spot UV varnishing on uncoated paper. However, it is essential to first prime the sheet and then varnish once, or in some cases twice, for the perfect result. Also bear in mind, that folding after varnishing may cause problems. Varnish is hard and not as flexible as laminate, so the outer layer may crack when the paper is folded. This can be avoided by scoring the paper where the fold should be. Relief printing The method calls for the printing press to be supplemented with a relief aggregate and a heater. After the normal printing process, a chemical powder is sprayed over the ink on the sheet. The sheet then goes into the heater where the ink and powder melt together and swell up into a relief. This then dries and hardens. The process is also called thermographic printing and all PMS colours can be used. Relief printing is most suitable for thin lines and texts. It is not possible, however, to emboss or foil block over relief print. Nor is it possible to relief print over foil blocking. This method is mostly used on business cards and celebration cards. Another method that gives a similar effect is embossing varnish. This is more widely used for covers and headlines. The varnish is applied in screen printing on top of texts and logos that have first been printed in the conventional press. The cover of this guide is decorated with embossing varnish to enhance the graphic. 100 Art Workshop Session 4 The post production

MUNKEN POLAR 150g/m² Session 4:1 Effect enhancing & post production Laminating Laminating involves applying a thin, plastic film or foil to the paper s surface. The method works well with smooth uncoated paper and is used in the same way as varnishing for greater protection against dirt and wear, as well as giving increased folding strength. Laminating the paper also produces a different surface finish compared to varnishing. This partly depends on which laminate you use, for example, there are matt, gloss or patterned laminates. It also depends on the roughness of the paper. For optimum laminating results on uncoated paper, select a grade with low roughness, since a rough paper surface makes it harder for the film to adhere, and may produce a slightly milky, greyish appearance especially when laminating dark surfaces. Just as with varnishing, it is important to use a minimum of spray powder in the printing process, as this too can result in reduced adhesion and detract from the appearance. There are two kinds of laminate: pre-sized laminates, and those which are sized during the laminating process. The non pre-sized laminates are generally preferable when working with uncoated paper. There is however an exception, i.e., when laminating digitally printed matter. Owing to the fact that inks in a digital press contain toner and silicone oil, it is difficult for the laminate to adhere properly. In this case, use presized laminate and a high temperature. window on the cover that reveals parts of what is on the first page. This can also be used for indexing folders, for instance. Die cutting is also used to produce self adhesive labels while leaving the release paper intact. Today there are also possibilities to cut complicated patterns and forms by laser-cutting the paper. Hole punching Hole punching is pretty much self explanatory. Holes are punched into the outer edge of a document so that it can be kept in a ring binder. Rather than a conventional office hole punch, the graphics industry instead uses a special drill to create holes in the sheets. Perforation If users need to be able to tear pages, coupons or similar from a document, perforation is a common way of making this easier by providing a row of small holes. Perforation is often performed on a flat bed press with a perforation rule, or using a scoring tool which is not unlike a toothed saw blade. Speaking of high temperatures, bear in mind that paper alters with changes in temperature and atmospheric humidity, yet a plastic laminate does not. In other words, laminating a sheet of paper before the ink has dried or if it is subject to abnormal moisture can cause problems. There is another kind of lamination which differs to that described in the section above, and it refers to glueing together several sheets to produce a single thicker one. For example, two 150 g/m² sheets can be joined to form a sheet weighing just over 300 g/m² (the glue also weighs a few grams). The laminated sheet can be made of various materials such as liner, cover paper, plastic film or metal foil. The cover of this guide is matt laminated to provide sturdiness and extra protection for frequent use. Die cutting Die cutting is a common method of enhancing the appearance, feel and message of a printed product. Die cutting involves using a die form to cut a pattern out of the paper such as a round Session 4 The post production Art Workshop 101

MUNKEN POLAR 150g/m² Session 4:2 Binding In most types of productions, there is an assembly line and it s not usually until the end stage that you finally see the result of all the hard work. In a graphical production, the assembly line ends with the binding. It is here that all the printed sheets and covers turn into a book, magazine or other product in the final step of the process. It s now you really hope that you have thought about everything mentioned in this guide. Bookbinding Before discussing the various binding, folding and scoring techniques, we need to go back a few steps. Before the sheet is printed, imposition is carried out. This entails organising the pages so that they end up in the right order. The number of pages that fit on each sheet varies depending on the size of the printing press and the format of the printed matter. In some cases only 4 pages might fit, in others 8, 16, 32 and even 64. The pages then have to be combined in the right order to form a printed product. Folding & scoring Folding can be divided into two separate processes, folding the inside pages and folding the cover. Folding the inside pages of the printed matter is done in a special folding machine with a feeder just like the printing press, and in the other end ready-folded sections will come out. The printed sheet is normally printed and folded, as mentioned above, in 4 64 pages per printed sheet; with the most common being 16 or 32. The higher the number of pages, the more folds are done and at certain point the risk for creases on the pages increases. To avoid this, the paper needs to be cut in the folds to let air slip out and to allow the paper to fold. Depending on the grammage, bulk and number of pages, the need to handle this in a correct way will be greater. It is easy to realise this risk by manually testing different papers in different amounts of pages. It is also important to ensure that the fibre direction runs parallel to the final spine of the printed matter so that it opens nice and easily. If this is not done, the pages will feel stiff and there s also a risk that waviness will occur which is certainly not the desired effect. Folding the cover normally means folding it once and the sheet ending up in 4 pages. The cover is also normally paper or board of high grammage and occasionally, the paper is so thick that it can be difficult to fold it without causing cracks and unevenness. The risk starts at a paper grammage of approx 150 170 g/m2 but it will, of course, differ from paper grade to paper grade. To avoid this, the paper is scored before folding, which basically involves pressing a channel into the paper where the fold is to run. It is especially important to score paper where images or tint plates run across the fold, as cracks are more noticeable in tints and images. For printing processes which involve drying the paper, such as in digital presses, even low thicknesses and grammages should be scored before folding. Binding The final phase in putting together paper, normally the folded sections, to form a book or other printed product, is called binding. Binding encompasses a wide range of methods, each with its own particular conditions. Here we will be covering some of the most common methods. Some remarks on combining different paper grades in books. As described in previous sessions, paper is very sensitive to changing humidity. If for some reason different grades are combined in one book, it is important to secure that the humidity of all sections is the same. Otherwise books will have bent covers, wavy book blocks, or stepping edges. Wire-stitching also called stapling is the most common and in fact the cheapest binding technique, and is used primarily in the production of brochures and other simple printed matter. Apart from being cheap, the advantage of the method is that it is fast and easily manageable, and is suitable for all grades of paper. As the name implies, the product is bound by passing one or more metal wires or staples through the pages and covers, just like stapling together office documents. The two most common methods are spine stitching and flat stitching. In spine stitching, the staples are driven through the folds on folded sheets, whereas in flat stitching they go through the outer edge of flat sheets. Perfect binding or adhesive binding is a common binding method in products of many pages, and it is ideal for uncoated paper grades as the paper absorbs the glue well, which ensures good adhesion. There are many types of glue depending on the equipment and paper that are chosen. Some digital printing techniques apply silicone oils or waxes on the paper, making it water or glue repellent. Special types of glue have to be used in such cases to prevent the books from falling apart. The actual binding process involves first collecting together the inside pages of the product, and then shaving off three millimetres or so on the spine side. Adhesive is then applied and the cover is attached. Perfect binding is a common technique in hardback and paperback book production. Thread-binding also called textile binding is the very strongest binding technique, as well as being one of the oldest and most expensive. Take an old book down from the shelf and check the binding and it is very likely to have been stitched with a linen thread in the spine. The method involves putting the printed and folded sheets in the right order and then, rather than gluing or stapling them together, stitching them together at the spine. The cover is then glued on. The inside pages are first trimmed down to the required size, depending on whether the cover is hard or soft. Threadbinding is suitable for all paper grades as no adhesive is used. Thread-binding has been used for this brochure but with an open spine. This kind of binding is often called French binding. Thread-sealing is a combination of threadbinding and perfect binding. Each sheet section is individually stitched on the spine side using a plastic thread, which melts together with the adhesive. Once all the sheet sections have been stitched, they are glued to the cover. As with perfect binding, uncoated paper works well with thread-sealing as the glue absorbs into the sheet and ensures a stronger adhesion with the cover. Spiral binding comes in several different variations: wire-o binding, classic spiral binding and GBC binding are just a few. Two things they all have in common are the fact that they are trimmed down to the right format before binding, and consist of loose sheets that are hole-punched and bundled together. The spiral binder is then attached, and these come in all kinds of shapes and colours. Trimming The very last stage in most print productions is the final trimming. The sheets have already been cut and trimmed several times depending on the size and method, but not to the exact format. Now that the product has been printed and binded, it has to be given a final trim to ensure the edges are attractive and even. 102 Art Workshop Session 4 The post production

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MUNKEN POLAR 150g/m² Have you ever wondered how to best spot varnish on uncoated paper? Find out on page 100! 106 Art Workshop Session 4 The post production

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MUNKEN POLAR 150g/m² 112 Art Workshop Summary Bear in mind

MUNKEN PURE 150g/m² Now that you ve gone through the sessions, here are some key points to bear in mind. See page 114! Summary Bear in mind Art Workshop 113

MUNKEN PURE 150g/m² Bear in mind Key points The knowledge in this guide can be summarised in a few short tips. This information can be used as a checklist or an introduction to a topic you may find useful. To fully understand each tip, we recommend studying the whole guide. Paper & image material Image adjustments can improve perceived quality, so consider increasing saturation and contrast. Total ink coverage (TIC) as part of the repro adjustment must be decreased to suit uncoated paper. Ensure that the ICC profile has the correct TIC value. Dot gain as part of the repro adjustment needs to be compensated for. Ensure that the correct curves are used in the ICC profile and/or paper compensation curves in the CTP. Screen ruling should not be too high, and an alternative is to use a stochastic screen for better definition. Proofing should be done before printing, however a soft proof on screen or on a digital proof, doesn t show the final result, only a true press proof will show that. Communication is vital to ensuring it s clear how the above will be handled and by whom, so that all involved get the right information and documentation. See more in the repro session Paper & print room before printing Humidity and temperature in the print room should be as close to the paper as possible. A good print and storage environment is at a relative humidity of 40 60% and at a temperature of 20 C. Condition paper in the original wrapping before printing. Differences in temperature between the paper and the print environment could easily give runability problems. Cold paper will also influence the paper and ink interaction, the ink will be colder and the tack and absorption will not be normal. A cold press and cold ink after a long stand still can give a higher ink tack, which can cause picking and linking during a start up. See more in the paper session Ink & damping water Use the correct ink type for the paper to avoid prolonged drying, set off and runability problems. It is optimal to use a specially adopted ink for uncoated that dries mainly by oxidation. Universal inks can be used, but duct fresh inks should be avoided. Ink tack should be normal, ink tack can vary and if it s too high, it might cause picking and linting. Damping water properties are very important for good functionality in the press. Securing the correct ph, hardness and conductivity is crucial, because it will influence the printability and the drying process. See more in the printing session During printing On uncoated paper, a higher back pressure is needed. Too low a pressure can cause the ink to not fully cover the surface, resulting in loss of definition and mottling. If this happens, increase the pressure until you reach an even print. Low back pressure will also make more ink stay on the paper surface and this can increase the risk for set off and a longer ink drying time. When dealing with ink density in the press, remember that uncoated paper needs more ink to reach the same density as on a coated paper. Therefore, the recommendation for uncoated paper is a lower density to avoid over inking. However, if the repro is correct and the total ink coverage is low, the ink density can be kept relatively high. Print powder should be used for uncoated paper, and it s important to use quite a coarse grained powder. The right sized granulates create a good air column between the sheets, which improves the drying and oxidation, as well as avoids ink set off between the sheets. After stocking the printed pallets, it is vital to keep the stacks as low as possible until the ink has completely dried. Otherwise, there is a risk of ink set off due to the pressure created in the lower end of the pallets. See more in the printing session Drying time Drying environment, temperature and humidity in the press and storage environment after print will influence the ink drying time dramatically. If the temperature is too low and the relative humidity too high, it will slow down the drying process. Offset ink dries in two ways: ink setting and the oxidation, and the importance of them will differ on uncoated and coated. The ink setting is the actual absorption of ink into the paper. On uncoated paper, the first setting phase will take up to 6 8 hours. During this time, the ink is still wet and the ink tack is low, but it s most often still possible to print the second side, printing wet in wet. At a certain point, the ink gets to tacky and then it will not be possible to handle the paper until it s completely dry. Oxidation of ink means that the ink will react with oxygen in the air and create a solid dry ink. Most offset inks have a certain level of drying by oxidation. Depending on the level of oxidation in the ink type, this phase and drying time will vary. The oxidation of ink can normally take up to 24 hours, but depending on the level of oxidation in the ink, up to 48 hours may be needed. Ink that is developed for uncoated paper has a high degree of oxidation, meaning a shorter drying time, whereas duct fresh inks have very low oxidation, meaning a very long drying time. During the oxidation phase, all handling of the printed paper should be avoided. See more in the printing session 114 Art Workshop Summary Bear in mind

MUNKEN PURE 150g/m² Bear in mind Summary charts Preparation & prepress Uncoated High bulk Uncoated Low bulk Coated Bulky Coated Matt Coated Silk Coated Gloss Total ink coverage 260% 260% 270% 280% 280 320% 320% Raster lpi 85 120 133 150 150 175 175 175 200 Dot gain Ink type Damping/ fount solution According to own test or ISO 12647 standard paper curves Preferably oxidative drying inks for uncoated paper. Universal inks work but might give longer dry time. Avoid duct fresh ink. Conditioning of paper Preferably oxidative drying inks for uncoated paper. Universal inks work but might give longer dry time. Avoid duct fresh ink. Normal setting inks for coated paper or universal inks. Normal setting inks for coated paper or universal inks. Normal setting inks for coated paper or universal inks. Normal setting inks for coated paper or universal inks. General recommendation: Secure a clean and stable system. IPA: max. 10% or preferably lower (Temperature is also important, otherwise the alcohol will evaporate too quickly). Damping water solutions: ca. 2 3%. Conductivity: 1000 1500 µs. (Too high normally means that the fount water is contaminated or has a too high salt level). Hardness: 8 12dB ph: 5.0 5.6 Important: There are different types of damping solutions that might need different targets and settings, as for example, the IPA free damping solution. Follow the fount solution suppliers recommendations. Temperature differences 5 6 7 8 9 10 15 20 25 Hours for 500kg paper 10h 11h 12h 13h 17h 20h 28h 45h 64h In the press This table is a simplification but gives a hint of the time needed for a normal pallet to reach equilibrium between the paper and the environment. Uncoated High bulk Uncoated Low bulk Coated Bulky Coated Matt & Silk Coated Gloss Back pressure 20 30µ 20 30µ 20 25µ 15 25µ 10 20µ Ink density K: 1.5 C: 1.25 M: 1.25 Y: 1.15 K: 1.5 C: 1.25 M: 1.25 Y: 1.15 K: 1.75 C: 1.45 M: 1.40 Y: 1.25 K: 1.85 C: 1.55 M: 1.50 Y: 1.35 K: 1.85 C: 1.55 M: 1.50 Y: 1.35 Note: density will differ due to different targets, but these levels will enable good runability in the press and a good print quality. Also note that the values will decrease in dry conditions compare to wet, and the difference between dry and wet ink will be higher on uncoated than on coated paper. These targets are for wet ink. Print powder Min 30µ Min 30µ Min 30µ 20 30µ 20 30µ Ink drying Uncoated High bulk Uncoated Low bulk Coated Bulky Coated Matt & Silk Setting 6 24h (48h) 6 24h (48h) Up to 24h (48h) Up to 24h (48h) Up to 24h (48h) Oxidation drying 6 24h (48h) 6 24h (48h) Up to 24h (48h) Upp to 24h (48h) Up to 24h (48h) Printing second side Wet in wet, during the first few hours. After drying completely up to 24 48 hours. Wet in wet, during the first few hours. After drying completely up to 24 48 hours. - - - When printing very heavy and dark images, and when using a very high ink density, a longer drying period should be planned for. Note that the oxidation phase on coated paper will only affect the post production; the ink will be dried on the surface within a few hours. Coated Gloss Summary Bear in mind Art Workshop 115

MUNKEN PURE 150g/m² Bear in mind Your own key points: 116 Art Workshop Summary Bear in mind

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MUNKEN PURE 150g/m² Bear in mind Your own key points: 118 Art Workshop Summary Bear in mind

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MUNKEN PURE 150g/m² Bear in mind Your own key points: 120 Art Workshop Summary Bear in mind

MUNKEN PURE 150g/m² Bear in mind Your own key points: Summary Bear in mind Art Workshop 121

MUNKEN PURE 150g/m² Bear in mind Your own key points: 122 Art Workshop Summary Bear in mind

MUNKEN PURE 150g/m² Bear in mind Your own key points: Summary Bear in mind Art Workshop 123

MUNKEN PURE 150g/m² Bear in mind Your own key points: 124 Art Workshop Summary Bear in mind

MUNKEN PURE 150g/m² Bear in mind Your own key points: Summary Bear in mind Art Workshop 125

MUNKEN PURE 150g/m² Bear in mind Munken Design Range qualities used in this guide Cover Pages 1 16 MUNKEN PURE 400g/m² MUNKEN PURE ROUGH 120g/m² Pages 17 32 MUNKEN LYNX 150g/m² Pages 33 48 MUNKEN LYNX ROUGH 120g/m² Pages 49 64 MUNKEN POLAR 150g/m² Pages 65 80 MUNKEN POLAR 170g/m² Pages 81 96 MUNKEN PURE ROUGH 120g/m² 126 Art Workshop Summary Bear in mind

Paper and image material Image adjustments can improve perceived quality, so consider increasing saturation and contrast. Total ink coverage (TIC) as part of the repro adjustment must be decreased to suit uncoated paper. Ensure that the ICC profile has the correct TIC value. Dot gain as part of the repro adjustment needs to be compensated for. Ensure that the correct curves are used in the ICC profile and/or paper compensation curves in the CTP. Screen ruling should not be too high, and an alternative is to use a stochastic screen for better definition. Proofing should be done before printing, however a soft proof on screen or on a digital proof, doesn t show the final result, only a true press proof will show that. Communication is vital to ensuring it s clear how the above will be handled and by whom, so that all involved get the right information and documentation. See more in the repro session Humidity and temperature in the print room should be as close to the paper as possible. A good print and storage environment is at a relative humidity of 40 60% and at a temperature of 20 C. Condition paper in the original wrapping before printing. Differences in temperature between the paper and the print environment could easily give runability problems. Cold paper will also influence the paper and ink interaction, the ink will be colder and the tack and absorption will not be normal. A cold press and cold ink after a long stand still can give a higher ink tack, which can cause picking and linking during a start up. See more in the paper session 114 Art Workshop Summary Bear in mind MUNKEN PURE 150 g/m² The key knowledge in this guide can be summarised in a few short tips. This information can be used as a checklist or an introduction to a topic you may find useful. To fully understand each tip, we recommend studying the whole guide. On uncoated paper, a higher back pressure is needed. Too low a pressure can cause the ink to not fully cover the surface, resulting in loss of definition and mottling. If this happens, increase the pressure until you reach an even print. Low backpressure will also make more ink stay on the paper surface and this can increase the risk for set off and a longer ink drying time. When dealing with ink density in the press, remember that uncoated paper needs more ink to reach the same density as on a coated paper. Therefore, the recommendation for uncoated paper is a lower density to avoid over inking. However, if the repro is correct and the total ink coverage is low, the ink density can be kept relatively high. Print powder should be used for uncoated paper, and it s important to use quite a coarse grained powder. The right sized granulates create a good air column between the sheets, which improves the drying and oxidation, as well as avoids ink set off between the sheets. After stocking the printed pallets, it is vital to keep the stacks as low as possible until the ink has completely dried. Otherwise, there is a risk of ink set off due to the pressure created in the lower end of the pallets. See more in the printing session Use the correct ink type for the paper to avoid Drying environment, temperature and humidity in the press and storage environment after prolonged drying, set off and runability problems. It is optimal to use a specially adopted print will influence the ink drying time dramatically. If the temperature is too low and the ink for uncoated that dries mainly by oxidation. Universal inks can be used, but duct fresh relative humidity too high, it will slow down inks should be avoided. the drying process. Ink tack should be normal, ink tack can vary Offset ink dries in two ways: ink setting and and if it s too high, it might cause picking and the oxidation, and the importance of them will linting. differ on uncoated and coated. Damping water properties are very important The ink setting is the actual absorption of ink for good functionality in the press. Securing into the paper. On uncoated paper, the first setting phase will take up to 6 8 hours. During the correct ph, hardness and conductivity is crucial, because it will influence the printability and the drying process. low, but it s most often still possible to print the this time, the ink is still wet and the ink tack is second side, printing wet in wet. At a certain point, the ink gets to tacky and then it will not See more in the printing session be possible to handle the paper until it s completely dry. Oxidation of ink means that the ink will react with oxygen in the air and create a solid dry ink. Most offset inks have a certain level of drying by oxidation. Depending on the level of oxidation in the ink type, this phase and drying time will vary. The oxidation of ink can normally take up to 24 hours, but depending on the level of oxidation in the ink, up to 48 hours may be needed. Ink that is developed for uncoated paper has a high degree of oxidation, meaning a shorter drying time, whereas duct fresh inks have very low oxidation, meaning a very long drying time. During the oxidation phase, all handling of the printed paper should be avoided. MUNKEN PURE 150g/m² Pages 97 112 MUNKEN POLAR 150g/m² Bear in mind Key knowledge Paper and print room before printing Ink and damping water Drying time During printing Pages 113 128 MUNKEN PURE 150g/m² Summary Bear in mind Art Workshop 127

MUNKEN PURE 150g/m² Colophon The Munken Guide to Uncoated Paper Munken Design Range Grammage g/m2 Shades Bulk Munken Polar Rough 90 100 120 150 170 300b Crisp white 1.4 Munken Polar 80 90 100 120 130 150 170 200 240 300b 400b Crisp white 1.13 Munken Lynx Rough 90 100 120 150 170 300b Natural white 1.4 Munken Lynx 70d 80 90 100 120 130 150 170 200 240 300b 400b Natural white 1.13 Munken Pure Rough 90 100 120 150 170 300b Cream 1.4 Munken Pure 80 90 100 120 130 150 170 200 240 300b 400b Cream 1.13 b Laminated paper. d Not standard production. Minimum 10 tonnes order. Please contact your sales representative. The information provided in this publication is considered to be true and correct at the time of printing. However, Arctic Paper reserves the right to make any changes that may be precipitated by unforeseen circumstances, without prior notice, which may impact on the accuracy of this information, and is therefore intended to be used as guidance only. If you want to order samples or a dummy for your next project, go directly to www.arcticpaper.com/dummyshop Arctic Paper. Design: Grow, Sweden. Printer: Göteborgstryckeriet. Printing press: Komori Lithrone S40. Screen: FM 20µ. Ink: Hostmann-Steinberg Resista Eco. Bookbinder: Förlagshuset Nordens Grafiska. All standard Munken products are available as FSCTM and PEFC certified. Certificates and reports: FSCTM, PEFC, ISO 14001, EMAS, Paper Profile. 128 Art Workshop Colophon

Design is in our nature. Munken is all about commitment to design, to nature and to detail. And you can always trust Munken for 100% design on 100% natural papers. Or to put it another way, with the choice of design or environmental concern choose both! www.arcticpaper.com