Production Process Course Documentation Anchor Faculty Dr. Tridha Gajjar Course Faculty Mr. Bharat Suthar Compiled by Saptarshi Das S1601113 MDes Graphic Design 2016-17
Acknowledgement The module on Production Processes was an extremely enriching one, with us getting an opportunity to understand the world of print and the vital role it plays in Graphic Design. I would like to thank our anchor faculty Dr. Tridha Gajjar for her constant direction, our faculty, Mr. Bharat Suthar for imaprting us wit this vast amount of knowledge. The entire team at NID Print Labs, Suresh Bhai, Hasmukh Bhai, Sachin Bhai for their unwavering support, and my classmates for their support whenever there was any confusion regarding understanding of class concepts or helping to review my work during the assignments.
Contents Introduction to Printing Printing: A timeline Print Processes Relief/Letterpress Printing Flexography Lithography Offset Printing Dry Offset Printing Gravure Printing Screen Printing Digital Printing Unconventional Printing
Techniques Printing Technologies Color in Printing Color Reproduction Color Models Color Gamut Trapping Graphics in Printing Types of Originals FM Screening Desktop Publishing Graphics : Vector vs Raster
Data input Devices Graphics: Printer Marks Paging and Imposition Ink Paper Post Press Operations Poster Printing Industrial Visit Book Binding
Introduction to Printing Print is an entity we encounter everyday in our daily lives. From our morning newspapers, to the road signs we encounter, to the books we read, the forms we fill up, print is all around us. This module was an opportunity to get into the depth of this process and understand the deeper working behind it. Printing may be defined as the process of transferring text and images onto a substrate; generally paper; using a medium such as ink. The technology has developed and advanced over the years, moving from woodblock printing to the printing press, which was a revolutionary step, and further proceeding through different stages to get to digital printing. The objective of this course was to develop a comprehensive understanding of pre-press, press and post-press processes in order to apply it efficiently in design.
Printing: A Timeline Paper Woodblock printingMovable type Printing press Etching Lithography Chromolithography Rotary press Offset printing Hot metal typesetting Photostat and Rectigraph Screen printing Xerography Phototypesetting Inkjet printing Dot matrix printing Laser printing Thermal printing 3D printing Digital printing
106 200 1040 1440 1515 1796 1837 1843 1875 1884 1907 1910 1938 1949 1951 1968 1969 1972 1984 1993
Print Processes
Relief Printing
Letterpress is the oldest method of printing with equipment and images printed by the “relief ” type printing plates where the image or printing areas are raised above the nonprinting areas. The image must be metal cast with a height of 0.918 inches prior to print versus offset printing plates which are comparatively cheaper and require less time to make. A worker composes and locks movable type into the “bed” or “chase” of a press, inks it, and presses paper against it to transfer the ink from the type which creates an impression on paper.
Letterpress Printing There are three different types of letterpress printing devices in use today: platen, flat-bed, and rotary presses.
Rotary Letterpress
Flat-bed Cylinder Letterpress
Platen-type Letterpress
There are two types of rotary letterpresses, sheet-fed and web-fed. The most popular types of plates used are stereotype, electrotype, and molded plastic or rubber. When printing on coated papers, rotary presses use heat-set inks and are equipped with dryers, usually the high-velocity hot air type. Web-fed rotary letterpress presses are used primarily for printing newspapers. These presses are designed to print both sides of the web simultaneously. Typically, they can print up to four pages across the web
Flat-bed cylinder presses use either vertical or horizontal beds. The plate is locked to a bed which passes over an inking roller and then against the substrate. The substrate passes around an impression cylinder on its way from the feed stack to the delivery stack. Ink is supplied to the plate cylinder by an inking roller and an ink fountain.
A platen press is made up of two flat surfaces called the bed and the platen. The platen provides a smooth backing for the paper or other substrate that is to be printed. The raised plate (image to be printed) is locked onto a flat surface. The plate is inked, the substrate is then placed on another flat surface called the bed and pressed against the inked plate producing the impression.
Flexography
Flexography is a rotary relief printing method using rubber or plastic plates and fluid inks or dyes for printing on fabrics and impervious materials such as plastics, as well as on paper. Flexography is used to print corrugated containers, folding cartons, multiwall sacks, paper sacks, plastic bags, milk and beverage cartons, disposable cups and containers, labels, adhesive tapes, envelopes, newspapers, and wrappers (candy and food).
Flexography Plate Cylinder
Impression Cylinder
Doctor Blade
Anilox Roller
Fountain Roller
The different parts of the flexographic system are as follows:
Fountain roller
Anilox roller
Doctor Blade (optional)
Plate cylinder
Impression Cylinder
The fountain roller transfers the ink that is located in the ink pan to the second roller, which is the anilox roller. In Modern Flexo printing this is called a Meter or “metering” roller.
This is what makes flexography unique. The anilox roller meters the predetermined ink that is transferred for uniform thickness. It has engraved cells that carry a certain capacity of inks that can only be seen with a microscope. These rollers are responsible to transfer the inks to the flexible-plates that are already mounted on the Plate Cylinders.
The doctor blade scrapes the anilox roll to ensure that the predetermined ink amount delivered is only what is contained within the engraved cells. Doctor blades have predominantly been made of steel but advanced doctor blades are now made of polymer materials, with several different types of beveled edges.
The plate cylinder holds the printing plate, which is soft flexible rubber-like material. Tape, magnets, tension straps and/or ratchets hold the printing plate against the cylinder
The impression cylinder applies pressure to the plate cylinder, where the image is transferred to the substrate. This impression cylinder or “print Anvil” is required to apply pressure to the Plate Cylinder.
Flexographic Process The flexographic process consists of three major steps: Image Preparation: The image is the mechanical art copy of the image clicked by camera or artwork to be reproduced. A simple proof is prepared to check for position and accuracy. Plate Making: The photomechanical plate making method begins with making an engraving. This is accomplished by exposing a metal plate through a negative and processing the exposed plate in an acid bath. The metal engraved plate is used to make a master.The engraving is placed in a mold press. The mold is produced by applying heat & pressure to the mold material, against the engraving under controlled temperature and pressure. The material fills the engraving on the metal plate. When its cooled you end up with a master mold for the plastic or rubber compound that will be pressed into the mold under pressure and elevated temperature to produce the flexible printing plate with raised areas that will transfer the ink. The second method of flexo plate making is relief plates. This utilizes a solid or liquid photopolymer. The sheet of photopolymer is exposed to light through a negative. The unexposed areas are then washed away with solvent or water wash. This is fast becoming the most common method of making plates. Printing: The image areas are raised above the non-image areas on the rubber or polymer plate. The ink is transferred from the ink roll which is partially immersed in the ink tank. Then it transfers to the anilox or ceramic roll whose texture holds a specific amount of ink since it is covered with thousands of small wells or cups that enable it to meter ink to the printing plate in a uniform thickness evenly and quickly, ranging between 140 CPI(Cells per inch) to 12000 CPI. To avoid smudgy look, the excess ink on the anilox roller is removed by a doctor blade. Ink is then transferred to the printing plate. The substrate is finally placed between the plate and the impression cylinder to transfer the image.The sheet is then fed through a dryer.
Lithography
Lithography is a printing process in which the image area and the non-image area co-exist on the same plane. That means the surface from which you print is completely flat. This is feasible because of a very useful chemical principle: ink is an oily substance, which means it repels water. If you can create a surface on which some parts contain a thin layer of water, those areas will repel ink. The image areas need be lipophilic (or oleophilic) – they accept ink – while the non-printing areas need to be hydrophilic – they are repellent to oil and receptive to water.
Offset Printing Inking Unit
Offset refers to the fact that the image is not transferred from a lithographic printing plate to a sheet of paper. Instead the inked image is transferred (or offset) from the printing surface to a rubber blanket and then to the printing surface. The process can be used to print on paper, cardboard, plastic or other materials, but these have to have a flat surface. The process of an offset printing system is as follows:
Dampening Unit
Water
Plate Cylinder
Cylinders; Impression, Blanket and Plate Cylinder: The plate cylinder is a large roll to which the printing plate is attached. The plate is usually made from aluminum. Its non-imaging parts will be covered by a thin layer of water that is applied by the dampening system. This means the ink which is fed by the inking system will only adhese on all the other areas. During printing this image created by ink is transferred to a rubber blanket that is attached to the blanket cylinder. From there is the image is transferred to the press sheet. An impression cylinder carries the paper through the printing unit and provides a hard backing against which the blanket can impress the image on the paper. Not all presses use impression cylinders: there are for example perfecting presses that print blanket-to-blanket: the impression cylinder is replaced by a second blanket cylinder, printing both sides of the press sheet simultaneously in a single printing unit. The inking system The ink fountain is a reservoir that holds ink. Offset ink is not a fluid ink, it looks more like a kind of thick paste. From the ink fountain this ink needs to be transferred to the printing plate or cylinder. From there that ink will be transferred to the paper or another substrate. The inking system is responsible for this transfer. It needs to break the thick, viscous ink down into a thinner, more workable and uniform ink film. This is done using a set of rollers. Presses can have up to 10 (or even more) rollers in their roller train. The amount of ink is usually controlled by so-called fountain keys that control the gap between the ink fountain and the first roller. The wider open this gap is, the more ink can be picked up by the roller. Controlling that gap is done manually with a screw on some presses but nowadays those keys are often motorized. The fountain keys are lined up in a series across the width of the ink fountain so that more ink can be transferred to the left part of a page if there are more images or solid tints on that side of the paper. Some presses do not use fountain keys: they periodically dip the first ductor roll in the ink fountain and control the amount of ink that is picked up by the duration of that dip. The inking system assures that a thin layer of ink that is typically 0.2 to 0.4 mils thick is transferred to the printing plate.
Blanket Cylinder
Impression Cylinder
The dampening system The dampening system makes sure the non-image areas of the printing plate are moistened so that they will repel ink. This is mainly done using water, but additives are needed for long print runs to improve the ink repellency, lower the surface tension, desensitize the non-image plate regions and make sure corrosion, mildew, bacteria, and fungi don’t cause issues. That’s why gum, alcohol, a fungicide, and other agents are added to the water of the fountain solution. To make sure an even layer of water is put down on the non-printing parts of the printing plate, a mechanism similar to the inking system is used. The dampening system is, however, less complicated and requires fewer rollers.
Inking Unit
Dry Offset Printing Plate Cylinder
Blanket Cylinder
Impression Cylinder
Dry offset printing utilizes a relief printing plate that transfers or “offsets” multiple colors to a rubber pad or “blanket.” The blanket then transfers an inked image to a substrate such as polypropylene drink cups. The “dry” in dry offset, refers to the absence of water in the inking system. This is In contrast to offset lithography wherein water is used to dampen and repel oil-based ink from the non-print areas of a printing plate. Dry offset ink is cured onto the substrate using high intensity ultra-violet light. UV ink has a viscosity similar to peanut butter, depending on ingredients and temperature. Some common products decorated using the dry offset process are: plastic beverage and dairy containers, plastic lids, cosmetic tubes, aluminium cans, industrial plastic buckets and pails.
Gravure Printing
Gravure printing is an example of intaglio printing. It uses a depressed or sunken surface for the image. The image areas consist of honey comb shaped cells or wells that are etched or engraved into a copper cylinder. The unetched areas of the cylinder represent the nonimage or unprinted areas. The cylinder rotates in a bath of ink called the ink pan. As the cylinder turns, the excess ink is wiped off the cylinder by a flexible steel doctor blade. The ink remaining in the recessed cells forms the image by direct transfer to the substrate (paper or other material) as it passes between the plate cylinder and the impression cylinder.
Gravure Printing The major unit operations in a gravure printing operation are: Printing Cylinder
Form Cylinder
Doctor Blade
Ink Tray
While the press is in operation, the engraved cylinder is partially immersed in the ink tray, filling the recessed cells. As the cylinder rotates, it draws excess ink onto its surface and into the cells. Acting as a squeegee, the doctor blade scrapes the cylinder before it makes contact with the paper, removing the excess ink from the non-printing (non-recessed) areas and leaving in the cells the right amount of ink required. The position of the blade relative to the nip is normally variable.
Next, the substrate gets sandwiched between the impression roller and the gravure cylinder: this is where the ink gets transferred from the recessed cells to the web. The purpose of the impression roller is to apply force, ensuring that the entire substrate is brought into contact with the gravure cylinder, which in turn ensures even and maximum coverage of the ink. Once in contact with the substrate, the ink’s surface tension pulls (part of) the ink out of the cell and transfers it to the substrate.
Then the inked substrate goes through a dryer because it must be completely dry before going through the next color unit and accepting another coat of ink.
A rotogravure printing press has one printing unit for each color, typically CMYK or cyan, magenta, yellow and key (printing terminology for black), but the number of units varies depending on what colors are required to produce the final image.
Screen Printing (Serigraphy)
Screen printing is arguably the most versatile of all printing processes. It can be used to print on a wide variety of substrates, including paper, paperboard, plastics, glass, metals, fabrics, and many other materials. including paper, plastics, glass, metals, nylon and cotton. Some common products from the screen printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards. The advantage of screenprinting over other print processes is that the press can print on substrates of any shape, thickness and size.
Screen Printing Process Squeegee Negative Space on Screen
Ink
Positive Image on screen Frame
Printed Image
Screen Printing Process
Unique Features of Screen Printing
Screen printing consists of three elements: the screen which is the image carrier; the squeegee; and ink. The screen printing process uses a porous mesh stretched tightly over a frame made of wood or metal. Proper tension is essential to accurate color registration. The mesh is made of porous fabric or stainless steel mesh. A stencil is produced on the screen either manually or photochemically. The stencil defines the image to be printed in other printing technologies this would be referred to as the image plate.
A significant characteristic of screen printing is that a greater thickness of the ink can be applied to the substrate than is possible with other printing techniques. This allows for some very interesting effects that are not possible using other printing methods. Because of the simplicity of the application process, a wider range of inks and dyes are available for use in screen printing than for use in any other printing process.
Screen printing ink is applied to the substrate by placing the screen over the material. Ink with a paint-like consistency is placed onto the top of the screen. Ink is then forced through the fine mesh openings using a squeegee that is drawn across the screen, applying pressure thereby forcing the ink through the open areas of the screen. Ink will pass through only in areas where no stencil is applied, thus forming an image on the printing substrate. The diameter of the threads and the thread count of the mesh will determine how much ink is deposited onto the substrates.
Utilization of screenprinting presses has begun to increase because production rates have improved. This has been a result of the development of the automated and rotary screenprinting press, improved dryers, and U.V. curable ink. The major chemicals used include screen emulsions, inks, and solvents, surfactants, caustics and oxidizers used in screen reclamation. The inks used vary dramatically in their formulations
Digital Printing
Digital printing describes the process of transferring a document on a personal computer or other digital storage device to a printing substrate by means of a device that accepts text and graphic output. As with other digital processes, information is reduced to binary code, or “digitized,� to facilitate its storage and reproduction. Digital printing has steadily replaced lithography in many markets, especially at the consumer and business level, as a result of its substantially lower production costs.
Digital Printing Techniques Mirror Digital printing can be done in various ways. Two technologies dominate the industry: Laser
Inkjet In an inkjet printer the image that needs to be printed is created by small droplets of ink that are propelled from the nozzles of one or more print heads. Inkjet devices can print on a wide range of substrates such as paper, plastic, canvas or even doors and floor tiles. Inkjet printing is used a lot for posters and signage. It is also economical for short run publications such as photo books or small runs of books. In-line inkjet printers are sometimes combined with other types of presses to print variable data, such as the mailing addresses on direct mail pieces. Xerography In xerographic printers, such as laser printers, the image that needs to be printed is formed by selectively applying a charge to a metal cylinder called a drum. The electrical charge is used to attract toner particles. These particles are transferred to the media that is being printed on. To make sure the toner is fixed properly, the substrate passes through a fuser that melts the toner into the medium. Laser printers are not only used in offices but also for small run printing of books, brochures and other types of document. These printers are also used for transactional printing (bills, bank documents, etc) and direct mail.
Photosensitive Drum Paper
Laser Printing
Digital printing is increasingly utilized for print jobs that were previously printing using offset, flexo or screen printing.
Ink Nozzle
In short run small format (A3 size) printing, digital is taking over from offset for both color and B&W printing. Quick printers and copy shops print digitally on presses from vendors like Xerox, HP, Canon, and Konica Minolta.
Image Data
Labels are also increasingly being printed digitally.
Heat or Piezo element
Billboard and point-of-sale or point-of-purchase jobs are being done by wide-format inkjet devices.
Ink Droplet Paper
Inkjet Process
In book printing publishing companies start to rely more on print-on-demand. The Espresso Book Machine pictured below is well suited for that job.
Unconventional Printing Techniques
Electrography
Collotype
It is a combination of scanner and printer where an electrically charged drum is used. Artwork is placed face down on a glass plate and is illuminated by fluorescent light which travels length of the image. Reflected image is directed through the lenses in to the charged drum. This charge leaks away where light from the image falls on the drum. A resin based powder (Toner) attracted to the image areas. This pattern of toner is transferred to the paper, where its fixed and fused by heat. Laser copier works like combined scanners and image setters by scanning the image digitally and using a laser to write the image onto electrostatic drum. There is no master copy generated.
Collotype Printing is a screenless Planographic technique for high quality reproduction. Invented in the 19th century, is little known today. Formerly it was the fi nest technique for the reproduction of paintings. In this process, a glass plate is first coated with light-sensitive gelatin solution and then exposed to continuous-tone negatives. It’s then soaked in glycerin, which is absorbed most in the non-hardened areas. Hardened areas accept the ink and the plate can be used to print a few thousand copies of the positive image.
Thermography
Magnetography
This works on similar principles as of a fax machine. A specially made paper that is coated with a dye is used in this process. When the paper is heated it turns black. So, during the imaging process, the image areas are heated and the spots on the paper turn black, giving us the reading matter printed. This is also a popular method employed for generating labels and barcodes. Because the process involves an induced change in the state of the substrate (paper), the process is limited to printing only in single color.
A non-impact printer technology that prints up to 90 ppm. A magnetic image is created by a set of recording heads across a magnetic drum. A toner is applied to the drum to develop the image, which is transferred to paper by light pressure and an electrostatic field. The toner is then fused by heat. The print quality is not as good as a laser printer, but the machines require less maintenance.
Printing Technologies Classification can be done on two basis; the first system involves the making of master copy and the subsequent reproductions from it. Conventional Printing: Conventional Printing methods work on the principle of pressure, hence subsequent copies are built from an original copy, known as a master copy, an inked image carrier.
Unconventional Printing: In unconventional printing, no master copy is created, and an image is generated each time for each reproduction.
The other system of classification of printing methods is based on the printer touching the paper to make an image. Impact printers: have a mechanism that touches the paper in order to create the image. The two main impact technologies are Dot matrix and Character printers. Dot matrix printers use a series of small pins to strike a ribbon coated with ink causing the ink to transfer to the paper at the point of impact. Character printers are basically computerised typewriters. they have a ball of bars with actual characters embossed on the surface. The appropriate character is struck against the ink ribbon, transferring the character’s image onto the paper.
Non Impact Printers: Non impact printers are mainly two types - laser printers and inkjet printers. When inkjet printer use a series of nozzles to spray the drops of ink directly on the paper, the laser printers use dry ink, static electricity and heat to place and bond the ink onto paper.
Color in Printing
Color Reproduction
Four color process printing:
Spot Colors:
Hexachrome Colors:
in this system a color image is separated into 4 different color values (called a color separation) by the use of filters and screens. This was done earlier with photographic film on a graphic arts camera, but is usually done digitally with software now. The result is a color separation of 4 images that when transferred to printing plates and sequentially printed on a printing press with the colored inks cyan (blue), magenta (red), yellow and black (the k in cmyk), reproduces the original color image. Most of colors are reproduced with just the four process ink colors. The four color printing process is universally used for the reproduction of color images and text.
Spot colors are printed with premixed inks on a printing press or screen printer. Each spot color is reproduced using a single printing plate or screen. To ensure that a printer uses the exact color that the designer intends, the Pantone Matching System (PMS) is used. Each PMS number references a unique spot color and these colors can be found on a swatch chart. By using this type of numbering system, people can convey the exact colors for a printed piece to each other without actually looking at the same samples. It’s important to remember that spot colors may not actually translate to matching processcolors. Unlike process printing, which prints dots of color, a spot color is printed at 100% and has no dot pattern.
Hexachrome is a six-color process printing system with a specially enhanced color ink set. With Hexachrome, we can now reproduce rich, vibrant solid colors, realistic skin tones and elegant pastels. The Hexachrome color gamut exceeds that of CMYK, allowing us to achieve the same bright, vibrant colors on press with which we design on computer. Hexachrome reduces our dependency on spot colors and allows we to easily re-purpose our designs for different applications, including the Web! Hexachrome is supported by many technology partners, ink manufacturers, software developers, proofing systems and printing devices.
Color Models
CMYK
RGB
CMYK stands for Cyan Yellow Magenta and blacK. This model is used for printing. In other words these are the 4 colored inks used inside of color printers. CMYK is a subtractive model, in fact in theory, cyan, yellow and magenta should combine among themselves to absorb all colors and produce black. But because of the small impurities found in all inks, they actually combine to form a muddy brown. This is one of the reasons for the black ink. Another reason is this: colored inks are more expensive than black ink. Besides, 3 inks means 3 ink layers during printing. And 3 ink layers cause the printed paper to become quite wet, so the paper will dry more slowly and the press can be slower. In other words more expensive. You have to care about CMYK when you have to print something.
RGB stands for Red Green and Blue. This model represents how your computer sees colors. In fact you have to know that each pixel in your screen can be ‘switched on’ like a little ‘light-bulb’ by means of a ‘light-ray’ produced by an electronic gun inside your monitor. This ray can be a shade of Red, a shade of Green or a shade of Blue. For this reason the pixel shot by the ray can assume a shade of red, a shade of green or a shade of blue. According to the RGB model, each shade of each of the 3 colors (Red, Green and Blue) is represented by a number ranging from 0 to 255. For example, the black color is represented by the ‘0 0 0’ RGB value (R=0, G=0 and B=0) while the white color is represented by the ‘255 255 255’ RGB value (R=255 G=255 and B=255). So the RGB model can represent more than 16 millions of colors. RGB is an additive model, because Red Green and Blue are additive colors. In other words when red green and blue are comined, they create white. Red + Green + Blue = White.
Color Models The main color models dealt with in color technology are as follows:
HSB
LAB
HSB stands for Hue, Saturation and Brightness. According to this model, any color is represented by 3 numbers. The first number is the hue, and its value ranges from 0 to 360 degrees. Each degree represent a distinct color. First there is the red color (0 or 360 degrees) and then there are all other colors (for example yellow at 120 degrees, green at 180 degrees and blue at 240 degrees), up to the violet color. All the rainbow’s colors are represented here. The second number is the saturation. It represents the amount of color or, more exactly, its percentage. Its value ranges from 0 to 100, where 0 represents no color, while 100 represents the full color. Finally, the third number is the brightness. You can enhance the color brightness adding the white color, or you can reduce it adding the black color. In this case 0 represents the white color and 100 represents the black color. The more this value tends to 0, the brighter the color is. The more this value tends to 100 the darker the color is.
LAB stands for Luminance (or lightness) and A and B (which are chromatic components). According to this model A ranges from green to red, and B ranges from blue to yellow. This model was designed to be device independent. In other words by means of this model you can handle colors regardless of specific devices (such as monitors, printers, or computers). The Luminance ranges from 0 to 100, the A component ranges from -120 to +120 (from green to red) and the B component ranges from -120 to +120 (from blue to yellow).
Color Gamut The color gamut of a device describes the entire range of color that can be reproduced by the device. Generally, the color gamut is specified in the hue– saturation plane, as a system can usually produce colors over a wide intensity range within its color gamut; for a subtractive color system (such as used in printing), the range of intensity available in the system is for the most part meaningless without considering system-specific properties (such as the illumination of the ink). When certain colors cannot be expressed within a particular color model, those colors are said to be out of gamut. For example, while pure red can be expressed in the RGB color space, it cannot be expressed in the CMYK color space; pure red is out of gamut in the CMYK color space. A device that is able to reproduce the entire visible color space is an unrealized goal within the engineering of color displays and printing processes.
Trapping
Trapping is a method of adjusting areas where two distinct, adjacent colors meet so that press misregistration won’t cause white spaces. If you knock out graphics or type you may have to create a trap to ensure that you don’t have white spaces due to misregistration.
Graphics and Printing
Types of Originals
Line Art
Continuous Tone
Halftone
Line art or line drawing is any image that consists of distinct straight and curved lines placed against a (usually plain) background, without gradations in shade (darkness) or hue (color) to represent two-dimensional or three-dimensional objects.
A continuous tone image is one where each color at any point in the image is reproduced as a single tone, and not as discrete halftones, such as one single color for monochromatic prints, or a combination of halftones for color prints. A gray scale or colour image format capable of illustrating continuous varying tonal range as opposed to line art. The most common continuous tone images are digital photographs.
Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size, in shape or in spacing. “Halftone� can also be used to refer specifically to the image that is produced by this process. Where continuous tone imagery contains an infinite range of colors or greys, the halftone process reduces visual eproductions to an image that is printed with only one color of ink, in dots of differing size. This reproduction relies on a basic optical illusion that that these tiny halftone dots are blended into smooth tones by the human eye. At a microscopic level, developed black-and-white photographic film also consists of only two colors, and not an infinite range of continuous tones.
Halftone Analysis The following definitions affect the result (quality) of the final output: Screen Ruling : The number of dots per linear inch measured along the axis of each row. Multiple coloured images have always created immense problems for the prepress technicians and printers. Ideally each colour in a multi coloured halftone picture must be EXACTLY 30 DEGREES apart. But 90 degrees divided by 30 equals 3 so we have a problem with a four colour process (CMYK ) picture because of the fourth colour. (an halftone screen has two axis, one 90 degrees to the other. Therefore only three halftone screen reference angles, 30 degree apart, can be used per 360 degrees as the situation duplicates for each 90 degree set). The pattern created by 2 or 3 halftone screens layed at 30 degrees to each other is called a rose pattern, a seemingly simple and unobtrusive pattern that normally does not offend the eye. However as soon as we diverge from this ideal we start see a moirĂŠ pattern that progressively gets worse. One colour out by even 1 degree will start to clash with at least one of the other colours and destroy the rose pattern; (= moire pattern). Screen Angle : defining the angle of the axis. Screen Dot Shape : generally Elliptical, Round or Square. Screen Dot Range - the minimum to maximum range always measured as a percentage, 0% = white, 100% = solid. Highlight Dot size : the smallest dot (% - original copy white). Shadow Dot Size : the largest dot (% - original copy black) . Midtone Dot Size : a grey dot (%) relative to the original copies middle greys.
FM Screening Stochastic screening or FM screening is a halftone process based on pseudo-random distribution of halftone dots, using frequency modulation (FM) to change the density of dots according to the gray level desired. Traditional amplitude modulation halftone screening is based on a geometric and fixed spacing of dots, which vary in size depending on the tone color represented (for example, from 10 to 200 micrometres). The stochastic screening or FM screening instead uses a fixed size of dots (for example, about 25 micrometres) and a distribution density that varies depending on the color’s tone. FM screening does not create rosette patterns.
Desktop Publishing History: Desktop publishing began in 1985 with the introduction of PageMaker software from Aldus and the LaserWriter printer from Apple Computer for the Apple Macintosh computer. The ability to create WYSIWYG page layouts on screen and then print pages at crisp 300 ppi resolution was revolutionary for both the typesetting industry as well as the personal computer industry. The term “desktop publishing� is attributed to Aldus Corporation founder Paul Brainerd, who sought a marketing catch phrase to describe the small size and relative affordability of this suite of products in contrast to the expensive commercial phototypesetting equipment of the day.
Graphics: Vector vs Raster Most images you see on your computer screen are raster graphics. Pictures found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels, commonly referred to as a bitmap. The larger the image, the more disk space the image file will take up. Vector graphics are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams. Paths are even used to define the characters of specific typefaces. Because vector-based images are not made up of a specific number of dots, they can be scaled to a larger size and not lose any image quality.
Calibration: The simplest calibration methods involve adjustments to the Contrast and Brightness settings of your monitor. Commonly done with device that change color frequently like monitors and printers. An intermediate method uses special software to calibrate your printer, scanner and other devices so that what you see on-screen, what you scan and what you print all look the same.
Raster Graphics
Vector Graphics
Data Input Devices
CCD Flatbed Printers:
Drum scanner:
Most versatile and popular image capturing device Lesser density range -CCD will not see all the shadow detail,in contrasty, transparencies, not reproduce these areas fully. Scanning resolution ~ 5500 dpi for true optical resolution Spec dust lying on a CCD sensor may cause streaks across the image in the scan direction
In a drum scanner, the original image (usually a color transparency) is attached to a transparent revolving drum—or cylinder—while a small point of light illuminates the image from within the drum, where this light is split, passed through red, green and blue filters, and picked up by a photomultiplier tube, which analyzes each row, pixel by pixel, storing the particular color or grayscale information for each pixel in a digital file. When one revolution is complete, the light source moves one pixel to the side, and images the next row, continuing this process until the entire picture is imaged. In the photomultiplier tube, the amounts of cyan, magenta, and yellow contained by the image are derived from the amounts of red, green, and blue light hitting it. The device stores the cyan, the magenta, and the yellow values for each pixel as one of 256 shades of gray.
Graphics: Printer Marks Key A - Star Target (not optional) B - Registration Mark C - Page Information D - Trim Marks E - Color Bar F - Tint Bar
The different printing marks and terms seen while printing are as follows:
Bleed
Crop Marks
Registration
DPI
Colour bar
Bleed is a printing term that refers to printing that goes beyond the edge of the sheet after trimming. The bleed is the part on the side of your document that gives the printer that small amount of space to move around paper and design inconsistencies.
A set of horizontal and vertical lines which indicate where a photograph, illustration, or page should be eliminated or trimmed.
In color printing, registration is the method of correlating overlapping colors on one single image. When printing an image that has more than one color, it is necessary to print each color separately, and to ensure that each color overlaps the others precisely.
Dots (or pixels) per Inch; Resolution that varies across media. For print, image files are optimized at 300 DPI. For the Web (GIF and JPEG file formats), files are optimized at 72 DPI, the number of pixels across one inch of most monitors.
To ensure that correct colours are printed, a colour bar is printed outside the area of the material that will form the final product.
Paging and Imposition
binding edges
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The positioning of pages on a press sheet in such a manner that when the sheet is folded into a signature and cut, the pages will be in the correct sequence. Imposition involves not just the correct positioning of pages on the same side of the sheet, but also the back printing, or the pages printed on the back of the sheet. Back-printed pages can be oriented in a variety of ways;
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third fold
first fold
Head-to-Head imposition: A form of back printing such that the top of the copy (or other printed image) on the back side of the sheet is the same as the top of the copy on the front side of the sheet, read simply by turning the page over, as the pages of a book.
second fold
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Head-to-foot imposition: A form of back printing such that the top of the copy (or other printed image) on the back side of the sheet is “next� to the bottom of the copy on the front side of the sheet, read by turning the page over from top to bottom.
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Head-to-side imposition: A form of back printing such that the top of the copy (or other printed image) on the back side of the sheet is at a right angle to the top of the copy on the front side of the sheet.
One Sided Imposition
Types of imposition: One side: One printing plate is used to print on one side as it passed through the press. Common in small, offset print operations 1
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Sheet Wise Imposition
Sheetwise imposition: Two printing plates are used. One plate per side. After one side is done, sheets are turned over and other side is done. Ganged imposition: When one job on each press sheet would be a very inefficient use of the equipment, more than one job is run on the same sheet. Signature imposition: Large single sheet is frequently passed through a printing press and then folded and trimmed to form a portion of a book or magazine.
Ink The different Constituents of ink are follows:
Pigment
Vehicle
Additives
Pigments are the visible portion of the ink. They may be in powder form (dry toner), in a concentrated paste dispersion known as a flush, or in a liquid dispersion. Important characteristics of pigment include specific gravity, particle size, opacity, chemical resistance, wettability, and permanence.
Made up of oils (petroleum or vegetable), solvents, water, or a combination of these, they carry the colorant through the printing press and attach it to the paper or substrate. Most vehicles contain resins which serve to bind the colorant to the printing surface. The vehicle is responsible for an ink’s body and viscosity, or flow properties. It is also the primary factor in transfer, tack, adhesion, lay, drying and gloss.
Additives can include waxes, driers and other materials which add specific characteristics to an ink or to the dried ink film, such as slip and resistance to scuffing and chemicals.
Ink Ink Characteristics
Ink related problems
Ink Drying
Body: Consistency of the ink. On prolonged exposure to air and the increase in heat produced by the roller, the consistency may vary from time to time.
Setoff : The transfer of ink from sheet to back of the next sheet. Caused by too much ink being applied or slow drying.
Absorption: Ink dried by absorption when printing application complete on absorbing surface such a s newspaper printor corrugated board.
Tack: Stickiness of the ink. Resistance of the ink film to split. Splitting occurs when the ink from printing plate is transferred to the printing blanket. Improper transfer leads to bad quality of print Viscosity: Degree that ink resists the flow ehn under force. Viscosity also can change with the frictional and heat generated by the roller train. Inkometer is used to measure the viscosity. Length: Ability of the ink to flow. Necessary for the ink to move properly through the roller train of the press to achieve best results. Opacity: Covering power of the ink. Differenrt pigments have different degrees of opacity beacuse of the substances used ti ptodue the pigments. Tinting strength: Ability of the ink to tpoduce a tine woth addition of white pigment Permanency: The degree in which printed ink resists the fading power of light. The rate that an ink fade is known as degree of light fastness and is especially important when printed items, such a s an outdoor billboard, will be exposed to a high level of light.
Ink adhesion: Result of set-off and slow drying ink, which in turn usually the result of poorly adjusted press settings. Mottling: Uneven appearance in the solid area of the printed document caused by uneven distribution of ink, non absorbent papers or faulty press adjustments. Crystallisation: Time between each color printing is more and if ink dries, it will not accept the next color.
Oxidation: Comes in contact with oxygen of atmosphere and converting the ink on film on substrate to a solid. Heat: The heat sets ink dry by evaporation in hot air dryers
Paper The word paper derived from the Greek word “papyrus,” which was a plant found in Egypt along the lower Nile River. About 5,000 years ago, Egyptians created “sheets” of papyrus by harvesting, peeling and slicing the plant into strips. Paper, as we know it today, had its origins in China. Traditional Chinese records give the credit for its development to one T’sai Lun. Paper is a natural product because it is manufactured from a natural and renewable raw material, wood. It also has another big environmental advantage: it is 100% recyclable.
Paper Grammage
Types of Paper: Coated paper: Has glossy or matte finish Generally very smooth and can be shiny More resistant to dirt, moisture and wear. Coating restricts the amount of ink that is absorbed by the paper and how thE ink bleeds into the paper Paper and clay or other coating applied to one or both sides is coated paper. Uncoated paper: Generally more absorbent of ink that a coated paper. Generally not as smooth as coated paper and tends to be more porous. Used for letterhead, envelopes and printed material that is aiming for a more prestigious or elegant look. Matte: These paper have a thin coating applied which is not buffed to a shine. It has a dull finish. Cartridge paper Thick white with stiff feel more rag contact preserved for long time used in sketchbook certificates and stamp paper Mirror coated: Cast coated with China clay mirror finish Cards Thicker paper ~200 gsm. Photo paper: For reproduction of photographs. Photo paper is usually divided into glossy, semi matte or silk, and matte finishes. Cartridge paper: Thick white with stiff feel more rag contact preserved for long time used in sketchbook certificates and stamp paper.
Greyboard: Lined or unlined board made from waste paper. It has rough texture good bulk and is grey in color. Used for packaging materials or cover for publications. Recycled paper: Made from waste paper mixed with fresh wood pulp. If the paper contains ink, then it must be deinked. Kraft paper, plastic coated paper and papers that are waxed are usually not recycled because the cost is high. Sorting is done before recycling. Woven paper: Writing paper with a uniform surface faint mesh pattern within the grain not ribber or watermarked used in text book coloured paper used in bill or record book. Bond paper: High quality durable writing paper similar to bank paper but having a weight greater than 50 gsm Letterheads and other stationary as paper for electronic printers. Made from rag pulp. Tracing paper: Translucent and resistant to oil grease. Map litho: Top surface is smoother, used for books, leaflet etc. Offset paper: Rough on both sides, more rag content, good for folding. Duplex board: Box board, used in cartons
The weight of paper in countries that use ISO paper sizes is defined by ISO 536 Paper and Board- Determination of Grammage. This standard defines Grammage as grams per square metre. Thus the weight of a single sheet of A0 paper defines the grammage of that paper type as A0 size is defined by ISO 216 as having an area of 1 square metre. An A0 sheet of 80gsm paper will weigh 80 grams, an A0 sheet of 100gsm paper will weigh 100 grams and so on.
International Paper Standards The three sizes of paper for international markets names A, B and C are as follows:
Post Press
Post Press Operations Commercial printing is classified into three major phases – pre press, press and post press. After the printing of texts and images is over (after pre press and press) the process of post press starts. This is the end of the entire printing process that gives finishing touch to the end product. Post press is subject to several sub processes that are implemented as per the type of the project and the job being handled. Here are the few basic types of post press operations in printing industry which are not always but are often used: Cutting: This is one of the most common operations of post press which are used in almost all project. For this purpose typical machines are used called guillotine cutter or “paper cutter�. These are special machines that are used for cutting large substrates of web-type into different sheets or pages. These machines vary in sizes, features, abilities, capacities and configurations; because they are build for individual purposes. Folding: For magazines, books, large press sheets need to be folded into signatures. This involves a series of right-angle folds in which the sheet is folded multiple times. Folding a sheet once makes four pages, two right-angle folds make eight pages. Other types of work require parallel folds in which two or more folds which are oriented in the same direction are made in a sheet. This is typically done for leaflets or brochures. Some common types of folds are: the half fold the accordion fold the gatefold the French fold the letter fold There are two common types of folding machines: the knife folder, also known as a right-angle folder, and the buckle folder. In general knife folders are used for heavier stocks, while buckle folders are used for lighter paper types.
Post Press Operations Assembling: In assembly, there are three steps to be followed - gathering, collating and inserting. Gathering involves placing bunch of sheets (signatures) one after another. This is done for assembling books having page thicknesses ranging between 3 to 8 inches. Collating is another process to gather individual sheets of paper instead of bunch of papers. The last step, inserting involves the process of combining signatures or bunch of papers by “inserting� one into another. Inserting is done for the papers having signature pieces having final thickness less than onehalf inches. Embossing and debossing Embossing is the process of adding a relief image to a book cover or other printed material. Sometimes an ink or foil is used to accent the relief image. When the stamped image is left as is, this is called blind embossing. Debossing is the opposite, creating a sunken image on the substrate. Binding In this category the printed material or pages are adhered together. Three most common binding techniques are used - adhesive binding, side binding and saddle binding. For accomplishing binding process, three individual types of covers are used. They are - self-covers, soft-covers and case-bound covers. Each of them is used as per the type of printing job. Die cutting Irregularly shaped printed matter such as coasters or labels are cut out of the substrate in a process called diecutting. The die contains knives or creasing rules that have been prepared specifically for a certain shape. Indexing Indexing refers to adding plastic index tabs or index thumb cuts to the edges of printed sheets. These can help readers locate specific information.
Poster Printing
Poster Printing Assignment As part of our assignment we had to print a poster (13.125 x 17.5 inches) at the NID Print Labs using two printing techniques, screen printing and offset printing methods. The constraints placed were that the poster could have only one color printed in offset and one color printed by screen printing method We selected a poster depicting the Heidelberg printing machine in greyscale, halftone dots, halftone lines and vector, and added a moire pattern on the background to see how does the image print in both mediums. The breakdown of the offset printed and screen printed pattern is shown below:
Screen Print in Blue
Offset in Orange
Poster Printing Assignment
Paint making for offset printing
Inking Unit of Offset Printer
Blanket Cylinder and Plate Cylinder
Screens Exposed to UV Light for Screemaking
Screens Ready for Screen Printing
Screen Printing Process in progress
Industrial Visit
Industrial Visit Art-O-Print is a partnership firm established in April 1996. The company specialises in printing and packaging materials with facilities equipped to manufacture large and small volumes of various products - Packaging Material, Braille on Pharmaceutical Packaging, Pharma Outserts, Pharmaceutical Product Packaging, Pharmaceutical Product Display Kit, Custom Sample Sachet, Pharma Product Display, Portable Batch Counter, Printed Pop-Up Card, Paper Bag. The first place visited in the trip was the computer lab where from a specific software is used to initiate the print process. The specifications like the layout, size, texture, typeface, arrangement, quantity, etc are clearly mentioned by the client. An offset unit was shown which was a 5 color machine setup. This was a 4 color CMYK + 1 unit for varnishing + 1 spot/metallic/texture printing unit. The high speed folding machine was also present which folded small sheets of paper which contained information regarding particular medicines. The Quality checker machine was an important machine in the industry which employed high end technologies since the company has to meet the requirements of international clients. Every copy of the product is compared to the master layout. The machine also has a Braille embosser (for the visually challenged). The field visit also included a visit to another industry which is also a part of the same company. This particular industry is specialized in making corrugated cardboards for packaging. The various machines for preparing different types of sheets and machines for stapling them together were shown. Finally, the field visit proved to be an eye opener to the complexities of the various Production Processes employed in modern industries. These processes and techniques play a crucial role in proper publication and packaging. Any miniscule discrepancy or change in any of these steps may lead to huge losses for the makers. It is of utmost importance for the designer to know about each and every process because only then he/she can hope to get desired results.
Costing Problem Calculate the cost of printing booklet from the following Specifications: Name of job Quantity Finished Size Open Size No of pages Paper Binding
What is printing? 1500 copies 14cm X 21cm, No bleed 21cm X 28 cm 128 pages + 4 page cover Bilt Sinar Art Paper 130gsm for inside pages and 210 gsm for cover Soft cover, section sewing and cover pasting at spine (perfect binding)
No. of colours: Paper cost: Printing cost: Binding cost:
Cover 4 + 1 colour Inside pages - single colour print Rs. 2300 per ream for 23” X 36” X 130gsm Rs. 3000 per ream for 30” X 40” X 130 gsm Rs. 6000 per ream for 23” X 36” X 210 gsm Four colour Rs. 3200 and single colours Rs.1000 per 1000 copies Rs. 12 per book
Solution Cost of Inside Pages:
Cost of Inside Pages:
Cost of cover:
Cost of Printing
(8X2) = 16 | (16X2) = 32 pages 1 book = 128 pages | 128 pages/ 32 = 4 sheets 4 sheets X 1500 copies = 6,000 sheets 6,000 sheets required, 500 sheets per ream 6,000/500=12 reams 1 ream = Rs 2300 12 reams = 12X2300 = Rs 27,600 + 2300 (1 ream for wastage) = Rs 29,900
(9X2) = 18 | (18X2) = 36 pages 1 book = 128 pages | 128 pages/ 36 = 3 sheets 3 sheets X 1500 copies = 4,500 sheets 4,500 sheets required, 500 sheets per ream 4,500/500=9 reams 1 ream = Rs 3000 9 reams = 9X3000 = Rs 27,000 + 3000 (1 ream for wastage) = Rs 30,000
Size of 210gsm ream is 23” X 36” 8 covers fit in 1 sheet Requirement is 1500 covers 1500/8 = 188 sheets = round off 200 1 ream = 500 sheets 200/500 = 0.4 reams 1 ream = Rs 6000 0.4 ream = 0.4 X 6000 = Rs 2400
4 colour printing per copy is Rs 3.2 1 colour printing per copy is Re. 1 Inside pages : No. of inside pages for (23” X 36”) 4 sheet per copy = 8 plates = 8 X 1000 = Rs 8000 X 2 = 16,000 No. of inside pages for (30” X 40”) 3 sheets = 6 plates = 6 X Re. 1000 = Rs 6000 X 2 = 12000 Since we make 1500 copies, printer considers it at 2 lots of 1000 copies each. thus 2000 copies Cover : No. of cover pages (Rs. 3200 X 2 = 6400) + ( Rs 1000 X 2 = 2000) = Rs 8400
130gsm sheet dimensions Inside pages paper cost + Cover cost+ Inside pages Print+ Cover page Print + Binding Cost
23” X 36” sheet fits 8 spreads 29,900
30” X 40” sheet fits 9 spreads 30,000
Total Cost
2400 16,000 8400 18,000
2400 12,000 8400 18,000
30” X 40” sheet : Rs. 70,800
23” X 36” sheet : Rs. 74,700
Binding As part of our assignments, we also visited the NID print Labs, and performed pad binding, perfect binding and hard binding exercises
Red - Pad binding Yellow- Perfect binding White - Hard binding and centre stitching
Bibliography Class Notes http://www.pneac.org/printprocesses/letterpress/#Applications https://www.prepressure.com/printing/processes https://www.prepressure.com/printing/processes/offset https://www.pantone.com/spot-vs-process-color http://www.pantone.com/pages/pantone/pantone.aspx?pg=3&ca=24&cca=6 http://dba.med.sc.edu/price/irf/Adobe_tg/models/rgbcmy.html http://www.aces.edu/dept/fisheries/education/pond_to_plate/documents/ExplanationoftheLABColorSpace.pdf https://www.opticentre.net/FAQ/Desktop-publishing-(DTP)/History-of-Desktop-publishing/ http://printwiki.org/Drum_Scanner http://www.selfgrowth.com/articles/types-of-post-press-operations-in-printing-industry http://img.directindustry.com/images_di/photo-g/22906-7264669.jpg http://encyclopedia2.thefreedictionary.com/Magnetography https://www.prepressure.com/finishing https://in.pinterest.com/pin/160581542942896922/ https://s-media-cache-ak0.pinimg.com/564x/42/06/bb/4206bbd5ded00b87307426a3e3038d28.jpg https://s-media-cache-ak0.pinimg.com/564x/7b/54/be/7b54be436fa5595a23c67bc76a69b751.jpg
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