Industrial Printing Technology II Notes PDF

UNIVERSITY OF CAPE COAST COLLEGE OF DISTANCE EDUCATION B. ED. IT (GRAPHIC DESIGN MINOR) READING NOTES LEVEL 200 ECD 202D: INDUSTRIAL...

UNIVERSITY OF CAPE COAST COLLEGE OF DISTANCE EDUCATION B. ED. IT (GRAPHIC DESIGN MINOR) READING NOTES LEVEL 200 ECD 202D: INDUSTRIAL PRINTING TECHNOLOGY II Electronic Printing Processes These are desktop publishing or industrial printing processes in which a computer-generated design or image is commanded straight from a PC into the printer for printing. These types of machines are often connected to the PC with a cable. It must be emphasized that it is not all electronic printing processes that rely solely on a command from PC to print an image, xerographic printers for instance, can print or photograph an image without a computer command. Some examples of electronic printing processes are: Laser printing, Ink-jet printing etc. Xerography The word xerography is a combination of two Greek words: Xeros, which means dry and graphien, meaning writing. Xerography therefore means dry writing. In other words, it is a form of dry printing. Xerography is popularly known as photocopy. It was invented in 1937 by Chester Carlson, a patent attorney and physicist who was searching for a method of copying patent drawings without using photography. All xerographic printing processes rely on the fundamental principle that Carlson applied in his original device which states that, unlike electrical charges attract; like electrical charges repel. Xerographic printing is based on six major steps: Charging, exposure, development, transfer, fixing and cleaning. Xerographic machines are available in black and white and coloured. The machine consists of feeding, printing and delivery units. Others have enlargement and reduction capabilities as well as collating and binding systems. It is used for rapid reproduction of printed materials and photographs. 1 Laser printing Laser printing is a marriage between xerography and computer. The word laser is an acronym for the phrase “Light Amplification by Stimulated Emission of Radiation. Laser printers employ the six basic printing process of xerography. However, the light source is a concentrated beam of light, which could be, reduced to the smallest beam that it is capable of microscopic precision. The main distinction between xerography and laser printing is that, the laser beam (light source) can be controlled by digitized information sent from a conductor with a laser light source rather than through reflection from an original image. Laser printers use toners and are electronically operated. Ink-jet printing This is a printing process in which an image is produced by transferring individual drops of ink from an orifice through small air gap to a printing surface. Ink-jet printing relies on computer input to form a dot matrix made up of individual drops of ink. Most large format printers are ink-jet. Lithographic printing Lithography is a printing process in which the image is created to lie flat on the image carrier. In other words, it is a method of printing from a flat surface. The basic principle behind the process is that, water and oil do not mix. Alois Senefelder invented lithography. He was born in 1771 in Germany. He was a young actor and play write who stayed in Munich in Germany in the 1790s. Due to the high cost of copper plate etching at that time, he experimented with several materials to discover a cheaper method of printing his plays. Eventually, he was able to invent a new printing method called lithography. In his experiment, he wrote his laundry list on a smooth Bavarian limestone with a compound consisting of wax soap and lamp black. He immersed the stone in acid and surprisingly, the list appeared on the stone in extremely low relief. He developed the process until it became formalized. The word lithography is a combination of two Greek words. “Lithos,” which means, stone, and “Graphien” meaning writing. Lithography therefore means writing on stone. In lithography, two main methods are used to prepare the image carrier: ❖ Stone method 2  ❖ Plate method Stone method ❖ Get a flat smooth limestone. ❖ Draw or write the image on the stone in reverse with a greasy material such as lithographic crayon or greasy ink known in German as “ Tusche”. ❖ Immerse the designed stone in a weak nitric acid and leave it for some time and then, remove it from the acid. The acid will etch the non-greasy parts of the stone and leave the greasy parts in low relief. ❖ Apply a coat of Gum Arabic on the entire surface to block the voids on the stone. Printing process ❖ Dampen the surface of the stone. The water will wet the non-greasy areas of the stone. ❖ Work out the printing ink on a glass palette with a brayer. ❖ Apply a layer of the printing ink to cover the entire surface of the stone. The ink will stick to the greasy image areas and however, repelled by the water-soaked background areas. The ink receptive areas (Image areas) are hydrophobic or water repellant whiles, the non- image areas are hydrophilic (accept water) and ink repellant. ❖ Put the printing paper on the inked stone and press evenly to transfer the image. ❖ Remove the printed sheet and dry. Plate method Zinc, Aluminum, stainless steel, chromium and thick paper can be used as image carriers. Aluminum sheets are generally preferred in industrial lithography. The thickness of the plate ranges from 0.005 inches to around 0.030 inches. The size of the plate is equal to the surface area of the lithographic press cylinder. Due to the smooth nature of aluminum, the surface is “grained” to provide “key” before the image is developed on it. (Graining is the method of roughening the surface of aluminum plate chemically or mechanically to provide toothing for the adherence of photo-emulsion.) After graining, the surface is coated with a photo-emulsion consisting of a light sensitive material combined with a “collodion” (organic compound that forms a strong continuous layer on the plate). Commonly used collodions are Gum Arabic, Polyvinyl Alcohol (PVA), Diazo and Photopolymers. The Sensitizer is called ammonium bichromate. Note that, the plate should be 3 coated and kept in a dark room. Nowadays, most industrial lithographic plates are available in pre- sensitized form. Transferring the image unto the Sensitized plate Three major processes are involved: ❖ Preparing the image or copy. ❖ Exposing the image. ❖ Developing and preserving the plate. Copy preparation ❖ This include the following activities: ❖ Type generation ❖ Image preparation ❖ Stripping and pasting of images ❖ Dummy preparation ❖ Section preparation ❖ Producing negative print Nowadays, there are computer software and electronic composition systems that allow layout artist to produce a complete copy on a computer screen and print out, therefore eliminating stripping, pasting-up and Dummy preparation. Exposing the image ❖ Position and fix the section at the coated side of the plate at right reading. ❖ Place the plate in the plate maker ( A light box equipment) and close it. ❖ Set the exposure time. ❖ Switch on the light in the plate maker to expose the image unto the plate. ❖ Remove the plate after exposure and develop. Developing the exposed plate 4  ❖ Mix the plate developer with clean water in a ratio of 1:3 (One part of developer to three parts of water). ❖ Put the plate on a flat surface and pour the mixed developer on the exposed side. ❖ Spread the developer evenly on the plate in a circular motion with foamed pad and leave it for some time to soften the unexposed parts of the plate to bring out the latent image. ❖ Wipe off the developer from the surface with a squeegee or foam pad. ❖ Rinse the plate with water and mob traces of water. ❖ Preserve the plate. This is done by applying a coat of gum Arabic at the exposed side of the plate with a foam pad. ❖ Allow the plate to dry and fix on the press plate cylinder for printing. Types of off-set lithographic press There are two main types of off-set lithographic press: ❖ Sheet-fed off-set press ❖ Web-fed off-set press Sheet-fed off-set press With this type, the sheets are cut to section sizes and loaded into the feeding unit of the press. When the press is operated for production, the sheets are pulled individually into the printing unit for printing and subsequently delivered after printing. It is available in single and multiple-colour printing unit presses. The single colour type has one printing unit and can print only one colour in a single run, whiles the multi-colour type has more than one printing unit and can print different colours in a single run. The colours that are printed in multi-colour off-set lithographic printing are cyan, magenta, yellow, black, and sometimes spot colour. Some modern off-set lithographic presses have a unit that prints clear coatings such as laqueer etc. Web-fed off-set press This type prints sheets in continuous rolls. The operating system is based on the following sections of the press: ❖ In-feed ❖ Printing 5  ❖ Delivery In-feed section The paper is delivered into the printing section from here. The section contains the following important devices: Roll stand: This holds the paper rolls Spicer: This automatically splices the end of one web to the beginning of another web. Web steer: this controls the side lay (Side by side position) of the in-feeding web. Tensioner: This maintains the proper tension on the web as it enters the printing unit. Printing section This section could be single or multiple-colour units and each printing unit contains one or more printing couples. A printing couple contains inking and damping systems; plate, blanket and impression cylinders and each printing couple can print one colour of ink. Delivery section This is the last section of the press where the printed sheets leave the press. The section contains the following important devices: Ink drier: This dries the ink on the printed sheet when it leaves the printing unit. Sheeter: This is a sharp blade, which cuts the moving web (sheet) to a required section size. Combined sheeter and folder: This fold the web into final sections and trims the sheet to size. Where no cutting and folding are required, the delivery section contains only a rewinder, which winds the printed web into roll for later processing. Operating principles of off-set lithography presses The Sheet is fed from the feeding section. It passes through the registration board and enters the printing section which consists of three significant units: cylinder, damping and inking units. When the press is operated for production, the damping and inking units supply fountain solution (water) and printing ink onto the plate cylinder simultaneously through a series of rotating and oscillating damping and inking rollers. 6 The cylinder unit consists of three cylinders of varying diameters, namely the plate cylinder, blanket cylinder and the impression cylinder. Each rotates at opposite direction to one another (Clockwise and anti-clockwise). When the damping and inking fall rollers fall on the plate cylinder, the image areas accept the ink and repel the water (ink receptive and hydrophobic ) whiles the non-image areas accept the water and repel the ink ( Ink repellant and hydrophilic). Whiles the cylinders rotate, the plate cylinder off-sets (Transfers) the inked image unto the blanket cylinder in reverse and the blanket cylinder further off-sets (Transfer) the image in ink onto the press sheet in right reading by pressing the sheet between the blanket and the impression cylinders and releases it. The printed sheet is pulled by revolving chain grippers onto the delivery board. The illustration below explains the operating system of the off-set lithographic press printing couple or unit: 7 Uses of lithography press Mechanical lithographic press is used to print on smooth, glazed and unglazed papers. It is used to print newspapers, calendars, books, labels, files, posters, book covers, paper bags, flyers etc. Papers Paper is a thin sheet of compressed vegetable cellulose fibres. They are classified into categories: Light papers and heavy papers. 8 Light papers: These are thin sheets of papers that are lighter in weight. E.g. Bank, bond, newsprint, cartridge papers etc. light papers are mostly used for writing, drawing and printing. Heavy papers: These are also called boards or cards. They are opaque, thick and vary in flexibility. They are glazed, unglazed, textured or patterned. E.g. Manila, Vanguard, strawboard, chipboard, graybeard etc. They are used for invitation cards, packages, labels, book covers, files, complementary cards, calendars etc. Sizes of papers Papers are usually sold in reams of standard sizes of sheets such as A0, A1, A2, A3, A4, A5 etc. The quantity of individual sheets packed into one ream is based on the following: ❖ Ream of handmade paper contains 472 sheets ❖ Ream of paper for industrial and electronic printing of book/documents/posters etc. 500sheets Note: The size of the paper reduces by half as the numeral increase. Therefore, in the examples given above the largest size is an A0 while the smallest size is A5. Historical Development of paper Papers are the basic printing surfaces in the Graphic communication design industry. Before the invention of paper, people expressed themselves by etching, printing and engraving pictures and symbols on stones, in caves and on bones. Later, they used other surfaces such as bee-waxed board, palm leaf, silk and clay tablets. Ancient Greeks used parchment and vellum prepared from untanned skins of animals, usually sheep, calves, or goats. Parchment or vellum is prepared by cleaning the skin and removing the hairs, scraping and smoothing both sides of the skin, and finally rubbing it with powdered pumice. Parchment was coarser than vellum because it was produced from the skin of older animals. Vellum on the other hand was a finer quality parchment made from the skins of kids, lambs, and young calves. Parchment has been used at least since about 200 B.C.; its name is derived from the ancient Greek city of Pergamum, where an especially fine quality of the material was produced. 9 The ancient Egyptians also developed a kind of cheap paper from the papyrus plant. They formed a cross-woven mat of reeds and pounded it into a hard, thin sheet. The name paper was developed from the word papyrus. The Egyptians used the papyrus paper to write their hieroglyphics. The first standard paper was invented by a Chinese court official called T’sai lun, in A.D. 105. T’sai Lun was eunuch attached to the Eastern Han Court of the Chinese emperor HoTi. He mixed mulberry back hemp and rags with water, mashed them into pulp, pressed out the liquid and hanged the thin mat to dry in the sun. T’sai Lun’s invention facilitated the development of printing in China and the neighbouring countries until about a thousand years later when Chinese print making techniques were introduced in Europe by the Moors of North Africa. However, they could not study the Chinese method of making paper from wood. As a result of rapid development of the printing industry in the west, the westerners also made paper from rags and clothes in the 1800s but their process of manufacture was slow, expensive and tedious. In 1798, Nicholas-Louis Robert a clerk at the paper making mill in Essenary, France, devised a machine that replaced hand dipping and produced paper in continuous roll. Due to financial constraints, Robert sold the patent to the Fourdrimer Brothers in England. They developed upon the machine but could not meet the massive demand for cheap and plentiful paper. This created severe scarcity of paper in Europe and America. The situation generated curiosity among paper making and printing enthusiasts which lead to the development of a wood grinding machine by Frederick Gottlob Keller of Germany in 1850, which was used to grind wood chips into fibres. A few years later, Hugh Burges, an Englishman advanced paper making another step by inventing a chemical pulping process. In 1865, C. B. Tilghman, an American scientist invented the sulphite process for dissolving unwanted resins in wood. All these scientific and mechanical advancements set the pace for mass production of paper. Since the 1900s, various cheap and fast paper manufacturing machinery, chemicals and processes have been developed and these have been used to produce different kinds of papers in mass quantities. Manual/hand papermaking method Raw materials required include straw, leaves, barks, rags or other fibrous materials. There are two basic processes involved in hand paper making: 10  ❖ Breaking up of raw material in water to form a suspension of individual fibres ❖ Formation of felted sheet Processes Breaking up of raw material in water to form a suspension of individual fibres: ❖ Wash the raw material(s) to remove all dirt and impurities by placing them in a vat/trough containing running water and allow it to dry. ❖ Pound the material with heavy pestle or hammer to separate or break-up the fibres to obtain a powder. ❖ Mix the powder with water in a vat/trough and allow the material to suspend in the water for some time. The liquid material formed is called ‘Half stuff’. Formation of felted sheet ❖ Dip a mold held in a duckle into a vat containing the half stuff; when the mold is removed from the half stuff the surface of the mold will be coated with a thin film of half stuff. ❖ Shake the mold forward and backwards and from side to side to distribute the half stuff evenly on the mold and also cause the individual fibres to interlock. This will strengthen the sheet. While the mold was being shaken, much of the water was drained through the mesh to form a wet sheet of paper on the mold. ❖ Put the mold with the wet paper aside and allow sufficient time for cohesion then remove the duckles. ❖ Turn over the mold to remove the sheet unto a woven woolen clothe called ‘Felt’ and lay another felt on the sheet. Repeat the same processes to form more sheets. This process of placing the wet paper sheet between two felts (sandwiching) is known as ‘Couching’ ❖ After couching a number of papers, the entire pile called ‘Post’ is placed in a hydraulic press and subjected to a pressure of 100 or more tons to squeeze out most of the remaining water in the paper. ❖ Remove the papers from the felt stack and press them several times by varying the positions of individual sheets in the process. Varying the positions of the sheets will improve the surface of the finished papers and the continuous pressing helps to remove all the remaining water in the sheets. 11  ❖ Hang the sheets in groups of four or five over ropes in a special drying room until all the moisture evaporate completely from them. ❖ For writing and printing papers, size the sheet after drying by dipping it into a solution of animal glue and dry it. The sizing will prevent absorption of ink into the sheet which can cause fussy/rough lines after printing. ❖ Press the sized sheet between two sheets of metals or smooth cardboard to obtain a smooth texture. The length of time and pressure exerted during the pressing will determine the smoothness of the surface of the sheet. Industrial paper manufacture The major raw material used to manufacture paper is wood. These woods are obtained as timber from the tropics. Different kinds of soft and hard woods can be used to manufacture paper. The timber is cut into logs in the forest and loaded into trucks which convey them to the factory for processing into paper. When the timber logs are offloaded in the factory, they are processed into pulp before it is further processed into paper. How to process wood into pulp: The processes involve in pulp making are: ❖ Debarking ❖ Chipping ❖ Pulping ❖ Bleaching ❖ Beating ❖ Refining ❖ Re-pulping ❖ Adding of additives ❖ Cleaning Debarking: This is the first stage in the pulp making process. It involves removing the outer covering of the wood. The logs are first packed in piles and loaded into a conveyor in a flume (A flowing trough of water) to go to the debarking plants. Two types of debarkers are used: ❖ Mechanical debarker ❖ Hydraulic debarker 12 Mechanical Debarker: This is the oldest type of debarking plant. It is a metallic drum into which is lined with steel bars vertically which rub off the bark covering of the logs upon rotation. After debarking, the barks are deposited into a conveyor and the logs are also transferred into another conveyor which sends them into the chipping plant. Hydraulic Debarker: This consists of a revolving stand in which a high pressure of water jets of 1500 psi pressure blows to peel off the barks of the logs. The barks are deposited into a running conveyor whiles the debarked logs also move into the chipping plant through a running conveyor. Chipping: This is the method of chopping the debarked logs into pieces of chips of about one inch. Chipping is done in a plant called “chipper”. The chipper consists of a disc fitted with sharp blade which rotates from the hub to the edge. The logs drop into the spinning disc at about 45 degrees angle which chops the logs into pieces in a few seconds. After chipping, the chips go over series of screening where oversized ones are sorted out and send to a re-chipper whiles the sawdust and the under sized chips are used for fuel and other profitable purposes. Pulping: This is the method of cooking, grinding or mashing the wood chips to obtain slurry. Pulping is also done to remove the fibres from the logs. There are three classification of pulping methods: ❖ Chemical pulping ❖ Mechanical pulping ❖ Chemical-mechanical pulping Chemical Pulping: This method involves the use of chemicals such as sulfate, soda and sulfite to dissolve the “Lignin” content in the wood. Lignin is a glue-like substance in wood which holds or binds the wood fibres together. In other words, lignin acts as a binding agent in the wood. Chemical pulping process involves cooking a compound consisting of soda, sulfate and sulfite in a digester of liquor into which the wood chippings are conveyed to be cooked in the chemical. The mixture is heated directly in the digester by adding live stream directly to the digester. Alternatively, the liquor is pumped through a heat exchanger which is heated. When the chemical cooking is done, pressure is released and chips (almost in a pulp form) are sent into a blow tank where a washer washes the pulp to remove the cooking chemicals and dissolve non-cellulose fibres. The washed pulp is now called ‘brown stock’. 13 Mechanical Pulping: In the mechanical pulping process, the logs are taken from the debarker to a grinder that tears the fibres from the logs. In the grinder, the logs are held against a grindstone by hydraulic pressures. The grind-off fibres mix with the cooling water sprayed on the stone to form slurry of pulp. The slurry passes over a series of screens where the good pulp called ‘accepts’ is removed and sent to a cleaning unit. Chemical – Mechanical Pulping: This is a combination of chemical and mechanical pulping processes. In this process the wood chips are half cooked in a chemical mixture to dissolve the lignin partially. The half-cooked chips are sent to mechanical grinders where the fibres are separated from the logs. This process produces a high-quality pulp than the others. Bleaching: This is an extension of the pulping process where by a chemical solution is used to remove stains of lignin and other coloured substances from the pulp to produce a bright white pulp. The main bleaching agents are chlorine gas, calcium hydrochloride, hydrogen peroxide and chlorine dioxide. After the pulp has been bleached it is used without washing. Beating: This is a process of separating pulp fibres from each other so that they will not hold together to form ‘shives’ or ‘lumps’ when they are formed or pressed into a sheet. Beating also changes the individual fibres of the pulp so that the paper maker can felt or press them unto a smooth, even sheet that will handle, look and wear well. In beating, the bleached pulp is transferred unto a beating plant which contains a beating roll fixed with a number of metal bars called ‘beating bars’. The beating roll rotates speedily in the pulp and in conjunction with bed plate separates the fibres. Refining: This is the method of cutting and shortening the pulp fibres to produce a uniform pulp. Refining is done in a refiner which consists of a bar studded rotating element which fits closely together. During refining, the pulp is suspended in water and it is pumped through the refiner continuously. In the process the fibres are cut and shortened. Re-pulping: This takes place after the pulp has been refined and dried. In re-pulping, the dried pulp or paper is re-suspended in water to break down the pulp fibres that might have held together during drying to individual fibres before is processed further. During re-pulping, no changes are made to the fibres properties. 14 Adding of additive: During the stock-flow system, (sequence of pulp making process) certain chemicals are added to the pulp at certain stage to improve its quality. The additives are used to improve the pulp before it is finally processed into paper. The four common additives used are: materials to change inter-fibre bonding, materials to improve looks and handling properties, internal sizing to improve water resistance of the paper and dyestuffs’ and pigments to give colour to the paper. Cleaning: This is the final or last process involved in the stock-flow system. The two major methods involved in cleaning are: Screening and Pressure drop cleaning. Screening: Screening is the method of removing clumps, dirt and order foreign matter from the pulp. Stock or pulp clumps are formed from undercooked wood chips, waste paper, slime growth and similar hard-to-break up materials. The importance of pulp cleaning is to achieve uniform fibre dispersion. Pressure Drop cleaning: This uses equipment called the centric cleaner or the cyclone cleaner. The stock enters into the cyclone cleaner through a tapering tube at the top left side of the plant. Whiles in the plant, the pulp is spiraled at high velocity and the heavier foreign matter is separated from the lighter fibres and move down as rejected which pass through the small end of the shaft. At the same time an inner spiraling column called ‘vortex’ moves up to the top of the shaft where the lighter fibres (Accepts) are removed. The high velocity at which the pulp spirals in the shaft creates a pressure in the shaft which separates the heavier clumps, dirt or foreign matter from the fine higher fibres to drop through the bottom of the shaft as rejects. How to process pulp into paper Paper making plants are amongst the largest industrial processing plants in the world because of the numerous complex steps or stages of processing wood logs to pulp and the further processing of pulp to papers. Paper making plants can produce paper over 380 inches wide at more than 4000 feet per minute. Nowadays, many industrial paper making processes are computer controlled but operative skills are also required in order to achieve quality production. The processes involved in forming paper with pulp are wet pressing, drying, sizing, calendaring and finishing. Wet pressing: The pulp slurry is delivered to the continuously moving fourdrinier wire through the head box at the wet end. Normally, the pulp slurry contains high percentage of water. As the 15 slurry travels along the length of the wire, the water is removed by gravity and vacuum and the remaining solids (pulp fibre) form a mat of paper. The mat pulp enters a wet press section where it passes between press rolls covered with wool and other rollers made of granite, brass or hard rubber. The caliber (Thickness) of the pressed sheet is partially controlled at this stage by constant adjustments. Drying: After the press sheet has left the wet press unit it still contains about 60% of moisture before it enters the drying section. In the drying section, it passes over steam-heated drying rolls about four to five feet. The paper is heated on one side and the other as it passes from roll to roll. The heat from the rolls dried off the moisture to 90%. Sizing: This is the process of running and pressing the dried paper through a vat of liquidized size. After the web of dried paper which may contain about 5% to 10% of moisture of dried paper has left the drying section, it enters the sizing unit of the plant which has two large rollers and a vat of sizing liquid. It runs through the sizing liquid and then between two rollers that press the paper to squeeze out excess sizing solution. The paper leaves the sizing press containing about 25% of water. The paper goes through another drying unit before it leaves to the calendaring unit. The main importance of sizing the paper is to harden the surface of the paper to resist penetration of ink, resist the effects of handing and fastens the loose surface fibre to the base sheet. Calendaring: After the sized paper is dried, it enters the calendaring unit which has eight or nine highly polished steel rolls 16 inches to 24inches in diameter. The paper passes over and around each roll, being pressed, smoothed and getting a more uniform thickness. During calendaring, the felt and wire marks that were in the paper from fourdrinier wire and the drying cylinders are smoothed. After calendaring the web of paper is taken up on a reel at the dry end of the paper making machine. On the larger machines paper is round in rolls with diameters up to 88 inches (225.5cm). After the initial calendaring, some papers are super calendared by running them through the steel rolls again in order to produce a highly smooth and polished finish for special use. Finishing: After the paper has come out of the paper making machine, it goes through several finishing steps before it is finally packaged for delivery or distribute to customers. The finishing steps includes: inspecting, sheeting, special finishing, re-winding and shipping. 16 When the large roll of paper comes out of the paper making machine it is re-wound on a reel. During the re-wound, the edges of the paper are trimmed and the paper is cut to required widths. The web of paper can also be cut into sheets from the re-winder or from any other finishing process. To cut the paper into sheets, the rolls are placed on reel stands which hold one a dozen rolls. From the reel the paper passes through ‘slitters’ which cut the paper into the correct width. The paper then goes through a cutter where a knife revolves on a cylinder. Each time the cylinder revolves, the knife cuts the sheets to a specific length. After being cut, the sheets are taken on moving belts to machines called ‘layboys’ which jog the sheets into uniform piles. Most modern layboys have counters that automatically insert a marker at the required number of sheets. Workers inspect, count and wrap the sheets into packages of the right amount. Nowadays, there are automated paper making machines that undertake all the activities from cutting to wrapping without using too much human effort. The large rolls of paper to be used for large presses are often wound and handled with care. The wrapped papers are delivered to the customers by shipping, airline, truck etc. How to create special effects in paper Different types of background treatments can be given to papers. Examples of such effects include watermark, embossing etc. Watermark: These are designs that are created into the paper without using ink. They are often created as identification sign. The importance of watermarks is to advertise the company that manufactured the paper, or the business that uses the paper. Elements such as logo, company names, service marks, slogans, etc. are normally created as watermarks. There are two major methods of creating watermark effects in papers: ❖ Candy roll method ❖ Rubber stamp method Candy Roll Method: The candy roll is a plant consisting of a cylindrical frame wrapped with wire into which a recessed or raised design of the symbol is created. The candy roll rides on top of the fourdrinier wire near the end where the pulp leaves the screen and enters the first press drying suction. As the wire watermark form touches the still fluid paper, it displaces some of the fibres to produce a specific pattern or design (watermark) in the paper. 17 Rubber Stamp Method: The rubber stamp roll method uses a metal cylinder on which the image or letters are created in relief. It is located in the wet press suction of the paper making machine. The relief image or letters are pressed unto the wet paper upon rotation of the cylinder when the wet paper is running on the machine at the wet end. The relief image produces a slight embossed effect at the back of the paper. This method is often used for cheap or lower-cost papers which are produced at higher speed. Embossing: This is the art of rising or depressing areas of a paper surface by applying pressure in a repeating pattern. Embossment is usually done by passing a web of paper through a pair of engraved rolls that press the pattern into the sheet. Embossment can be produced on one side or both sides of the paper. Commercial press Activities In a standard medium-scale commercial press house, different technical activities go on during the production chain. These activities are classified into pre-press, press and post-press activities. Following are brief descriptions of each of the classifications: Pre-press Activities These are activities that are carried out before printing. They include the following: ❖ Copy editing ❖ Typesetting ❖ Layout Design ❖ Proof-reading ❖ Image setting Copy Editing These involves reading through manuscript or copy submitted to a press house by an author or client. The initial reading is done to identify and correct all grammatical errors in the script such as spelling mistakes, punctuation errors, mistakes in sentence structure, paragraphing ambiguities, etc. Typesetting 18 This is carried out after copy editing. It involves typing the text with computer and selecting appropriate style and font of typeface for the work. During typesetting, the copy is further edited to identify and correct any mistake that could not be identified during copy editing. Tis editing is done in comparison with the master script (manuscript). The computer-generated text is then given to the author to proof-read through and approve it before it is processed further at the press house. Layout Designing When the typeset is approved by the author, the text is handed over to the Graphic design to design the pages of the work. The designer gathers appropriate images(illustrations) for the work and edit them. After that he employs different layout principles and processes to plan every page. After page layout planning, he copies that typed text and paste on the appropriate page and select appropriate typeface and font for the text depending on the function of the text on the page. The layout designer uses varying sizes of font to achieve good hierarchy of the type. He also imports appropriate edited images and insert them in the work. When the layout design is completed, the work is printed for proof-reading. Proof-reading This involves correcting mistakes in proof prints. Proof-reading includes checking good selection of typeface and fonts, hierarchy of text, the use of emphasis, good layout formats, letter, word and line spacing, the use of colour scheme, colour contrast, good selection and placement of illustrations and the overall aesthetic and communication appeal of the design. Proof-reading also complement the duties of copy editors to check grammatical, spelling and punctuation mistakes. In proof-reading, economic signs or proof-reading symbols are used to indicate mistakes in the copy and direct layout designers on what mistake to correct. The proof-reader gives the work back to the layout designer to correct the mistakes and make another proof print for final proof-reading. Page planning The layout designer further plans the serial arrangements of the pages in the work. This is done by using a dummy. (Dummy is a small sheet of paper which is folded once or more times to create pages which are numbered serially to plan the pages of a book.) Note a dummy could contain four, 19 eight, sixteen or thirty-two pages depending on the number of times in which the sheet is folded. For example, single fold (Folio) will produce four pages, double fold (Quarto) will produce eight pages, a third fold (Octavo) will produce sixteen pages in that other. Section/signature Preparation After dummy preparation, the layout designer uses the dummy as a guide to prepare sections or signatures. The layout designer selects two large sizes of sheet on the computer. Example, A2 and use the dummy as a guide to copy individual pages of the work and paste them at their correct positions on the sheet serially. The number of pages arranged on each side (front and back) of the section depend on the number of pages in the dummy. (The process of copying, arranging and pasting a number of pages on a large sheet is termed as imposition). Image setting This involves photographing the designs of individual sections unto a light transparent plastic sheet called laser film. In image setting, full colour designs (Bitmap or continuous-tone images) are broken down into half-tones of Cyan, Magenta, Yellow and Black (CMYK) by using appropriate commands on the computer. (The process of breaking down a continuous-tone image into half- tones is termed as colour separation). Each separated colour (Half-tone) is commanded to transfer (Photograph) unto a laser film through an image setting or image processing machine. Plate Making This involves photographing the image on the laser films unto pre-sensitised plates. Each half-tone film is fixed on the photo sensitive part of the pre-sensitised plate and placed on a plate maker(A plate maker is a light-tight box-like machine into which a number of high wattage ultra-violet lights are fixed and the top of the box is covered with a thick plain glass). When the plate carrying the image is placed on the glass, the ultra-violet lights are switched on, the top of the plate maker is closed and a time is set to expose the image. When the exposure time is due, the exposed plate is removed from the plate maker and developed. The development is done by applying a chemical called developer unto the exposed side of the plate to soften the unexposed side of the sensitive chemical (Photo emulsion). After that, the chemical is left to stay put on the plate for few minutes and then washed with clean water in a sink 20 to expose the latent image the plate. The plate is rinsed and a coat of Gum Arabic is applied unto the plate to preserve it. The plate is dried and used for the printing. Printing Activities This is the actual reproduction of the design unto printing sheets. Before the press machine is commanded, the prepared plate is fixed unto the plate cylinder on the press plant and lock very well. The printing sheets are jogged and packed unto the delivery board at the feeding unit of the press. The printing ink is applied into the ink duct and fountain solution is also regulated to fill the water duct. The printer then adjusts the ink and fountain solutions uniformly and the machine is commanded to make trial prints until proper prints re obtained. The machine is the commanded to print the work. Post-press Activities Folding, Collation, Insertion, Gathering and lamination When the individual sections are printed out, the sections are folded into the actual size of the book with a tool called the born folder. For multi-section books, the sections are gathered (gathering is the process of placing one section on the other serially). Most folios are inserted (Insertion is putting a single-folded sheet into each other in correct sequence). Unfolded printed single sheets are also collated (Collations is the process of arranging printed single sheets in correct sequence). Some book covers are laminated before binding. Binding This is the process of collating, gathering, inserting of printed sheets and joining the leaves of printed sheets into books, such books include pamphlets, magazines, receipts, reports, registers, cheques etc. Trimming This is the last activity in the post press activities. After the printed sheets are bound the three unbound edges are cut off to obtain a straight edge. Trimming is also done to obtain the actual size of the book. Voluminous books are cut with an industrial paper cutting machine called Guillotine. 21 TROUBLE SHOOTING IN COMMERCIAL PRESS PRINTING In industrial printing, trouble shooting is the art or process of identifying and correcting problems or faults in printing. There are common problems that affect the quality of printouts in commercial lithography. Generally, there are four broad factors that cause problems in commercial lithographic printing: ▪ Damping solution PH level ▪ Ink considerations ▪ Paper considerations: Paper acid content, paper grain direction and paper surface texture ▪ Mechanical problems (Incorrect press adjustments, poor maintenance culture etc.) Damping solution PH Level Damping solutions consists of water, Gum Arabic and acid combined in different proportions. It is the acid concentration in the solution that can cause the problems in printing. The measure of acidity in the solution is determined by PH scale which ranges from 0-4(0 is very acidic and very alkaline) range 7 (Mid-point) is neutral. The acceptability of PH scale for fountain solution ranges from 5.5-4.5. Most manufacturers specify a recommended PH level to be used for their plates. The printer can measure the PH level of a solution by using a Litmus paper PH indicator. High Acid PH Scale Fountain Solution Can Cause Variety of Problems in Printing: ▪ A strong acid solution can shorten the life of a plate. The acid tends to deteriorate the image area of all surface plate and can eventually make the image “walk off the plate”. ▪ When the pressroom humidity is high, the action of the acid with ink will cause drying problems on the press sheet. ▪ High acid fountain solution will also break down the ink. The acid will attack the ink and makes it paste-like or emulsified. The emulsified ink will make the rollers appear glazed. The problem can be corrected by cleaning the rollers and re-inking the ink-duct. ▪ Too low acid level (PH level from 7-4), the action of the moisture layer on the non-image areas will decrease water receptivity, and the plate will scum with ink. Ink Considerations In industrial off-set lithographic printing, the printing ink can also cause problems in print quality which result from the characteristics of the printing ink. These ink problems can often be corrected by adding appropriate additives. Three common problems associated with press inks are: Tinting: This is the slight discolouration over the entire image area of a printed sheet. This is caused by a reaction between the ink and the water fountain solution. If the ink is too water soluble, it will bleed back into the water fountain through the damping system. If tinting occurs, both the ink and water systems should be cleaned and a different ink formulation is used. Picking: This is a number of small patches occurring over the entire image area of press sheet. It is caused by linty or poorly coated paper, or ink that is too tacky. Also, small particles of torn paper from the surface of the press sheets and feedback into the inking system. This can be resolved by cleaning the inking system or mixing the ink with a reducer or non-pick compound. 22  Slow drying: This occurs when the printed material delays in drying. Simple common drying problems can be eliminated with the addition of a drier compound to the ink. However, too much drier can also increase the dry time of the ink. Over inking on a coated paper (Non-absorbent) paper can significantly increase drying time. Paper Considerations: The nature of paper used to print in off-set lithography can also affect the quality of the printed material. Three basic considerations must be made when selecting paper for a press work: Paper acid content Acid content of a paper affects the drying of printed sheets. Generally, uncoated printed papers will not dry properly in humid atmosphere if the PH is below 5. Also, most coated papers with PH of between 6 and 7 would cause ink-drying problems under high humidity. However, coated papers with 7.5 PH can dry under most humidity levels. Acid content of every press paper can be obtained from the paper manufacturer. Paper grain direction There are two main directions of paper fibres (Grains) on press sheets: Grain long and grain short. Press sheets are described as grain long when most of the paper fibres are parallel to the longest dimension of the sheet. Press sheets are also described as grain short when the paper fibres are at right-angle to the longest dimension of the sheet. The illustration below shows the two directions of grains on paper: 23 In off-set lithographic printing, grain direction of press sheet is considered when feeding the press with sheets. Grain long feeding is with the grain direction parallel to the direction of travel of the sheet through the press. Grain short feeding is with the grain direction at right-angles to the direction of travel of the sheet. Grain long printing takes place when the grain of the paper is parallel to the axis of the plate cylinder. grain short printing is when the paper grain is at right- angles to the plate axis. Research has proven that cellulose fibres expand as they absorb moisture. the expansion can be up to five times as great across the width of a fibre as long as its length. This suggests that as printing sheet comes into contact with fountain solution during impression, the individual fibres in the sheet can change size, with the greatest increase in the dimension across the grain. If the sheet has to be run through the press several times to receive ink colours, each pass can add more moisture to the fibres and can cause different changes in the sheet. These changes can make it extremely difficult to fit one colour image to another. Most off-set papers are supplied grain long. This is because, it enhances perfect multicolour image registration when fed into the press. Paper surface texture This refers to the kind of finish given to the paper. paper finish is either smooth or rough, coated or uncoated. Coated papers are papers in which the surface has an added layer of pigment bonded to the original paper fibres to smooth out the rough texture of the natural material. Coated papers 24 generally carry more printed detail and produce a better finished image. However, they are more difficult to print than uncoated papers. Coated papers are coated at one side (C1s) or coated on both sides(C2s). The surface appearance can vary from dull to high gloss. Uncoated papers are made of only the raw interlocking fibres. they have rough finish than coated papers. because off-set lithography transfers image from a flat surface, the press does not print well on rough textured surfaces. It always prints well on smooth surfaces (Either coated or uncoated). Off-set lithographers must observe the following when printing on coated papers: ▪ The sheets tend to jam-up as a result of static electricity between the coated sheets on the infeed table. To avoid this, the pile of sheets should be carefully fan or blow with air and the feeding must be adjusted with start-up sheets before actual run is begun. ▪ The blanket cylinder should be carefully checked for quality -specifically glaze build-up. Glaze has the tendency to pick and split or tear coated paper. ▪ Too much ink will cause set-off (Transfer of an image from the printed face of one sheet in the pile to the bottom face of the next sheet in the pile) of the image in the delivery pile. ▪ Overcoating can also cause the paper to stick to the blanket cylinder. It can also increase the drying time of the printed material. Rollers and cylinder alignments should be carefully checked when using coated sheets. Mechanical problems These problems are often caused by incorrect press adjustments, poor maintenance culture etc.) Some of the common printing faults that occur as a result of mechanical problems include the following: Scumming: This is a situation in which non-image areas of a printed material accepts ink. It is caused by: ▪ Over inked press ▪ Insufficient moisture on the plate ▪ Dirty dampener covers ▪ Dampener covers tied too tightly. ▪ Light dampener from roller pressure to the plate ▪ Low acid level of the fountain solution Blurred Copy (Double Image). This is Caused by: ▪ Loose blanket- If the covering of the blanket cylinder is loose. During press run, the blanket is pressed against the plat cylinder and tend to flatten or stretch out. ▪ Excessive Impression- Too much impression will tend to roll the blanket ahead of the impression cylinder and cause a set -off from the press sheet back to the blanket, resulting in blurred image. ▪ Over inking Gray, Washed-Out Reproduction. This is caused by: ▪ Too much moisture 25  ▪ Insufficient ink ▪ Incorrect plate-to-blanket pressure ▪ Incorrect impression-to-blanket pressure Gray, Washed-Out Reproduction. and Scumming. This is caused by: ▪ Glazed ink rollers ▪ Glazed blanket rollers ▪ Too much ink from roller pressure ▪ Too much dampener form roller pressure ▪ Too low impression ▪ Too much moisture and glazed blanket and ink rollers Printer’s Hickey: Small particles of ink or paper attached to the plate or blanket. This can be solved by stopping the press and cleaning the plate and the blanket cylinders. Too dark reproduction: This is when the image prints too dark. This is caused by: ▪ When half-tones and half-tone reverses fill in ▪ When the printed sheet dries slowly which may be caused by too much ink, too much impression-to-blanket pressure or not enough plate-to-blanket pressure. Weak spots: this may be caused by: ▪ Incorrect plate-to-blanket pressure ▪ Incorrect impression -to-blanket pressure ▪ Low spots in the blanket ▪ Blind image on plate caused by dried gum Arabic or overly strong fountain solution, or a glazed blanket. Image breaks down while plate is running: This is caused by: ▪ Too much dampener from roller pressure against the plate ▪ Too much ink from roller pressure against the plate ▪ Too much plate-to-blanket pressure ▪ overly strong fountain solution ▪ End play in fall rollers Careers in Commercial Printing This embraces all the activities that go on in a typical printing house. In commercial printing, Graphic designers learn about all kinds of mechanical printing processes such as Lithography, Letterpress, Flexography, Intaglio etc. They also study typography, image conversion, plate development and preservation, bookbinding and finishing processes, quality control, types of 26 printing papers, inks and other press materials. Graphic designers also study press management and safety. There are various specialized vocations in commercial printing; these are Copy editing, proof-reading, Layout Designing, Typesetting, Photo convection, Plate making, Printing, Book binding, estimating, production management and publishing. Copy Editor These are specialists who correct spelling, punctuation, grammatical mistakes and ambiguities in scripts and soft copy. They also check sentence structure and proper arrangement of paragraphs, appropriate headings, spacing and relationship between text and illustrations used in a copy. Copy editors must be well versed in languages especially English Language with exceptional writing skills. They must be fast readers, have eyes for details and have high level of concentration during reading. They must also have practical and theoretical knowledge and experience in Graphic communication design. Graphic Designers who are very good in English Language and script writing and have some reasonable experience in press operations can work as Copy Editors in press and publishing houses and advertising agencies. Proof-reader These are specialists who correct mistakes in proof prints of hard copies. They check good selection of typeface and fonts, hierarchy of text, the use of emphasis, good layout formats, letter, word and line spacing, the use of space, colour scheme, colour contrast, good selection and placement of illustrations and the overall aesthetic and communication appeal of the design. They also complement the duties of copy editors to check grammatical, spelling and punctuation mistakes. Proof-readers can work as freelance practitioners or employed in publishing houses and advertising agencies. Experienced Graphic designers who have strong background in English Language can work as proof-readers. Typesetter A typesetter is also called a Compositor or Typographer. This is a specialist who selects typefaces or fonts to develop the textual content of a copy. A compositor should have knowledge and experience in types of font and their uses, types of spacing and spacing devices, forms of layouts, punctuation marks and their uses. They must also have practical experience in typesetting machines and their operations. To become a compositor, one must understudy a skillful and 27 experienced typesetter or typographer in a press house for some months or years as an apprentice. He can also read other lettering and typography publications to top up his knowledge in typography. It is advisable that typesetters also have fair knowledge in English Language to enable them further check spelling mistakes when composing words. Photo converter This is a professional who has knowledge and practical experience in the operations and uses of process cameras and other photo conversion machines. Photo converters prepare chemical grid screens and use them in conjunction with a process camera to convert photographs from full-tone (continuous-tone) to half-tone thereby breaking the colours and tones in the photograph into varying dots sizes unto a thin transparent plastic sheet called acetate. The photographs are usually separated into four colours and unto separates sheets. The colours are Cyan, Magenta, Yellow and Black. To qualify as a photo converter, one can undergo some months of practical training as apprentice under experienced photo converter in a press house. Plate Maker A plate Maker is a technician who strips photographs or images and typed text unto a chemically treated sheet or plate and exposes it though a plate exposing equipment called the Plate Maker and a chemical developer to create the copy on the plate for printing. Plate Makers also preserve and dry developed plates. Plate Maker must be experienced in image cropping and trimming. He must also have good sense of scaling, proportion and measurement. He must also have adequate knowledge in the chemistry of plate processing and preservation materials such as types of plate development sheets, chemicals and preservation chemicals. A plate Maker must also know how to operate plate makers and the skills involved in processing a plate. To become a plate-making technician, one must go through some months of apprenticeship under an experienced plate maker in a press house. It must be emphasized that nowadays, there are electronic image setters which are connected to a personal computer where the design is generated and commanded to separate the colours unto the acetate directly through the image setter. 28 Printer Printers are also called Machine Operators in a press house. They are required to be knowledgeable and experienced craft men who have years of practical experience in handling printing press machines such as letterpress and single and multiple colour lithographic printing plants. Printers must be knowledgeable in the operative principles of printing press machines and maintenance. Printers must also have knowledge in types of printing inks and papers and their printing quality as well as the chain of activities that go on at the production unit. Thus, pre-press to press. This will enable him to arrest all kinds of unnoticed mistakes in the plate before printing it to hard copy. Printers are regarded as the core press staff in press houses because they are the ultimate transferors of the copy to a readable material so any evidence of incompetence in their work would mar the quality of the work and this can affect the company negatively. For this reason, they are the highly remunerated technicians among the production staff in press houses. To train as a press printer, one can pursue a three-year City and Guilds intermediate programme in printing at Tema Technical Institute. Printing can also be learnt through some months of apprenticeship training under experienced printer in any standard printing house such as Check- point, Comp print, Graphic Communication Groups Company Limited, Ghana Publishing, New Times Corporation, Ghana Universities Press, Buck Press, Saint Francis Press, etc. Book Binder These are professionals who collate, gather, insert and join leaves of printed sheets into books, pamphlets, magazines, receipts, reports, registers, cheques etc. Book Binders also undertake other finishing activities such as stitching, perforation, lamination etc. They have knowledge and experience in different kinds of binding materials, tools and equipment as well as their maintenance. To qualify as a professional bookbinder, one must take some months of apprenticeship training under experienced bookbinder in a standard press house. Apprentices can also read publications on bookbinding to enrich their knowledge. Estimator These are professionals from other fields that work in collaboration with the production manager in a press house. Estimators prepare production budgets for a press house. Details of their functions 29 in a press house include calculating direct and indirect costs as well as profit margins of jobs or contracts. Estimators must have high aptitude in mathematics and cost accounting. Professionals such as mathematicians, accountants, statisticians, quantity surveyors, project management graduates and others are often employed as estimators. Graphic designers who have reasonable working experience in production management and high aptitude in mathematics can also be employed as estimators in a press house. Production Manager A Production Manager in a press house is a management employee who works as the general supervisor of all production activities that go on in the press house. This presupposes that, a press production manager must have a holistic theoretical and practical knowledge in all the press activities. In addition to his technical skills, he is also supposed to have good management and interpersonal skills, this is because, he develops production procedures, processes, guidelines, and safety rules and regulations for the production team and monitors their effective implementation. The production Manager is the one who negotiates charges with clients and agrees on specification with clients. He also prepares specifications for all the units in the production team and prepares the budget for both material and production cost for the production units. He is also the one who sees to it that proper quality control measures are strictly observed during the production process to minimize wastage and unnecessary mistakes, which can affect the quality of production. They often liaise with estimators to make financial and logistical forecast for the press house and come up with appropriate costing for jobs. To qualify as a production manager, one must have a diploma or degree certificate in Graphic communication design or publishing studies from a recognized tertiary institution. However, anybody with a reasonable level of academic qualification and working experience in a general press house for some years can equally be employed as production manager in a press house. Layout Designer A layout designer is a creative artist who plans and designs Graphic communication design works for display or reproduction in the print and electronic media. Layout designers in press houses design all kinds of Graphic communication works such as textbooks, manuals, book covers, labels, 30 posters, complimentary cards, brochures, leaflets, invoices, tickets, postage stamps, files, annual books, calendars, receipts, etc. Layout designers must be very good in idea or concept development and be highly imaginative. They must have fair knowledge in elements and principles of design, colour psychology and application, and composition drawing and illustration. They must also have control over the use of many computer graphics software programmes such as Coral Draw, Adobe Illustrator and Photoshop, flash and other programmes such as Page Maker, Quack Express, InDesign, Publishing, MS Word, etc. Professional Graphic designers who hold diploma or degree certificates in general Graphic design are usually employed by press houses, advertising agencies and TV stations as layout designers. However, other private computer schools offer certificate and diploma programmes in computer graphics and such people can also be employed as layout designers. Publisher Publishing simply means the production and sale of books and other creative works. Publishers in the print media finance the publication and sale of Textbooks, Storybooks, Magazines, Newspapers etc. written by authors and journalists. In publishing, the publisher enters into contractual agreement with the author to determine the percentage of profit to be made by each party. Before the book is published the publisher and the author negotiate all copyright legalities with authorities (authors) whose intellectual properties the author might have consulted in the development of the script. In other words, they make sure that all reference materials are properly acknowledged. Failure to do this will lead to ‘plagiarism’. The published book therefore is registered (Patented) in the name of the author and the publisher so no other person will have the legal right to reproduce any part of the book or the entire book by manual or electronic means. Reference Materials Adams, Faux, & Rieber. (1988). Printing Technology (3rd ed., p. 169, p. 310). New York, Delmar publishers Inc. Breckhuizen R. J. (1992). Graphic Communications (4th ed., p. 127). New York. Glencoe, McGraw-Hill Company. 31 Dennis, E. A., & Jenkins, J. K. (1991). Comprehensive Graphic Art. New York: Glencoe/McGraw-Hill. Agyarkoh, E. (2017). Graphic communication design for schools and colleges (First edition). Cape Coast: Paslet Printing Press. Compiled by: Dr Eric Agyarkoh Lecturer, Communication Design Department of VOTEC, UCC Tel: 0243371268 32