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Module 2: Printing Processes

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  1. Module 2: Printing Processes Instructor: Doughlas Remy

  2. Topics Covered in This Module • The U.S. printing industry • Definition of printing • Major printing processes (overview) • Where’s the ink? Where’s the paper? • Early relief printing • Text and artwork before and after the invention of photography • Relief (Flexography, Letterpress) • Planographic printing (offset litho) • Gravure (Intaglio) • Screen printing (silkscreen, stencil) • Digital (electronic) printing • Spot colors and process colors • Continuous tone vs. halftone • Quiz • Answer Forms for Printing (major printing processes)

  3. What you should know about the U.S. printing industry • It has a very low profile. • It is composed mainly of small businesses. • It has revenues of about $1 billion annually. • It is the nation’s largest employer.(It employs nearly 1 million people, or 220,000 more than the auto industry.) • There are nearly 100,000 printing establishments in the U.S. • Pre-press is considered to be a part of the printing industry. Source: http://www.wmrc.uiuc.edu/info/library_docs/manuals/printing/domestic.htm

  4. Definition Printingis basically the transfer of images from a source (usually printing plates) to a target surface (usually paper) through the application of a medium (usually ink). Sources Targets Media most common Plates (e.g., aluminum, polymer, rubber) Type forms (used in letterpress) Templates (used in screen printing) Blocks (made of wood, metal, lino, plastic, stone) Jets (used in inkjet printing) Inks Toners Dyes Paints Paper Fabric Metal Plastic

  5. Major Printing Processes

  6. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure) • Screen (aka silkscreen, stencil, serigraphy) • Digital (aka electronic)

  7. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure) • Screen (aka silkscreen, stencil, serigraphy) • Digital In a category by itself because it is for low-volume printing; and its technology is so different from the others.

  8. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure) • Screen (aka silkscreen, stencil, serigraphy) • Digital Now a major printing process and growing exponentially. Its technology is very different from that of the first three on this list.

  9. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure) • Screen (aka silkscreen, stencil, serigraphy) • Digital We will focus on the first three for now.

  10. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure)

  11. Major Printing Processes: Where’s the ink? Where’s the paper?

  12. Where’s the ink? The first three—relief, planographic, and gravure—are easier to understand if we compare the location of the ink in these cross-sections of the printing plates used for each: Relief Ink is on a raised surface. Planographic Ink is on a flat surface. Ink is in wells or reservoirs. Gravure • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure)

  13. Where’s the paper? (1) 1. The paper may be attached to a flat surface, against which a type form or a printing plate is pressed. lever attached to screw NoteThis way of placing the paper was a feature of the earliest printing methods and is rarely used today. (It’s very slow.) type form Wooden hand press (aka screw press), a reproduction of Gutenberg’s press.

  14. Where’s the paper? (1) A layer of oil-based ink is applied here, and then a roller arm (not shown here) pivots up to collect the ink and then rolls it onto the “chase,” which contains the relief image. Lever Press This was a later development, using the same principle of attaching the paper to a flat surface. The “chase” (relief image) Paper attached here. Note that there is no screw. Message from Ed Evetts at CCS Printing in Bellevue: ..the disc is where the operator places the ink for the press. The ink-carrier roller-arm (not apparent in the illustration) rotates up and rolls across the flat part of the disc, picking up a layer of ink on the roller. Then, on the down-stroke, the ink-carrier roller-arm rotates down and applies a layer of ink to the raised-surface of the copy in the chase.which Doughlas refers to as the "Type form" in the illustration. FYI: As the ink-carrier roller-arm rotates up to get more ink, the sheet attached to the paper-bed rotates to contact the chase and get "printed". When the ink-carrier roller-arm rotates down to apply more ink to the chase, the paper-bed rotates away from the chase so that the operator can pull off the printed sheet and insert a fresh sheet for printing .

  15. Where’s the paper? (2) Cylinder Letterpress 2. The paper may be attached to a cylinder, which then rotates as an inked type form passes beneath it. Paper Type form NoteThis way of placing the paper, like the previous one, was time-consuming and was abandoned in favor of the last two methods (next slides). Ink Rollers Impression Cylinder Press bed

  16. Where’s the paper? (3) 3. Sheets of paper pass between two flexible printing plates (attached to cylinders) that are carrying the image. NoteThis technology did not become possible until a means could be found for making the printing plate thin and flexible enough to attach to a cylinder. Note The process of printing on both sides of the paper (recto and verso) is called “duplexing.”

  17. Where’s the paper? (4) 4. A continuous “web” of paper passes between two flexible printing plates (attached to cylinders) that are carrying the image.

  18. Where’s the paper? (4) Why “Web”? The American Heritage Dictionary has 11 definitions of “web.” # 1: “A textile fabric, especially one being woven on a loom or in the process of being removed from it.” # 11: “A continuous roll of paper, as newsprint, in the process of manufacture in a paper machine or as it comes from the mill.

  19. Major Printing Processes • Relief(primarily flexography, which evolved from letterpress) • Planographic (offset lithography) • Gravure (aka Intaglio, Photogravure, Rotogravure) • Screen (aka silkscreen, stencil, serigraphy) • Digital

  20. Major Printing Processes: Early Relief Printing

  21. Modern signet rings Relief: Letterpress – Historical overview Signet rings were first used in ancient Babylonia. a wax seal No further progress was made in the Western world until the Gutenberg era (15th century).

  22. Relief: Letterpress – Early Chinese printing • Meanwhile, the Chinese were printing from wood blocks as early as the 2nd century A.D. This was made possible by their invention of paper in A.D. 105. • Papyrus had been too fragile. • Vellum* was too expensive. *Vellum is a thin tissue taken from inside the hides of newly skinned animals.

  23. Relief: Letterpress – Early Chinese printing The Chinese developed movable type around the tenth century A.D., and were even doing two-color printing with it. By the 13th and 14th centuries, they had three-color and four-color printing. At first, they used clay type, but later developed metal (copper) type. Movable type was not as practical for the Chinese language as it was for European languages, because it required between 2000 and 40,000 separate characters.

  24. Relief: Letterpress – Early Western printing Earliest Western print technology grew up in the Rhine River Valley in the mid-fifteenth century and was probably not influenced by earlier developments in the Far East.

  25. Relief: Letterpress – Early Western printing The first printing presses in the West were screw-type presses designed primarily to bring pressure on the printing form, which was placed face up in a flat bed. Click here for photos of screw-type presses from the Museum of Printing Presses.

  26. Relief: Letterpress – Early Western printing Consider this: Letterpress printing from raised metal type was the primary means of mass communication for over 400 years.

  27. Relief: Letterpress—Later Developments • Later developments in the West: • In the 17th century, springs were added to the press to aid in lifting the platen rapidly. • Around 1800, iron began to be used in the construction of presses, and levers were substituted for the screws that brought the platen down onto the form. • The process was still slow (300 impressions per hour), but much larger forms could be used, so multiple pages could be printed simultaneously. “Old Reliable,” platen letterpress, 19th century.

  28. Relief: Letterpress—Later Developments Cylinderswere not used in letterpress until the 19th century. Cylinder Letterpress Paper The ink rollers apply ink only to the raised areas. Then the ink is transferred to the paper, which is on the impression cylinder. Type form Ink Rollers Impression Cylinder Letterpress images can be sharp and crisp. However, the pressure of the plate or cylinder surface on the paper may also spread the ink slightly. Press bed

  29. Relief: Letterpress—Later Developments

  30. Relief: Letterpress A cylinder letterpress

  31. Major Printing Processes: Relief Printing: Text and Artwork Before and After the Invention of Photography

  32. Relief: Letterpress—Text and Artwork • Before the invention of photography and the development of modern printing techniques, the raised image in relief printing could only be produced in two ways: • For text: Metal type • For artwork: Engravingor etching. These techniques leave a flat, raised surface to which the ink is applied. Engraving is simply cutting away the areas that will not receive the ink. Etchinginvolves making incisions on a plate that has been coated with an acid-resistant material, and then applying acid to the entire surface.

  33. Relief: Letterpress—Text and Artwork Note that artwork had to be in the form of either engravings or etchings if it was to be printed. In both techniques, the area that will not receive the ink is removed—either by direct cutting or by application of acid. Wood engraving, 1830: View of Rochester with a Section of the Aqueduct Etching: The Soldier and his Wife, by Daniel Hopfer (ca 1470-1536)

  34. Relief: Letterpress—Text and Artwork Electrotyping(first used in 1838) was a technique for making duplicate plates from original relief plates. To create an electrotype duplicate: Make a mold of the original plate, using any one of various materials (copper, lead, zinc, etc.) Place the mold in an electrolytic solution (e.g., copper sulfate and sulphuric acid). Place a sheet of the same or a different metal in the solution, parallel to the mold. Pass an electrical current through the solution. The mold acts as the cathode and the other metal sheet as an anode. Metal passes from the anode to adhere to the cathode (the mold). Separate the newly-deposited layer of metal from the mold. mold metal sheet tank containing electrolytic solution

  35. Relief Printing—Text and Artwork After the Invention of Photography After the invention of photography, it became possible to dispense with lead fonts and type forms altogether. Photographic transparencies could be used to make plates, and this led to the demise of letterpress. To understand platemaking from photographic transparencies, we must first understand what a halftone screen is.

  36. Relief Printing—Text and Artwork After the Invention of Photography • Halftone screens: • Physical screens (either glass plates or contact sheets), consisting of grids through which light may pass. • Placed between a photographic transparency and a photosensitive plate. • Light passes differentially through the transparency and then through the halftone screen to the photosensitive plate. • The light reacts with the chemicals on the plate to produce areas that are receptive to ink. • These ink-receptive areas, if examined under a magnifying glass, will appear as grids of dots. Glass plates Contact Sheets

  37. Relief Printing—Text and Artwork After the Invention of Photography

  38. Relief Printing—Text and Artwork After the Invention of Photography Two kinds of halftone screens: Older screens consist oftwo thin glass plateswith scribed parallel lines running across them; these are cemented together so the lines form right angles. The thickness of thescribingvaries depending on the screen frequency, but the lines and the open spaces are always of equal width. These are now uncommon. Instead, most printersuse contact sheets made of film. Unlike glass screens, the dots on these screens are not completely open. Each dot is clear in the middle with increasing opacity toward the edges. Glass plates Contact Sheets

  39. Relief Printing—Platemaking Light source After the invention of photography, relief images could be produced using film positives (or negatives), halftone screens, and photopolymer plates. These plates are made of pre-coated photosensitive plastics, from which unexposed, non-image areas are chemically dissolved. Film positive Halftone screen Printed halftone image on coated light-sensitive plate. More intense light burns larger dots.

  40. Relief Printing—Platemaking Darker areas are recessed. Ink will be applied to the lighter areas, which are raised. the transparency the halftone screen the plate Keep in mind that the image on this plate is composed of hundreds of thousands of dots. Also note that the plate would not actually look like this. This image only illustrates the difference between the variable sizes of the dots (0-100%), which translate into amount of ink applied.

  41. Relief Printing—The Demise of Letterpress Letterpress has been almost entirely replaced by other printing technologies, especially flexography and lithography (more about these shortly), but it still has a limited “niche” appeal for printing wedding invitations, menus, business cards, etc. It has a very elegant “embossed” look and is very “tactile.” Lead typesetting (hot type) is mostly an anachronism. This invitation was printed using another kind of relief printing—flexography—which uses photopolymer plates.

  42. Major Printing Processes: Relief Printing: Flexography • Relief (letterpress and flexography) • Planographic (offset-lithography) • Gravure (aka, intaglio, rotogravure, photogravure) • Screen (aka, stencil, silk screening, screen printing, serigraphy) • Digital (aka, electronic)

  43. Flexography • Like letterpress, flexography is a form of relief printing. • Flexography uses: • plates of photopolymer or flexible rubber. • thin, fast-drying, water-based inks. • high-speed web presses. • Flexography is widely used for printing gift wrap and packaging materials because of its brilliant colors. Wine bottle labels printed by Richmark Label, Seattle, WA

  44. 44 Flexography • Flexography is also used for the following: • Corrugated containers • Folding cartons • Paper sacks • Plastic bags • Milk cartons • Disposable cups • Labels • Adhesive tapes • Envelopes • Newspapers • Food and candy wrappers Other commercial printing by Richmark Label, Seattle, WA

  45. Flexography For more information about flexography, visit the following sites: http://desktoppub.about.com/od/flexography/ http://www.pneac.org/printprocesses/flexography/index.cfm

  46. Major Printing Processes: Planographic (Offset Litho) • Relief (letterpress and flexography) • Planographic (offset-lithography) • Gravure (aka, intaglio, rotogravure, photogravure) • Screen (aka, stencil, silk screening, screen printing, serigraphy) • Digital (aka, electronic)

  47. Haven’t I seen “litho-” in other words? Planographic (offset lithography) • By far the most important and versatile printing process today. • Developed at the end of the 18th century by Aloys Senefelder. • The first chemical printing process. • Most newspapers are printed on offset presses. The prefix “litho-,” from the Greek lithos, means “stone.” The lithosphere is the solid part of the earth, as distinguished from the hydrosphere and the atmosphere. The “Paleolithic” era is the era of ancient rocks. • Five major printing processes: • Relief (letterpress and flexography) • Planographic (offset-lithography) • Intaglio (gravure) • Screen (stencil, silkscreen) • Digital

  48. Planographic (offset lithography) But… Wet limestone repels oil-based ink. An image drawn with a grease pencil repels water and attracts ink. • Five major printing processes: • Relief (letterpress and flexography) • Planographic (offset-lithography) • Intaglio (gravure) • Screen (stencil, silkscreen) • Digital

  49. Planographic (offset lithography) To print the image on the paper, simply press the paper onto the stone. Printed image Sheet of paper Limestone with inked image + paper • Five major printing processes: • Relief (letterpress and flexography) • Planographic (offset-lithography) • Intaglio (gravure) • Screen (stencil, silkscreen) • Digital

  50. Planographic (offset lithography) Modern litho presses don’t use limestone. They use thin aluminum plates that carry both the image areas and the non-image areas. (Polyester plates are used for some jobs that involve line copy or that require short runs only.) The image areas are not raised. They are chemically receptive to oil-based inks, whereas the non-image areas are not receptive to the inks. The plates, attached to cylinders, are first exposed to water, and then to ink. The image is then transferred to a rubber blanket that is on a second cylinder. Printed image • Five major printing processes: • Relief (letterpress and flexography) • Planographic (offset-lithography) • Intaglio (gravure) • Screen (stencil, silkscreen) • Digital