Reproductive technology
Under reproduction technology in the prepress procedures are meant to deal with the reproduction of images and texts and for the production of printing forms for the various printing methods serve. This does not apply to printing forms created by artists, such as copperplate engraving , steel engraving , woodcut and the original lithograph . These are original works and not reproductions.
Reproductive technology has developed faster in the past forty years than in the previous hundred years. Anyone who was trained in one of the coveted and well-paid professions as typesetter , chemigrapher or lithographer in the 1950s was considered a craftsman . Today skilled workers, increasingly women too, with special knowledge of image processing work there. The apprenticeship is called media designer for digital and print media .
The reproduction technology is made up of two production stages, namely firstly the data acquisition of the template and subsequent processing, and secondly the actual printing form production.
Overview of the printing processes
Today, according to DIN 16500, a distinction is made between four main printing processes, namely relief , gravure , flat and screen printing depending on the type of printing form .
In letterpress printing, the printing elements in the printing form are raised and colored with printing ink, while non-printing areas are recessed. The printing form is colored by means of ink-carrying rollers. For high pressure include letterpress , flexographic and Letterset -pressure.
In planographic printing processes, printing and non-printing elements lie in one plane. The pressure principle here is based on the chemical opposition of fat and water. Printing areas of the printing form take on the greasy ink, while non-printing areas are moistened and repel ink. Flat printing processes include offset printing , stone printing and collotype printing .
The printing picture elements of the gravure printing process are recessed and are filled with liquid ink. Non-printing areas are slightly raised so that the printing ink can be removed with a squeegee . Rotogravure printing processes include machine rotogravure printing , as well as steel and copper engraving and etching .
The printing form in the screen printing process is permeable to color, while non-printing areas are covered. The printing ink passes through the printing form onto the material to be printed. Screen printing processes include screen printing and risography .
There are also other printing processes that cannot be assigned to any of the aforementioned, for example electrostatic printers such as laser printers , copiers and digital printing machines , as well as inkjet printers .
History of reproduction technology in planographic printing
In 1798, invented Alois Senefelder the lithography and stone printing, two pioneering discoveries on the way to modern reproductive technology. Senefelder was the first to try to reprint existing copperplate engravings in another way, i.e. to reproduce them. With the chromolithography developed by the Franco-German lithographer Godefroy Engelmann in 1837 , it was possible to reproduce colored templates, albeit in laborious manual work. Up to this time there were only color prints with one or more clay plates as etching in gravure or as woodcut in relief printing.
Further inventions during the 19th century accelerated the development of reproductive technology. In 1837, discovered Louis Daguerre , the photograph after Joseph Nicephore Nièpce been 10 years of photographic recordings in previously heliography had made process. In 1861 James Clerk Maxwell developed the filter technology for color separations and in 1881 Georg Meisenbach developed the glass engraving grid . This created all the prerequisites for using photography for repro technology and printing form production.
Meisenbach discovered a process in Munich in 1882 that he called autotype , which could be used to print photographic images of zinc plates in relief printing. In 1883 the first screened photo appeared in a German newspaper. A little later photography was also used in flat printing and photolithographers processed color separations and copied them onto lithographic stones. Photography was used in gravure printing by exposing the picture to light-sensitive pigment paper and then transferring it to the printing plate. This process was called heliogravure and was invented by Karl Klietsch in 1879 .
Chromolithography (approx. 1840–1940)
In 1837 the Franco-German lithographer Godefroy Engelmann from Mulhouse (Alsace) patented a colored variant of lithography under the name Chromolithography , which was to be a widespread process for high-quality color illustrations until the 1930s. Chromolithographs consisting of up to 8, 12 and even 16 colors were not uncommon.
As a template or original, the chromolithographer received a painted picture from an artist or graphic designer, from whom he produced a contour drawing on stone, which marked the outlines and color differences of the original with fine lines. This contour plate served the lithographer as a guide for the precise elaboration of the intended individual colors. Using the transfer printing process, copies of the contour plate called gossip were then made on a number of stones that corresponded to the number of colors provided. A gossip only hinted at the contours in a light shade and later disappeared during the print preparation of the finished chromolithography.
A typical 10-color chromolithography, for example, consisted of the colors 1. blue, 1. red, yellow, 2. blue, 2. red, black, 1. gray, 2. gray, gold and text. After the lighter colors had been worked out, printing was started. With the help of thin crosses, which were called register marks or register marks , the motif to be printed could be printed over each other precisely and precisely over all colors. After printing each color, the chromolithographer checked the progress of his work and then processed the next darker color. Texts for the images were created on special stones by type lithographers . Finally the finished proof was presented to the customer, who could express his change requests. When printing, a color scale was created in which all printing inks were individually visible, as well as the respective overprint. The printer on the lithographic high-speed press used the color scale as a guide for the color and color guidance. After the customer had corrected the job, the job was ready for printing. The edition could now be printed in the high-speed press.
Photolithography (approx. 1890–1950)
The originals or templates were mostly painted pictures and retouched black and white photographs. For this purpose, the graphic artist provided a layout and final artwork with texts and line drawings .
In photolithography , a distinction had to be made between three process stages, namely firstly the creation of the photographic color separations , secondly the manual correction by the photolithographer and thirdly the transfer of the image to the stone by the stone copy, as well as the preparation of the lithographic stone for printing.
The repro photographer created color separations from the colored original with the help of color filters . A four-color printing required depending on a color separation for yellow, red, blue and black. The repro specialist calls these colors yellow or yellow, magenta , cyan and depth or black . During the exposure, a color filter was placed in front of the lens that corresponded to the complementary color of the color separation, i.e. a violet filter for yellow, a green filter for magenta and an orange filter for cyan. Black, which only served to increase the contrast, was recorded without a filter.
In order to be able to print the color separations, it was necessary to break it down into raster points. This rasterization was also carried out in the reproduction camera, in that the photographic plate to be exposed was preceded by a rotatable raster disk, the glass engraved grid . In four-color printing , in which several screen angles are printed on top of each other to display a color image, attempts were made to avoid the moiré effect by using an angular distance of 30 ° per color separation. A line recording was made of the final drawing .
The photolithographer assessed the color separations at a light table and made the necessary corrections. He had certain chemicals and tools available for this. The chemicals included Farmer's attenuators to lighten tonal values, as well as mercury enhancers and Keilitz paint to darken tonal values. Red chalk was used to cover opaque areas. In addition, the photolithographer used peelable or washable masking varnish with which he could protect parts of the picture that could not be changed. He now had the opportunity to process the color separation as a whole in a flat bowl with Farmer's attenuator or amplifier. He made partial retouching with a brush. However, all corrections were made based on his personal judgment and experience. The aim was to come as close as possible to the original in the print result.
The finished retouched negatives served as templates for the stone copy. A prepared stone was made photosensitive with an egg white chromate solution, which consisted of a solution of distilled water , dry protein , ammonia and ammonium dichromate . In a stone copier, the exposure with carbon arc light was carried out from the negative onto the stone, as a result of which the exposed areas were hardened. Then the stone was rolled in with black printing ink and the copy developed under water. The unexposed areas came loose and a positive reversed color separation appeared on the stone. This could now be edited manually again before the stone was prepared for printing and then printed.
Offset reproduction (since 1910)
The transition from photolithography to offset reproduction was fluid and the process steps were partly similar. The name photolithograph was transferred to offset reproduction, although this no longer had anything to do with the stone. It was not until 1956 that this apprenticeship was renamed as the master printer specialization offset . Few professions have undergone a technical change that is as serious as that of the specialists in reproduction. In the 1950s, many, predominantly small, reproduction companies emerged that specialized in prepress for letterpress and flat printing.
Conventional process (1910-1970)
The originals or templates were painted pictures and retouched black and white photographs, later also color slides . The graphic designer or advertising agency supplied the layout and final artwork with texts and line drawings or the typesetting on baryta paper and film.
From the color templates, the repro photographer created color separations with the help of color filters, now no longer directly rasterized, but as halftone negatives . The master preparers, the former Fotolithograf, put them color correction masks forth, which combined with the Halbtonnegativen and in the contact device by means of contact screen were screened. The result was a color-corrected raster slide that hardly required any manual corrections. The color-corrected color sets were often printed in order to check them and, if necessary, to correct them manually. Images, texts, drawings and other picture elements were then copied together. For this purpose, the individual parts of the picture for each color were mounted on a mounting film. The template preparer had previously punched a hole register on the edge of the mounting foils so that the foils could be placed exactly one above the other using a fitting strip. Cut-out masks for the images, as well as texts, drawings and background tones were mounted on separate foils. Negatives were now produced from all assembly foils in the contact device. The contact device was in a darkroom and the exposed films had to be developed and fixed manually. In the course of the 1960s, the developing machine replaced manual labor. In the next step, the negatives were copied together to form the final film, which was no longer allowed to be processed and served as a template for the offset printing plate. This method of working was very material-intensive, because the artwork preparer often needed between 20 and 30 individual films to complete the four-color set.
Next, the job was printed. For this purpose, the end films had to be mounted on a light table on a transparent mounting foil with the layer side up. The master copy manufacturer used dowel pins to fix each additional color assembly precisely on top of one another. The transfer was then carried out layer by layer in the copier frame onto precoated photosensitive printing plates, which were initially made of zinc and later of aluminum. The plates were exposed to UV light and under vacuum. Areas blackened in the film remained uncured as printing image areas on the printing plate and were then washed out in a developing machine. Finally, the plate was coated with a gum arabic solution. Now the order could be printed in the proof press and presented to the customer for assessment. After the correction, the reproduction company delivered the films together with a proof scale to the commissioned printer.
Klischograph and drum scanner (1963–1995)
In the 1950s, the Hell company in Kiel developed the Klischograph , which was to revolutionize the production of clichés in letterpress printing. The Klischograph was an electronically controlled engraving device for the production of print-ready clichés. The successor was the Vario-Klischograph, with which foils colored around 1968 could be engraved, which could also be used for offset reproduction by copying them onto film. They partly replaced the color extracts from the reproduction camera. At the beginning of the 1960s, the first drum scanners were developed that electronically scanned colored originals and produced color-corrected halftone negatives. From these, rasterized positives for offset printing were created using a contact grid in the contact device. The decisive breakthrough in scanner technology came when the first laser scanners came onto the market in 1971 . The best known and most successful was the Chromagraph DC 300 from Rudolf Hell . These devices were able to output color-corrected and screened color separations of high quality. This meant that the color separations from the reproduction camera were no longer required.
Proof process (since 1972)
An important innovation was the emergence of the analog proofing process , with which the specialist was given a quick means of control. At the Drupa 1972, the DuPont company presented the Cromalin ® , which quickly prevailed over competing products such as Matchprint and Remak . Cromalin ® is a color proofing process developed by DuPont, with the help of which the color result of a scan could be checked in advance without having to be printed. The colored proof as a control of the scan soon became state of the art . One advantage of the analog proofing process was that it reproduced the halftone dots of offset printing and was characterized by the reproducibility of the results. As a result, they were increasingly accepted by printing companies as a substitute for a proof.
EBV systems (1980–1995)
The electronic image processing (EBV) was presented for the first time at the Imprinta in 1979 . The complex page mounting systems from Hell, Crosfield and Scitex were supposed to replace the tedious manual work of the master copy manufacturer. The EBV system cost around one million DM in the smallest entry. At the time, skeptics believed that only the largest companies could afford such a system. By the end of the decade, however, around 2,500 systems had been installed worldwide. At Drupa 1990, nine providers offered 15 different EBV systems.
These systems usually consisted of a work preparation facility, one or more scanners, an input and an assembly station, one or more computers and a plotter for proof and film output. The image data was fed in from the scanner and the position and details of the images could be determined via an input or layout station. Line elements, text and graphics were scanned by a flatbed scanner and converted into data. All assembly work and retouching were carried out interactively on the screen by the EBV operator and the result was output as a color proof. Finally, the recording was made on film using the plotter.
Desktop Publishing (since 1990)
The English term desktop publishing (DTP) describes the creation of documents with texts, graphics and images on the computer. Due to the further development of PC technology and standard software at the beginning of the 1990s, EBV was gradually shifted to the PC. Depending on the equipment, this new system only cost a fraction of the previous EBV systems. By 1995 Apple and Microsoft covered almost 90% of the operating systems . Apple technology in particular influenced electronic image processing and page design. Image design software such as Photoshop , Corel Draw , Illustrator and Freehand together with TIFF and Postscript data formats enabled the data transfer .
The development of the digital camera since 1998 replaced the scanner in data acquisition. Currently, the data for the page structure, i.e. layout, texts, graphics and images, are created directly in the advertising agencies or editorial offices. The only remaining tasks for the repro company or repro department are special color and tonal value corrections, the merging of different data formats, the production of proofs suitable for production printing and the production of printing formes, today mostly using computer to plate or computer to press .
Digital printing form production (since 1995)
In the computer to plate process (CtP), the printing plate is imaged directly with computer data in an imagesetter, without going through a film. The previous manual assembly of the films is no longer necessary, so that the resulting errors, such as poor register, no longer occur. In addition, better printing results can be produced with directly imaged printing plates, since the edge definition of the halftone dots is higher and smaller halftone dots can be produced. The printing plate is developed online, i.e. directly in the imagesetter or in a separate developing machine.
The latest development since 2008 is called Computer to Press or Direct Imaging , in which the printing plates are imaged directly in the printing machine. This eliminates the need to manually clamp and set up the printing plate. The advantages of this process are the shortening of the set-up times for the printing press and the automation of all associated operations. The printing plates can either be written on once or several times and are exchanged if necessary.
Digital printing (since 1995)
With digital printing , a group of printing process is referred to, in which the printing image is transferred directly from a computer in a printing machine, without requiring a static pressure mold is required. Digital printing is cheaper than offset printing for smaller print runs. Since digital printing is now working with low production costs, many books by unknown authors are already being published at marketable prices and in commercial quality. Even the book-on-demand , the book on order , falls into this category. The personalized book offers a new field for digital printing . Digital printing is currently experiencing a boom through digital photography, because millions of photo books, calendars, greeting cards and other printed matter are ordered directly by consumers and produced using digital printing.
Individual evidence
- ↑ a b c d e f g h i Development of repro technology, accessed on July 8, 2009 ( MS Word ; 64 kB)
- ↑ Overview of the printing processes, accessed on July 8, 2009
- ↑ Georg Meisenbach (1841–1912), accessed on July 9, 2009 ( Memento of the original from February 25, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Heliogravure, accessed on July 9, 2009 ( Memento of the original from February 21, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c Jürgen Zeidler: lithography and stone printing. Ravensberger Buchverlag 1994, ISBN 3-473-48381-8 , pp. 84-89.
- ↑ Photolithography, accessed on July 8, 2009 ( Memento of the original of July 3, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Jürgen Zeidler: Lithography and stone printing. 1994, pp. 71f.
- ↑ Conventional methods in offset printing, accessed on July 10, 2009
- ↑ Vario-Klischograph, accessed on July 10, 2009 ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ Chromagraph DC 300 laser scanner, accessed on July 10, 2009 ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ a b c From craft to industry, accessed on July 10, 2009
- ↑ a b Computer to Plate, accessed July 11, 2009
- ^ Digital print, accessed on July 12, 2009
literature
- Walter Domen: The lithography: history, art, technology. Dumont paperback books, Cologne 1982, ISBN 3-7701-1431-0 .
- Henry Cliffe: Lithography Today, Technology and Design. Ravensburg 1968.
- Helmut Kipphan: Handbook of the print media. 1st edition. Springer Verlag, Heidelberg 2000, ISBN 3-540-66941-8 .
- Jürgen Zeidler: Lithography and stone printing in trade and art, technology and history. Ravensberger Buchverlag, 2008, ISBN 978-3-419-53486-1 .
- Jürgen Zeidler: lithography and stone printing. Ravensberger Buchverlag, 1994, ISBN 3-473-48381-8 .
- Dieter Fiebig, Karl-Heinz Beck: Reprotechnik. Programmed instructions for the sentence maker. School + Profession, Elmshorn 1977, ISBN 3-88013-122-8 .