Research into different commercial print processes
http://en.wikipedia.org/wiki/Letterpress_printing
Letterpress printing
Letterpress is relief printing. It involves locking movable type into the bed of a press, inking it, and rolling or pressing paper against it to form an impression. [1] It was the normal form of printing text from its invention by Johannes Gutenberg in the mid-15th century until the 19th century and remained in wide use for books and other uses until the second half of the 20th century. In addition to the direct impression of inked movable type onto paper or another receptive surface, letterpress is also the direct impression of inked printmaking blocks such as photo-etched zinc "cuts" (plates), linoleum blocks, wood engravings, etc., using such a press.[citation needed] With certain letterpress units it is also possible to join movable type with slugs cast on a Linotype machine.
Letterpress printing remained the primary way to print and distribute information until the twentieth century, when offset printing was developed. It was also an extremely important technological innovation, making printed material available to a wider range of classes of people.
In about 1440, Johannes Gutenberg is credited with the invention of modern movable type printing from individually cast, reusable letters set together in a form (frame or chase). He also invented a wooden printing press, based on the extant wine press, where the type surface was inked with leather covered ink balls and paper laid carefully on top by hand, then slid under a padded surface and pressure applied from above by a large threaded screw. Later metal presses used a knuckle and lever arrangement instead of the screw, but the principle was the same. Ink rollers made of composition made inking faster and paved the way for further automation.
With the advent of industrial mechanisation, the inking was carried out by rollers which would pass over the face of the type and move out of the way onto a separate ink plate where they would pick up a fresh film of ink for the following sheet. Meanwhile, a sheet of paper was slid against a hinged platen (see image) which was then rapidly pressed onto the type and swung back again to have the sheet removed and the next sheet inserted (during which operation the now freshly inked rollers would run over the type again). Fully automated, 20th-century presses, such as the Kluge and "Original" Heidelberg Platen (the "Windmill"), incorporated pneumatic feed and delivery of the sheet.
The invention of ultra-violet curing inks has helped keep the rotary letterpress alive in areas like self-adhesive labels. There is also still a large amount of flexographic printing, a similar process, which uses rubber plates to print on curved or awkward surfaces, and a lesser amount of relief printing from huge wooden letters for lower-quality poster work.
Rotary letterpress machines are still used on a wide scale for printing of self-adhesive and non-self-adhesive labels, tube laminate, cup stock, etc. The printing quality achieved by a modern letterpress machine with UV curing is on par with flexo presses. It is more convenient and user friendly than a flexo press. Water-wash photopolymer plates are used which are as good as any solvent-washed flexo plate. Today even CtP (computer-to-plate) plates are available making it a full-fledged, modern printing process. Because there is no anilox roller in the process, the make-ready time also goes down when compared to a flexo press. Inking is controlled by keys very much similar to an offset press. UV inks for letterpress are in paste form, unlike flexo. There are various manufacturers of UV rotary letterpress machines, viz. Dashen, Nickel, Taiyo Kikai, KoPack, Gallus, etc. which also offer hot/cold foil stamping, rotary die cutting, flatbed die cutting, sheeting, rotary screen printing, adhesive side printing, and inkjet numbering. The central impression presses are more popular than inline presses due to their ease of registration and simple design. Printing of up to nine colours plus varnish is possible with various online converting processes.
A small amount of high-quality art and hobby letterpress printing remains—fine letterpress work is crisper than offset litho because of its impression into the paper, giving greater visual definition to the type and artwork. Today, many of these small letterpress shops survive by printing fine editions of books or by printing upscale invitations and stationery, often using presses that require the press operator to feed paper one sheet at a time by hand. They are just as likely to use new printing methods as old, for instance by printing photopolymer plates (used in modern rotary letterpress) on restored 19th century presses.
The process requires a high degree of craftsmanship, but in the right hands, letterpress excels at fine typography. It is used by many small presses that produce fine, handmade, limited-edition books, artists' books, and high-end ephemera such as greeting cards and broadsides. Setting type by hand has become less common with the invention of the photopolymer plate.
To bring out the best attributes of letterpress, printers must understand the capabilities and advantages of what can be a very unforgiving medium. For instance, since most letterpress equipment prints only one color at a time (unlike presses for offset printing which often use four-color process printing), printing multiple colors can be challenging. The inking system on letterpress equipment is less precise than on offset presses, which can pose problems with some graphics: detailed, white (or "knocked out") areas, such as small, serif type, or very fine halftone, surrounded by fields of color, can fill in with ink and lose definition. However, a skilled printer can overcome most of these problems. Working with a letterpress also gives the printer the option of using a wider range of paper, including handmade, organic, and tree-free. Letterpress printing allows for a large variety of choices. The classic feel and finish of letterpress papers takes printing back to an era of quality and craftsmanship that is not often found in other printing methods today. Even the smell of the ink, more apparent on a letterpress-printed page than with offset, often appeals to the collector.
While less common in contemporary letterpress printing, it is possible to print halftoned photographs, via photopolymer plates, on letterpress equipment. However, letterpress printing's strengths are crisp lines, patterns, and typography.
Creating files for Letterpress is similar to conventional printing with these exceptions:
- Ink Color: Files are created using spot colors, not CMYK or RGB. A spot color is specified for each color to be used. Typically one or two colors are used.
- Paper Color: Dark ink on a light paper gives the best image. Inks are translucent and the paper color will show through. For light colors on dark paper, foil stampingor engraving should be used instead of Letterpress. To build up the color density of a specific color, Letterpress pieces can be run through the press two times using the same color.
- Screens: Grayscale images can be used if made with a coarse screen (85 line or less). A second color should be used instead of screening a color in most cases.
- Thickness: Art must be above ¼ point and with no hairlines.
- Fonts: Type must be five points or larger for best results. For reversed type the point size should be 12 point or larger, smaller type can fill in. An outline stroke is often applied to allow for ink gain.
- Solids: Letterpress solids will print differently from conventionally printed lithographic solids. While Letterpress does lay down a thick film of ink, the process tends to show the texture of the sheet. Also, solid areas do not give the appearance of depth that fine type and thin lines do. Solid areas can also cause the paper to ripple, especially on thinner sheets.
- Registration: Letterpress does register well, however, it does not have the capabilities of modern offset printing. Trapping and key lines do not work well in letterpress printing. A blank area should be incorporated between colors. Black and very dark colors may be overprinted over lighter colors.
- Depth: The type depth is dependent on the paper. Typically Letterpress papers are thick and soft to allow the type to create a deep impression. When fold-over items are created, the printer will typically back off on the pressure to avoid embossing the backside of the piece.
- Image and File Prep: Letterpress excels at line copy and type, so vector images work well. Crop marks should be shown as a register color. Images need to bleed(extend past the trim line).
- Die cut, Emboss and Scores: These effects work well with most Letterpress paper. Images to be embossed or die cut should be called out in a different color layer (typically magenta). Scores should be indicated with a cyan line. Any intricate shapes or patterns should be reviewed with the printer. For thick cover stocks many printers use a kiss cut rather than a score.
- Envelopes: It is best to print on the flap of a ready-made envelope. Other areas of the ready-made envelopes can be printed but bruising may occur on the other side of the envelope.
Several dozen colleges and universities around the United States have either begun or re-activated programs teaching letterpress printing in fully equipped facilities. In many cases these letterpress shops are affiliated with the college's library or art department, and in others they are independent, student-run operations or extracurricular activities sponsored by the college. Many are included in degree programs. The College & University Letterpress Printers' Association (CULPA) was founded in 2006 by Abigail Uhteg at the Maryland Institute College of Art in order to help these schools stay connected and share resources.
The current renaissance of letterpress printing has created a crop of hobby press shops that are owner-operated and driven by a love of the craft. Several larger printers have added an environmental component to the venerable art by using only wind-generated electricity to drive their presses and plant equipment. Notably, a few small boutique letterpress shops are using only solar power.
In London, St Bride Library houses a large collection of letterpress information in its collection of 50,000 books: all the classic works on printing technique, visual style, typography, graphic design, calligraphy and more. This is one of the world's foremost collections and is located off Fleet Street in the heart of London's old printing and publishing district. In addition, regular talks, conferences, exhibitions and demonstrations take place.
The St Bride Institute, Edinburgh College of Art, Central Saint Martins College of Art and Design, The Arts University Bournemouth, University for the Creative Arts Farnham and London College of Communication, run short courses in letterpress as well as offering these facilities as part of their Graphic Design Degree Courses.
The Hamilton Wood Type and Printing Museum in Two Rivers, Wisconsin houses one of the largest collections of wood type and wood cuts in the world inside one of the Hamilton Manufacturing Company's factory buildings. Also included are presses and vintage prints. The museum hold many workshops and conferences throughout the year and regularly welcomes groups of students from Universities from across the United States.
