Friday, 4 May 2012

Theory Into Practice Letterpress Process Research.

Letterpress printing is relief printing of text and image using a press with a "type-high bed" printing press and movable type, in which a reversed, raised surface is inked and then pressed into a sheet of paper to obtain a positive right-reading image. 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 usesuntil 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.
In the 21st century, commercial letterpress has been revived by the use of 'water-wash' photopolymer plates that are adhered to a near-type-high base to produce a relief printing surface typically from digitally-rendered art and typography.
Letterpress printing is the oldest form of press printing in the world. Letterpress has become an atypical method of printing, having been replaced in large part by faster and cheaper printing methods such as offset and flexographic printing. It is still available in many specialty printing shops and is used for a variety of purposes including business cards, letterheads and embossing. The letterpress process uses relief printing plates. On relief plates, the image is a raised surface. Historically, these plates were cast out of metal, but have been largely replaced with photopolymer material plates due to lower expense and reduction of chemical byproducts. There are three methods of letterpress printing: rotary, platen and flatbed.

  • Flatbed letterpress printing is a slow process and, as such, is rarely done in the United States. On flatbed printing presses, the plate is affixed in the same manner as on a platen press. The printing plate is inked by a roller. The impression cylinder pulls a sheet paper around it by way of small grippers that are attached to the cylinder. As the paper is pulled around the impression cylinder, the entire bed with the plate moves under the impression cylinder, transferring the ink to the substrate as it goes.
    The process of letterpress printing is virtually unchanged; type and cuts (ornamental or image plates) are arranged and locked in place into a ‘chase’ (a metal frame that is inserted into the press), and can be used on any press that will take materials that are ‘type high’ (this standard measurement is .918″).
    All type is relatively similar in that it is the same height and has markings that help the user determine what typeface it is and what foundry produced it.  Since letterpress is a relief printing process, the type is in reverse – hence the phrase “Mind your p’s and q’s.”
    Thanks to the development of standards, type comes in common sizes ranging from 6 to 72 point in metal (give or take).  Wood type is measured by ‘line’, or pica, and comes in a large variety of sizes.
    There are many interesting set up pieces (known as leads, slugs and quads) that help letterpress printers achieve really fantastic tricks, such as combining different point sizes of type together, setting type on curves and angles, and printing in multiple colors without altering the set up.
    Many small and intricate border and ornamental pieces are veritable designer candy; some are so detailed and miniscule that they cannot be replicated in a magnesium or polymer plate.  This is also true of many 19th century typefaces that are shaded, outlined or have lots of ornaments characters.
    Letterpress printing with antique type has many distinct characteristics that may or may not be appealing to everyone.  It is not designed to produce a heavy impression in paper, as the type is soft and would be ruined.  In fact, the concept of a deep letterpress  impression is a very recent development.

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