Letterpress presses

Today, flexographic presses and letterpress presses, for newspaper printing, use t q)es made of photo-sensitive polymeric materials that can be formed directly from a light image. The polymeric cylinder when properly developed presents raised areas that reproduce the image to be printed. 

Letterpress is printed directly by the rehef method from cast metal or plates on which the image or printing areas are raised above the nonprinting areas. Ink rollers apply ink to the surface of the raised areas, which transfer it directly to paper. Flat-bed cylinder presses are available but most letterpress is printed on rotary presses. 

It s beautiful letterpress Plantin, pressed richly into fine paper by one of William s most gifted heirs, sitting well in the hand, the jacket heavy matte paper with a roundel of Izzy s engraving of the Solmani Press sign, which hung above the workshop, festooned with ivy. The roundel is blocked in gold on the boards too. It s Izzy s history, the official version, the story of record I notice she even refers to herself in the third person. It s my history, and not my history. 

Letterpress was printed at the Janus Press, Vermont, and the seven collagraphs printed at the Central School of Art, London, by Susan Johanknecht in an edition of forty copies"— Colophon... 

Besides having to flow from ducts and to split efficiently between rollers, a letterpress ink also has to wet quickly all the surfaces with which it comes into contact. On the press these may be various metals, rubbers, and plastics, while the substrate can be any one of a wide variety of materials. For a liquid to wet a surface it must have a lower surface tension than the substrate. The surface tension of a liquid is related to the contact angle that the liquid makes with the substrate. The contact angle is defined as nil for complete wetting and greater than 90° for increasing non-wetting tendencies. 

The term "electrostatic technique" tends to be usually associated in many minds with Leyden jars, high voltages and corona wires. There were indeed attempts in the late 1930 s and 1940 s to transfer paste type inks — mainly letterpress -across a gap by means of high voltages, air ionization and ion bombardment. The objective was to eliminate pressure and to permit the use of light weight presses. None of these schemes have found commercial applications. 

Letterpress and lithographic inks can be formulated from these thermally-catalyzed vehicles. Their main advantage is that they can be cured with the present flame or hot-air dryers, to give carbon dioxide and water plus small amounts of alcohols and formaldehyde. Moreover, the properties of these inks films are very good, particularly their reds-tance to scuffing, abrasion, or scratchiig. In addition, they handle well on the press distribtion system or on the printing plate, and their shelf life is adequate (3-6 months). 

Debossing—the same as letterpress except that no ink is involved and the characters are pressed quite hard into the substrate. Used occasionally for paper, but more normally for blister and strip packs. This method is likely to generate complaints, due to the difficulty of reading it clearly. 

Originally known as the aniline process, due to the use of water based aniline inks on paper (see Figures 16.5 and 16.6). Flexographic is a rotary letterpress process employing cylinder plates made from rubber, nitrile rubber, or special polymers. Excessive pressing may lead to squeeze-out, hence limitations to coarse half tones on certain equipment. 

The term has more than one interpretation, as some dry offset work is performed on conventional offset-litho presses (minus damping) using shallow relief plates. Alternatively, there are special machines for printing round or cylindrical items, i.e. plastic bottles, collapsible tubes, rigid tubes (seamless) (see Figures 16.7 and 16.8). These are normally two or four colour machines, using letterpress plates. Some six colour units are also used. 

Better print fidelity and sharper images attained on offset (both sheet and web fed), letterpress, and rotogravure printing presses... 

Wallis FG, Cannon RV (1969) Letterpress platemaking. Pergamon Press, Oxford, p 11... 

Letterpress printing The process used for paper is adapted to plastics by the use of special inks and transfer rolls, and possibly a modification of press speed. Flexible printing plates are usually employed, made of vinyl or rubber. It is the oldest method of printing flat plastic substrates and uses a press for rehef printing ffom metal type or raised surfaces formed ffom wood, metal, or linoleum. Leach RH, Pierce RJ, Hickman EP, Mackenzie MJ, Smith HG (eds) (1993) Printing ink manual, 5th edn. Blueprint, New York. 

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