Топик По Английскому Языку (Воронов Р. И.) / Offset printing

Offset printing.
Litography is a method of printing using a planographic plate on which image and non-image areas are on the
same plane and the difference is defined by chemical properties. The basic principle of lithography, which
means literally "writing on stone", is actually based on the principle that grease, or oil, and water do not
mix. It was discovered by Alois Senefelder of Munich about 1798.
Offset printing is a printing mathod when the inked image is transferred to the substrate with the help of
the second cylinder coated with rubber ("offset") blanket.
Plate systems are the major printing processesi offset, lithography, letterpress, flexography, gravure and
screen printing which are used to print quantities of reproductions for the newspaper, commercial, magazine,
catalog, book, packaging, label and other large printing markets.
Offset lithography - this is the major plate printing process. It uses thin metal plates with the image and
non-image areas on the same plane, it uses the offset principle in which ink is offset from the plate
to rubber blanket on an intermadiate cylinder, and from the blanket to the paper on an impression cylinder.
A main advantage of the offset principle is that the resilient rubber blanket produces a clearer impression
on a wide variety of paper surfaces and other materials with both rough and smooth textures. Offset-printing
produces smooth print without embossing, an ink ring or serrated edges. Offset presses have three printing
cylinders (plate, blanket and impression). as well as inking and dampening systems. On most offset presses,
as the plate cylinder rotates, the plate comes in contact with the dampening rollers first, and then the
inking rollers. The dampeners wet the plate so the non-printing areas repel ink. The inked image is then
transferred to the rubber blanket, and paper or other substrate is printed as it passes between the blanket
and impression cylinders.