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Alois
Senefelder of Munich discovered the basic principle
of Lithography, priting on stone, around 1798. Working
with a highly porous stone, Senefelder sketched
his design with a greasy substance, which was absorbed
by the stone. He then wetted the entire surface
with a mixture of gum Arabic and water (fountain
solution). Only the stone areas absorbed the solution;
the design area repelled it. Rolling on an ink made
of soap, wax, oil and lampblack, this greasy substance
coated the design but did not spread over the moist
blank area. A clean impression of the design was
made when a sheet of paper was pressed against the
surface of the stone.
Artists
soon used this new process to make reproductions
of the works of old masters and, in time, recognized
it as a valuable medium for their own original works.
Lithography received its biggest boost during the
mid 1900's when new recognition and popularity encouraged
printers to find more practical and faster methods
of printing illustrations.
The first
steam litho press was invented in France in 1850
and introduced in the U.S. by R. Hoe in 1868. Lithographic
stones were used for the image and a blanket-covered
cylinder received the image from the plate and transformed
it to the substrate. Direct rotary presses for lithography
using zinc and aluminum metal plates were introduced
in the 1890's. The first offset press was developed
in 1906 by Ira A. Rubel (a paper manufacturer) by
accident. An impression was unintentionally printed
from a press cylinder directly onto the rubber blanket
of the impression cylinder. Immediately afterward,
when a sheet of paper was run through the press,
a sharp image was printed on it from the impression
which had been offset on the rubber blanket. A.
F. Harris had noticed a similar effect. He then
developed an offset press for the Harris Automatic
Press Company in the same year, 1906.
The offset
process came to be the most popular form of printing
during the 1950's as plates, inks, paper, etc. improved.
By the late 1950's, offset printing dominated all
other printing pro cesses because it provided sharp
clean images. While the offset printing process
gave sharper, cleaner reproductions over letterpress,
it was also less expensive in comparison to gravure.
Today, the majority of printing (over 50%), in cluding
newspapers, is done by the offset process.
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