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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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