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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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