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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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