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Paper is made by forming a felted mat of intertwining
fibers. This is done by passing a liquid suspension
of the fibers through a screen. When the water drains
away, the sheet is removed from the screen and allowed
to dry. Because the fibers are mainly cellulose
(the basic structural component of plant cell walls),
their interaction with water and their adherence to
one another create the strength and flexibility that
are characteristic of paper.
The first paper was made from macerated tree bark, plants,
and grass by the Chinese in A.D. 105, and sizing
(filling the paper surface to reduce the spread of ink)
had been developed in China by A.D. 700. The art of
papermaking traveled from China to Korea and Japan and
then to the Arab world, where rags were first used as
the raw material for the fibers.
When papermaking spread to Europe, the beginnings of
mechanization appeared with the first use of the stamper,
a device for more speedily macerating the rag into pulp.
By 1495 papermaking was practiced throughout Europe.
Gelatin size was first used in 1337, produced as animal
glue from hides, horns, and hooves. The
finished paper was dipped into the hot gelatin
solution to impart a smooth, stable finish designed
to both strengthen the paper and make surface pigments
and inks less liable to spread. The mechanization of
paper production in the early 19th century led to a
wide variety of paper forms, especially after the introduction
of mechanical wood pulp.
Identification
It is comparatively easy to distinguish paper from other
materials, but very difficult to identify specific types
of paper. For modern printed papers, the date of publication
is usually the best guide to the type of paper. But
there are many variations, especially after 1820, when
various fibers were being tested (from straw to esparto
grass) and different combinations of bleaches and chemical
paper sizing
agents used. These tend to complicate identification,
so that accurate identification is possible only through
chemical and fiber analysis.
Machine-made paper differs from handmade paper in several
ways, but most noticeably in the alignment of the fibers.
In handmade paper the action of dipping a mold
or su (Japanese) in the liquid suspension of water and
fibers and the shaking and draining of the water from
the screen cause the fibers to intertwine randomly,
adding to the paper's strength. By contrast, machine-made
paper is made on a continuous roll, and the rotary action
of the machine causes the fibers to be aligned in one
direction, making the paper somewhat weaker along the
"grain,"
or machine
direction. This grain is also present
in other paper products, such as board and folder stock.
Paper folded against the grain can pucker and form uneven
creases, and paper moistened with adhesive
will stretch much more across the grain than along it.
To determine grain direction in supplies, the paper
can be flexed in both directions; the grain direction
will offer less resistance. Another simple test can
be performed by tearing the paper in both directions,
as paper will always tear much more easily along the
grain.
Because of the alarming rate of degradation of modern
paper, a great deal of effort has gone into developing
chemically stable papers, based mainly on alkaline buffered
types. In recent years most Western countries have embraced
alkaline paper production. Because paper manufacturing
involving the old acid processes is known to pollute
waterways, the atmosphere, and the soil, government
regulations have pushed the industry to develop cleaner,
less polluting processes.
Thus much of the paper now produced in industrialized
countries is fortuitously nonacidic and alkaline. But
cheap ground wood paper is still manufactured for newsprint
and other impermanent uses. Such paper deteriorates
rapidly and has led to serious "brittle paper"
problems in libraries throughout the world. These problems
are especially severe in developing countries, where
much of the book paper production is acidic and the
climate is unfavorable.
Condition Concerns
Paper is strongly affected by the environment. It is
easily damaged by high humidity and temperatures, which
hasten its chemical deterioration. Ground wood pulp
paper deteriorates especially rapidly because of the
chemicals it contains—principally acids and lignin—and
soon becomes brittle. The widespread use of ground wood
pulp paper, with its short, weak fibers and high acidity,
causes serious problems for libraries and archives having
to preserve materials that rapidly become brittle and
unusable. Paper made from chemical wood pulp or even
from rag can also deteriorate because of the use of
harmful bleaches and sizing
materials such as alum-rosin
combinations. Because much of the world's book paper
after 1860 was produced from ground wood, all libraries
and archives face a major crisis of preservation.
• Diagnostic Tests
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