Paper Is Made
machine to make paper was developed in France
around 1798. Although papermaking machines have
been greatly improved and enlarged since then the
basic processes remain the same. A modern
papermaking machine may be several hundred feet
long and may turn out hundreds of tons of paper
in a single day.
The various steps in the
papermaking process are shown in the illustration
below. Continue on down the page for a
step-by-step explanation of the process.
Step 1: Gathering the
Raw Material Paper can be made from
almost any fibrous material. The Arabs used to
make it out of linen and flax and rags, or out of
various vegetable fibers. We still use all of
these things and many others -- hemp and jute,
cornstalk, straw, old rope, bamboo, and many
others -- but the main thing we use is wood. At
one time thousands of square miles of trees had
to be cut down in order to make just a few
hundred feet of paper, but modern plants
frequently use scraps left over from lumber mills
and the parts of trees that are too small to make
into lumber, as well as trees specially grown for
the paper mill.
Step 2: Cleaning the
Raw Material Whole trees must be cut
into managable lengths and then stripped of their
bark before the papermaking process can begin.
The debarking is typically done by a revolving
drum in which projecting blades cut away the bark
and leave a fairly smooth log. The logs must also
be washed down to remove loose dirt and foreign
objects. Lumber mill scraps can usually skip the
debarking process but must still be cleaned
before proceeding to the next step.
Step 3: Chipping
Once debarked and cleaned the logs/scraps are
sent to a huge machine that reduces them to
Step 4: Digesting
The wood chips are dumped into a huge cylinder
called a "digester," in which they are
soaked in a bath of chemicals -- mainly
bisulphite of lime -- and cooked under pressure
for about eight hours. All wood contains, along
with the cellulose that make paper, a great deal
of other material that will slowly decay; the
digesting process removes this other material,
leaving just the cellulose.
5: Beating and Churning The digested
mixture is passed to a machine that beats and
churns it. The mixture goes in with a consistency
much like that of cottage cheese and comes out as
a smooth milky liquid similar to that of thin
"Setting" of Fibers The
mixture then goes into the Jordan Engine, a huge
revolving tank with revolving blades that cut the
wood fibers into even lengths. It is at this
stage that various "fillers" -- such as
talc or china clay -- and/or "sizing
agents" are added. These fillers and sizers
are what give the finished paper its specific
color, strength, and fineness/roughness of
writing surface. The mixture is now ready to be
turned into what we recognize as paper.
7: Screening The now latex-consistency
pulp mixture passes through a strainer that takes
out any remaining lumps and is then sent to the
machine which will turn into paper. The pulp
mixture runs as a filmy sheet or "web"
upon a fast-moving belt of fine copper-wire mesh.
The belt carries it along, letting the water drip
out of it and also drawing the water out by
suction; and it shakes the pulp a bit from side
to side to settle the fibers firmly. Toward the
end of the trip on the wire belt the sheet may
pass under what is known as a "dandy
roll" where it receives a watermark.
Step 8: Blotting
From the "dandy roll" the pre-paper
product passes through a pair of felt rollers
that "blot up" much of the leftover
Step 9: Squeezing The sheet
then passes through a series of steel rollers
that squeeze even more water out, as well as help
stiffen the sheet.
Step 10: Drying The final set
of drying rollers are heated from the inside and
remove the last traces of moisture.
Step 11: Ironing The final
stage involves sending the long sheet through
what is known as a Calendar Stack. This stack of
rollers "irons" the sheet flat. The
more rolls there are in the stack, the smoother
the paper becomes. The finished paper is rolled
up and the process is complete.
Richards Topical Encyclopedia
New York: The Richards Company, Inc., 1961
Paper University www.tappi.org/paperu/welcome.htm
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