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December 13, 2002
A: FROM MENTOR JOAN LUSK IN
RI
This site gives an interesting history of papermaking, with
some explanation of the techniques: http://www.cbbag.ca/Papermaking.html
You'll see that not all paper is made from trees - lots
of other fibers have been used and are still used. At http://www.tsha.utexas.edu/handbook/online/articles/view/PP/drp1.html
I learned that in Texas ..."attempts were made over the
next several decades [from 1863] to produce paper from rags,
cornhusks, hemp, cotton and cotton linters, spanish broom,
silkweed, flax, cane bagasse, and any other fibrous material
that was available. None of the early attempts was successful,
however, until 1893, when John G. Fleming purchased a bankrupt
mill in the Oak Cliff suburb of Dallas. The Fleming mill prospered,
and its output grew from about eight tons a week to more than
1,000 tons a week by 1943. In later years the pulp furnished
for the Fleming mill was made up of 80 percent waste paper
and 20 percent wood pulp. The mill chiefly produced cardboard,
egg cartons, wallpapers, and a variety of other building-grade
papers. " Using waste paper for 80% of the fiber rather
begs the question of how to make paper from scratch!
At the first site mentioned, I learned "By mid-[19th]-century,
it was discovered in Germany that wood pulp could be used
to make paper, but it took two more discoveries, soda-ash
and sulphite treatments, to make wood pulp practical. The
sulphite would be a bleach; I wonder what the soda ash (alkalai;
sodium hydroxide) was doing? Via http://www.cbbag.ca/links.html#mak
I found http://www.bluep.com/~stiffe/plant.html
and learned that the alkaline washing of the fibers removes
plant acids and lignin. "A way of telling if a particular
plant is suitable for papermaking is to bend the leaf and
if it bends without snapping it will probably be suitable."
These last two sites lead to lots of neat projects!
Oh, to return to the trees! In the late 1940's a paper mill
in
Corinth, New York, got its wook the old fashioned way: logs
were
floated down the Hudson and caught by a floating chain of
logs across
the river. Some of the log washed up on shore and never became
paper.
My grandparents had a cabin on the river above the mill, and
we
grandchildren collected the stray logs to use as make-believe
horses
when swimming and playing in the water. In the 1950's the
paper
company switched to carrying the logs from the forests by
truck - no
more losses along the river. No free transport, either; and
no
romantic lumberjacks leaping from log to log in the river.
I never
actually saw the massive movement of logs, or any lumberjacks
-
school was in session during the early spring floods.
And to return to the sulphite! The stench of a papermill is
unforgettable and unmistakable - sulfur oxides in the air
can be
smelled 40 miles from papermills I have known, for example
the one in
Woodland, Maine. I don't remember any such stink from the
mill in
Corinth - maybe it didn't make white paper but unbleached,
brownish
paper?
A definition of "Kraft paper" from the Oxford English
Dictionary: A
strong smooth brown paper made from unbleached soda pulp.
Also
attrib. In full, kraft paper, kraft brown. And a brief history
of
the use of the term "kraft" indicates that sulfite
is involved... so
bleaching may be optional or a matter of degree:
1907 G. CLAPPERTON Pract. Paper-Making (ed. 2) 37 'Kraft'
brown
papers. Ibid., No Kraft yet produced in this country combines
the
crispness and elasticity which form so distinctive a feature
of the
Kraft papers produced by the best Scandinavian mills. 1914
E. A. DAWE
Paper 56 Kraft browns may be described as glazed browns, as
they are
sometimes finished with a glazed surface both sides. A special
kind
of pulp is used for krafts. 1920 Glasgow Herald 12 June 5
In the case
of sulphite and kraft processes the pulp is prepared by cooking
chips
of wood under pressure with different liquor solutions. 1930
Economist 8 Feb. 303/1 The market for kraft paper must be
regarded as
declining, but the Swedish newsprint mills are well supplied
with
orders. 1959 Gloss. Packaging Terms (B.S.I.) 67 Kraft liner,
a kraft
paper used as the outer or inner facing in the manufacture
of solid
and corrugated fibreboard, and in the manufacture of fibreboard
drums
and tubes. 1968 Economist 3 Feb. 63/2 Swedish pulps are mainly
for
kraft, including sack paper, and newsprint. 1969 T. C. THORSTENSEN
Pract. Leather Technol. ix. 143 In the manufacture of paper,
lignin
of the logs of the wood chips is released by cooking the chips
with
bisulfite in accordance with the Kraft process.
This is probably more than you wanted ! I got carried away
- like on
a log in a river.
December 12, 2002
A: FROM MENTOR MOLLY WILLIAMS
IN MI
Very briefly, the trees are converted to wood chips. The chips
are
put in a digester to separate the wood fibers. Then the fibers
(in
a water slurry) are transferred to a belt that goes around
a heated
drum to squeeze out the water and dry the sheet. For a bit
more
detail, go to the website of TAPPI, the professional organization
for pulp and paper scientists and engineers. They have a section
called "Paper University" for teachers and students.
Its website is
at: http://www.tappi.org/paperu/
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