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TECHNICAL NOTE NUMBER 212
UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE
FOREST PRODUCTS LABORATORY
MADISON 5. WISCONSIN REVISED December 1953
AMERICAN WOODS FOR PAPERMAKING
The paper industry ranks sixth among prime manufacturing industries
from the standpoint of value of products and employs more than 420, 000
production workers. More than nine-tenths of the paper is made from
wood pulp. About 14percent of the total volume of wood harvested cur-
rently from American forests is used for the production of wood pulp.
Paper, as one of the indispensable commodities, has created a new de-
pendence on the forests and has increased their importance.
The consumption of pulpwood in the United States in 1952 was nearly
26. 5 million cords. Spruce, balsam fir, pine, and hemlock have long
been the principal pulping woods. They and 1 or 2 other less-used soft-
woods now comprise about 86 percent of the pulpwood used. More than
half of the softwoods used are the southern pines. The remaining 14
percent are hardwood species. About 20 species are included in the
hardwoods and miscellaneous softwoods. Experiments at the Forest
Products Laboratory indicate that many other woods can be used. Re-
ports of results of experiments on a number of them can be obtained
from the Laboratory.
As indicated above, the principal woodslus te
paper may be broadly classified as to botanical characteris1tic- p-
ing qualities as either softwoods or hardwoods. '" -_
Softwoods (Cou ers) D-E
J S_ --- OSJTORy
All spruces are suitable for pulping by any of the processes, a
make high-quality pulp except Sitka spruce, which yields a rather coarse-
Western hemlock is similar to the spruces in pulping quality, although
in the groundwood process it requires a little more power than spruce
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to produce pulp of the same quality. Eastern hemlock is not so suitable
as western hemlock for groundwood. Though chemical pulps made from
eastern hemlock are darker, require more bleach, and are weaker than
spruce pulps, this wood is used in fairly large amounts.
All pines are readily reduced with the alkaline processes (sulfate and
soda), and the pulps can be bleached satisfactorily under proper condi-
tions. The young, fast-growth southern yellow pines and lodgepole,
ponderosa, sugar, eastern white, and jack pines are suitable for ground-
wood pulps. However, the groundwood pulps obtained from pines cause
more orless trouble inpapermaking because of their pitch content. For
making light-colored, unbleached groundwood pulp, the pine must be
relatively free of heartwood.
The heartwood of pine is difficult to pulp by the sulfite process. With
modifications of the standard sulfite process, shortleaf, longleaf, lob-
lolly, slash, jack, lodgepole, red, pond, sand, and Virginia pines can
be made into fair-quality pulps for papermaking. However, the present
production of pine sulfite pulp is mostly used for making rayon.
All true firs are as readily pulped as spruce by any process and, with
the exception of red fir, are comparable in quality. Red fir yields a
rather dark mechanical pulp, and the sulfite and sulfate pulps made from
it are more difficult to bleach than those of spruce.
Baldcypress, Douglas-fir, the larches (tamarack), and the redcedars
are not suitable for the generally acceptable grades of groundwood pulp.
Douglas-fir, pretreated with steam or hot dilute alkali, can be ground
for pulp suitable for shipping container boards. These woods are rela-
tively difficult to pulp by the sulfite process, but with modifications the
process may be used with some of the species to produce pulps of ac-
ceptable quality. All may be reduced by alkaline processes. A consid-
erable amount of Douglas-fir sawmill waste is pulped by the sulfate proc-
ess. The strength characteristics of the pulps vary widely with the spe-
cies. For example, Douglas-fir pulp excels in certain properties while
western redcedar pulp is superior in others. The yield of pulp from
redcedar is relatively low.
The white-cedars are readily and fairly acceptably pulped by all proc-
esses. The yields, in comparison with other woods, are normal on a
weight basis, but because of relatively lower density, they are lower on
a cord basis.
Hardwoods (Broadleaf Trees)
Because of their similar pulping characteristics the pulp industry has
classified as "poplars" a number of hardwood species, including some
that botanically do not belong to the poplar family. Included in the group
are such true poplars as aspen, cottonwood, and balsam poplar, as well
as yellow-poplar, which is not a true poplar. Together, these species
constitute an important group of hardwoods used for pulp and paper manu-
facture. They are among the softer and lower density woods of the
hardwood species. They can be pulped by chemical, semichemical,
and groundwood processes by which they yield short-fibered pulps rela-
tively low in strength but suitable for many uses. The bleached chemi-
cal pulps, which possess certain quality advantages, are used in print-
ing and wrapping papers of higher grades and in specialty boards; and
the unbleached pulps are used in the cheaper printing and wrapping pa-
pers. The unbleached semichemical pulps can be used in wrapping and
newsprint paper, container boards, and insulating board. The ground-
wood pulps are used in book and other printing papers and in insulating
A common regional grouping classes sweetgum, the tupelos, red maple,
and elm as "soft" hardwoods for pulping purposes, although actually
they are harder than most of the woods in the "poplar" group. These
woods, plus beech, the birches and other varieties of maple, constitute
another large group of hardwoods yielding pulp with similar qualities.
All can be pulped by the chemical and semichemical processes, and the
pulps can be used for about the same purposes as those described above
for the "poplars." The groundwood pulps, though short-fibered and low
in strength, have value as filler stocks. The quality of the hardwood
groundwood can often be improved by chemically treating the sticks of
wood before grinding (chemigroundwood). Experimental work shows
that most of the woods in this group are adapted to the manufacture of
newsprint, book, toweling, and specialty papers, structural corrugating
board, hardboard, and purified cellulose for rayon manufacture.
In recent years, oak, once regarded as one of the poorest of pulping
woods, has been increasing in use and it now can be considered as an
important pulpwood. It is pulped by the soda, sulfate, and semichemi-
cal processes. The pulps find use in corrugating board and, after bleach-
ing, in printing papers.
UNIVERSITY OF FLORIDA
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Miscellaneous hardwoods used for paper making include principally ash,
chestnut (after tannin extraction), willow, and such less-used species
as alder, basswood, buckeye, butternut, catalpa, sugarberry, hickory,
locust, sassafras, and sycamore. All may be pulped by the soda, sul-
fate, and semichemical processes, most of them quite readily. The
lighter colored species are, in general, suitable for pulping by the
groundwood process. Their principal use is in book, magazine, and
cheap printing papers, and in corrugating board.
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