-----------+-------------+--------------+-----------+--------------------
| | | | Acres required for
| | | | sustained supply.
| | | |---------+----------
| | Raw material | Annual | |
Material. | Pulp yield. | required per | growth | For | For 1 ton
| | year. | per acre. | 25-ton | of fiber
| | | | mill. | per year.
-----------+-------------+--------------+-----------+---------+----------
Wood | Two cords | 15,000 cords | 0.37 cord | 40,500 | 5.4
| yield 1 ton | | (about | |
| of fiber. | | 0.55 ton).| |
| | | | |
Hemp hurds | One ton | 25,000 tons | 2.5 tons | 10,000 | 1.33
| yields 600 | | | |
| pounds | | | |
| of fiber. | | | |
-----------+-------------+--------------+-----------+---------+----------
The most important point derived from this calculation is in regard to
areas required for a sustained supply, which are in the ratio of 4 to 1.
Every tract of 10,000 acres which is devoted to hemp raising year by
year is equivalent to a sustained pulp-producing capacity of 40,500
acres of average pulp-wood lands. In other words, in order to secure
additional raw material for the production of 25 tons of fiber per day
there exists the possibility of utilizing the agricultural waste already
produced on 10,000 acres of hemp lands instead of securing, holding,
reforesting, and protecting 40,500 acres of pulp-wood land.
The annual growth per acre, although decidedly in favor of hurds, has
little bearing on the project, because the utilization of the hurds is
subordinate to the raising of hemp, and the paper manufacturer probably
could afford to use only hurds resulting from the hemp industry.
=PHYSICAL TESTS OF THE PAPERS PRODUCED.=
Samples of paper produced in the seven tests were submitted to the
Leather and Paper Laboratory of the Bureau of Chemistry. The report of
that bureau on its tests is given in Table III.
TABLE III.--_Report of the Leather and Paper Laboratory of the Bureau of
Chemistry on papers manufactured from hemp hurds._
-----------+-----+------+-------------------+----------+
| | | Weight of 500 | |
Laboratory | Run | | sheets. |Thickness,|
No. | No. | Ash. +---------+---------+ 1/10000. |
| | | | | |
| | |25 by 38.|25 by 40.| |
| | | | | |
-----------+-----+------+---------+---------+----------+
| |_Per | | | |
| | ct._ |_Pounds._|_Pounds._| |
31570 | 144 | 13.9 | 48 | 50-1/2 | 33 |
31571 | 143 | 14.5 | 49 | 51-1/2 | 35 |
31572 | 142 | 9.5 | 49-1/2 | 52 | 33 |
31573 | 141 | 10.9 | 48 | 50-1/2 | 38 |
31574 | 140 | 11.4 | 42 | 44 | 30 |[Transcriber's
31575 | 139 | 13.4 | 55 | 58 | 40 | note: Table III
31576 | 138 | 10.4 | 56 | 59 | 40 | continues below]
-----------+-----+------+---------+---------+----------+
-----------+--------------------------+----------+-------------------------
| Strength (Mullen). | | Folding endurance.
Laboratory | | Strength |
No. +--------+--------+--------+ factor +-------------+-----------
| | | |(25 by 40,| |
|Average.|Maximum.|Minimum.| 500). |Longitudinal.|Transverse.
| | | | | |
-----------+--------+--------+--------+----------+-------------+-----------
| | | | | |
| | | | | |
31570 | 15.0 | 17.0 | 11.0 | 0.30 | 5 | 3
31571 | 14.0 | 14.0 | 13.0 | .28 | 4 | 4
31572 | 19.0 | 20.0 | 19.0 | .37 | 8 | 6
31573 | 16.5 | 18.0 | 11.0 | .33 | 10 | 8
31574 | 14.5 | 16.0 | 13.0 | .33 | 7 | 6
31575 | 19.5 | 20.0 | 17.0 | .34 | 8 | 5
31576 | 20.0 | 20.0 | 19.0 | .34 | 23 | 15
-----------+--------+--------+--------+----------+-------------+-----------
There is no system of numerically recording the general appearance and
"look through" of a paper, but it can be stated that only papers Nos.
143 and 144 are satisfactory in these respects, the other samples being
more or less thickly specked with shives. The general character and
tests of these papers correspond very closely with No. 1 machine-finish
printing paper, according to the specifications of the United States
Government Printing Office, which call for a sheet not exceeding 0.0035
inch in thickness, strength not less than 12 points, free from
unbleached or ground wood pulp, and ash not over 10 per cent. The
strength factor of such papers is about 0.28. The ash should not be over
10 per cent for this grade of paper, but in spite of the larger amount
used the physical tests are sufficiently high. It is to be noted that
the physical tests of samples Nos. 138 to 142, inclusive, are higher
than in Nos. 143 and 144, in which 23 per cent of soda poplar was used,
which shows clearly that hemp-hurd stock imparts strength and folding
endurance to a greater extent than does soda-poplar stock. From these
preliminary tests it would be concluded, therefore, that hemp-hurd stock
acts similarly to soda-poplar stock, but will produce a somewhat harsher
and stronger sheet and one of higher folding endurance. Undoubtedly,
there is more dirt in the samples than would be tolerated by the trade,
but this was to be expected, since in this preliminary work the raw
material was sieved by hand screens instead of by automatic machines
which would sieve more thoroughly.
=CONCLUSIONS.=
There appears to be little doubt that under the present system of forest
use and consumption the present supply can not withstand the demands
placed upon it. By the time improved methods of forestry have
established an equilibrium between production and consumption, the price
of pulp wood may be such that a knowledge of other available raw
materials may be imperative.
Semicommercial paper-making tests were conducted, therefore, on hemp
hurds, in cooperation with a paper manufacturer. After several trials,
under conditions of treatment and manufacture which are regarded as
favorable in comparison with those used with pulp wood, paper was
produced which received very favorable comment both from investigators
and from the trade and which according to official tests would be
classed as a No. 1 machine-finish printing paper.