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Agric. Dcpf.



,



Issued April 12, 1907.

United States Department of Agriculture,

BUREAU OF CHEMISTRY Circular No. 34.

H. W. WILEY, Chief of Bureau.



EXAMINATION OF PAPERS.



INTRODUCTION.

For the past five years the Bureau of Chemistry has examined and
tested papers for the various Departments of the Government service,
and since the establishment of the Leather and Paper Laboratory it
has conducted investigations looking to the improvement of papers
and the utilization of farm products in their manufacture. The
Bureau has now the equipment and experience for conducting this work
on a large scale. The work so far done has shown that the papers
supplied for Government use too frequently fall below the specifica-
tions, lack durability, or in some way are not adapted to the purpose
for which they are intended. Valuable documents and scientific work
are recorded on papers which will rapidly deteriorate, thus rendering
the records useless. In this circular the methods and tests by which
the composition and value of paper are judged, examples illustrative
of the nature and interpretation of results, and brief outlines of the
characteristics which the more important classes of paper should
possess are given. Under statutory authority the Bureau makes tests
for any branch of the Federal service, wherever located, and will
also prepare, or assist in the preparation of, specifications which are
accurately descriptive of papers suited to any given purpose for any
branch of the Federal Government.

H. W. WILEY, Chief.

Approved :

JAMES WILSON, Secretary.

WASHINGTON, D. C., March 12, 1907.

27646 No. 3407



NATTTRE OF EXAMINATIONS MADE.

It is rarely necessary to make all the tests given in the following
list, as usually a few determinations will definitely show the value of
a sample for a given purpose. The nature and extent of the exami-
nation to be made can only be determined after the receipt of the
sample and of a full statement from the sender as to the object of the
examination that is, whether the value of the paper for a given pur-
pose is to be determined or its agreement or disagreement with
certain specifications is to be established.

At present the Leather and Paper Laboratory and the Micro-
chemical Laboratory are equipped to make the following physical
and chemical tests, classified as quantitative and qualitative:

QUANTITATIVE TESTS.

(1) Kind of fibers or stock, i. e., rag, esparto, spruce, ground wood, etc.

(2) Quantity of each kind of fibers or stock as per cent of rag, of spruce, of manila, etc.

(3) Average length of fiber.

(4) Weight per square meter or per ream.

(5) Thickness.

(6) Mean breaking weight.

(7) Mean breaking length.

(8) Loss of strength on folding.

(9) Mean stretch.

(10) Loss of stretch on folding.

(11) Transparency.

(12) Moisture and ash.

(13) Absorptive power of blotting paper.

QUALITATIVE CHEMICAL TESTS.

(1) Kind of sizing.

(2) Character of sizing.

(3) Kind of loading.

(4) Reaction.

(5) Bleaching agents.

(6) Chlorids and sulphates.

DESCRIPTION OF QUANTITATIVE TESTS.

Inasmuch as strength varies with the direction of the paper, tests
are made on strips cut both lengthwise and across the sheet. The
average of these tests gives the "mean" mentioned in the following
descriptions. All of the strength tests are based on an atmospheric

[Clr.84]

(8)



humidity of 65 per cent. When so desired strength is reported as
pounds per square inch, as determined by the standard American
testing machines, no correction being made in this case for variation
due to the moisture content of the air, as these machines give only
approximate results.

Unless otherwise requested, weight, thickness, and strength will be
expressed in the metric system.

(1) Kind of fibers or stock is determined by microscopical exami-
nation.

( 2) Quantity of each hind of fiber or stock is determined microscopic-
ally by a count of the fibers of the different materials present, and will
be expressed as "percentage by count" on the basis of the stock.
The Bureau is not yet ready to say how close this "percentage by
count" will agree with "percentage by weight/' but there is every
evidence that the error, if any, is not greater than obtains in the man-
ufacture of paper. The actual percentage of stock in a paper is
found by substracting the sum of the moisture, ash, sizing, and color-
ing from 100. As the determinations of sizing and color are not usually
made, the percentage of stock in all such cases can only be approxi-
mated.

(3) Average length of fibers is determined by microscopical meas-
urements and is expressed in millimeters.

(4) Weight is expressed in grains per square meter, or, when so
requested, in pounds per standard ream (24 by 36 inches).

(5) Thickness is expressed in millimeters, or, when so requested, in
thousandths of an inch.

(6) Mean breaking weight is the average weight in kilograms (1
kilogram = 2. 2046 pounds) required to break a strip of air-dry paper
15 mm wide and 180 mm long (0.5905 inch wide and 7.087 inches
long).

( 7) Mean breaking length is the mean length of moisture-free paper
expressed in meters (1 meter = 3. 2808 feet) which if suspended by
one end would break of its own weight.

(8) Loss of strength on folding is the decrease in strength caused .by
folding the paper a stated number of times under a uniform load of
7 kilograms, and is expressed as percentage on the basis of the mean
strength.

(9) Mean stretch is the elongation before breaking of the paper
when subjected to a pull sufficient to break it, and is expressed in
percentage.

(10) Loss of stretch on folding is the decrease in stretch due to fold-
ing the paper a stated number of times under a uniform load of 7
kilograms, and is expressed on the basis of the mean stretch.

[Cir. 84]



(11) Transparency is penetrability to light and is expressed as the
thickness of the paper through which a standard flame can be barely
distinguished.

(12) Moisture and ash are expressed as percentage on the basis of
the air-dry paper. Loading as distinguished from the normal min-
eral content of the paper and that added in the sizing and coloring
can not be definitely determined, but may be approximated for dif-
ferent kinds of paper. At present no corrections will be made for the
loss on ignition of water of constitution or hydration present in
China clay or other loadings, but the practice of the Bureau may be
changed at any time on this point.

(13) Absorptive power of blotting paper is shown by the height in
millimeters to which water will be drawn in ten minutes' time by a
strip of the paper 15 mm broad.

QUALITATIVE TESTS.

(1) Kind of sizing includes a statement as to whether rosin, animal
sizing, starch, or casein (as far as the latter can be differentiated from
animal sizing) has been employed.

(2) Character of sizing refers to the resistance of the sizing and for
the present is reported as " excellent," "good," "poor," and "very
poor."

(3) Kind of loading is reported as clay (kaolin), pearl hardening
(sulphate of lime), agalite, barytes (blanc fixe or permanent white),
silicate of soda, etc. (See also "12. Moisture and Ash.")

(4) The reaction of a paper may be alkaline, neutral, or acid, and
papers are reported as alkaline, neutral, faintly acid, and strongly
acid.

(5) Bleaching agents when present will be reported.

(6) Ohlorids and sulphates are reported at present as "trace,"
"low," "medium," and "high."

SOME TYPICAL PAPER TESTS.

The accompanying tables are illustrative of the two principal phases
of paper tests, i. e., those whose purpose is to determine whether or
not the papers delivered comply with the specifications, and those to
establish suitability for a given purpose. Some tests made in this
Bureau on papers delivered on contract to one of the Federal
Departments are reported in Table I, and show the salutary effect on
the quality of the goods which was produced by the institution of such
examinations.

[Cir.34l



TABLE I. -Composition of papers delivered on contract before and after institution of
tests, as compared with the specifications.



Sample.


Specifications (stock).


Composition of papers de-
livered before tests were
instituted.


Composition cf papers delivered
after tests were instituted.


Rag.


Wood pulp.


Rag.


Wood pulp.


Soda
process.


Sulphite
process.


Soda
process.


Sulphite
process.


No. 1 ...

No. 2


Per cent.
Rag, 100 ..


Per cent.
60.5
55.0

55.0

59.0
al8.0


Per cent.
26.5
30.0

28.0

28.0
640.0


Per cent.
13.0
15.0

16.0

13.0
42.0


Per cent.
100
100

75

74
All manila.


Per cent.


Per cent.


Rag, 100.


j


No. 3
No. 4....
No. 5....


Rag, 75; wood pulp by
sulphite process, 25 . .




25
26


Rag, 75; wood pulp by
sulphite process, 25




All manila






1





a Manila.



^Ground wood.



The total quantity of paper ordered on this contract was nearly
3,000,000 pounds. As the price of chemical wood paper is from 3 to
3 cents a pound, while rag paper is worth from 15 to 20 cents a pound,
and manila paper brings 5 cents a pound as compared with unbleached
chemical wood paper at 2f to 3 cents a pound, the saving to the Gov-
ernment in value of goods received by the institution of these tests
is readily seen to be enormous.

The tests reported in Table II represent an extended study of the
better class of writing papers as to their quality, strength, and relative
value for permanent records, and are illustrative of the examinations
made to determine suitability for a specific use. The kind of stock,
strength, sizing, and ash show the general quality and nature of the
paper, and on these determinations, together with the loss of strength
on folding, the reaction, and the quantity of salts present in the
paper, an opinion as to the relative durability of the papers submitted
may be formed.

TABLE II. Examinations of writing papers, with special view to their durability for

permanent records.



Serial numbers.



jjcterininations.


1128.


1129.


1130.


1131.


1132.


1204.


1205.


1206.


1207.


Stock:
Rag percent..


100


100


40


100


100


100


100


89


71


Wood pulp (sulphite process),






86










11


29


Wood pulp (soda process), per
cent






35














Weight (per sq. m.) grams. .
Thickness . millimeters


90

0.108


113
0.125


123
0.116


104
0.113


90
0.104


108
0.120


110
0.129


116

0.125


105
0.116


Breaking weight kilograms. .


8.0


9.3


7.9


9.4


7.6


10.5


10.3


9.5


6.1


Breaking length meters. .


6,344


5,843


4,564


6,466


5,942


6,792


6,651


5,764


1,998


Loss of strength on folding . .percent. .
Stretch do .


9
6.5


10
4.7


66
3.1


24
5.5


19
5.2


22
5.6


21
4.9


33

4.1


38
2.6


Loss in stretch on folding do


15.0


35.5


90.3


15.1


33.2


47.9


43.5


65.7


68.5


Ash do....


0.73


0.72


0.69


0.60


0.81


0.56


0.67


0.94


3.75


Sizing


(a)


( a )


()


6 )


( 6 )


( 6 )


CO


( 6 )


( 6 )


Reaction .


(4


(d)


(4


c)


d


(d)


w


w


(<0


Chlorids


(e)


M


()


e)


(4


Trace.


Trace.


Trace.


Trace


Sulphates


w


14




e)

^ '


(e)


(e)


()


(e)


()























o Animal and rosin.

& Animal, rosin, and starch.

c Neutral.



d Faintly acid.
t Medium.



fClr.34]



In examining the results on these nine papers it will be seen that
all except Nos. 1130, 1206, and 1207 are satisfactory as to the kind
of stock which they contain. In breaking length the same three
papers are lower than the others and show a greater loss of strength
under the folding test. Papers Nos. 1130 and 1207 are below the
standard in stretch, which for this class of papers should be at least
4 per cent. The three papers first mentioned also show the greatest
decrease in stretch in the folding test. In ash all of the samples are
satisfactorily low except No. 1207. The sizing of all is good, although
it would be better to omit the starch from Nos. 1131 to 1207, inclu-
sive. In reaction Nos. 1128, 1130 and 1131 are neutral, while all of
the others are faintly acid, which is undesirable. All of the samples
contain more sulphates than should be found in the best ledger
paper, and the same is true of chlorids for Nos. 1128 to 1132, inclu-
sive. Considering all the evidence, papers Nos. 1130, 1206, and 1207
would be rejected on stock, strength, and folding; Nos. 1130 and
1207 also on stretch, and No. 1207 on ash as well. The other papers
are all good, with the advantage in favor of No. 1128 on account of
its neutral reaction and small loss of strength and stretch on folding.

CHARACTERISTICS OF PAPERS FOR VARIOUS PURPOSES.

The selection of suitable papers for specific purposes is not always
an easy matter, and the following broad statements as to the char-
acteristics that different papers should have may be of service to
purchasers in preparing specifications; more detailed specifications
could be suggested for any particular case.

The value of a paper may be considered from two points of view-
that of quality and that of utility. In the former case the question
of cost is considered but little, the object being to secure an article
of the finest kind and most pleasing appearance. Such papers are
used for special purposes, for example, fancy writings, editions de
luxe, etc., and constitute but a small part of the papers made. Con-
sidering the utility of a paper, it should have the special characteris-
tics which make it suitable for a specific purpose, the finish, texture,
and stock being no better than the work to be performed demands.

RECORD PAPERS.

The papers used for recording deeds, for court records, vouchers,
receipts, ledgers, and all Federal, State, and county records which
are preserved for many years and subject to much handling, should
be strong and uniform, and to this end should be of the best rags
and manufactured by the best processes, being well washed to remove
bleaching agents and soluble salts. Such a paper should not be over
bleached; should be well but not over sized, using animal sizing and

[Cir.34]



8

a minimum quantity of rosin to insure good erasures; it should be
neutral, or nearly so; should not be loaded; should be loft or pole
dried rather than machine dried, and should have a smooth, even
surface.

BOOK PAPERS.

For publications of permanent value book papers should be of the
same general character as record papers. The sizing should be of
rosin alone. When loading is used it should not exceed 10 per cent. *
For less valuable books papers of lower grade containing, in addition
to rag stock, chemical wood pulp, esparto, etc., maybe used and less
care exercised in their making. For books and papers of transitory
value rag stock need not be used, second-class stock, such as chem-
ical wood pulp, esparto, etc., serving every purpose. Overloaded
papers should not be used for any class of work, as they are needlessly
heavy and much weaker than the same paper unloaded. Loading
makes a paper more opaque and better suited to the use of certain
inks ; it also serves as a substitute for beating, in that it hides imper-
fections in a poorly made sheet. For books containing a large number
of pages a thin paper, provided it is sufficiently opaque, should be
used, in order to secure a volume of good proportions. For coated
papers the same general specifications hold, except that more loading
is permissible.

WRITING PAPERS.

The best grades of writing papers used in correspondence which
partakes of the nature of permanent records should be strong, uni-
form, well-made rag papers not loaded and quite similar to record
papers. A cheaper paper may be used for less permanent corre-
spondence, being of poorer quality as to stock, texture, etc.

ENVELOPE PAPERS.

As envelopes are but short lived they need not be of the strong
rag papers described above. It is sufficient that the envelope have
a good writing surface, be opaque, and strong enough to carry its
contents safely to their destination and appear well when delivered.
Any stock and character of paper of the desired color which will
fulfill these requirements will serve the purpose. For instance, a
well-made paper containing 50 per cent of rag and 50 per cent of sul-
phite stock is satisfactory for the ordinary correspondence envelope.
Very strong papers are of course necessary for international use or
the transmission of large and heavy documents. Envelope papers
should not be loaded, should be well sized, and have an even, firm
surface.

[Cir.34]



9

BLOTTING PAPERS.

The value of blotting papers is determined by their absorptive
power. They should be rather loosely made and the best grades
should not be loaded.

WRAPPING AND BAG PAPER.

The important qualities for wrapping and bag paper are strength
and pliability, which should not be sacrificed for other character-
istics. Jute and manila are recognized as giving a paper of this kind,
but any stock which will insure the properties named may be used.
A paper known as " Kraft brown," made by a special method of
treating wood, is now coming into prominence for these purposes.
It apparently is much stronger than the ordinary papers heretofore
made from chemical or mechanical wood pulps and promises to serve
as a substitute for jute and manila papers in certain cases.

Papers used for wrapping polished metals should be free from acids.
The more perfectly wrapping papers resist water the better, provided
that strength is not sacrificed in securing this quality.

DIRECTIONS FOR SECURING AND FORWARDING SAMPLES.

If possible, each sample for examination should consist of ten
sheets 12 by 12 inches, and each sheet should be taken from a dif-
ferent part of the lot of paper. The sheets must be shipped flat
and so packed as not to be broken or creased in transit.

Samples positively must not be folded or rolled. If it is impos-
sible to secure ten sheets of the desired size, smaller samples may
be taken, but the examination made may be limited by the quan-
tity and condition of the sample.

Each sample must be fully identified by numbers or other marks
and labeled with the name of the sender; name of manufacturer,
when obtainable; the class to which it belongs, as "ledger," "book,"
"writing," "blotting," etc.; the purpose for which it will be used;
the manufacturer's or dealer's claims as to quality, as "all rag,"
"half sulphite and half soda," etc.; weight and size per ream, and
cost per pound.

The sender should not fail to indicate the nature of the examina-
tion desired that is, whether compliance with specifications is to be
determined or suitability for a given purpose. If the former exam-
ination is desired, a copy of the specifications should be furnished,
and if the latter, the purpose for which the paper is to be used should
be stated.

[Clr.34]



10

Samples should be forwarded by mail or prepaid express, addressed
as follows, and the Bureau notified by letter of the shipment of the
samples :

BUREAU OF CHEMISTRY,

U. S. Department of Agriculture,

Washington, D. G.
LEATHER AND PAPER LABORATORY.

Attention is called to the fact that examinations can not be made
for individuals, manufacturers, or dealers.

F. P. VEITCH,
Chief, Leather and Paper Laboratory.

lCir.34]

o



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