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Edward A Dawe.

Paper and its uses : a treatise for printers, stationers and others online

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be issued for a sample portfolio, and these folded to a
convenient size, each sheet marked with stock number or
description to prevent confusion. Reference to stock
lists will furnish price, quantity in stock, and other
necessary particulars.

A separate account should be kept of off-cuts, which
accumulate rapidly. Some can be cut to useful sizes, and
it is frequently more economical to trim them at once
to the nearest regular size, to parcel them in reams, and
to mark the contents on the wrapper. A corresponding
entry should be made in the oddment book and issues
duly noted. All jobs worked on off-cuts should be
charged as though the ordinary stock for such jobs had
been used, and the charge sheet and invoice should
show that oddments have been issued, or it may be
difficult to explain change of paper or price when
repeat orders are executed.



CHAPTER XVI
PAPER TESTING 1

A FULL scheme for the analysis and testing of papers
will include the following : Checking the weight of
the ream and sheet ; the thickness of the ream and
sheet ; examination of the physical and chemical
constituents fibre, sizing, loading, and colouring
matter ; testing the tensile strength and elasticity,
the resistance to folding or crumpling, and micro-
scopical examination of the fibres. It is not necessary
to carry out all these tests on every paper, but it is
well to be prepared, if required, to compare two
samples, using appropriate tests.

Weight. The weight of the ream is checked on
the scales, and variation should not exceed 4 to 8 per
cent, above or below the nominal weight. (See various
kinds of papers under " Variations in Weight," on
page 136.) A sheet of paper is weighed on a balance
which gives a direct reading for a ream of 480, 500,
or 5 1 6 sheets. The demy scale is a very useful little
balance. A metal plate is supplied with the scale, a
piece of paper is cut exactly to the size of the plate

1 It is more convenient to use the metric system of weights and
measures, as small quantities and dimensions are dealt with, and
the decimal method is easier to use. Metric equivalents are :

i millimetre (mm.) ='03901. I in. =25*4 mm.

i gramme (grm.) ='03502. i oz. =28*35 grm.

i cubic centimetre (c.c.) = 'O35 fl. oz. i fl. oz. =28*40 c.c.

9 6



PAPER TESTING



97



with a sharp knife. The piece is placed on the end of
a hook, and the scale, marked for reams of 480, 500,
and 5 1 6 sheets, gives the weight of a ream of demy of
the substance of the pattern, and by reference to
tables the equivalent
weight in any other
size can be found.

Size. The size
of the paper is
checked, and the
papermaker guaran-
tees to be within one-
half per cent, of the
measurement ordered.
The paper is tested
at the same time for
squareness.

Thickness of
Sheet. For testing
the thickness of the

sheet a micrometer is used. The screw micrometer
is not so exact on a yielding material like paper as
is the spring micrometer, which gives the reading on a
dial in thousandths of an inch. Machines are obtain-
able in pocket or stand form, giving measurements as
close as ^oV <j of an inch. The micrometer serves to check
the thickness of supplies of paper or cards, and to
indicate the bulk of a volume consisting of a certain
number of pages or leaves, enabling covers for books
to be prepared before the printing is completed.

Tensile Strength and Elasticity. These tests
may be carried out on various machines. The method
adopted is to cut strips of a standard width, clamp in
the machine clips which are a definite distance apart,
and to place the strip to be tested under tension by




FIG. 14. Paper Scale.



98 PAPER AND ITS USES

turning the handle of the machine, until breakage of
the paper takes place. The machine registers the
strain put upon the strip, and also the elongation which
the strip sustained before fracture. The Marshall
machine takes strips of various lengths and widths,
and registers the tension on a hydraulic pressure gauge,
the stretch being measured exactly and calculated on
the length of the strip used. Leunig's testing machine




FIG. 15. Marshall's Paper-Testing Machine.

A, Cylinder in which compression of liquid is produced by turning wheel B.
C, Registering dial. D, Clips for securing slips.

E, Clips for registering stretch. F, Cutting knife.

G, Cutting gauge.

registers breaking strain and stretch on two scales.
The strip, f inch wide, is clamped between twoclips
7 inches apart, and, by turning a handle, the strip
under tension raises a weight at the end of a lever.
The strain exerted by the weight is indicated on a
scale marked in quarter-pound divisions. The stretch
is registered at the same time by a pointer actuated
by a separate rack. The stretch scale and pointer are



PAPER TESTING 99

kept in unison with the strength lever, and the elonga-
tion at the time of fracture is registered. This
machine, although expensive, is acknowledged to be
the best for high-class papers where the narrow strip




FlG. 1 6. Leunig Paper-Testing Machine.

can be used. The Carrington machine for coarse
papers takes a strip 2 inches wide and 7 inches be-
tween the clips, the strain is exerted by a weighted
lever, and the reading is in pounds.



100 PAPER AND ITS USES

Bursting Strain. For quick comparative tests
there are a number of machines to choose from. The
list comprises the Mullen, Southworth, Woolley,
Ashcroft, Eddy, and Rehse machines. Testing on
the Mullen machine is by hydraulic pressure which is
communicated through the medium of glycerine to a
rubber diaphragm. The paper is clamped over the
diaphragm ; the handle of the machine is turned, pressure
being exerted until the paper bursts ; the reading is
given on the gauge in pounds per square inch. The
Southworth gives a similar indication, but the fluid is
oil, and a steel plunger punctures the paper. The
Woolley machine is actuated by a spring and gives a
comparative figure. The Ashcroft is a very compact
machine, a very small plunger piercing the paper, the
dial reading indicating the bursting strain in pounds
per square inch. Two machines of this pattern are
made, one for thin papers, and the other for papers of
ordinary and thick substances. The Eddy machines
are screw machines, also made for thick and thin
papers, and the result is given in similar terms to other
machines. The Rehse machine is a cylindrical machine;
pressure is exerted by a spring, and the pressure in
pounds is registered on one scale, and from figures
given on another scale the stretch can be calculated.

These machines are exceedingly useful for rapid
comparisons of papers, the tests being made at the
same time. Slight variations in results can be obtained
by turning the handles of the machines at varying
speeds, but if a uniform rate is maintained, scarcely any
other precaution is necessary in their use.

Opacity. While it is possible to obtain apparatus
for exact determination of the degree of opacity in
paper, comparison can readily be made in a simple
manner. A printed page is covered by pieces of the



PAPER TESTING



101



papers to be compared brought edge to edge over
the printed matter, and the comparative degree of opa-
city observed by the ease, or otherwise, with which the
lettering can be seen through the papers.

Surface or Finish. The degree of polish which is
given to the paper may be compared by feeling with
the hand, and also by looking along the sheet. The
comparisons can be brought to a numerical basis, but
apparatus which would seldom be used is required for
that purpose.

Resistance to Wear. An ingenious machine is
made for testing the resistance which paper offers to
wear as exemplified by repeated folding. A narrow
strip is clamped at each end, kept under constant tension
by springs, and folded backwards and forwards until
breakage occurs. Some idea of the comparison can
be seen by taking the following results :

FOLDING MACHINE TESTS



i




Number of Folds before Breaking.




Equivalent






Description of Paper.


Weight in
Demy.


Strong


I
Weak Mean of Two






Direction.


Direction.


Directions.












Japanese vellum -


28


15,840


6,174


II,OO7


Manilla - - -


80


5,783


5,448


5,616


Loan hand-made


37


2,581


1,416


1,998


Ledger mould-made - 39


i,344


1,023 1,183


,, machine-made 39 i> 2 43


1,123 J , l8 3


Bank hand-made - 12 1,036


846 941


Typewriting machine-made 9 763


413 588


all -rag




Blue-laid machine-made, air- 29 510


394 452


dried




Blue-laid machine-made - j 28 94


86 ; 90


Printing paper - - - ! 17 15

1


9 12



The tests by the folding machine, being conducted
on a very narrow strip, are only moderately reliable.



102 PAPER AND ITS USES

To compare papers a more primitive method may be
employed. It has the virtue of simplicity, and yet it
gives a fair index to the amount of wear which the
paper will withstand. Take a piece of the paper to be
tested, about 6 inches square, roll it into a ball, then
spread it out flat ; repeat the performance, and notice
how many such treatments the paper stands before
perforation takes place. Papers which are very resistant,
such as all-rag papers and air-dried browns, will assume
a cloth-like appearance as they become softer, and it
will be a long time before perforation takes place.

Sizing. To test papers for efficiency of sizing write
rather heavily upon the surface with ordinary pen and
ink. Red ink is usually more penetrative than black,
so it is better to use a good black ink as a standard
test. As some papers, such as account book papers,
have to stand erasure, they should be tested for ink
bearing after abrasion of the surface.

To test for gelatine sizing cut up a small quantity
of paper and boil for a few minutes in a beaker
containing sufficient water to cover the paper. Pour
off into a test tube, cool, add a few drops of a 2 per
cent, solution of tannic acid. A flocculent precipitate
indicates that the paper has been sized with gelatine.
Heat the liquid, and the precipitate will coagulate and
cling to the sides of the test tube. A comparative test
is made by taking an equal quantity of each kind of
paper, boiling in similar quantities of water for the
same period, and adding the same amount of tannic
acid solution, and comparing the results.

Resin sizing is determined in a different manner.
A comparatively large quantity of paper is extracted
in a small quantity of liquid. Take a strip of paper,
about 8 inches by I inch, pleat it repeatedly until it
can be placed in a test tube, and cover it with rectified



PAPER TESTING IO3

spirit. Place the test tube in a beaker containing
water, and heat slowly. The spirit will boil before
the water reaches boiling point, and in a short time the
resin will be dissolved. As soon as the solution is
cool, pour it into a test tube half full of distilled water,
and the resin will appear as a ring, whitish in colour,
at the junction of the two liquids. If the test tube
is shaken up the opalescent appearance of the liquid
indicates the presence of resin.

Starch. A very weak solution of iodine in potassium
iodide is dropped on the paper with a glass rod, or a
strip of the paper is dipped into the solution. If a
very small quantity of starch is present in the paper
a blue reaction will take place, and the larger the
amount, the darker the coloration. Therefore in order
to form an opinion as to the quantity of starch used,
a very pale solution must be used, or the colour may
be too dark to enable one to make comparisons. An
aqueous extract of the paper may be treated with the
iodine solution, and if a comparative test is to be made,
it is necessary to work on each paper with identical
quantities of water for boiling, and iodine solution for
testing. A faint colour must not be taken as evidence
of added starch, as in rag pulp it is very difficult to
remove starch from the raw materials.

Colouring Matters The tests for colours should

be for the purpose of discovering whether they are
reasonably fast to light and when wetted. The first
can be tested by exposing the paper to a steady light
not sunlight for a period according to the time of
year. A photographic printing frame with a black
disc on plain glass is a convenient method of testing,
and if, after forty-eight hours in summer, and a pro-
portionately longer period at other times, the difference
between the exposed and protected areas is marked,



104 PAPER AND ITS USES

the paper must not be used where a permanent colour
is required. Some tints will bleach completely with
the treatment, and should be avoided as stock lines.
To test water-fastness a piece of paper is left in
warm water, or placed in cold water and heated slowly.
If the colour is soluble it will very soon tint the
water.

Coloured papers for pasting to book covers or
boxes should be tested by pasting down to the boards
intended for use. Some boards have a curious effect
on certain tinted papers, owing to the presence of
chemicals in the finished boards, and acidity or
alkalinity may render change of covering paper
necessary.

Absorbent Papers. Blotting paper may be tested
by the mounting, test. To carry this out, cut strips
from each direction of the paper length and width
6 inches long by I inch in width. Make a pencil
mark half an inch from the end, and immerse the strip
as far as the pencil mark in water or ink. The fluid
immediately commences to mount the strip, and the
speed at which this takes place is an indication of the
relative initial absorbency of papers tested by this
method. In practice, blotting paper must absorb im-
mediately, as the pressure usually applied will, if the
paper is not sufficiently absorbent, spread the ink.
For this reason the rising of the fluid should be marked
and checked in the first ten to sixty seconds, and when
several tests in each direction have been made, the
figures tabulated and the mean rate calculated. It
is convenient to measure in millimetres rather than in
fractions of an inch. Ink makes the better testing
fluid, as the way in which the blotting paper carries up
the colouring matter can be seen at once, and a paper
which is superior in this respect will usually be the



PAPER TESTING IO5

better paper. The zone test is an elaboration of the
ink test. A small quantity (i c.c. or '5 c.c.) is allowed
to fall a drop at a time upon the blotting paper, and
when the blot is dry, the area of the outer non-
absorbent zone, its proportion to the inner absorbent
zone, and its regularity will serve as an index to the
behaviour of the paper in use. Other factors in the
choice of blottings are the resistance to wear, absence
of fluff, and the resistance to surface dirt. A very rough
blotting paper may not be entirely satisfactory in those
respects, but, on the other hand, a very smooth paper
may be produced at the expense of absorbency.

Copying papers are tested in the copying press
with a document written with copy able ink, and the
efficiency of the paper judged either by comparison
with a standard sample, or merely by the clearness 'of
the resulting copy.

Duplicating papers may be tested by drawing a
fine pen charged with writing ink across the surface,
and immediately rubbing the ink to see if it smears.
Half-sized duplicating papers have the same method
applied^but should be allowed five to ten seconds after
writing. These methods are superseded by the use of
the duplicating machine, if available.

Mineral Matter Loading. A weighed quantity
of paper say I gm. is torn into small fragments,
placed in a porcelain crucible, previously weighed, and
subjected to the intense heat of a Bunsen burner until
the paper is consumed and the residue reduced to a
white ash, or in any case until all carbonaceous matter
is burnt off. See that any black deposit on the crucible
is burnt away. Cool the crucible, weigh it with its
contents, deduct the weight of the crucible, and the
weight, multiplied by 100, will give the percentage of
mineral matter present in the paper.



106 PAPER AND ITS USES

Weight of crucible 6-25 gm.

Weight of paper - - i - oo ,,

Weight of crucible and ash 6-365
Deduct weight of crucible 6*25
Weight of ash - '115x1 00=11-5 percent.

The ash, if not required for subsequent examination,
can be thrown away, the crucible wiped out and weighed
again to check the net weight of ash. It is usual to
calculate the whole of the ash as added mineral water,
although all fibrous materials have ash of some weight,
e.g.) cotton '12 per cent, esparto 3^ to 5 per cent. A
delicate balance with weights from 50 gm. to I mgm.
is advised for exact results.

Fibre Composition. It is necessary to exclude
mechanical wood from most papers, and its detection
is rendered easy by the use of certain solutions. A
solution is made up of I gm. of phloroglucine in
50 c.c. of rectified spirit with 25 c.c. of concentrated
hydrochloric acid added. If a drop of this solution
is placed on paper in which mechanical wood is present
an intensely red coloration will follow. The amount of
mechanical wood may be estimated by the depth of
colour, but this is very difficult, as may be proved by
comparing the results obtained on papers containing
40 and 70 per cent, of mechanical wood respectively.
Some aniline colours are altered in colour by the
acid of the solution, although the colour is not
the same as that given by mechanical wood, and it
appears and fades in a different manner. A solution
of 2 per cent, of aniline sulphate (i gm. in 50 c.c. of
water) will give a yellow coloration in the presence of
mechanical wood. As wood fibres, jute, and some other
fibres which have not been thoroughly cleaned, give
colour reactions as though mechanical wood were



PAPER TESTING IO?

present, the microscope should be used for con-
firmation.

Papers containing straw or esparto fibre are coloured
pink, pale or deep according to the quantity of these
fibres present, when heated in a weak solution of
aniline sulphate. Strips of paper treated at the same
time will afford comparative tests. Bamboo paper
gives a pink reaction in the heated aniline sulphate
solution, but some grasses, such as delta grass, are not
affected.

Microscopical Examination. Colour reactions re-
veal the presence of mechanical wood, straw, and esparto
in papers, but the reagents used do not reveal the
presence of chemical wood or rag fibres, nor do they
distinguish between cotton and linen fibres. In order
to obtain more exact conclusions the microscope is
employed. Although a powerful microscope is a
valuable possession, a moderate instrument is pre-
ferable ; a microscope equal to the " London," with a
combination of eye-pieces and objectives to give
magnifications of 59 to 270 diameters, will be found
excellent for the examination of fibres. A supply of
slips, 3 inches by I inch, and half an ounce of cover
glasses | inch diameter will be required.

The fibres in most cases are securely fastened with
the sizing materials, and to remove these the paper
is boiled in a weak solution of caustic soda. After
boiling, the paper is washed, and, with teasing needles,
little pieces of paper picked out and placed on a glass
slip. Or the paper is placed in a test tube with a little
water, the thumb placed over the mouth of the tube,
and by shaking violently the paper is soon reduced
to pulp. A very small portion of pulp is placed
on the slide, and superfluous moisture carefully re-
moved with filter paper. A stain makes the markings



108 PAPER AND ITS USES

on the fibres more easily seen, and if a suitable stain
is employed, some differentiation in colouring the
various fibres takes place.

A good standard solution is iodine in potassium
iodide, with an accessory acid solution :



IODINE SOLUTION.


ACCES


Iodine -
Potassium iodide
Water -


1-15 gm.
2-0
20 c.c.


Glycerine
Water -
Sulphuric



10 C.C.

5
- 15

A drop of the iodine solution is placed on the fibre
on the slide. After a minute or so it is blotted off, and
a drop of the accessory solution is added. The fibres
are separated with teasing needles (needles mounted in
wooden handles) until well distributed on the slide.
A cover glass is cleaned by rubbing with a piece of
wash leather, and dropped on the slide. The excess
of solution is carefully absorbed with the filter paper,
and the slide is ready for examination. A description
of each of the principal fibres is given, with the normal
dimensions of the unbeaten fibres and the coloration
given by the solutions specified. For general examina-
tion the lower powers of the microscope will be found
most useful, the higher magnifications being employed
for studying the markings and other characteristics of
the fibres. The dimensions given of cotton, linen, and
hemp fibres will not be met with in papers made from
those materials, as in beating the lengths are shortened,
and frequently the fibres are split longitudinally.
Tissues, copyings, and Bible papers show the greatest
reduction of the fibres.

Cotton. Fibre 30 to 40 mm. x 'O2 mm. Stained
violet-red to brown. The fibres are long flattened
tubes with large channel and numerous twists, blunt
ends, and some fibres have cross markings. For a
blotting the fibres are cut into short lengths, and the



PAPERMAKING FIBRES

Magnified 50 diameters








IJ



FIG. 17. Rag Fibres Unbeaten.
A, Linen. B, Cotton.



FIG. 1 8. Rag Fibres Beaten.



c









FIG. 19. Hemp.




PAPER TESTING 109

characteristics can be easily observed. The fibres are
reduced in diameter as well as in length by prolonged
beating for strong papers, the ends are frayed, and it is
not easy to identify the cotton in a finely-beaten rag
mixture (Figs. 17 and 18).

Linen. Fibre 30 to 40 mm. X -025 mm. Stained
violet-red to brown. Linen is the fibre from the stem
of the flax. The fibres have thicker walls than cotton,
from which it is easily distinguished in its unbeaten
state, being a smoother, rounder fibre, with marks like
joints at intervals, small cross markings, and pointed
ends. When beaten finely it is not possible to
distinguish linen from cotton (Figs. 17 and 18).

Hemp. Fibre 20 mm. x*O2 mm. Stained, un-
bleached fibre, yellow to brown ; bleached, brown-red to
wine-red. In general appearance the fibre is similar to
linen, with slightly thinner walls, more markings, and
at the places where joint markings occur are also little
hairs. The ends of the fibres are rounded or flattened.
The fibre in paper is usually beaten so finely as not to
be recognised (Fig. 19).

Manilla Hemp. Fibre 7 mm. x'Q2 mm. Stained
yellow to blue, according to amount of bleaching and
cleaning of the raw material. The fibres are like hemp
fibres, but the canal is much larger, and accompanying
the fibres are many oblong transparent cells, sometimes
occurring like blocks of bricks (Fig. 20).

Jute. Fibre 2*5 mm. x '022 mm. Stained, un-
bleached, yellow ; bleached, brown. Jute fibres resemble
linen and hemp, but the central canal is irregular in
width, widening in places and narrowing again. The
ends of the fibres are pointed and somewhat flattened
(Fig. 21).

Straw. Fibre 1-5 mm. x '015 mm. Stained
greyish to blue. Similar to esparto, but the fibres are
more flexible, and become kinked when made into



1 10 ^ PAPER AND ITS USES

paper. Serrated cells and transparent oval cells are
present (Fig. 22).

Esparto. Fibre 1*5 mm. x '012 mm. Stained
greyish-blue to colourless. The fibres are very fine and
short with pointed ends. Characteristics of esparto are
the comma-shaped hairs and the serrated cells (Fig. 23).

Bamboo. Fibre 4 mm. x 'o i 5 mm. Stained yellow
to pale brownish-green. Resembling esparto, with
cylindrical fibres with pointed ends, and usually a large
number of transparent oval cells are found in paper
made from bamboo (Fig. 24).

Chemical Wood. The fibres vary considerably in
length and thickness. Stained blue to colourless.
Consisting of flat ribbon-like fibres, broad flat cells
pitted and perforated, others similar to sections of a
plant stalk, they are on the whole unlike any other
fibres. A few fibres resemble linen fibres, but com-
parison will reveal differences. The differentiation
between pine, spruce, poplar, birch is unnecessary for
ordinary paper testing (Fig. 25).

Mechanical Wood. Stained yellow. This pulp
is unmistakable, owing to the broken pieces of various
sizes and shapes, fragments of fibres torn away from the
original wood, held together by cells, and showing pits
and pores. Most newspapers are made of a mixture


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Online LibraryEdward A DawePaper and its uses : a treatise for printers, stationers and others → online text (page 7 of 12)