perfectly uniform, but the whole web vacillates from being too dry to
being too moist, while between times the manipulation is exactly right.
The result, obviously, will be a variation in finish over the whole
width of the paper instead of over a portion. Moreover, too much drying
makes the paper fuzzy and likely to become wavy, besides weakening the
fibers.
Another result of uneven pressing is to make the paper thinner where
the pressing is hardest. Such a defect is quite obvious in a pile of
paper, as the top will not be as level as it would be in paper that is
uniform in thickness throughout.
Assuming that the paper is perfect as it leaves the driers there is
still a chance that one or more of the calender rolls may get out of
true, especially when starting a run after they have been idle long
enough to get cold. Under such conditions they often heat up and expand
unevenly so that the pressure is harder in some sections than in
others. The result is a thin streak in the paper. Whether the thinness
be caused by poor pressing or calendering, it can easily be detected
in a roll of paper, as the thin streak makes a soft spot in the roll
which can quickly be located by tapping the roll all the way across. A
muffled rather than a ringing sound discloses soft places.
This defect, if bad, may cause considerable trouble on a web press, as
no amount of manipulation will make the paper draw evenly as it runs
into the press if the edge of the roll is slack.
Occasionally, segregated areas in paper are found to vary in finish,
and when these do not run in continuous streaks they may often be
caused by the felts which carry the paper through the press rolls
having become clogged up in spots so that the water can not pass out
evenly from the paper through the felt. This must be guarded against by
occasionally stopping the machine and washing the felts, or changing
them, as the occasion dictates.
Such damp spots in the paper crush in the calendering and make
blackened areas in the paper. Uneven drying may also have been
occasioned by slackness of the drier felt which holds the paper
against the driers. In sheeting the cheaper grades of book paper it is
customary to cut off from a number of rolls simultaneously, which often
accounts for a variation in finish or bulk in sheets from the same case.
Of course, when any of these symptoms appear it is the duty of the
men on the machines to correct them, and in the continuous course of
paper-making it is inevitable that felts become filled up and require
washing or changing, or that the variations of consistency in the stuff
should call for some form of regulation. Stuff which runs too moist on
the wire will often “crush” under the couch roll, producing a curdled
appearance. Stuff run with insufficient water will not form evenly. The
skilful machine-tender avoids these extremes.
TRADE CUSTOMS.--In recognition of the many variable elements in
paper-making, trade customs have been established, such as allowances
for a normal variation in the weight of paper above or below the
nominal ream-weight, and reasonable allowance should be made for normal
variations in other characteristics.
Eternal vigilance and alert judgment are certainly required for setting
high standards in the manufacture of paper. It is a matter of common
observation that mills using practically the same raw materials vary
widely in their reputation for uniformity and excellence of product.
The reason for this is to be found in the human element.
CALENDER DEFECTS.--A number of difficulties may arise from much less
excusable causes than those mentioned. For example, the paper sometimes
may run slack through the calenders, with the result that it wrinkles
and cuts in diagonal jags called “calender cuts.”
Sheets containing such defects sometimes elude the finishers, and on
the printing-press such a sheet may crack and go around one of the ink
rollers. On a web press the trouble from such a defect would be even
worse, causing breaks and necessitating delays on the press. It is more
difficult to exclude calender cuts from roll paper, as it is not always
easy to see them in the fast-running paper, so that an occasional cut
is not an unforgivable sin.
Among other defects arising on the calenders are little scarlike
depressions in the paper, made by small scraps of paper which have
become lodged on a calender roll and are embossed into the web at each
revolution of the roll.
HOLES, DIRT, ETC.--In very light papers, holes are sometimes found,
the most likely cause of which may be picking under the dandy roll or
grease spots on the wire cloth. Of less frequent difficulty are the
so-called pinholes, caused by sand or grit, while slime spots, or spots
caused by slight bundles of fibers, are also occasionally noticed.
Dirt and specks originate from careless handling of rags or paper
stock, and are also derived from shives of undigested wood in the
wood-pulp.
Streaks in the paper may originate from a crease in the wire, and
mottled effects denote some fault in the handling of the paper in the
wet stages of making.
Again there are times when sheets are not cut quite square, which is,
of course, inexcusably careless. Likewise, the packing of paper may
be done in a careless manner, and cases too loosely packed, if set on
end, often cause a wave in the paper, which sags in the case instead
of remaining tight and flat. It is desirable that cases of paper be
kept flat in storage and not set on end. Cases should be made from
well-dried boards, and waterproof lining-paper should be used to
exclude all dampness. When paper is finished in rolls it is fair to
demand that the rolls should be wound evenly and hard, and all breaks
should be carefully spliced and flagged.
COLOR.--The foregoing troubles are mechanical. Other difficulties
may exist, even when the paper is handled well on the machine, owing
to errors in composition. The color may vary, and the term “color”
includes the various shades called white, as well as tints. Color is
affected by water conditions. In the case of mills which depends upon
river water, the water sometimes becomes so dirty that it severely
handicaps the paper-maker, in spite of his filtering apparatus, and at
such times it becomes difficult to get as bright and lively shades as
under favorable conditions.
Dyestuffs do not always work uniformly, and, therefore, absolute
matches of color from run to run are not to be expected. Shortcomings
of this nature should be regarded with some lenience.
In this class of difficulties, discrepancies in sizing are the
less pardonable and are more apt to be noticed when hard sizing is
requisite, as in writing-paper or index bristol. In such cases a lack
of sufficient sizing is an incurable fault, for which the manufacturer
is responsible. There are occasions when excess of sizing would be
troublesome--for example, in a smooth-finished book-paper it would be
likely to cause offsetting, but this trouble may be alleviated by using
less ink, or, if necessary, by slip-sheeting.
It would be difficult to catalogue all possible sources of trouble, but
we have at least covered the principal defects of uncoated papers.
PACKING.--Occasionally troubles may be charged to faulty packing--cases
too loosely packed when stood on end permit the paper to sag, thus
causing a curling tendency at one end of the sheets.
The use of unseasoned case lumber or cases and inferior case lining
give access to moisture, the effect of which is discussed herein at
length.
The susceptibility of coating to picking may be determined by applying
hot sealing wax. If the wax after cooling is pulled off with only
the coating adhering it may be assumed that a “tacky” ink would work
the same, whereas if the paper tears out with the wax--it proves
conclusively that the coating is well sized.
COATED-PAPER TROUBLES.--Coated papers have their characteristic
shortcomings. The picking of small particles of the coating is perhaps
the most common fault, and is caused by insufficient adhesive elements
in the coating mixture. Other troubles are traceable to some of the
defects of the body stock. Irregularity of the finish is sure to come
from faulty application of the coating or careless calendering. Grit
or bubbles in the coating is likely to result in a porous surface. The
sour odor of some coated papers is due to decomposing casein or glue.
Casein used as an adhesive in most coated papers is a product from skim
milk. It contains lactic acid which must be neutralized in preparing
the coating mixture. For this purpose an alkali such as soda or ammonia
is used, and when properly handled the coating should be neutral. An
alkaline coating will cause re-etching on lithographic plates or stones.
Starch coatings or combinations of starch and casein are cheaper than
full casein and do not yield as high a finish and when improperly used
have often been the cause of picking.
THE PRINTER’S RESPONSIBILITY.--The second group of difficulties,
or those for which the printer is to blame, may originate with the
improper storage of the paper. As pointed out, the standing of cases on
end is conducive to wavy paper. Dampness is a prime cause of trouble,
as will be sufficiently shown later on, but it is elementary to say
that paper should never be exposed to moisture.
ENGRAVINGS.--The troubles of ignorant or inefficient pressmen and
foremen are often laid to the paper, especially where half-tone
printing is involved. In the first place, too little attention is given
to securing proper originals for the half-tones. Retouching is omitted
in a fit of false economy, for at this very stage of the game it was
never truer that “An ounce of prevention is worth a pound of cure.” Too
much care can hardly be given to securing good engravings.
Secondly, the selection of a proper half-tone screen is frequently
overlooked. While no hard-and-fast rules may be set, the best one,
when in doubt, is to include with the engraver’s order a sample of the
paper on which the cuts will be printed. He can judge, taking into
consideration the subject and the stock, which screen is advisable. In
general, it may be affirmed that 120 or 133 line screens are best for
uncoated smoothly finished papers, and 150 or 175 line screens are most
satisfactory for coated stock.
INKS.--Next comes the suitability of the ink, and there again the
ink manufacturer’s advice, always available, is often neglected; but
experience proves that certain papers yield best results with certain
inks. Such matters can only be determined by actual experience, but
when in doubt consult the ink-man.
MAKE-READY.--Finally, the make-ready should be intelligently varied
according to the subject and the paper. The best printers agree
that different papers to some extent require individual treatment.
A make-ready suitable for a coated paper is not necessarily equally
satisfactory for an uncoated half-tone paper or even a dull-finished
coated stock. But it is not within my province to go further than to
emphasize these warnings.
GRAIN.--The question of the grain in paper is certainly, in many cases,
within the control of the printer when ordering his paper, but its
importance is very frequently overlooked. In machine-made papers there
is a distinct grain that is caused because a majority of the fibers
point in the direction that the stuff flows on the machine, just like
logs floating in a river.
This grain direction is noticeable in folding, the crease being
smoothest with the grain, because folding across the grain encounters
the most resistance and breaks many of the fibers. This is especially
noticeable in fairly heavy book-papers, in bristol boards and
cover-stock, all of which should be scored for folding.
Cut cards, to have the maximum stiffness, should be so trimmed out of
the sheet as to have the grain run in the long direction of the card.
Even in book-papers, where flexibility is desirable, it is necessary
to have the grain run up and down the page. There are occasional
cases when the grain is deliberately arranged to run across the page
to acquire more rigidity. A wide page of light-weight paper might
otherwise be too limp. Moreover, this arrangement makes for stronger
bindings, as the stitches or wires pass around the bundles of fibers
instead of cutting between them. The English books are mostly made up
in this way, but they do not open so easily as when the grain runs
parallel to the binding. Paper is materially weaker across the grain
and can withstand only about half the tensile strain that it could bear
with the grain, although crosswise it is more elastic.
There is one very serious objection to making books or catalogues
“cross-grained.” This is on account of the way fibers are affected
by moisture. The cellulose fiber expands in diameter on absorbing
moisture, for which it has a great affinity. Indeed, a cellulose fiber
is only stable under uniform atmospheric conditions. The expansion of
each fiber in diameter makes paper expand much more across than with
the grain. Obviously, the total expansion of a sheet equals the amount
each fiber expands times the number of fibers that side by side go to
make up the sheet.
When the glue is applied to a book in process of binding, it causes an
expansion of all the moistened fibers.
If the grain runs parallel to the shelf-back no harm results, as the
paper is free to expand toward the side margin, but if the grain is
at right angles it usually makes a cockle in the binding because the
moistened edges of the leaves expand while the dry portion beyond where
the moisture penetrates retains its shape and resists the elongation
of the wet edges. Consequently the expansion of the fibers expresses
itself by cockling.
REGISTER.--In all printing, when close register is necessary, the
danger of poor register from the expansion of paper is minimized when
the dimension across the grain is the shorter. Lithographers invariably
prefer to have the grain run the long way of the sheet on this account.
Moreover, they rack the paper before printing in order to get it
thoroughly seasoned. To protect it from atmospheric changes that may
occur during the printing process, they use slip-sheets of considerably
larger dimensions, so that there is a generous margin of slip-sheet
around each printed sheet, which helps to exclude the air from the
edges of the printed paper.
MOISTURE IN PAPER.--It is true that some papers are more prone to
expand than others, especially if they have been run too dry on the
machine. Paper is not naturally bone-dry. Under average weather
conditions, it contains six or seven per cent of moisture.[D] When in
the making it is turned off far below its normal moistness, it seeks
to obtain this moisture from the air at the first opportunity, and
in acquiring it expansion takes place. Unless the expansion pervades
the entire sheet, wavy edges will result. Similarly when the air
becomes dry exposed edges of paper give off some moisture and shrink
accordingly leaving a boggy center to the sheets.
[D] See Herzberg table, page 64.
SEASONING.--This process of acquiring normal moisture is usually
called “seasoning.” As paper is probably never turned off at its
full normal moisture, it is most desirable that it should be allowed
time to season. It is not unusual to have people speak of new paper
being too “green.” This may not have been an uncommon condition of
hand-made papers which were dried entirely naturally, but, so far as
machine-dried paper is concerned, I doubt if it is ever too green,
though it is frequently made too dry.
CONDITIONS BEYOND ABSOLUTE CONTROL.--Believing it to be impracticable
to leave the precise normal moisture in machine-made paper, I have
deliberately refrained from classifying this difficulty with faults
chargeable to manufacture, and the general recognition of this
circumstance indicates the wisdom of ordering paper long enough in
advance to permit of a period of seasoning. In fact, this phenomenon
of expansion or contraction of cellulose fibers places difficulties
originating from this source in the class of conditions beyond absolute
human control, but a study and understanding of the subject will
enable one to prevent, or at least to minimize, such troubles. It
consequently becomes the business of the printer to inform himself as
thoroughly as possible on the subject. Static electricity is an element
beyond absolute control and the source of much trouble. Both phenomena
could be controlled by proper atmospheric conditions in storage and
press rooms, but it is an expensive matter to equip rooms and install
the necessary apparatus. The amount of trouble arising from these
elements is often sufficiently costly in time and material to warrant
investigation as to the expense involved.
The least a printer can do is to maintain hygrometers in his pressroom
so as to keep track of atmospheric variations, and be guided
accordingly.
STATIC ELECTRICITY IN PAPER
Among the “paper troubles” due to conditions for which neither the
paper-maker nor the printer is responsible, none is more bothersome
than the presence of static electricity in paper. These static charges,
which are created by friction either in the making or handling of
paper, develop magnetic propensities in the sheets, causing them to
behave in ways which seem nothing but freakish until their nature is
understood. Some sheets stick together as if they were glued, while
others appear repellent to one another. Likewise, they may act in the
same manner toward the fly-bars of the press. It is next to impossible
to “feed” sheets so charged, and there is every likelihood of the ink
from one sheet offsetting to another.
Every one familiar with the magnet knows that there are in magnetism
two poles, the positive and the negative; that two substances of
opposite polarity attract one another, but that substances of the
same polarity repel each other. Static electricity--or frictional
electricity, as it is also called--exists both in positive and negative
charges, and sheets of paper containing static charges are governed
accordingly.
Paper, when dry, is an insulator to electricity, but when moist it
becomes an excellent conductor. Consequently, too much drying in
manufacture increases the likelihood of electrical troubles, because it
makes the paper more retentive of electricity with which it may become
charged.
Pure air is also an insulator of electricity, which finds its paths
through the air by means of the dust particles in suspension. Moisture
in the air forms a connection between the dust particles through which
the electricity easily passes into the ground, but when the air is dry
this medium is lacking, so that substances containing static charges
are deprived of these channels of conductivity. Cold air can not hold
so much moisture as warm air, so that its insulating properties are
increased. It is, consequently, in cold weather when this sort of paper
trouble is at its worst.
These facts suggest the first steps of prevention to take against
static electricity. First keep the air in the pressroom warm, and, if
necessary, increase its humidity. It is also advisable to keep the
paper in a warm room, for it has often been noticed that paper coming
cold into a pressroom gives much trouble.
The entire virtue of the so-called electric annihilators for moistening
the tympan of a press comes from the moisture they contain. Ordinary
glycerin, which is cheaper, will answer as well. These applications
are undesirable because they cause the packing to swell, and, in
consequence, detract from the adjustment of the overlays.
There is a simple and not very expensive device on the market called
the Thompson electrical neutralizer that has been found helpful. It is
provided with a tinsel cord such as is used in decorating Christmas
trees. The cord is stretched across the press so that the sheets are
brushed by it as they pass to the delivery board, and are thus offered
a connection whereby the static charges may escape into the ground. A
second device of merit consists in a gas pipe with flames at frequent
intervals over which the printed sheets pass in close proximity on
their way to the delivery board.
The most successful neutralizer with which the writer is personally
familiar is the Chapman. By means of an alternating current of
electricity, it supplies through a special apparatus alternating
discharges of positive and negative electric currents against the
sheets of paper as they are carried along the press. In the presence of
such a current the charges on the paper become their own destroyers, as
they draw out of the alternating current only the kind and quantity of
electricity which is sufficient for their complete neutralization.
There have been quite a number of other inventions, an account of which
the writer published in _The Printing Art_, Vol. XIX, No. 1, March,
1912. All are based on one of the following principles:
1.--Making paper a conductor by moistening.
2.--Making the air a conductor by humidifying.
3.--Inducing static charges out of the paper by means of grounded
wires or gas flames.
4.--Neutralizing the static charges in the sheet with charges of
opposite polarity.
Another solution of this problem, as well as of the problem of
expansion of paper and consequent poor register, could be reached by
the construction of an insulated pressroom. The air for this room
should be supplied through an apparatus in which it could be brought
to any required degree of temperature and humidity. The paper would
naturally have to undergo sufficient airing in such a room as to
become acclimated. After that, if the conditions remained constant,
there could be no difficulty in getting register, so far as the paper
was concerned, and a proper amount of warmth and moisture would also
dissipate all static electricity.
It is difficult to anticipate or to completely cover all conceivable
paper troubles, and when some one which may not be diagnosed on the
basis of the general principles enumerated, consultation with some
paper expert should clearly be sought. The author will be glad to
communicate on such subjects.
CHAPTER ELEVEN
THE PAPER TRADE
The distribution of paper is cared for in part by direct sales from the
mills to consumers, such as large publishers of newspapers, magazines,
and books, and manufacturers of paper commodities, such as tags, boxes,
stationery, toilet accessories etc.
The sale is also conducted to some extent by brokers, who operate
principally in a few of the larger cities, especially those located
within easy shipping distance from the mills, where the handicap of not
carrying a large warehouse stock is at a minimum.
The broker carries no stock as a rule, with the exception of a supply
for regular contracts. Occasionally the mills will carry a stock for
the broker. A few firms specializing on contract business have made
distinct successes in this branch of the paper business, but the broker
is not an important figure in the paper trade, taking the country as a
whole.
The most important distributing factor to the printing trade, is the
paper merchant, who with his large purchasing power, accumulates ample
and varied stocks, at minimum cost (having the advantage of carload
prices and freight rates), and stands ready to distribute in large or
small quantities, whatever is required. He also helps in a considerable
measure to finance his trade by extending credit.
There is a distinct tendency toward “chain stores” one of the more
prominent of which now comprises eight warehouses and seventeen branch
offices, covering practically the entire country. These large factors
frequently control the entire output of several mills, and sell to the
smaller jobbers, as well as to the printers and consumers.