LITHOGRAPHIC PRESS WORK
Preparing the Design--Treatment of an Ink Drawing--Chalk
Drawings--Alterations--Value of Impressions--Offsets--The
Lithographic Hand-roller--Proving--Registration--General
Features--Transferring--A Commercial Necessity--
Arrangement--Choice of Paper--Transference to Stone--
Preparing the Forme.
The operations directly associated with lithographic press work are more
or less of a preparatory character. The preparation of a design, in its
progressive stages, from the lithographic draughtsman to the printing
machine, is usually carried out in conjunction with the press. Only
under exceptional conditions or for some particular class of work is the
lithographic press actually employed for printing purposes. Its ready
adaptability to the ever-varying thickness of lithographic stones, and
the manner in which pressure can be applied at will, as well as the
intense sharpness of such pressure, render it peculiarly suitable for
the work now under discussion. Such operations will be better understood
and probably more easily remembered if they are described in a sequence
such as might be presented under average commercial conditions. Taking a
design as it leaves the lithographic draughtsman, _i.e._ in the form of
a greasy drawing on stone, the first object of the printer is to so
prepare it as to preserve the conditions described in Chap. I. page 2.
This he may accomplish in the following manner.
Cover the whole stone with fresh strong gum and allow it to dry. Then if
it be an ink drawing, wash off the gum with water, and remove the
drawing ink from the surface of the design with a few drops of
turpentine and a piece of clean rag. Proceed to roll up with a
lithographic hand-roller charged with good black printing ink. The
consistency of this printing ink can only be determined by the character
of the work under treatment. It is therefore a matter of experience
rather than rule. Heavy designs covering large areas can be worked up
with moderately thin ink, while work of a finer description will most
probably require a stronger ink for its successful treatment. Between
these two extremes there is a variety of conditions and effects which
will require a ready recognition and an intelligent adaptation or
modification of any operation which may be described. It may even be
advisable to _rub up_ the work with a piece of soft rag and printing
ink, but the clearness and crispness of the drawing can best be
preserved by a complete removal of the greasy ink with which the drawing
was originally made. More particularly is this desirable when heavy,
solid work is in close contact with work of a finer description, for the
excessively greasy character of the artist's drawing ink has a dangerous
tendency to smear or spread and to thicken the design, unless a
reasonable amount of care is exercised. After rolling up the work as
well as possible, and having decided that it is firm and strong and is
fully charged with ink, dry the stone perfectly and dust over the design
with finely powdered resin or French chalk. With a piece of water of Ayr
stone polish away any scum or dirt which may surround the work, and etch
it quickly with a weak solution of nitric acid. Cover up with strong gum
and dry it. The design is now ready either for proving or transferring.
The treatment of chalk drawings, grained stones, or transfers from
grained paper needs a slight variation of the operations already
described. The preliminary etching is generally carried out by the
draughtsman by flooding the stone with a mixture of gum and acid, after
which the gum solution is allowed to dry. The chemical change which
takes place during this etching is often described as one in which the
soap present in lithographic chalks is changed to an insoluble compound.
This chemical change is perhaps a somewhat contentious matter, but the
effect and not the principle involved is to us the matter of primary
importance, and this effect is such as to actually prevent any spreading
of the design on the stone beyond the lines of the original drawing.
Returning once more to the operation, wash off the gum, and, having
removed the excess of water in the usual way, roll up firmly with a
strong black ink. Instead of washing out the drawing with turpentine
immediately, work off the original chalk by rolling up with a good nap
roller and taking frequent impressions. In this way the grain of the
drawing will be gradually developed and rendered fit for further
operations. The stone can then be passed to the prover or transferrer.
A French writer, in referring to the importance of really good _chalk_
drawing and printing, as well as to its artistic and technical value,
once said: "The printer requires a fair appreciation of that subtle
suggestiveness which gradations of tone can impart to a chalk drawing
before he can hope to successfully reproduce the artist's original
conception. A good printer handles his roller over a chalk drawing with
the same feeling as that with which a violin player handles his bow. By
movements rapid or slow, and by greater or less pressure over certain
parts, he charges the drawing to the proper tone."
If at any time the original work requires alterations, they may be
executed in the following manner. Roll up the design firmly in strong,
black ink, and, after fanning the surface dry, dust it over with French
chalk. Make the necessary erasures with water of Ayr stone and etch with
fairly strong nitric acid. Polish slightly, and wash well with a
plentiful supply of clean water. Pour over the stone a very weak
solution of alum, and again wash thoroughly with hot water, so that its
rapid evaporation may leave the work ready for immediate manipulation.
Alterations may be made by transferring or drawing. In either case it is
advisable to gum up the work with strong gum and allow it to stand until
dry. The subsequent treatment of any alteration will, of course, depend
upon their character and extent. As new work, they should be carefully
handled.
It is most important that a very _weak_ solution of alum should be used.
Being an alkali, a strong solution would have a tendency to dissolve the
greasy particles of the drawing and cause them to spread and thicken.
It is always advisable to take an impression from each design, whether
it be in ink or crayon, before it is laid aside for subsequent
manipulation. These impressions will not only reveal any inaccuracies or
weaknesses which might otherwise pass unnoticed, but also serve as a
useful record and for comparison with other transfers or impressions
which may be required.
There are other phases of preparatory work which come within the scope
of the lithographic pressman, and as they frequently constitute an
intermediary stage between the first drawing of the draughtsman on stone
and the making of transfer impressions to facilitate reproduction, a
description at this point will be appropriate.
It may be that a key forme only has been prepared, or perhaps an outline
forme with sufficient detail. In either case a number of offsets
equivalent to the number of colours necessary for the completion of the
design will be required. These are made by taking good, solid
impressions in stiff black ink from the key or outline forme. Dust these
over with a mixture of three parts Venetian red and one part lamp-black.
Lay them in convenient positions on a well-polished dry stone, and run
them through the lithographic press with a light yet firm pressure. The
result will be faint yet sufficiently clear offsets of an outline which
will enable the lithographic draughtsman to prepare any number of
formes, and these will register or fit each other and the original
drawing with perfect accuracy. Such outlines will in no way affect the
work of the draughtsman, and will disappear at the first application of
the gum sponge or moisture in any form.
[Illustration: FIG. 9.]
A lithographic _nap_-roller (Fig. 9) facilitates the work of the
pressman in the preparation and development of original drawings on
stone, and becomes an absolute necessity when crayon drawings on grained
stones are operated upon. The preparation and preservation of a roller
of this description requires a more than average amount of care and
attention. The best rollers are covered with French calf-skin with a
soft, velvet-like nap, and may be prepared as follows. Run the roller in
crude castor oil for a short time until the leather becomes soft and
pliable, then work out the superfluous oil by repeated rolling in medium
varnish, occasionally scraping off the varnish with a broad blunt knife.
Continue this for a day or two, then gradually work into the skin some
good non-drying black printing ink. The roller thus prepared may be
somewhat harsh, but a few days' use will bring it into condition. An
occasional application of tallow or lard, say about once a week, will
keep the roller skin soft and pliable, and counteract the hardening
effect of constant contact with the damp surface of the lithographic
stone and the oxidisation of the printing ink.
Proving the work of the lithographic artist, though not always an
absolute necessity, is a helpful and most important function. In its
progressive stage it enables both designer and lithographer to observe
the realisation of their colour schemes, and to amplify or minimise if
necessary the effects they desire to produce. Errors of judgment or of
detail can be rectified before the work reaches a more advanced stage.
Again, a finished proof offers something of a tangible character for an
expression of approval or disapproval, and serves as a useful and
helpful guide to the printer throughout the subsequent operations.
This will show clearly the importance of the prover's work, and though
it is not by any means an unusual proceeding to _prove up_ even the most
elaborate designs in the lithographic printing machines, it is, for
obvious reasons, more convenient to confine such work to the press. It
may therefore be regarded as an intermediate operation, distinctly apart
from the preparation of the original drawing which precedes it, and the
arrangement for machine printing which follows. The distinctive and
pre-eminently the most important feature of proving is the manner in
which one colour is registered with another; and although the methods
usually adopted are of the simplest possible character, the most
scrupulous care is requisite for their successful application. It
appears to be an almost ridiculous plan, so simple is it, to cut away
the angles formed by the register lines after the first printing (Fig.
10A), and then to place them to corresponding lines on each colour
forme, or to pierce the register lines as in Fig. 10B, passing a fine
needle through each puncture into corresponding holes drilled in the
stones and allowing the sheets to fall into position,--yet these
operations demand constant care and attention.
[Illustration: FIG. 10A.]
[Illustration: FIG. 10B.]
The mixing of colours for proving, and the general principle of their
application, are matters which are almost entirely under the control of
the printer. Their selection and the manner in which they are employed
are both determined by the individual character of the work. It is
impossible to indicate any "rule of thumb" guide for their application
or manipulation. The individual fancy of the artist, or the wish of a
customer, are the only probable complications which may have to be
considered. Then again, many phases of the work are more or less
experimental, when the resourcefulness of the printer may be tested, and
the mechanical features of his work be relieved by the exercise of
intelligent application, if not of artistic perception. Very rarely is
it possible to print from the litho-draughtsman's original drawing, and
even when it may be convenient to do so, it is, in the majority of
cases, unadvisable on account of the element of risk involved. There is
an ever-present danger of the stone breaking,--a catastrophe which would
necessitate an entire reproduction of the design, and even under the
most favourable conditions the constant attrition produced by the
rollers, etc., would have an appreciable effect on the work, and in
course of time destroy its value for graphic reproduction.
Many other equally cogent reasons why duplicates of the original should
be made for printing purposes present themselves. The chief of these is
an essentially commercial one. To reproduce half a million impressions
from a single small drawing would obviously depreciate the commercial
value of lithographic printing very considerably, and although there is
no record of the circumstances under which the duplicating of original
work by means of transfers was first evolved, it is only reasonable to
suppose that it was the direct outcome of a necessity which was as
peremptory in its demands as it has been far-reaching in its effects.
The method is one by which any number of impressions can be made on a
suitably prepared paper, and with a sufficiently greasy pigment. These
can be re-transferred to a lithographic stone, and in this way
facsimiles of the original may be secured and arranged in the manner
most convenient for machine printing. Great care is necessary in making
these transfer impressions. They must be perfectly solid, yet not
overcharged with ink, _i.e._ they must be clean and sharp, and as nearly
an exact replica of the original work as it is possible to make them.
That the further description of these operations may be as lucid and
practical as possible, we will apply it to ordinary work-a-day
conditions, and suppose that a design in three workings has been
lithographed and prepared for transferring as already described. The
size of the work is 7-1/4 in. by 4-1/2 in., then the paper on which it
is to be printed ought to be double crown, 20 in. by 30 in. This will
allow 1-1/2 in. for the gripper and 1/2 in. margin at the back and
sides. Sixteen transfers can be pulled from each colour forme on a thin,
transparent transfer paper. Mark out a sheet of stout paper as in Fig.
11, and arrange the transfers in the position indicated by the dotted
lines. The gripper margins A A are determined by the construction of the
machines, and may be varied accordingly.
Varnished transfer papers may be laid down on a slightly warmed dry
stone, and if French transfer paper be used the stone must be slightly
damped. If the sheet of transfers is laid down to a board--Fig.
12--uniformity of gripper margin will be assured throughout the series,
and the work of the machine printer facilitated.
[Illustration: FIG. 11.]
Pull it through the lithographic press with a gradually increasing
pressure in the usual way. The varnish transfer paper will be
sufficiently tacky to adhere slightly to the surface of the stone, so
that the pressure may be repeated again and again with perfect safety.
It may not be possible to remove the base upon which they were arranged,
as it is usual to secure them in position with paste. At this point the
manipulation of the two varieties of paper differs slightly. The thin,
transparent variety is usually fastened down to its paper base with
syrup, glucose, or some sticky composition of a similar character. This
paper backing can be removed immediately after sufficient pressure has
been applied to fix the transfers to the stone. As this transfer paper
is adhesive it is necessary to damp the surface of the litho-stone
before it is laid down, when, of course, it will readily adhere, even
under a moderately light pressure.
[Illustration: FIG. 12.]
The further preparation of work, after being transferred in this manner,
is in many respects similar to the treatment of new work, but with this
important difference. A new transfer should almost invariably be worked
up with a soft rag and black ink, the latter being thinned down with
turpentine and varnish. Gum up the work, and allow the gum to dry. Roll
a piece of soft rag into a pad, and charge it with printing ink which
has been thinned down. Wipe off the gum on the surface of the stone,
leaving only a thin film over the work. Rub up the transfers with the
rag already prepared, and when fully charged with ink cover them with
fresh gum. If possible they should stand for one or two hours, when the
rolling up and etching may be proceeded with.
Accuracy of register can be ensured by the second and third sets of
transfers being patched up to the first forme in the following manner.
Make two fairly strong black impressions of this forme on a stout
unstretchable paper. Fix these up on a glass frame in such a position as
to allow the light to pass through them, and carefully place each
transfer in its exact position. They can then be laid down on separate
stones in the same way as the first set. These are the simple outlines
of the transferring process. In detail they may, of course, be modified
to meet the exigencies of peculiar conditions, which in lithography are
frequently the controlling powers, and at all times are matters of vital
importance.