ETCHING LINE TRANSFERS.
For etching transfers on zinc, whether photographic or direct, we shall
require the following apparatus: A slab of iron about 24 × 18 inches
and 1/2 or 1 inch thick, supported horizontally upon four legs, and
heated by an atmospheric burner, arranged somewhat like a gridiron so
that the heat is even all over. A set of rollers on litho stock, one
of leather, one of flannel, and one or two glazed rollers, the same as
lithographers use for tint printing—we also require an etching box—_i.
e._, a wooden tray, 30 × 24 inches, and 8 inches deep, well made of
seasoned wood, lined with either pitch (with a little tallow added), or
gutta-percha, and mounted upon rockers.
This box will require a firm table for its support during the etching,
said table standing as close as convenient to a sink and water tap.
The other requisites used during etching, are, nitric acid, turpentine,
gum Arabic of a good quality, some powdered nutgalls, three or four
sponges, some finely powdered resin, a flat camel’s-hair brush, a
solution of shellac in spirits of wine, and the following inks:
First the etching ink, composed of beeswax one-quarter ounce, Russian
tallow two ounces, bitumen half an ounce, middle varnish two ounces.
Melt these together in a pan over a fire, or Bunsen burner, stirring
well during the operation, so as to mix them thoroughly; when all are
melted, add five ounces of ordinary letterpress printing-ink, and
thoroughly mix; then allow to boil and continue the heat until the gas
escaping from the bursting bubbles explodes upon the application of a
lighted taper; then remove all from the fire, and allow to cool.
For a hard ink, for use after the plate is etched deep enough, and the
resist is cleaned off, mix
Beeswax 1/2 ounce.
Resin 1 ounce.
Shoemaker’s Wax 1 ounce.
Black Litho Ink (about $1 a pound) 2 ounces. |56|
Melt, then cool and mix with turpentine to make it the consistency of
soft soap.
Now, with these and a solution of gum Arabic (in cold water), the
thickness of cream, add one-quarter pint of a decoction of nutgalls to
each quart of gum solution. The decoction of nutgalls is made by adding
one-quarter pound of bruised nutgalls to one and one-half pints of
water, in an earthenware vessel (not metal); boil, then allow to stand
at the fire and simmer gently for six hours, keeping the vessel covered
over; then allow to cool, filter and add the proper quantity to the
above gum solution.
We will assume that a suitable place is provided for carrying on the
operations to be described, in the shape of plenty of bench room, and a
good light to work by.
The first stage in etching a zinc plate in relief is, to slightly warm
it upon the hot plate, then allow it to cool (by-the-bye, it will be
very convenient to have a clean litho stone handy for placing the plate
upon to cool quickly). The plate being cold, with a piece of soft
sponge carefully smear it over with the gum solution, allow the gum to
dry, spontaneously, in a cold current of air; if heat be applied the
gum will crack and bring away the image from the plate.
Whilst the gum is drying, with a palette knife place equal parts of
transfer ink (page 44) and of etching ink (page 54) upon one corner of
the inking slab, then thin to the consistency of cream, with middle
varnish, thoroughly incorporating the three ingredients with the
palette knife.
Now place a little of this ink upon the leather roller and roll
vigorously upon the slab, so as to distribute the ink thoroughly upon
both roller and slab; be careful not to get too much ink on the roller,
nor to have it too thin; in fact, work the ink as stiff as is possible.
Now lay the zinc upon a piece of clean paper, and sponge it gently over
with a wet sponge, so as to loosen the film of gum, then squeeze the
sponge nearly dry, and pass it over the plate again, so as to insure it
being evenly damp all over, but be careful not to make it too dry.
Now proceed to roll up, by passing the charged roller to and fro over
the plate, using moderate pressure and slow motion, recharging the
roller at short intervals from the inking slab. Occasionally use the
damp sponge so as to keep the plate sufficiently damp to resist the ink.
If the roller slides instead of rolling, wipe it with an old linen rag,
which will remove the moisture; then recharge the roller again upon the
slab. |57|
The rolling is continued until the whole image is an intense black,
when it is carefully dusted over with very finely powdered resin
applied with a broad camel’s-hair brush, taking care that all the image
gets covered. Then rub it gently with a wet, soft sponge and place it
in the etching box containing a mixture of water and nitric acid, the
acid being only just perceptible to the taste.
The plate should remain in this for one minute (the box being kept
rocking); it is then removed, and thoroughly washed back and front
under the tap. Rub it gently with a clean soft sponge.
This etching is merely to remove any traces of gum or dirt from the
zinc which would interfere with the shellac varnish holding.
Now dry the plates, using gentle heat, then coat the back with thin
shellac varnish to protect it from the acid; do the same to the margin
of the picture on front, also varnish the centre of any very broad
whites up to half an inch of the image, so that the acid dissolves no
more zinc than is necessary. Now examine the image carefully, and if
any of the lines are defective touch them up, and make any alterations
and additions required.
The plate is now ready for the first etching, for which purpose a
little nitric acid is added to the water in the etching tray—precise
directions cannot be given as to how much acid to add, as so much
depends upon the area of zinc on the plate that requires dissolving;
practice, however, will soon enable the operator to judge the proper
quantity. If too much acid is added, the plate will quickly be covered
with myriads of minute bubbles, in which case it must be instantly
removed, well washed, and the bath diluted with water before the plate
is reimmersed. If, on the other hand, there is too little acid present,
the action is too slow, and more must be added.
The first etching must be carefully watched, and the rocking continued,
until the application of the finger-nail to the margin shows that the
zinc inside has been dissolved away to a depth of about the thickness
of a visiting card.
The first etching is the most important of the whole, as unless a
sufficient depth be attained the sharp lines will not be obtained; and
as the ink is not yet capable of resisting too strong acid, great care
must be taken that the work is not damaged; proceed cautiously, adding
acid from time to time as required.
As a rule, the first etching will take from five to ten minutes (the
tray being kept rocking all the time).
When it is judged that the first etching has been carried far enough,
remove the plate from the tray, wash it well under the tap, rubbing
gently with a |58| sponge, so as to remove the scum left by the acid,
dry by means of gentle heat, then allow it to cool.
When the plate is quite cold, smear it over with gum solution, and with
a piece of cardboard, fan the gum dry.
Now sprinkle the inking slab with turpentine, and with a cloth wipe
the slab clean. Take a piece of etching ink and thin it with middle
varnish, mixing them well with the palette knife upon the slab; now
take the leather roller, and with the palette knife place a little of
the ink upon it, and roll up on the slab until both roller and slab are
well coated; but on no account must there be too much ink, nor must it
be too thin.
Now lay the zinc down on the bench, on a piece of clean paper, and with
the wet sponge carefully wash off the gum; then wipe all superfluous
water off the plate, and roll up with the leather roller charged as
above; roll the plate first one way, and then the other, keeping the
zinc evenly damp all over, else the ink will catch in the whites, and
probably spoil the picture. When the rolling is completed, and as much
ink as possible has been piled on, the zinc will be nearly dry. If not,
allow it to stand in a cold current for a little time, then take it to
the drawer in which the powdered resin is kept, and smear the plate
all over with the powder. Now brush as much of the resin away as will
come, using the brush from all sides, so that all the lines get evenly
coated, not only on the top, but upon the sides; this being done, take
a damp sponge and carefully remove the superfluous resin from the
whites, or unprotected zinc.
The plate is now ready for the second etching, and the solution in
the etching tray must be reinforced by the addition of a little acid;
but do not add too much at once. It will be far best to add a little
at a time, and then, as soon as the zinc shows there is no action
going on, add a little more; an easy and simple method of ascertaining
whether any acid be present or not is to wipe the bare metal with the
tip of the finger, and if that spot (which will be brighter than the
surrounding parts) does not speedily resume its dingy color, the acid
is exhausted.
The plate being immersed in the solution, set the tray rocking, and pay
attention to the remarks above. At the end of ten minutes remove the
plate from the tray, wash it under the tap, rub it gently with soft
sponge, then remove as much of the water as possible, and examine the
progress made by the acid. This can be seen by the lines being bare
below the ink, in which case the etching has been carried far enough,
and if not stopped, there would be danger |59| of under-cutting; if,
however, no progress has been made, add a little more acid to the
solution, replace the zinc, and rock again for another five or ten
minutes.
The second etching being effected, the zinc is carefully washed, and
the scum left by the acid is carefully sponged away; now stand the zinc
up near the hot plate, so that it will get the benefit of a gentle
heat, and when quite dry lay it upon the hot plate (which should be
heated to a temperature of 120° to 150° F.) face up, with a piece of
brown paper between the zinc plate and the hot plate.
As soon as the zinc plate begins to get hot, there will be a tendency
to curl slightly away from the hot plate, which, if allowed, would
prevent the ink being evenly melted. To prevent this, take a brad-awl
in each hand, and press down the sides of the zinc, taking care not to
touch any of the picture.
Allow the zinc to remain on the hot plate until the ink and resin are
melted and run down to the bottom of the etching, then remove it and
lay it on the cold slab until the plate is cold.
When cold, smear the plate with the gum solution, fan it dry (_never
use heat for drying the gum_), moisten with wet sponge, roll up again
(use the leather roller), using the ink pretty stiff on the inking
slab; keep the surface of the zinc well moistened. When the roller gets
too much water upon it, pass a piece of damp cheese-cloth over it to
remove the water; then roll the roller vigorously on the slab until it
again bites the ink. Continue rolling the zinc until all portions have
received due attention from the roller. N. B.—Some of the closest work
will be quite blocked up this time, and each subsequent rolling will
block up more and more, until only the very open work will be left.
Now allow the zinc to get dry, then cover it with resin, brushing from
all sides, so as to coat the sides of the lines as well as the top, and
then remove all superfluous resin from the whites with a damp sponge.
The zinc is now ready for the next etching, for which more acid is
added to the solution in the etching tray.
Rock the tray carefully, watching the zinc to see that the acid is
neither too weak nor too strong, until the progress can be seen by
examining the plate; the time, with the proper quantity of acid, is
twenty to thirty minutes.
When the etching has proceeded far enough, after washing and sponging,
again allow it to dry, then place it upon the hot plate until the ink
is melted and runs down the sides of the lines; then cool, smear with
gum, fan dry, moisten with sponge, and roll up as before; dry, cover
with resin, using a |60| camel’s-hair brush, then dampen with a sponge
and give a fourth etching, using the same precautions as to strength of
acid and duration of rocking as before.
Now cool the plate; get a little more ink on the roller, and roll the
plate whilst cold. When the surface of the lines has a nice even coat
of ink upon each and all (coarse and fine), again warm the zinc on the
hot plate until it is just too hot to hold in the fingers; then cool
it again, varnish the back with shellac varnish, then make a mark with
a blunt point, in the ink on the margin, so as to lay a short line of
zinc bare to the action of the acid.
The round of operations is repeated; but for rolling up for the fifth
and subsequent etching, a flannel roller is used, and more ink will be
required upon the slab; it will also require to be a little thinner.
For some subjects six or seven etchings will be required, whilst for
others—especially where there are whites that are too small for cutting
out with a fret saw or router—ten or twelve etches will be required.
Practice, the best teacher, will soon enable the operator to judge how
many are required.
The etching having been carried as deep as is judged sufficient,
sprinkle the plate liberally with turpentine, and with a stiff
scrubbing brush loosen the ink from the lines, and wash it off with a
solution of American potash.
The plate being cleared from all ink, etc., is now examined carefully.
The sides of the lines will show each etching, by a series of irregular
steps. If the plate be put into the press in this condition, the
chances are that before many copies had been made, these steps would
take more or less ink from the rollers, and blur the image; therefore,
before passing it into the hands of the printer, the plate will require
etching two or three times more, to get rid of these irregularities.
This is done by warming the zinc on the hot plate, and then, whilst
still warm, rolling up with a fine glazed roller charged with the hard
etching ink from a clean inking slab.
Roll the zinc firmly, first one way and then the other, so that all
the tops of the lines get well coated with ink; now make a mark on the
margin with a blunt point in the ink, so as to lay a short line of zinc
bare to the action of the acid.
Next empty the etching tray, put into it some clean water, and add
sufficient acid to make it taste like strong vinegar; in this immerse
the plate, and keep rocking for ten or fifteen minutes, or until the
mark on the margin, when felt with the finger-nail, shows that it has
attained a depth about the same as that obtained in the first etching.
|61|
Now wash the plate under the tap, and wash off the ink with turpentine,
followed by a solution of American potash; again wash and dry on the
hot plate. Now examine, and if the lines are free from the steps, the
plate is finished, but if not, the operation must be repeated until the
steps are all removed.
Be careful to cover the surface of the block thoroughly with the ink,
else the acid will spoil the picture.
The plate is now ready either for mounting for the press, or for
electrotypes being taken from it; if the former, the deep whites
are cut away with the router or fret saw, the edges are trimmed or
bevelled, holes are drilled and counter-sunk at convenient places, for
the insertion of nails or screws to fix the zinc to the wooden block,
to make the surface type high.
The object aimed at in the instruction in Part I. is the production
of relief blocks on zinc from an original in black and white, which
original may be a drawing made purposely for reproduction, or it may
be from a drawing already in existence, a woodcut, or engraving,
the picture being rendered entirely in line, or a chalk drawing may
be used. In fact, any subject that is capable of being worked from
either at a type press or by ordinary (monochrome) lithography. Washed
drawings, or oil or water color drawings are not applicable.
In fixing plans, or drawings on the easel, prior to photographing them,
if they are cockled, and difficult to get flat, pins may be placed
anywhere, so long as the lines are not interfered with, for these pins
may be painted out with a camel’s-hair brush and gamboge or Indian ink.
It is important that the plans or drawings be as flat as possible, as
if the lines are cockled, they will not be photographed straight.
In photographing drawings on tracing paper or cloth, a piece of white
paper should be placed behind them.
When, from an original of black lines on a white ground, it is desired
to make a reverse block—_i. e._, white lines on a black ground—a
negative is first made from the original, and from that negative
a transparency is made; and a print made upon the zinc from that
transparency will be a reverse of the original.
Thus far I have tried to make plain the details of a process which is
as fascinating and as pretty as any in photography, and which supplies
results which could not be attained by the most expert workers two
years ago. And since those experts first obtained even tolerable
results by zinc etching, like |62| everything else in photography,
it has made wonderful progress. At first we were delighted and
content when a block was obtained with relief sufficient to enable
us to print it upon an ordinary press with type. But now we can
get from the zinc surface all the qualities which are given by the
lithographic stone. Indeed, the process of zincography bears a very
strong general resemblance to that of lithography; of course, it
varies therefrom in matters of process detail. The manipulations of
zincography, however, are no more complicated in their nature than the
details of printing, etc., from stone. Crayon drawings, ink work in
line and stipple, rubber work, in fact, anything that can be drawn on
stone can be drawn on properly prepared zinc, with the exception of
engraved lines (intaglio), the structure of the zinc not giving the
yielding brittleness of stone. The great departure made possible by
zinc plates exists in the fact that they can be bent to the surface of
a cylinder, thus displacing the reciprocating bed and stop-cylinder
of the lithographic press with the continuously rotating plate and
impression cylinder of the zincographic press, which, at the same
driving speed, produces double the number of impressions printed on
the lithographic press. To Mr. Bernard Huber, of the Huber Printing
Press Company of Taunton, Mass., belongs the credit of designing the
only American zincographic press in existence, and which is now in
successful operation in several lithographic establishments. It is a
thoroughly American machine in design and construction, and while no
glowing prophecies of its immediately taking the place of lithographic
presses are indulged in, yet this kind of press has its place and use,
and will by its qualities win favor in the trade.
Many lithographers are beginning to give correct attention to
zincography, but few are willing to give the time and constant
experimenting to the subject that has been given by Messrs. Harris &
Jones, who during the past three years have operated the zincographic
presses in their lithographic establishment known as the Providence
Lithograph Co. Having taken the selling agency of the Huber
zincographic press, they offer to those who _buy_ the press full
instructions in zincographic surface printing.
These suggestions are given right here, first because we are now about
to take a step higher in zinc etching—a step which will lead us to
results which lithography can scarcely equal in some particulars—and
second, because it is the policy of this work to withhold no
information which the novice will need in supplying himself with a
perfect outfit for doing the best of work. For the same reason the
advertisers have been chosen, rather than received in the usual way.
|63|
PART II.
PHOTO-ENGRAVING IN HALF-TONE.
CHAPTER I.
RETROSPECTIVE.
The former chapters have treated entirely upon the production of blocks
in line—_i. e._, where the picture has been made by a draughtsman,
the half-tones and gradations being communicated by a greater or less
thickness of line, or by dots, or stipple, or hatching.
The picture for such blocks may have been specially drawn for the
process, the same size or larger, or it may be a copy of some woodcut
or engraving already in existence, but if it is desired to reproduce
blocks from drawings, paintings, or photographs, then an entirely
different method must be adopted, and the smooth gradations of
half-tone levelled, so to speak, so as to bring the high lights and the
shadows upon one plane.
In photographs from nature (or from washed drawings or paintings) the
scale of gradations runs, as it were, in a series of short steps from
the deepest shadow to the highest light, and a block made, say in
bichromated gelatine, from such a negative can give no half-tones, as
the inking roller could only touch the deep shadows properly.
Now the subject of making photographs applicable for the illustration
of letter-press, instead of woodcuts, has occupied the attention of
experimentalists from the early days of the art-science, as the records
of the Patent Office show.
The first patent, dated 1852, bears the honored name of Mr. Fox Talbot,
and although it is for intaglio printing, and therefore a little out of
place under the above heading, still it claims our attention as giving
a method for breaking up the half-tones of the photograph, by placing
muslin, crape, etc., between the photographic cliche and the sensitive
surface; or a glass plate may be covered with fine lines, or glass may
be coated with powder, which is caused to adhere. |64|
In 1854, Paul Pretsch broke up the half-tone by the reticulation of
gelatine, caused by the admixture with iodide of silver and bichromate
of potash; this was spread upon a silvered copper plate, dried, and
exposed to light under the half-tone negative, then washed in cold
water and borax, or carbonate of soda, then in alcohol, coated with
copal varnish, and immersed in a weak solution of tannin, after which
an electrotype could be made, or a transfer made to zinc or stone.
In 1855, A. J. Berchtold produced a grain by printing upon a photograph
in black or in any color, from a plate or block or other surface, or
by perforating or making strokes, lines, or dots upon it, by roller or
other instrument. Repatented in 1883, by Brown, Barnes, and Bell.
In 1860, E. J. Asser used starch, and in 1865, J. W. Swan used a tissue
of gelatine mixed with charcoal or other chemically inert grit; in
the same year Messrs. E. & J. Bullock published, perhaps, the most
important specification, describing all, or nearly all, practical
methods of obtaining grain, the most important of which are the
placing of any fine fabric between the lens and the sensitive surface,
or between the camera and the object, or copies of granulated or
recticulated structures or fabrics could be used, or such copy could be
placed in contact with negatives, and both copied together.
In 1879, J. W. Swan made negatives by moving, during exposure, the
Bullock’s screen, placed in front of a sensitive plate. Meisenbach’s
method, patented a little later, is somewhat similar.
If a Woodbury relief is thinly coated with transfer ink, and then laid
upon a piece of ordinary litho transfer paper which has been embossed
with lines, or dots, or stipple, by being pressed in contact with wire
gauze or an engraved plate, and the inked relief and the embossed litho
transfer are then subjected to heavy pressure, a grained image is
impressed upon the transfer paper, which can be transferred to zinc,
and then etched in relief.
The method of making a grained negative to be now described, shortly
stated, is done by interposing a screen, either before the sensitive
plate in the dark slide of the camera (when copying a photograph) or
placing the screen behind a transparency on glass when transmitted
light is used. In the first instance the image projected upon the
sensitive plate, having first to pass through the screen, is broken
up by the dots upon the screen, the result being a definite grained
negative. In the second instance, the screen being placed in contact
with the transparency, a similar result follows. The first method
is most generally used, as the print does not require the careful
focussing necessitated by the second.
|65|
CHAPTER II.
MAKING GRAINED NEGATIVES.
THE SCREEN.
For making grained negatives, the apparatus, chemicals, and
manipulations described in Chapters I. and II., Part I., for line
negatives, are required, with perhaps a little increased care to secure
clean and bright negatives.
The first requirement will be a proof, on fine white paper, from a
machine-ruled plate, or a plate with fine dots or stipple; a favorite
being plates ruled diagonally and straight, either in single lines or
crossed. These plates must be of good size, say 18 by 15, ruled with
lines as fine as possible, 100 or 150 to the inch. The ruled sheet must
be perfect, as any defect in it will be fatal.
Such a proof being secured, it should be carefully mounted with starch
paste upon a stout piece of smooth cardboard, and should be carefully
shielded from all chances of being soiled, as the slightest stain
or mark upon it will unfit it for use. As such a fine line is very
difficult to focus, especially in making the smaller screens, it will
be found a good plan to cut four narrow strips of good, bold type, and
paste these at the four corners of the sheet, just outside the ruling;
these slips of type will be easy to focus, and will render the task of
making the screens easier.
Plates ruled with single lines, either diagonally or horizontally, may
be used instead of the cross ruling, and are by many preferred.
Those in possession of a ruling machine may make these ruled sheets by
ruling a large litho stone, and pulling impressions from that stone.
If this is done once, and done well, the sheets will last a lifetime;
and if the stone be sufficiently large, and the lines very fine, the
screens may be used for blocks 15 by 12 inches or larger.
To copy this ruled sheet, remove the mirror from the lens, and put the
lens in the camera in its ordinary position; then pin up the sheet
on the easel, and, after seeing that the easel and camera are quite
parallel, proceed to make a series of negatives from the sheet, making
screens of various degrees of fineness, varying from a coarse grain for
a coarse photograph, to the finest possible for |66| photographs full
of delicate half-tone, and from three inches to ten inches wide. Many
subjects will need screens made especially for them. The screens must
be free from speck or stain, and should be made upon very thin glass.
The nitrate bath should be in good condition, and the collodion ripe.
Such negatives take a good deal of time making, but as they are the
foundation of the process, and with care will last for years, the
trouble must not be grudged.
The screen negatives being made, they must be varnished with a good,
hard, well-filtered varnish, applied in a room quite free from dust.
The screens must be made by the wet collodion process. The ordinary
gelatine dry-plate is utterly useless for such work. Gelatino-chloride
plates might do, but the exposure is so very long that there is risk of
shaking the camera during exposure.
THE GRAINED NEGATIVE.
For the first method a good vigorous photograph is selected, placed in
position on a copying board, and the camera adjusted so as to get the
image on the focussing screen the size wanted the mirror being used, as
the negative must be reversed.
A collodion plate is now prepared and well drained; then one of the
transparent screens is fixed in front of the carrier by drawing pins,
by passing strips of gum paper over, or by fixing with fine tacks
a piece of thin card at the top, and one at the bottom, slightly
overlapping the screen, and holding it firmly in a sort of rebate.
The carrier is now placed in the dark slide, the sensitive plate in its
place, the door of the slide closed and fastened.
The exposure is now made in the camera, and if the screen is properly
transparent the time will not be very much more than when copying in
the ordinary way.
The development of the exposed plate is done by means of the developer
given in Chapter I., and the result must have all the details of the
photograph, while the lines of the screen must be clear and free from
veil.
The negative is washed, fixed in cyanide, washed again and then
intensified, first immersing it in the solution No. 1, Chapter I.,
until bleached, then thoroughly washed and blacked with No. 2 solution,
again washed, and varnished with the water varnish, or dried and
varnished with benzole varnish.
For the second method we shall require, instead of a paper photograph,
a transparency on glass. |67|
The transparency may be made on a gelatine dry-plate by printing in
contact with the negative, or an enlarged transparency may be made,
either on a dry plate or by the wet collodion process.
The transparency should be made by contact, when the original negative
is of larger size than the block required; the enlarged transparency is
used if the negative be smaller or the same size as the block.
The development of the transparencies on gelatine dry-plates will be
treated of later, but if wet collodion be used, the manipulations will
be the same as for negatives, except that the image is in reverse
gradations, the lights being clear glass, and the shades dense and
black. Every detail in lights, shadows, and half-tones must show
distinct and strong.
[Illustration: Fig. 5.]
For the production of these enlarged transparencies, an enlarging
camera will be required, which may be provided by having an arrangement
in front of the ordinary camera, fitted like the accompanying figure,
consisting of two boxes, one sliding within the other, the negative
from which the transparency is to be made being placed in a carrier at
B.
In the illustration the sides are shown open, but only for simplicity,
as they must be quite opaque. In using such an arrangement, the camera
must be brought under the skylight of the studio, and the light
reflected through the negative, by placing a large sheet of white paper
at an angle of forty-five degrees in front of the negative.
Another and perhaps better method will be to cut a hole in a dark-room
at a proper height for the camera, and fix the negative in the hole,
then adjust the focus upon the screen, illuminating the negative by
means of a reflector fixed at an angle of forty-five degrees.
The transparency being secured, it is varnished, and all blemishes or
spots removed by means of a sable brush, and a little carmine color; it
is then placed in contact with a suitable screen, and the two together
are inserted in the |68| place previously occupied by the original
negative. Now adjust the camera so as to get the image on the focussing
screen the proper size, and proceed to make a grained negative by the
wet collodion process exactly as described in Chapter II., Part I.,
and above. When a negative containing all the details of the original
negative broken up by the fine grain of the screen is obtained, it may
be dried and varnished, and then it is ready for printing upon the zinc.
All pinholes, etc., should be stopped by means of a fine sable brush
and Indian ink. The printing on the zinc should be done by the bitumen
process, Chapter VI., Part I., as the albumen is not nearly so perfect.
If, however, the albumen process be preferred, the printing is done in
the same way as described in Chapter V., but extra care must be taken,
first, that the zinc plate is thoroughly and evenly polished; secondly,
that the graining bath is kept weak with plenty of alum in, so as to
have the grain on the plate as fine as possible; thirdly, that no
speck of dust, dirt, or any air-bubbles be on the film after coating,
and that the whirling be effectually done so as to get the sensitive
coating as even as possible.
The inking up requires no comment, as it must be done as evenly and
thinly as possible, for both line and half-tone.
In development, a little more energetic friction will be necessary, but
extreme care must be taken not to abrade the ink surface. Continue the
rubbing until all the details are developed, and bear in mind that the
finished block will be exactly like the zinc after development.
In printing these half-tone zincs, it often happens (like printing
in silver) that to get the best results some portions will require
less exposure than others. The best way to stop back any portion or
portions, is to cover the front glass of the printing frame with
whiting mixed with water to the consistency of thick cream; apply with
a rag over the places in the negative, before exposing to light, and
at the end of one-third, or in case of very deep shades, one-half the
exposure, clean off the whiting and finish the exposure without any
obstruction to the light.
The exposure to a grained half-tone negative will be one-half to double
as long as a simple line negative.
A perfect print on the zinc must contain all the grain intact, for
if there is any break in its continuity, it is of no use to proceed
further with it.
The printing in bitumen requires no more comment than to say care is
necessary to avoid dust. The smallest speck will be likely to spoil an
otherwise perfect print.
|69|
CHAPTER III.
ETCHING IN HALF-TONE.
WHEN THE PRINT IS IN ALBUMEN.
The zinc plate with the image upon it in ink, is dried, then warmed
slightly on the hot plate, cooled, and coated with thick gum* and
fanned dry (not dried by heat, or the gum is certain to crack and bring
away the image or part of it); then wash it under the tap, and rub it
gently with a fine sponge so as to remove all gum from the ink, but
not from the zinc. Next proceed to roll up as directed in Chapter V.,
using the India-rubber roller charged with stiff ink. The surface of
the zinc should be kept well covered with water. Use as little pressure
as possible, but let the motion be fairly rapid, and if any portions of
the image should smear, roll rapidly with slightly increased pressure.
* See page 55, Part I., Gum and Nut-galls.
This operation of rolling up the image is the crucial one, for unless
it is done properly, when it is finished, the result is a strong black
and perfectly even image; it is of no use proceeding further with it,
for in fact the picture must be perfect.
The rolling up being done, any touching up that may be required can
now be done, and any fine details clouded over, or made indistinct by
the grain, strengthened or opened out. Additions should be made with
transfer ink thinned with turpentine, laid on with a very fine sable
brush. The whites are put in by scratching through the ink with a fine
etching needle.
To rest the hand upon in doing this touching up, so as to avoid
touching the image, a bridge is used made of a strip of smooth wood,
one inch wide, quarter of an inch thick, and sufficiently long to well
span the plate; at each end of this strip nail narrow strips a quarter
of an inch thick to serve as the feet for the bridge to stand upon.
Then the zinc may be slid under it without touching the surface against
the under part of the bridge.
The zinc is now ready for the first etching in the rocking tray.
The nitric acid solution must be very weak indeed to the taste, the
presence of acid being just perceptible. The time of immersion in the
first bath must not be longer |70| than thirty seconds; then the zinc
is removed, washed under the tap, and gently rubbed with a sponge; dry
it gently on the hot plate, allow the zinc to cool, coat it with gum,
fan it dry, rinse it under the tap and rub it with a sponge; then again
roll up, when it is ready for the second etching; that is done in the
same bath as the first, without any addition of acid. Keep the tray
gently rocking for three minutes, then again withdraw, wash it under
the tap, rubbing with sponge, coat with gum, fan dry, wash under the
tap rubbing gently with sponge, and again roll up, using the ink on
the roller a little thicker, but stiff. When the image has taken the
ink equally, place it on the hot plate and allow the zinc to get hot
enough to melt the ink slightly; then allow it to cool, and place it in
the etching bath, slightly reinforced with a few drops of nitric acid.
Immerse it this time for five minutes.
The operations of washing, gumming, rolling up, etc., are to be
repeated until it is judged that the etching has been carried far
enough. The time of immersion in the acid solution with each etching
may be lengthened, but take special care to keep the bath weak until
near the last etching, when the strength may be slightly increased.
The resist is cleaned off with turpentine and a stiff brush, and then a
proof is pulled. If further etching will improve it wholly or in part,
the plate is inked up and again subjected to the action of the acid
bath.
If only portions require reëtching, cover the rest with bitumen
varnish; but it will be scarcely safe to give more than one etching
after cleaning off the original resist.
WHEN THE IMAGE IS IN BITUMEN.
A bitumen image is etched in the first bath in which the acid is
just perceptible to the taste, without any preliminary rolling up.
The duration of the first etching may be prolonged for three or five
minutes; then the plate is withdrawn and well washed. Remove any scum
with a soft sponge; then dry it in a cold current, and smear it with
gum, fan it dry, and roll up with a leather roller charged with stiff
ink, until all portions of the image have taken a film of ink. Now
reinforce the nitrate bath with a few drops of nitric acid, and again
immerse the plate, rocking the bath for ten minutes; watch the picture
carefully so that in case of undercutting the plate may be removed
before any mischief is done.
The plate is again removed, washed, rubbed with a sponge, and dried; it
is |71| then warmed on the hot plate, so as to slightly melt the ink,
then allowed to cool, smeared with gum, fanned dry, damped over with
a wet sponge, and rolled up, the roller being charged with stiff ink.
The plate is now ready for another etching, for which the bath must
be strengthened by the addition of more acid. The immersion (rocking
all the time) may be fifteen or twenty minutes, after which the plate
is withdrawn, washed, rubbed with a sponge, and if it is thought
another etching would improve it, the cycle of operations is repeated,
beginning with warming the zinc on the hot plate.
After the resist is cleaned off (which with bitumen must be done first
with turpentine and then with benzoline) further etching may be given,
if deemed necessary, first inking up well with the hard ink mentioned
in Chapter VIII., and then reimmersing in a weak bath of acid and
water. If only a portion requires reëtching, those parts that are not
to be touched, are protected by coating with bitumen varnish.
The plate being etched, now requires finishing.
The outside zinc is removed with a circular saw and then the edges are
filed and holes drilled at an angle, so that the metal can be fixed
upon the block.
|72|
CHAPTER IV.
PRINTING FROM THE BLOCK.
A half-tone block to give results commensurate with the care needed
in its preparation, must be handled by the machine man with care and
consideration.
The blanket on the tympan or cylinder must be replaced with something
harder, else the soft pressure of the blanket will blur the print.
The block must also be made ready, not by putting cut-outs on the
tympan or cylinder, but underneath the block, and there as thin as
possible.
The ink must be good and not too thin; the rollers must be free from
flaws and not too tacky. In fact, as much care is required on the
press as during the photographic and subsequent operations. Indeed
photo-engraving and zinc etching would have come into popular use
more rapidly than they have, if printers had been willing to give
them the special “making-ready” attention they require. Despite all
prejudice and indifference, “process-engraving” so called, has made
continuous improvement ever since it came into use, and the good work
goes on. The most delicate gradations of light and shade discernible
in nature, may, from the photographic plate, be rendered in pure black
and white by means of any of the methods given in this work. All that
nature displays, and all that imagination compels, may be reproduced
indefinitely.
With regard to the storage and keeping of zinc blocks after using, Mr.
T. Bolas, in the _Photographic News_ of September 24, 1886, says, “they
should not be washed with the usual lye, but should have a few drops
of paraffine oil poured upon them; and after this has been well rubbed
in by a soft brush kept for the purpose, the paraffine should be well
wiped away with a soft cloth. If the block is to be stored away for a
long time, it should be waxed. The best way of doing this will be to
make it rather warmer than is necessary to melt wax, and then to rub it
over with a piece of yellow bees’-wax, after which the excess is wiped
off with a piece of flannel.”
Sometimes zinc blocks are electroplated with copper or nickel (a
necessity when they are to be used for certain color work), and such
blocks should also be treated in the same way as the bare zinc, as they
cannot be safely cleaned with the lye solution.
|73|
CHAPTER V.
THE TRANSFER OF THE DRAWING, AND ITS TREATMENT BEFORE ETCHING.
According to the methods of producing them, classify the drawings as
follows:
(_a_) Freehand drawings in crayon or ink, drawn with lithographical
chalk on rough paper, or with pen and chemical Indian ink on paper
prepared for transferring.
(_b_) Lithographical transfer of engravings, pen-and-ink crayon
drawings, or drawings on stone.
(_c_) Transfers from relief plates made in copper, steel, zinc, or lead
(music).
(_d_) Anastatic transfers.
(_e_) Fat or resin prints from photographic negatives.
Proceed as follows:
(_a_) _Transfer of hand-drawing._—Place the drawing to be transferred
with its face upon a sheet of clean, white paper, and moisten the
back with a weak solution of nitric acid (1/2° Baumé), by means of a
sponge. Over-moistening causes obliteration of the drawing, fringing
of the single lines, and the running together of the hatched portions.
The correct degree of moisture can be ascertained when the side
prepared and drawn upon grows slightly sticky, and when the drawing
becomes glossy. This will take place in from four to five minutes
after moistening. This time is to be spent in arranging the zinc in
the press, after having freed it from all greasiness. Place a card on
the rolling press below the drawing and the zinc; above it, a sheet
of good blotting-paper, a sheet of Bristol paper and are of pressing
board; then make a trial print with the press, a clean piece of paper
taking the place of the drawing. The correct pressure is a matter of
experience; it is advisable to begin with a pressure less by one sheet,
in order to be able to increase it during the process of transfer.
In the lithographic press the ink-block is first to be adjusted; since
it needs a greater “setting in” than the rolling press, the zinc must
be cut larger. It must extend three centimetres on all sides beyond
the drawing. The edges of the cut plate must be well ground off, in
order that the ink-block may not be |74| caught; at all events, it is
advisable to have the latter smaller than the plate. Observe that the
range of the press should be regulated; then place the zinc directly,
without any intervening layer of paper, on a solid stone; lay upon it
a clean sheet of paper, a blotter, a sheet of Bristol paper, and a
pressing board well covered with tallow. Make a trial by drawing the
sheet through at a moderate pressure. If all is arranged, the work of
transfer can be started. The temperature of the zinc should now be
about 35° C.
Place the drawing down carefully, without moving it about; upon it the
blotter, the Bristol paper, and a pressing board, and draw it through
three times with constantly increasing pressure; turn the plate in
a contrary direction, and draw it through three times in the same
manner. Now place a moistened sheet of good paper between the blotter
and the drawing, and draw through, first with weak, and then with
strong pressure, three times in both positions. Instead of turning the
zinc, the ink-block may be reversed. This finishes the operation of
transprinting, and the next question is the loosening of the paper from
the zinc. Here we can pursue two methods: first, we can have hot water
and a porcelain tray at hand; place the copied plate in the tray, and
pour the water upon it. The coated layer bearing the drawing begins to
separate from the paper. Shaking the tray promotes this action, and
soon the paper will loosen itself from the layer which remains attached
to the zinc. With the second method proceed thus: moisten the back of
the copied drawing, thoroughly with a sponge and cold water; allow it
to soak in, warm the plate to 60°–65° C. and carefully rub all parts by
hand. The layer will again separate by degrees from the paper, which
latter we can then easily lift off from the plate.
On account of the strongly gelatinous layer, crayons on grained paper
should only be moistened moderately before and after the first rolling,
in order to avoid the coiling of the paper.
Hand-drawings on paper without coloring require treatment with stronger
acid (I recommend nitric acid, 4° Beaumé). At the same time the drawing
should be cut as close as possible. To draw it through securely, place
it as usual upon the zinc, and above it a piece of prepared copy paper
moderately moistened, and a trifle larger than the drawing, then a
blotter, a Bristol board, and a thick card, and draw through as before.
The coated copy paper sticks tight to the zinc after the first rolling;
it also retains the drawing in its first position, and allows repeated
rolling. If the original was over-moist when |75| copying, it sticks
to the zinc and separates with difficulty; if the moistening was just
right, two perfect copies can often be made from the same original.
I have attempted to copy drawings on a fatty zinc surface, and to etch
them strongly, but, far from being satisfied with the result, I prefer
the above method.
(_b_ and _c_) Copies of lithographs, type, plates for printing of any
kind, plates for _deep_ printing, I make on well satinized copying
paper*; in making the prints, I employ a copying ink as thick as
possible, with the addition of a few drops of a thick solution of
asphaltum in lavender oil, rolling a long time with but little color,
so as to get a sharp rather than a heavy print.
* Instead of the paste-gelatine-chalk, I prefer to prepare
the surface with a decoction of semina psyllii.
Plates for _deep_ printing, I heat equally throughout before applying
the color. Instead of color, I rub them with chemical Indian ink, wipe
the surface carefully, even polish it finally with a ball and some
Frankfort black. I then draw it through and again heat it uniformly, so
that the copy comes off of itself. Fine, sharp transfers, with perfect
relief, are thus obtained.
(_d_) Anastatic copies are no longer of great value, since they always
turn out roughly and cannot compare with photographic copies. Although
I possess a safe method, I believe that I will have to omit it on
account of the limited space of my work and the minute importance of
the results.
(_e_) Photographic fat or resin prints should be treated like ordinary
prints. Moisten them on the back with water—which is preferable to
placing them between moistened blotting-paper, since the drawing does
not grow too wet—and wait till they are easily flexible. Drops of water
on the film can and often do destroy the proof. Draw the plate through
with increasing pressure and one intermediate moistening. Prints in
fatty inks necessitate a temperature of plate of 35° C. Prints with
dissolved etching varnish (resin) as a printing film should have from
50°–60° C. When loosening the paper avoid warming, but moisten well.
Sticking of the gelatine film happens, especially with Husnik’s paper;
a safe remedy is to dry the copy in strong light, after developing.
Old sensitized paper, on the contrary, seldom sticks at all, and fresh
paper should always be sought.
In printing with the rolling press, I observe that the rollers of the
press need only once to be regulated, and that greater or less pressure
can be attained by thicker or thinner covering of the print with
sheets of paper. This gives much greater security than can be had when
constantly readjusting the rollers. |76|
THE FURTHER TREATMENT OF THE TRANSFER.
Should we now proceed directly to etch the copy, the acid would act
through the drawing, which is as yet but loosely attached to the zinc,
and would at last cause the lines to appear broken, if not destroy them.
It is, therefore, necessary to replace the loose copy by a possibly
dense etching varnish, attached fast to the zinc, and to produce an
intimate connection between the latter and the etching varnish. Here we
meet a difference between the French and Austrian methods. The former,
totally based on the lithographic process, favors the use of a resinous
dense color as a _strengthening material_, whereas the Austrian method
employs an ordinary copying color and endeavors to form an etching
varnish by sprinkling and melting in a quantity of finely pulverized
resin. In the method of etching with copper sulphate, it was attempted
to restrict the corroding action of the sulphuric acid by the following
method: The drawing, rubbed with color and thinly besprinkled with
resin, was slightly melted in, then sprinkled and rubbed with the
finest silver graphite or real water-gold. It was thus made an electric
conductor. A thin coating of copper was then deposited on the drawing,
which, in point of fact, hindered the destruction of the film. At the
same time, however, the process became uncontrollable, since often a
deposit of amorphous copper became tightly fastened to the metallic
surface. The lateral action could not well be ascertained, since the
narrowest parts were often clogged with metal, without preventing
corrosion from below.
The French method of etching is this: A thick solution of gum-arabic
is mixed with extract of nutgalls; this is carefully spread over the
surface of the plate by means of a fine sponge, and dried by a fan.
Then a knife’s point full of etching color (composed of 500 grammes
chalk color, 40 grammes coagulated mutton suet, 40 grammes soap, 125
grammes yellow wax, 40 grammes margarin, and 40 grammes oleine, melted
in the warm bath and passed through the color mill) is dissolved in
oil of turpentine, and a portion of this solution is spread uniformly
on the grinding stone by means of a fine sponge, so that the latter
contains a similar layer of color throughout. The fatty gum film
is then washed, with a wet sponge, free from fat and acid; a fresh
quantity of the gum and nutgall solution is poured out, and the copy
is by degrees strengthened by rubbing on the etching color with a
sponge. This is repeated until the drawing has attained the proper
strength throughout. The superposed layer of gum is then washed off,
the superfluous water is removed with a sponge, a wet cloth, and
blotting-paper, dried with a fan, then gently warmed. |77|
Now the plate is to be dusted with the finest pulverized resin,
consisting of equal parts of Syrian asphalt, washed in alcohol, and of
mastic; the superfluous resin is removed with a brush and some cotton;
the plate is then carefully heated, without beginning to melt the
resin, however.
This, by the French method, finishes the plate for etching. Only weak
acid is safe for such a plate, however.
According to the Austrian method (practised by me for several years),
we proceed as follows: The copied plate is first copiously coated with
a cold saturated solution of gallic acid, and then with a pure solution
of gum. Without allowing it to dry, I remove the superfluous preparing
materials with a wet sponge, and pour on some fresh gallic acid, as
with an excess of acid the drawing assumes a more brilliant black color.
The strengthening with ordinary copying color I effect, as the case may
be, with the rollers, the sponge, or by coating.
(_a_) _Strengthening with the Rollers._—I roll out some thick copying
ink with good, rough rollers which have been frequently used, and begin
to roll the transfer plate while still damp, without any pressure, till
its surface begins to dry. I then grasp the handles of the rollers
more firmly and blacken the dry plate uniformly, giving it a thin
coat of ink. This done, I moisten it a little and roll it regularly
with rollers freshly treated with color, so that the picture comes up
harmoniously and strongly.
Rolling off during drying keeps the gum solution from the drawing while
drying on, and keeps open the connection for rolling in.
Before going further I will explain the terms used*: To roll in is
to give color or ink, and is done slowly, with tightly grasped handles
and certain pressure. Rolling off is effected with loosely grasped
handles, without pressure, and quickly, and is intended to draw off
with the rollers any excess of color on the plate. _To work out_ or
_make the rollers_ means to bring fresh color on it from the grinding
stone, and is done with strong pressure and strong traction. The
correct management of the rollers rests in the wrists. To _reverse the
rollers_, to _change the handles_, means to turn the rollers around,
to make the left-hand handle the right-hand one, and thus to correct
irregularities in the distribution of color. After every advance and
return on the stone or plate to be blackened the rollers are newly
adjusted. The plate thus strengthened must be well |78| washed with
clear water, to be dried, and at times even to be retouched with a
brush and color dissolved in oil of turpentine.
* Color and ink are synonymous. “Burn in” and “melt in” mean
the same.
(_b_) _Blackening in_ with a sponge. The initiatory etching is done
with gallic acid, the gum coating put on and additional gallic
acid poured over; then some turpentine solution of copy color, the
consistency of syrup, is rubbed over the plate until the picture is
uniformly strengthened. If, as may happen in hand-drawings, the color
should become massed and not attach itself smoothly, it must be washed
off with turpentine and then clean color must be rubbed on.
This operation requires great delicacy. After having finished the
blackening in, rinse well, dry with a sponge and thick blotting paper.
Heat, so as to vaporize the last remnants of dampness, and retouch.
(_c_) A peculiar method of strengthening, nowhere described, as far as
I know, is that of drying the plate after coating it with gum, then
washing the gum with water; then, after drying, of covering the plate
with a thin solution of wax, asphaltum, rosin, and shellac in ether,
and of carefully coating the quickly drying film with gum. The film
remains on the lines of the copy, but easily detaches itself from the
bright metallic spaces, which have an insoluble combination with the
gallic acid and gum, and are thus protected from the fat.
_Faults in strengthening_ are caused by the following:
_a._ By ink which is too thick or too thin, or which has not been well
ground. Stripes are caused by the dissolving of the color which is
already present.
_b._ By excessive dampness on the plate (it does not take the color;
the color in the sponge changes to a slimy emulsion).
_c._ By too great pressure with the color sponge the fine parts are
lost. The same is the case with careless washing of the color of
hand-drawings.
_d._ In _rolling on_ excessive moisture on the plate spoils the work.
The surface of the rollers becomes glossy and must be again inked.
_e._ In pouring out the ink a very thick layer prevents the
strengthening of the finest lines.
Dirt on the plate often comes from handling the drawings; it must be
scratched off and the plate must be perfect before proceeding.
Now comes the changing of the ink into an etching varnish. But before
beginning we must cover the free edges of the zinc for the distance
of half a centimetre around the drawing with a solution of ink in
turpentine; the same applies to large white surfaces in the drawing,
which it is more convenient to cut out with a scroll saw. Then subject
the plate to the finest asphaltum |79| powder, passed through a
hair-sieve, and cover it by the dusting brush copiously with powdered
rosin. Continue the rubbing on of fresh powder for a minute, until the
ink is saturated, then dust out the superfluous powder with the dusting
brush and fine cotton, so that the metal is bright (no film should be
perceptible on looking over it).
The plate should now be heated to about 60° C., till the color of the
asphaltum changes from a coffee tint to a dead (matt) black. Place the
plate in this condition a second time with the asphaltum, which is
again absorbed rapidly. Dust off carefully as before and burn in again
till the color changes to a somewhat shiny black; the yellow tint must
be avoided, because this degree of burning exposes the lights in the
closest hatchings to the danger of running together.
Thus the coat of color is changed into an etching varnish of excellent
resistance and adhesion, and the plate is ready for etching.
THE ETCHING AND ITS INTERMEDIATE TREATMENT BEFORE MOUNTING THE CLICHÉ.
_Introductory remarks._—If we examine a wood cut or an electrotype with
regard to the depth of its narrow and wide-line complexes, we can at
once determine a plane for the closest hatchings; in a uniformly deep
layer the lines lie at a moderate distance apart, and those of the
highest lights are very deep. These three planes are situated higher
or lower according to the very narrow or very wide series of lines.
This gives a natural division of the different stages of etching, and,
according to the three depths, we distinguish the _sharp etching_ or
_etching on_ in which the engraving must advance far enough to place
the narrowest portions sufficiently low; _middle etching_, which has
to accomplish the same for the moderately narrow portions, and _deep
etching_, which must attain sufficient depth for the highest lights.
On account of the lateral action of the acid it is impossible to etch
down perpendicularly, but a wider covering is taken for each stage. Of
these wider coverings there remain after etching all around the relief
two terrace like grades, which must also be removed.
We have, then, in addition to the above, three sorts of etching, a
_round etching_, in which the grade remaining from the deep etching is
to be removed, and a _clean etching_, or a removal of the wire-edge
left after middle etching.
This natural subdivision is found in the old French method as well
as in the |80| new method, and both coating and the acids are of a
strength proportionate to the different stages of the work.
We have already alluded to the lateral action of the acid; it is a
factor that taxes the care of the etcher in the highest degree. In the
beginning of the action of the acid, the edge of the metal under the
coating is exposed the more, the longer the action lasts; here, of
course, the dissolving power becomes apparent. The deeper we go, the
more the metal under the line is exposed, and the action on the lateral
edge continually increases. In the effect of the acid we distinguish
thence, a perpendicular and a lateral action. Since the latter cannot
be removed by changing the character of the acid, we must give it a
part in this process of dissolving metals, but at the same time must
invent a method which will prevent the lines from growing thin.
But in order to do this we must know the relation of the perpendicular
to side action. Both are in proportion, a result both of theoretical
and practical consideration. In order then to attain a certain depth of
etching, a proportional lateral protection must take place, which is
by degrees destroyed by the lateral action. Since this lateral action
sets in at the beginning of the work, the dimension of the line must
be secured from the start. This is done in the Vienna method by the
already mentioned formation of the etching varnish, by means of dusting
with resin and burning in, by which an almost imperceptible growing of
the width of line is attained. The French method endeavors to correct
this by using a very weak acid and a correspondingly thin coating,
but coating oftener and etching at every new coating, as we shall see
below. Also the coating for middle and deep etching must be arranged in
accordance with the principles above elucidated. As deep as the middle
or deep etching is desired, so wide must the lines be surrounded by
etching varnish.
ETCHING BY THE FRENCH METHOD.
We have already seen (p. 76) how a copy is made by the French method
for etching, and we now continue the development of this process.
Into a tray pour 4 litres of water at 18° C., add 15 c.cm. nitric
acid and mix well by shaking. Then place the prepared plate into the
bath and rock it for seven or ten minutes (according to the fineness
of the drawing), rinse well with water, remove the remaining water
with blotting paper, and, finally, dry thoroughly with a fan. (Do not
forget to dry the back.) Now warm the plate from the back, moving the
flame about continually, so as to secure uniform heating and prevent
warping of the zinc. The asphalt powder, which is as |81| yet but
loosely attached, is more intimately connected with the subjacent ink
through this heating process. The combination becomes evident from
the assumption of a black lustre. With the appearance of this, stop
heating, and lay the plate on a cold stone to cool. This done, spread
some gallic acid over it with a soft sponge, and without washing it
off, spread gum on the surface of the plate, and hasten the drying with
a fan.
Mix some etching ink with varnish and work it out into a thin layer
with good rough rollers. If the rollers are in order, wash the coat of
gallic acid and gum from the plate, remove superfluous water and _roll
in_ (the manner similar to that used in lithography). The surface of
the plate should not be more than moderately damp, so that the rollers
may not slip. If a coat of color has been uniformly deposited, wash the
plate with clean water, remove the excess with a sponge and blotter,
dry by fan and remove all moisture by heating to 45° C. Dust the warm
plate again with asphaltum (remove the excess), and warm it a trifle
to secure better adherence. Strengthen the bath by the addition of
15 c.cm. nitric acid, and etch again for seven or ten minutes under
continued shaking. Then rinse the plate, remove the water and dry with
a fan, and burn in the resin powder well. Careful inspection will now
show a successful and uniform but still weak relief.
As before, the plate is coated with gallic acid and solution of gum,
is dried, washed, and _blackened in_, in which treatment one-third
“wax pomatum”* is mixed with the etching ink. After washing and
drying heat the plate up to 60° C., thus causing an imperceptible
widening of the drawing. After coating dust once more with asphaltum,
warm it and cover only the back and the white rim around the drawing
with a solution of shellac (1 part ruby shellac in 10 parts spirits).
Strengthen the bath with 20 c.cm. of acid and bathe it for seven to
ten minutes, shaking the bath regularly. Continue until you see that
the lateral action of the acid has almost wholly destroyed the lateral
covering produced by heating. Do not, however, etch too long, and do
not mistake the _over_-hanging coat for the other. Then follow washing,
drying, melting on some resin, cooling, coating with gum, blacking
in with equal parts of etching ink and “wax pomatum,” then washing,
drying, greater heating (70° C.) (so that by increasing the ink each
line receives lateral protection), cool and dust to excess with the
finest resin dust. |82|
* Wax pomatum is prepared by cutting beeswax into fine
parts and covering it in a wide-necked flask with oil of
turpentine. In a few days a jelly-like mixture will remain,
which serves the above purpose.
As we have now reached the necessary depth for the narrowest portions,
we use, instead of the asphaltum, resin, which melts easily and spreads
out readily, in order to attain protection for our middle etching.
Strengthen the bath with 30 c.cm. acid, and bathe until the lateral
action of the acid has reduced the lateral coating to a narrow edge.
Then wash, dry, melt on some resin, cool, prepare with gum. Blacken in
as before, but employ one-third etching ink and two-thirds wax pomade
and apply so thickly that all the narrowest spaces of the drawing are
completely filled with color. Continue warming until the ink, which was
applied, has well covered each line; then dry and use resin as before.
The acid may now be strengthened by 100–158 c.cm., according to the
strength of coating chosen. Bathing must be continued until the edge
that has run off begins to grow narrow. Wash, dry, burn in resin, cool,
coat with gum, and blacken in by rollers with clean wax. Continue
heating until each line is well covered by ink. Always dust until the
ink is fully saturated and then heat gently.
Strengthen the bath 200 c.cm. and begin the _deep etching_. According
to the depth to be attained repeat the manipulation of strengthening
once or twice. Whenever a corrosion of the lateral coating becomes
apparent, coat freshly, adhering to the above order of operation. For
obtaining the necessary depth ink is applied about _ten_ times, adding
wax each time to facilitate the spreading when warming.
In order to attain a fine, regular lateral coating, great ability in
manipulating the rollers is necessary, since without such the correct
degree of strengthening is never attained. Irregular coating leads,
of course, to irregular melting of the ink; one spot then is already
sufficiently wide, while another is not yet covered. In such cases
coating with a brush must be resorted to.
If the necessary depth is attained, the plate is to be freed carefully
from the coating with a brush and oil of turpentine, and then placed in
fresh sawdust, which absorbs the oil of turpentine and leaves behind
a clean surface. Now the work can be criticised in all its parts. To
every coating is a corresponding narrow edge of etching, which is now
to be removed in order to make the plate fit for printing. To removing
these edges we must devote our attention. We begin with the top one,
and make preparations thus: Roll out on a clean, warm stone with
faultlessly smooth rollers a very thin gauze-like layer of etching ink.
Likewise warm the zinc plate and roll it in all directions without
pressure till the picture becomes beautifully black. |83|
Pressure must not be employed, but the coating must be obtained by
renewed _working out_ of the rollers on the _color-slab_, and repeated
coating. When at last the desired strength is obtained, dust with the
finest asphaltum powder, blow the traces of dust out of the hollows,
and warm till the layer becomes slightly brilliant. Next, etch in a new
bath of 4000 c.cm. of water and 40 c.cm. of acid for 7 minutes, wash,
and dry well; then, with more ink on the rollers, coat the dried plate,
dust once with resin, heat gently, then apply the asphaltum and burn in
strongly. Thus the first relief is protected laterally, and the first
grade can be etched down completely, without endangering the drawing.
To remove the second grade, we repeat washing, and put on etching ink
mixed with one-third wax. Rolling must continue till the narrowest
spaces of the etching are completely closed. Then follow dusting with
resin, warming, and placing the warm plate in the asphalt, dusting,
removing the excess, and finally burning in.
With this coating a further rounding of the grades can take place (in
a bath of 10° Baumé). Continue this process until all the grades are
removed and the etching appears as perfect as a cast plate.
Since hitherto all publications on chemigraphy have duly described
this method, I believe that I should not enter into further details,
improvements, etc. Suffice it to call attention to weak points. In
view of the new method later to be described, the reader may make a
comparison between the two.
A very weak point is the method of strengthening based on the
lithographic process of superimposing new color upon the old color.
In consequence of the repeated melting in of resin, this latter
acquires an uneven surface, which can be blackened in only with great
difficulty. Equally untrustworthy is the lateral protection by _melting
off_, which is only attained with safe uniformity by skilled workers.
And what is more, with the weak coating at the beginning; even weak
acid often works its way through to the etching, so that the finished
etching appears slightly porous, and gives no dense black print. Also
shaking, which is to promote the removal of the metallic mud and the
gas bubbles from the lines of the etching, has an unsatisfactory
effect, inasmuch as the single lines are often thus under-washed.
But the principal defect is that no accurate determination of the
degree of each operation can be made, everything depending on the
delicate execution of the process.
The time that the etching of a correct, deep cliché requires by this
method is from eight to ten hours. This procedure also demands better
trained hands |84| than the Austrian, which, in large establishments,
is based on a division of labor, and in which men trained in a single
manipulation, under good supervision, accomplish the maximum work
surely and excellently.
Furthermore, the expenses of the manufacture on a large scale are
far greater, since each etcher draws a greater salary than a workman
skilled in a few manipulations, such as the following method requires.
THE AUSTRIAN METHOD—THE ETCHING ON.
I have already shown how a transferred plate should be prepared for
etching by this method. Before proceeding to the details, however,
we will prepare the etching baths, which, by the way, may always be
employed for several plates. Corresponding to the three steps of
etching, we require three baths of different concentration to be
determined by means of an areometer with a Baumé scale. The bath for
_etching on_ is prepared in strength of 2° Baumé at a temperature
of 18° C. There must be a quantity sufficient to cover the plate to
a depth of 4 to 5 centimetres. The bath for middle etching requires
10° Baumé and a temperature of 18° C.; the bath for deep etching,
18° Baumé. These baths are prepared at the beginning, and are used
for the five successive stages of etching. If, after continued use,
the bath for deep etching should grow weak, it may be used for middle
etching. For protecting the trays, I recommend a coat of gutta-percha
over a well-coated inner surface of asphaltum. Everything being ready,
immerse the prepared plate in the bath, and with an etching-brush brush
the surface of the plate uniformly for two minutes.
The hairs of the brush must only rest lightly on the metallic surface.
For determining time, use sand-glasses of two, three, and five minutes.
After two minutes, take the plate out of the acid, wash it well with
water, and examine it carefully. If the effect has not been uniform,
see that two minutes more can be safely given in the etching bath. If
by any sort of careless handling the plate has been injured, dry it
with blotting-paper, vaporize the remaining dampness, and cover the
soiled spot with very thick solution of asphaltum in turpentine. Cool,
and continue brushing lightly for two minutes in the bath.
At the end of this time, wash and examine again. Even now everything
will be intact. With very fine drawings, however, lateral action has
already progressed so far that, under all circumstances, the exposed
edges must be covered. Coarser drawings generally stand one or two
minutes more.
To try the depth of etching: with your finger-nail on the edge of the
black |85| rim, feel how far the etching-on has proceeded. As soon as
the finger-nail catches, the depth is sufficient, and the sides of the
lines may be covered.
For this operation the plate needs, above all, thorough washing, drying
on both sides by blotting-paper and gentle heat, and a temperature
of 45° C. At this temperature place the plate into the finest
resin-powder, and rub the latter several times over the warm drawing,
using for this purpose a fine brush. The protection, which has grown
sticky through heating, retains a thin coating of resin, which, after
dusting off the bright metallic spots with a brush and fine cotton,
and after careful fanning off, is reheated to about 50° C. At this
temperature the plate is returned to the white rosin, receives a good
dusting-in, and being freed from excess as before, is heated to about
65°, so that the easily fusible rosin begins to spread out. At this
moment extinguish the light, and put the plate into the asphaltum,
which will attach itself copiously to the sticky resin. Brush the plate
well with the substance, remove any excess from the bright spots, heat
to 80° C.; then place it again into the asphaltum, brush it, clean
it by removing any excess, and heat it to 100° C., when a complete
combination of the resinous mass takes place, and a uniform etching
varnish is formed. This last coating is extremely regular, and it is
wonderful to see the accuracy with which the lines have been covered.
Beginners are warned to pay attention to the careful cleaning of the
bright parts of the plate when brushing and dusting it; should any
resin remain behind, it melts on, and grows by degrees to a strong
yellow tint, which is very difficult to remove, but very easy to guard
against. Never forget to dust off the back.
While the plate is still hot, lean it against the wall, face in, and
the back covered with a solution of shellac.
Now the plate is ready for further etching, which is carried on for two
minutes in the first bath. At the end of two minutes, wash and examine
critically. In almost every case we may etch for a third, or even a
fourth time. It is, however, sufficient for the beginner to know that
he has sufficiently etched in two spaces of two minutes each, after
preparing with resin. Trying and examining with the finger-nail on the
black edge will show a fine relief. Should it be possible to etch for
a third space of two minutes, or even of one, without danger, it is
preferable to do so. It should be a rule to proceed as far as possible,
judging from the character of drawing and coating. Experience is easily
gained in two or three trials, since anything can be examined at any
moment. Beginners would do well to use a magnifying-glass with good
field of view in examining, when they can observe the most sensitive
portion, and |86| all changes may easily be noticed. The brush should
be used lightly, to prevent scratching. Usually, it is fastened at
right angles to a stick to protect the hands from the effect of the
acid.
To raise the plates out of the tray, lay a gutta-percha thread into the
bottom of each tray, fastened at one end to the top edge of the tray,
projecting over the same on the other side. The plate is placed on the
thread while etching. It may be removed without touching the bath by
pulling the free end of the thread.
As already remarked, the spreading of ink on a surface which is more
or less rough is difficult. For this reason the plate, when etched-on
after my method, is to be washed out with oil of turpentine. A strong
brush should be used for this, and some of the oil rubbed over the
plate without pressure. You must cause a dissolving, not a rubbing off,
of the coat. On continuing the addition of turpentine, the metal grows
bright. Take, then, a handful of the coarsest of pine-wood sawdust and
rub off the surface. This removes instantly every trace of turpentine,
leaving a clean surface behind. For the sake of security, pour on more
turpentine, rub with a somewhat softer brush, and remove again with
clean sawdust.
It is important that the wash-table should always remain free from
sawdust, which latter should fall through the grating into a suitable
receptacle. If this rule is disregarded, the wash-brush will soon be a
conglomerate of sawdust and hairs. Sawdust and turpentine will stick to
the brush so tightly that a new brush will have to be purchased.
Now we again examine our work. It is a mark of success if the relief
still shows its original smoothness in all its parts, and has nowhere
grown porous. All the parts must be clear in their correct proportional
strength, as seen in the transfer.
The treatment of the plate from the time of transfer to the close
of the etching-on takes: for the saving of the edges and the white
portions of the drawing, 2 minutes; for preparing twice with asphaltum,
4 minutes; for varnishing the back and coloring the plate, 4 minutes;
for etching-on the lateral protection, 4 to 5 minutes; for preparing
twice with resin, asphaltum, and varnishing, 16 minutes; for renewed
etching, 4 to 5 minutes; and for washing, 5 minutes—that is, 33 minutes
in all. Add 7 minutes for inspection and retouching, and 40 minutes
will be the space allowed for etching-on. |87|
MIDDLE ETCHING.
In order to give to the middle tints of the drawing the depth necessary
for printing, we begin with a new blacking-in. We need for this purpose
excellent, smooth, and hard rollers, which are immersed in minium and
linseed oil, and are then left to dry for a short time. Contrary to the
French method, we need here a thin composition for the etching ink,
obtained by concocting equal parts of paraffine, suet, beeswax, and
ordinary ink, prepared in an excess of good linseed oil. (Ready-made
color of right composition may be had of E. Liesegang, in Dusseldorf,
and other dealers.)
This color, when of right composition, possesses the power of absorbing
resin-powder, and changes in combination with the same, when heated, to
a compact, very solid, yet brittle mass.
Of this color, which is soft as butter, take a portion on a
knife-point, and spread it upon the smooth rollers, forming a perfectly
uniform layer. The complete covering is done by rolling, changing the
adjustment at intervals. When a perfectly uniform, oily coat is spread
on the color-slab and the rollers, begin rolling-in the washed plate.
Do not exert any pressure, but roll, carrying the handles so as to
black the relief only from the surface of the rollers. Of course,
it cannot be prevented, and is of no consequence, if ink attaches
itself to the large white spots. Rolling continues till the oily brown
coating has deposited itself uniformly. Exercise care in order not to
get more ink on some spots than on others. The plate, now completely
rolled, is placed in the finely powdered resin, with which it must
be completely covered. For the space of two minutes the oily color
absorbs the powder, which should, therefore, be strewn on it and rubbed
off repeatedly. If saturation in the cold has taken place, dust off
lightly with brush and cotton, blow off well, and heat uniformly to
35° C. The resin should not melt now, but should only grow sticky and
combine intimately with the color, which forms the binding material.
This change is observed immediately in the change resulting in the gray
resin coat. As soon as the change occurs (beware of unequal heating),
again place the warm plate into the resin, saturate as before, dust
out, blow strongly on the bright, metallic spaces, to remove remaining
traces of resin, and heat to 50°–55° C. At this temperature cover the
film with fine asphalt powder, dust off as before, and heat to 65° or
70° C. In this condition the plate is again saturated with asphalt,
and the layer, after careful dusting and blowing, is heated until it
grows slightly |88| brilliant. Thus a complete coating is formed, and
the plate has the appearance of Fig. 6. The black spots represent the
dirt which has clung to the intensest lights, and must be removed.
But before attempting this, we varnish the back of our plate with a
solution of shellac, and cool it completely in water.
[Illustration: Fig. 6.]
Now take a very coarse scraper, ground with a sharp edge; hold it
between the index and middle fingers, and scratch away the dirt from
the light spots, making the edge of the scratcher draw the strokes
close together. The brittle backing breaks off finely, and in a few
minutes the dirt is removed and the plate is ready for etching. If
(which will only happen to beginners) the drawing should be scratched,
the exposed spot must be covered, by means of a brush, with a thick,
warm solution of asphalt in turpentine; the dirt which was scratched
loose is brushed off, and the plate goes into the bath for middle
etching for about three minutes. Brushing and washing follow in the
same way as in the previous operation. At the expiration of three
minutes inspect (with or without a magnifying glass); places that have
been uncovered must instantly be covered with asphaltum, as already
directed. Etching is continued till the lateral coating no longer
protects the first relief, which generally takes place after the third
period (in about nine minutes) in a new bath, but requires twelve
to fifteen minutes in an old one. It is proved by the existence of
only a narrow thread alongside of the relief. The moment can be well
ascertained. If we wish to be sure of it we may do so by exposing the
edge of the black rim at different places; the width of the thread
is then apparent, and a safe conclusion may be drawn from the single
spots as to the whole plate. If not enough middle etching has taken
place, the thread remains wide and requires an extraordinary clean
etching, which may lead to the picture growing thin and endanger the
finest lines. Care, then, is necessary to ascertain the right moment of
suspending the middle etching, and of continuing in the above-described
manner with oil of turpentine, brushing, sawdusting, and washing.
After drying and brushing off the sawdust with a strong brush, we
have the clean plate ready for examination. We observe the grade of
etching produced by |89| middle etching parallel to the contours of
the different parts, and can safely assert that the process has taken
its natural course. Etchings without real deep places (as high lights)
might here be _etched clean_—that is, might undergo removal of the
formed _etching grade_. Yet it is preferable to place the edge of the
drawing as low as possible, to prevent a tendency to crookedness,
so-called facetting, and to get a deep edge for nailing the plate on
wood. The outward appearance of the etching improves considerably, and
the cliché can be fastened much more securely. The chemigraphist must
endeavor to satisfy the demands of the printer in all respects, and
should omit nothing that serves to perfect his work. Thus only can he
gain a good reputation both for himself and for his work.
DEEP ETCHING.
Having been successfully treated in the middle etching process, the
plate needs only depression of the larger light spots. Some simplify
this part of the work by cutting out the highest lights by means of
a chisel, reverse ground. This can easily be done after a little
practice, and often saves time and acid. Care should be taken with the
chisel; the plate should lie on a flat surface and the cutting twist
be executed lightly and regularly. If this course is decided upon and
is applied to the highest lights, proceed to the execution of the deep
etching. Such chiselling does not happen in my laboratory, since I
prefer to etch all plates alike to their normal depth.
An excess of ink is now well spread over the rollers and the plate
is rolled in all directions. Close up all the middle tints and give
the acid room only in the densest lights. This coating is done by
warming the regularly covered plate to 31° C., and allowing the ink to
flow down rapidly and cover the recesses. A second coating with slow
manipulating of the rollers and manipulation of the handles without
pressure, will yield a sufficient coat from above. If, despite this,
certain parts should not be sufficiently blackened, rub on more ink
till the covering is sufficient and the side protection perfect.
As in middle etching, we must proceed to the formation of an etching
varnish by dusting with gums, placing into resin, by lightly rubbing
this resin on in constantly renewed layers, till the absorptive power
of the ink ceases; then warming and dusting warm with the same resin to
complete saturation; then raising the heat as above, and dusting with
asphaltum to saturation, heating stronger and finally placing the hot
plate into asphaltum, which again secures all parts covered with ink
and resin. |90|
At the different times of removing the dust, pay particular attention
to the bright metallic parts. Over-removal of dust removes resin from
the layer; under-removal leaves behind an obstinate yellow tint in the
bright spots. Practice and experience readily prove the best teachers
in this respect.
The final heating of the etching varnish must be pushed so far that
an intimate connection is effected between all of its parts. This is
easily noticeable from the uniform gloss of the mass. While still hot,
the back of the plate is carefully varnished and cooling is promoted by
dipping it into cold water.
[Illustration: Fig. 7.]
But few spots are to be removed by chiselling (see Fig. 7), for the
rollers have only blacked the middle of the highest lights. These
spots, as indicated in middle etching, are scratched bright with a
chisel. It is important always to scrape off the white edge around the
drawing. Scratching of the plate does not even happen with beginners,
except in cases of gross carelessness. If it does happen, a good
covering with the turpentine solution of asphalt must be used. When
this is all done properly we proceed to etch.
The process of etching by the aid of a brush is continued in periods
of five minutes each. It is necessary to examine the side covering
carefully at the end of every operation; a diligent brushing off of
the surface is also to be recommended. Etching is continued until, by
degrees, the lateral coating decreases and the grade grows narrower. At
this juncture—that is, after about five to six operations (twenty-five
minutes) the necessary depth is attained. In few cases (and almost
always with beginners), it happens that a single coating does not
suffice for deep etching without endangering the plate. In such cases
wash the plate, coat it a second time, and form a second etching
varnish.
When the depth is satisfactory the plate is washed and the new grade
may be criticised.
After a proper examination, we proceed to the
ROUND ETCHING.
Its object is to remove the last formed grade. Coat the plate with a
very uniform coating of ink, corresponding to the one used in middle
etching. A |91| criterion for correct coating is, that only the grade
caused by middle etching be covered, while the grade from deep etching
must remain exposed. Remember also that in heating the plate a further
spreading is caused by melting.
To the inexperienced it may happen that the grade caused by deep
etching is of variable width. These places must be removed by working
over with a graver before continuing, as otherwise we will not attain
symmetrical round etching.
The plate prepared for the latter treatment is only dusted once in
resin, and then blown out. It is then heated to 45° C., and is dusted
and heated twice with asphaltum at increasing temperature, just as in
both the previous processes. Nothing now remains to be scratched away.
After having varnished the back, the plate is etched in the middle
etching bath two or three times for three minutes. At the end of each
period examine whether another whole period is necessary, or whether
rounding the plate requires less time. When this is over (several
parts, which perhaps were already finished beforehand, have been
covered), wash and approach the next problem, the removal of the grade
resulting from the middle etching. This is called
CLEAN ETCHING.
Upon the clean, smooth rollers spread thick transfer ink and roll it
out perfectly. It is advisable to warm the stone previously with a
little alcohol, which promotes the working out of the color. When the
surface of the color has become perfectly uniform the plate is rolled
in slowly and without pressure. Pressure would deposit too much color
in the finest recesses, and prevent the clean etching and sharpening of
the same, thus causing lack of harmony in the prints.
It is better to coat the shadows with a pad, as they require more color.
The plate, thus blackened, is to be dusted once with the finest asphalt
powder, then freed from excess by dusting off and blowing until the
coating becomes brilliant.
Clean etching then takes place in the bath for etching on, in
periods of one minute each, and repeatedly until the last thread has
disappeared.
Now everything is ready for a proof, and for subsequent mounting.
Fig. 6 shows a print of the little picture given during the process of
middle and deep etching, and admits of an instructive comparison during
the progress of the work. |92|
Proofs are made from the cleaned plate (the back of which has been
scratched clean) in the following manner: Upon a good lithographic
roller place a quantity of the best ink and coat the etching uniformly.
Help the shadows along by dabbing on some ink with a leather pad.
When this is done, carefully rub off the excess in the lightest
spots, and fix the plate in the rolling-press; place on it a sheet of
well-calendered tissue paper, next a sheet of writing paper, a sheet
of Bristol paper, and a cardboard. With very little pressure (the
thickness of one cardboard less than in the transfer) draw it through.
If the print is too weak, place paper below, sheet by sheet. The
stronger spots may be blackened separately.
[Illustration: Fig. 8.]
FINISHING AND MOUNTING THE PLATE.
The first thing to be done is the removal of the black edge left by
etching and the sawing out of such spots in the drawing as were spared
for this from the beginning. The waste may be removed by means of
a circular saw or a fine-toothed carpenter’s saw. Do not, however,
forget to leave behind a margin of about three millimetres for the
purpose of nailing the plate to the wood. The edges must be smoothed
with a graver, filed and chipped off to a suitable plane, since sawing
produces a sharp edge.
To remove the spots spared in the drawing, bore a hole through the
metal at that spot with an American gimlet, introduce a scroll saw, and
thus cut out the metal. The edge should be worked over with a dog-leg
chisel.
By aid of the borer we also make the conical holes in the edge, through
which the nails are to be hammered. Elevations caused on the back of
the plate by boring should be removed by filing.
The block of wood which is to raise the height of the plate to that of
type should be cut from perfectly dry maple, oak, or mahogany wood.
With the plate it must just reach to the top of the type; the sides
must be parallel, and all should be perfectly smooth.
Cutting at right angles can be done with a circular saw or with the aid
of a mitre saw used by printers for such work. For exact examination
of height, |93| pass the block and zinc through the caliber-bridge
(Fig. 9). Roughen the base and top surface of the block with a
toothing-plane. When convinced that the block fits perfectly, nail the
etching upon it, taking care to drive the heads of the nails well into
the holes provided for them, otherwise they will show in the print. If
other small details are noticed, they may be removed with a dog-leg
chisel.
[Illustration: Fig. 9.]
This finishes the plate for delivery.
In the expounded explanation of my chemigraphical method, the following
arrangement may serve the beginner as a guide to the manipulations from
the beginning to the end of the work:
1. Planing the plate. 2. Grinding it out. 3. Freeing from fat, and then
testing its cleanliness. 4. Transferring the drawing to the metal. 5.
Preparing the metallic surface after transfer. 6. Strengthening the
transferred drawing by rubbing, rolling, or flooding it as directed.
7. Transmutation of the transferred drawing into a resisting etching
varnish by double besprinkling and burning in of asphaltum, subsequent
to covering the edges and large light parts, and after varnishing the
back. 8. Sharp or preliminary etching, strengthening with resin powder,
and finishing preliminary etching. 9. Washing and examining the work.
10. Coating with etching ink for middle etching. 11. Formation of the
etching varnish by double dusting and increasing burning-in of (_a_)
resin and (_b_) asphalt; varnishing the back. 12. Chiselling out the
lights of the picture. 13. Middle etching. 14. Washing and examining
the result. 15. Coating for deep etching. 16. Formation of etching
varnish by dusting, heating with increasing strength of resin and
asphaltum; varnishing the back. 17. Deep etching. 18. Washing out and
examining. 19. Coating for round etching. 20. Formation of etching
varnish by single dusting and warming of resin, and double dusting
and burning-in of asphaltum; varnishing the back. 21. Round etching.
22. Washing and examining the plate. 23. Coating for clean etching.
24. Formation of etching varnish by single dusting and burning-in of
asphaltum at a high temperature. 25. Clean etching. 26. Washing and
scraping the back. 27. Proofs. 28. Cutting out and mounting the plate.
|94|
CHAPTER VI.
HINTS FROM ALL SOURCES.
Although the number increases almost every week, there are but few
persons who understand photo-reproductive processes in all their
details. Those who do, have been so chary of giving of what they know,
that our literature on the subject is very scanty indeed. Consequently,
as all the hints that are obtainable are very welcome, I have collated
a few from various sources, and make a mosaics of them here for the
general good.
Every would-be photo-engraver, if he is not already a skilled
photographer, should obtain and study a good photographic text-book. If
he proposes to make his own drawings, he should also obtain Burnet’s
_Essays on Art_. The first will not only teach the best formula for
the production of negatives, but it will also enjoin the importance
of being careful, cleanly, and exact in all the manipulations. The
second will teach how to draw according to the best rules of art.
Remember always, the old injunction, _whatever you are, be best_! After
the regular photographic manipulations are well looked after, the
preparation of the drawing should have attention.—EDWARD L. WILSON.
AS TO THE DRAWING.
There are two separate and distinct styles of drawing for reproductive
purposes, whether the artistic engraver be employed, or any of the
means of automatic engraving be used. These two methods are technically
known respectively as _fac simile_ drawing, and drawing in wash. The
former consists in the sole employment of lines, in which the shading
is to be produced as well as the outline of a picture. Every line and
mark that is subsequently to appear in the engraving must be traced
in the original. This description of drawing is applicable to wood
engraving, to line engraving upon copper or steel, as well as to all
the methods for automatically producing blocks for relief printing. The
line method is also universally adopted by etchers in _intaglio_.
Successfully to prepare drawings for photographic reproduction it is
essential that some knowledge should be possessed of the fundamental
principles of |95| photography, as well as an acquaintance with the
capabilities of the particular process of production which is to be
employed. Thus, the material upon which the drawing is to be made
should be of such a character as will yield a strong and well-defined
contrast to the lines of the drawing; while the pigment employed for
the drawing should be as black as can be procured. White Bristol
board of fine surface, and the best India ink meet these conditions.
A blue-black does not form a desirable drawing medium, but the
introduction of red or orange into the composition should serve to
intensify the photographic image. To draw upon a dark orange-colored
paper with a pale blue-gray ink would be simply to disregard all
photographic principles, for the photographic value of the paper and of
the ink would be nearly equal, and the drawing would consequently be
lost.
Uniformity of color in the drawing is also desirable, and the artist
should resist the natural tendency to express distance and to produce
his effects by diminishing the intensity of color in parts of his
picture. From a drawing uniform in color a satisfactory negative is
obtained; but, in the other case, the photographer must estimate an
average duration of exposure, and will rarely escape the dilemma
of some portions being overexposed while others are comparatively
undeveloped. This theory receives illustration from the fact that
very good subdued effects can be obtained from well-executed pencil
drawings, where this uniformity of color is preserved. A longer
exposure may be required, but every part of the picture will be equally
developed.
To return to the matter of the paper used, color is not the only
important consideration. If the surface of the paper is irregular and
coarse in texture, such as painters in water-color delight in, good
results must not be expected. A negative, taken in the ordinary way
from a drawing made on such material, would inevitably reproduce all
the inequalities of the texture of the paper, to the manifest injury
of the more delicate parts of the drawing. In reproductions from old
prints or printed books, the conditions and character of the paper
present some of the greatest difficulties with which the photographer
has to contend. The ridges in the surface of the paper cast shadows
which are too faithfully reproduced in the negative. The employment of
a diffusive rather than a direct light is the usual remedy, but the
best way of dealing with the difficulty is that employed in the studio
of the Autotype Company. The original is laid upon the floor under a
strong light, and the camera set at an angle of forty-five degrees.
Mr. Alfred Dawson informs me that he inclines to the opinion, founded
upon |96| his extensive experience and untiring experiment, that it
is desirable to get rid of the surface of the paper altogether, by
covering it with a substance similar to an enamel.
In conclusion, the conditions required in the successful preparation of
drawings for photographic reproduction, may be thus briefly summarized:
That a sufficient photographic contrast should exist between the
pigment employed and the material upon which the drawing is made; that
a paper should be selected which is smooth and without water-mark, and
white; that the drawing material may be pencil or ink, in which blue is
not a component.—JAMES S. HODGSON.
FADING OUT THE PHOTOGRAPH.
For newspaper line work excellent results may be obtained by drawing
over a photograph, and then fading out the photographic parts not
wanted. There are several methods, but the following is the most
simple and the easiest to manage: Make a weak solution of cyanide of
potassium and add a flake or two of iodine. When the drawing is made
with water-proof ink and on a photograph printed upon bromo-gelatine
paper the above solution flowed over it will at once cause such
portions of the image as have not been drawn upon with the ink, to fade
away and leave nothing but a fine ink sketch against a perfectly white
background.—ROBERTS & FELLOWS.
THE REVERSAL OF DRAWINGS (NEGATIVE PRINTING).
This very simple and very safe method is to be recommended especially
for advertisements in papers and for titles of books, and can be made
both by aid of photography (by a transparency) and without it, in the
following manner:
Make a copy, on copy-paper, of the drawing to be reversed, using an
ink of gum, glycerine, and aniline, and transfer it carefully, without
using too much water, when loosening. Dry the plate, and pour over it
a solution of 1 part of asphaltum, 1 part Venetian turpentine, in 18
parts benzole; then allow to dry upon a plate. Place the plate into a
weak soda solution, and develop with a fine pad of cotton, till the
drawing stands clear. Ordinarily I employ the following method: A plate
prepared for transfer is uniformly cleansed with gallic acid and then
coated with gum, as in the case of blackening a transferred drawing,
while both solutions are left to dry spontaneously. This done, the
coating of gum and gallic acid is thoroughly washed off, and the plate
is carefully dried and gently warmed. The transferred drawing must be
made on |97| paper with an easily soluble layer composed as follows:
dissolve 100 grammes of wheat starch—_i. e._, starch _made_ of wheat—in
400 c.cm. of rain-water; raise 1 litre of water to boiling and dissolve
therein: 50 grammes of common salt, 75 grammes of glycerine, 50 grammes
of gelatine, and 25 grammes of molasses; when these are well dissolved
and taken up, add slowly the wheat-starch, stirring continually; then
allow to boil a short time so that we may dissolve it without an excess
of water after the ordinary transfer of the picture. When this has been
done, we wash it again with a soft brush and water, dry, dust twice,
and burn in thoroughly with asphaltum. Place the plate in a very weak
bath of nitric acid (10 cubic centimetres of acid to 1 litre of water),
and rock it lightly for about two minutes until the zinc changes color.
Then wash, dry, and warm.
The combination of gum and gallic acid is broken up by this etching
in all those places which were not protected through the transferred
drawing, and the latter itself, in the subsequent blackening with
chemical India-ink, forms the coating and protection against a
combination of the zinc below. It is best to blacken it with a brush
and to warm the plate until the ink has become dry. Now moisten again
with gallic acid and gum, wash the plate (without great pressure) with
spirits of turpentine, rub on more of the solution of gum, and blacken
as usual. Practice will insure safe working by this method.—J. O. MORCH.
ETCHING APPARATUS.
It does not come within the province of this work to instruct in the
preparation of inks and colors for etching or for printing, since such
articles are better purchased of the dealers ready prepared. In all
cases the choicest results are obtained by using the best apparatus
and the purest materials. There is no economy in “getting on” with the
“cheap.”
A few hints as to some of the “tools” which are found convenient in
practice: For sifting the fine _resin dust_, a machine is employed,
known to sieve manufacturers as “the _composition_ sieve.” It consists
of the ordinary sieve, having on each side a cover with a bottom of
calf skin. The sieve-bottom is made of the finest silk texture. (See
Fig. 10.)
For fixing and melting-in of the drawing on metal, I use a grate made
of a wooden frame with diagonal iron rods. This form is preferable
to the ordinary grate, because it allows the flame free access to
the metal plate. Inasmuch as the heat is strongest in the _centre_,
the cross-bars protect the centre of the plate from burning and from
warping. The source of heat is either an alcohol |98| lamp (Fig. 11)
in which cotton soaked in alcohol is ignited (the cover shown in the
drawing serves to smother the flame), or a strong gas flame (Bunsen
burner). The adoption of the latter mode is advisable.
[Illustration: Fig. 10. The Sieve.]
[Illustration: Fig. 11.]
Formerly I employed a plain cast-iron heating-plate, with a gas or a
petroleum flame. The zinc plate, however, being in direct contact with
the hot surface, warped very much. I obviated that somewhat by covering
the heating-plate with a piece of wire-gauze. The strata of hot air
thus obtained between the cast-iron and the zinc plate heats the latter
equally throughout, and prevents warping. Still I prefer the direct
method.
For freeing the plate from resin-dust, employ a strong pair of ordinary
bellows.
The table (Fig. 12) for washing the coating material from the plate
consists of a heavy framework, upon which rests a wooden grate. A
massive table-board is not to be recommended, as the dirty sawdust
adheres to the same, while with the other it easily falls through the
openings into a box, and leaves the table free and clear.
[Illustration: Fig. 12.]
The measuring or calibre-bridge (see Fig. 7) serves to determine
accurately whether the ready plates have the height of type. A rule of
forty |99| centimetres will suffice for any plate. No plate should
leave the workshop without having been tested as to its thickness or
height on this instrument.
The zinc plane is of ordinary construction, to the bottom of which
is attached a double layer of hard wood. The iron being arranged for
scraping can be inserted in a position just the reverse of the ordinary
plane.
The “hand-bridge” is a strong ruler, thirty centimetres long, and five
centimetres wide, to the ends of which are fastened two blocks of wood
one centimetre high. It serves as a support for the hand in retouching.
The rollers of the “chemigraphist,” and also the pads, are of greatest
importance. For etching by the French process we need a good, rough
roller, and a faultless, smooth one; for the Vienna process only the
latter is needed, in addition to a smooth, tight leather ball or pad,
such as was used in the art of printing prior to the introduction of
rollers. A perfectly smooth surface is obtained by covering the rollers
with a dryer, and allowing them to dry in the open air. A solution of
shellac with camphor, applied like furniture polish, also yields a fine
surface.—J. O. MORCH.
THE BEST DRYING BOX.
After bichromatizing the gelatine sheet for printing the transfer
image, I proceed with the drying in a box constructed as follows:
The box has four walls or sides of cloth, or any other stuff that
allows the air to pass through, and must have a solid bottom, which
will allow the attachment of a heating apparatus beneath it. In this
box is a cylinder which turns on its own axle, and which can be set in
rotation from the outside when the box is closed. Upon this cylinder
the gelatine paper, as we may call it, is placed, and the box closed.
A very equalizing drying is thus obtained, by keeping the heating
apparatus under the bottom of the box constantly at a steady, uniform
heat. By these means, it will be noticed:
1. That an uneven running down of the chrome-layer is avoided,
and uneven drying also positively prevented in consequence of the
centrifugal force.
2. That the drying by the draft of air is regulated, and at the same
time the air can be driven to a more rapid current.
3. That the grain formed by this extraordinary method is unusually
perfect, and the nature of the grain more pleasing to the eye than when
formed by chlorides.
4. That, as already stated, a rolling up or an uneven drying is hereby
|100| positively prevented, as the paper is placed tight around the
cylinder. And now for the main advantage:
This so dried paper is ready for use, and, when exposed to light, under
a negative, produces a perfect and correct picture, which, when rolled
up with transfer ink and developed in water, is ready for transferring
direct on to the lithographic stone, or on to a metal plate, and to be
further proceeded with as usual.—EDWARD MEISSNER.
TO PRODUCE GRAIN ON A NEGATIVE.
The negative is taken, and a solid pigment of Chinese ink sprinkled
on it with the Air Brush, by which it gets a wonderfully fine grain.
A coarser grain is made in a similar way, by sprinkling with a knife
over a tooth-brush that has been dipped in Chinese ink. The Air Brush,
however, will always be found the most suitable instrument, and now a
wide field for its use is opened to artists of all classes. Instead
of using Chinese ink, gamboge, or any other solid and well-covering
pigment may be used.
For the practical photo-engraver, lithographer, photo-lithographer,
and other men of experience in photo-mechanical processes, no further
explanation is required. They will at once see the _superiority_ of
this process over everything that has hitherto appeared. After the
information we have just given, they will all be enabled to do work by
this process. It will henceforward be easy to produce photo-lithographs
for lithographic printing as well as printing plates for the type press
_without difficulty, in a short time, and at trifling expense_.—FRED.
BUEHRING.
ON THE USE OF ACIDS.
A few hints on use of the acids will form my contribution to your work:
In order to obtain a proper resistance and firmness in the lines, it is
necessary to prevent the acid from making the base that supports them
too thin, and to strengthen the base by giving the depression the form
of a V, and the base itself the form of an A. The depth must be great
enough in the broad blanks to prevent the roller from sinking (although
there is no danger of this when the lines are close together), and thus
soiling them. A useless depth between very thin sides might weaken
them; but, in the process employed, the attack by the acid continues
only in proportion to the width of the spaces to be excavated. |101|
These results are obtained as follows: The prepared plate bearing the
design is inked with a thick ink containing a little wax, and is placed
in a trough with acidulated water, which slightly attacks the metal.
The trough is mounted so as to rock, and is kept in motion by a lever
actuated by a steam motor. The water moves to and fro over the entire
surface, and keeps continually washing the parts that are not protected
against its action. No local saturation, therefore occurs, and the
continuously renewed liquid attacks the bottom as well as the sides
of the hollow. The sides would soon be rendered too thin were the
biting-in too long continued, and for this reason the first attack
is made with great care. It is upon this that depends the sharpness
of the proof. The acid used is nitric, so dilute that it is scarcely
perceptible to the taste, and in the proportion of about one and a half
ounces to a quart of water. The acidity is kept up by a small quantity
of acid of 36°, that falls drop by drop from a bottle provided with a
cock. After about a quarter of an hour, the plate is taken out, and the
operation repeated as generally directed.
Remember this: At every new biting-in the acidity of the bath is
increased, and, when the broad parts alone remain exposed to the
attack, acid of 6° B. may be used. In this state, the zinc plate, taken
from the bath and washed and dried, is treated with benzine, and then
with potash, in order to remove all fatty matter. It may then be seen
that the sides of the hollows do not exhibit a regular sloping surface,
but a series of ridges corresponding to the series of bitings-in. As
these might take the ink, and affect the purity of the lights and
shades, it is necessary to remove them by an operation analogous to
the first, but carried on quickly in an opposite direction. With this
intent, the plate, well cleaned and heated upon the iron table, is
inked while hot, with a composition formed of two parts printing ink
and one part each of resin and beeswax. This ink, which can be used hot
only, descends along the sides of the depressions, and when it has got
half way to the bottom the plate is cooled, and the inking is renewed
so as to well cover the entire surface.
It must not be believed that in practice these operations can be
conducted without extreme care. A want of attention, unsuitable ink, or
a too high or low temperature, may lead to the loss or poor execution
of the piece. It is often objected that the lines in this style of
plates have not the boldness of those produced by the graver. It is
not for us to answer the question whether this is a merit or a defect;
artists generally endeavor to employ paper with an irregular and
granular surface, and which is far from giving such boldness; |102|
and he perhaps would be poorly appreciated who should present upon
glazed paper a drawing made with the pen and resembling a picture made
with the graver. It is the artist’s business to produce the work such
as he desires the Gilloteur to render it.—GILLOT.
MULTIPLICATION OF ZINC ETCHINGS BY GALVANIC MEANS AND BY STEREOTYPING.
Multiplication of printing-blocks by galvanoplastic, or stereotyping,
is not so easy as in case of woodcuts or type. The main difficulty
lies in some peculiarities of the process of etching, especially if
the plate has been produced by the French method. The reproduction
of a form is often impossible, since the matrix is caught on certain
rough spots and then tears, thus rendering galvanoplastic reproductions
imperfect.
Having very frequent opportunity of making matrices from plates, I call
the etcher’s attention to several points upon which the success of the
work depends. On no condition whatever may any parts of the plate be
corroded from beneath, as wax or gutta-percha will invariably tear when
lifting off the impression (mould).
In the second place, the bottom of the etching must be perfectly
smooth, not rough; the single grades, left by etching, must be removed,
and the lines must incline perfectly smooth toward the depth of the
etching.
In stereotyping, the process of drying presents special difficulties,
since with heat the wood warps and distorts the plate; the cold
process, on the other hand, does not give equally sharp impressions.
For this purpose I have mounted the plates on lead instead of on wood,
and am thus enabled to get sharp impressions and to apply hot drying.
Instead of paste, I employ light magnesia; instead of oiling the plate
before planing or rolling it in, I give it a high polish with stearine
oil and rouge by means of a circular brush, and brush it once more with
talc. Thus I am sure of success.
PREPARING ZINC PLATES ON THE PRINTER’S PRESS.
A wood-cut gives the _outrunners_ of the finest portions in a plane
which runs downward; an etching, on the contrary, shows the whole
engraving in one plane. According to this the _outrunners_ (the
borders) often print somewhat hard, unless care is taken to alleviate
this fault. This will be easy to the experienced workman. |103|
Starting from the fact that a zinc plate is easily bent, place
something under the back of the _heavy_ portions in mounting, and when
nailing drive the nails tight in the white lights and on the edges;
thus the borders are deepened, and _print_ softer.
In this manner an experienced and practised hand can produce effects
impossible in any other way.
For printing on rotary machines, galvanos are used in many places. But
a zinc plate may be excellently fastened in the following manner:
Clean the back well and solder the back with soft solder, as is
customary in galvanic backing. Then attach it lightly to its place on
the wooden or metal block, hammer or roll in the plate without paying
special attention to the zinc plate, dry the matrix, and lift it from
the form. After preparing for casting take the zinc plate from the
wooden block, bend it while hot, put it back into its position in the
matrix, cover the edges with tissue paper and paste, dry the edges
with an iron, place into the casting apparatus and cast as usual. In
this manner the zinc plate (metal, cast from a matrix) is in place at
exactly the height of the type and will print excellently. (The face
is to be slightly oiled before fastening in the matrix, to prevent any
sticking of the lead.)
As a _cover_ for the printing cylinder, I have always found paper most
serviceable, although covers of English leather are also advantageous,
especially for large editions. I should not recommend felt.
The rollers for printing zinc plates should be held with somewhat
stronger tension than for printing of wood-engravings.
As a method of preparing, I recommend the gradating of the lights and
shades, known to every intelligent machinist. Wherever possible, highly
calendered paper should be used, as it gives the best results.
ETCHING WITH SULPHATE OF COPPER SOLUTION.
Nitric acid may be replaced by sulphate of copper, especially in
the first periods of etching, and etching can be obtained both in a
galvanic way and by easy shaking of the tray. The sulphuric acid of
the copper sulphate combines with the zinc and the copper, and when
liberated, precipitates as an amorphous, muddy substance.
Although this process has almost entirely fallen into disuse, the most
important points are treated of below.