A treatise on photogravure in intaglio by the Talbot-Klic process

A TREATISE ON PHOTOGRAVURE.

Den

A TREATISE

ON

PHOTOGRAVURE

IN INTAGLIO BY THE TALBOT-KLIC PROCESS.

BY

HERBERT DENISON, F.R.P.S.

7l

LONDON :
ILIFFE & SON, 3, ST. BRIDE STREET, LUDGATE CIRCUS, E.C,

LONDON :

ILIFFE AND RON, 3, ST. BRIDE STREET, LUDGATE CIRCUS, E.G.
WORKS: COVENTRY.

PREFACE.

; I HE rapid growth in importance of photo-
^ gravure in intaglio, both in art and as an
industry, together with the paucity of in-
formation on the subject contained in a convenient
form, afford sufficient apology for the publication
of this treatise.

The practical details and directions herein con-
tained are the result of considerable experience and
experiment, and the author trusts that his labours
may enable many who are now strangers to the
process to experience some of the pleasures enjoyed
by himself in becoming intimately acquainted with
its resources.

The author is indebted to Mr. Thos. Bolas,
F.C.S., F.I.C., for the historical notes contained
in Chapter XIV.

H. D.

CONTENTS.

PAGE

CHAPTER I.— Introductory 9

CHAPTER II.— The Negative .... 19

CHAPTER III.— The Transparency 21

CHAPTER IV.— The Gelatine Resist 38

CHAPTER V. — The Copper Plate .... 46

CHAPTER VI. — The Ground .... ... 5°

CHAPTER VII. — Mounting and Developing the

Resist 63

CHAPTER VIII. — The Mordant 70

CHAPTER IX. — Etching the Image 76

CHAPTER X. — Photogravure in Line .... .... 85

CHAPTER XI. — Printing from the Plate .... 90

CHAPTER XII.— Afterwork on the Plate .... 100

CHAPTER XIII. — Steel-facing the Plate .... 122

CHAPTER XIV. — Historical Notes 129

CHAPTER I.

INTRODUCTORY.

A photogravure plate is one of metal,
preferably of copper, which bears on its
surface in intaglio an etched represen-
tation of the subject to be reproduced. In
.other words, the portions of the plate repre-
senting the shadows and half-tones of the
subject are sunk, instead of being the
highest points — as in the case of half-tone
and other blocks intended for use in
ordinary letterpress printing — and the por-
tions representing the high lights of the
subject still retain the original level and sur-
face of the plate.

This intaglio state of the plate is the
result of the action of a mordant or
etching fluid upon the metal, whereby the
latter is etched or eaten away wherever the
mordant comes in contact with it.

As the name given to the process Process

JT mecha

indicates, in photogravure the etching of
the metal is controlled by photographic

1O A TREATISE ON PHOTOGRAVURE.

means, and the process is therefore a
mechanical one, to some extent at least, as
distinguished from an " etching," properly
so-called, and, because of its more or less
mechanical nature, photogravure has been
severely decried by the supporters of other
oric»»i work from intaglio methods of producing pictures.

With regard to original work, a print

from a photogravure plate is open to the

same criticism as a print direct from the

negative, which is its foundation ; and

this, notwithstanding that the former is

widely separated in its characteristics from

a print by any purely photographic process.

But it appears only reasonable to contend

that in passing judgment on a picture the

method of its production should be left

entirely out of consideration, and that the

visible result, and that only, should be

regarded. After all, the true value of a

picture is as a means of decoration, and

the fact that in a photographic picture

use has been made of the action of light

should not detract from its value any more

than does the fact that a painter also

avails himself of the resources of nature in

using the pigments that go to make his

picture.

A TREATISE ON PHOTOGRAVURE. II

In the reproduction of paintings and 5f0pt™d^^ by
drawings, however, photogravure -stands
on a different footing. The object here
is to produce the most truthful and
accurate reproduction possible of the
original. As to accuracy of outline, there
can be no serious contention that the
engraver surpasses the lens ; and in inter-
pretation, photogravure has a distinct
advantage over the engraver, in employing
half-tone, instead of line, to reproduce a
half-tone picture ; and if photography is
not yet quite equal to rendering with
absolute truth the entire range of colours
found in a picture, this difficulty can be
overcome by handwork on the negative,
supplemented by corrections on the copper.

The mechanical nature of photogravure T^chtk£ r«»ro
is distinctly in its favour for reproductive
purposes ; there is no opportunity for the
individuality of the engraver to leave an
impress on the print antagonistic to that of
the painter. It is the work of the painter
in its entirety that the reproduction should
portray — not a portion only of his work con-
taminated with the style and mannerisms
of another, in whom, possibly, the possessor
of the reproduction has no interest. The

12 A TREATISE ON PHOTOGRAVURE.

great increase within recent years in the
number of photogravure reproductions of
pictures proves that these advantages are
appreciated by painter-artists,
outline of general It will probably lead to B. better under-

tntaglio methods. * +

standing of the photogravure process if the
essentials common to plates by that process
and to all intaglio plates are first considered,
with the assistance of an outline of the
methods of production of the chief varieties
of such plates. These are three, namely —
engravings, etchings, and mezzotints.

An engraving, as distinguished from an
etching (for the term equally applies to an
etching in so far as the image is in both
varieties engraven on the metal by removal
of a portion of its surface), is produced by
the removal or digging out of portions of the
metal — whether copper or steel — in lines
or dots (stipple). The tool employed is a
burin, consisting of a thin steel rod fastened
into a wooden handle, round in shape, but
with a flattened side, the cutting end of the
tool being ground off flat at an angle of about
40°. With the handle held in the palm, the
flat side being downwards, the burin is pushed
along the plate, ploughing its way through
and removing the metal in its progress.

A TREATISE ON PHOTOGRAVURE. 13

The result is governed by the form of
the incision, whether straight or curved, its
depth, and the proximity of one line or dot
to another. The shape of the incision can
be further varied by the use of burins made
from steel rods of different sections.

An etching differs from an engraving in Etchine-
that the removal of the metal is the result
of the corrosive action of a mordant in
place of the mechanical action of the burin.
The plate is entirely covered with an
" etching ground," impervious to acids,
composed of wax with certain ingredients
added to render it less brittle. The subject
is then drawn upon the plate with needles
of varying fineness, which, in their transit,
remove the etching ground, and so lay bare
the metal to the action of the mordant.

When the drawing is complete the plate
is immersed in a weak etching bath,
composed of an acid diluted with water,
and as the etching proceeds the plate
is removed from time to time, rinsed and
dried, and then the portions which have
been sufficiently bitten are stopped out with
varnish. This done, the plate is re-immersed,
and the etching proceeds until it is necessary
again to stop out, and so on until the

14 A TREATISE ON PHOTOGRAVURE.

darkest lines are sufficiently deep. The
wax is then removed, and the plate is ready
to be printed from.

Mezzotint engravings differ considerably
from the foregoing varieties. The plate is
first roughened over its entire surface by
being rocked to and fro in various directions
with a steel tool somewhat resembling the
rocker of a cradle in appearance, and having
its convex edge serrated. These saw-like
teeth on the 'edge of the rocker indent the
plate, and as the metal is not removed, but
displaced only, it rises slightly round each
indentation, thus increasingits depth, andpro-
ducing what isknown technically as a "burr."

A plate, if properly rocked, would, if
printed at this stage, yield a perfectly black
impression. The picture is produced by
removing with a scraper both burr and in-
dentations where the whites of the subject
are to be, removing them partially only,
and to a greater or less degree for the half-
tones, and leaving the plate untouched in the
darkest portions of the picture.

From subsequent descriptions, it will be
seen that a mezzotint plate more closely re-
sembles one produced by photogravure than
either of the others previously described.

A TREATISE ON PHOTOGRAVURE.

In the case of all intaglio plates, the >rilK;tag!i*
method of printing is by filling the de-
pressions with a stiff fatty ink of a special
nature, and afterwards removing the ink
from the surface only by means of muslins
of different qualities, the final polish to the
high lights being given by the hand.

The plate is laid on the iron bed of a
copper-plate press, a piece of plate paper
quite limp with moisture is placed on the
top, with three or four pieces of blanketing
on the paper, and the whole is passed
through the rollers. The pressure, aided by
the yielding nature of the blanket, forces
the paper into the depressions of the plate
where it comes into contact with the ink,
and on raising the paper from the plate, the
former will be found to have licked up the
ink, and retained it on its surface. The
paper and ink together in reality form a cast
of the subject depicted on the plate.

From this brief outline (the subject of Essentials of in.

taglio plates.

printing will be more fully dealt with here-
after) it will be readily understood that in
order that the ink, in the process of cleaning
the surface or " wiping," may not be
removed from the depressions as well as the
surface of the plate, it is essential that it

l6 A TREATISE ON PHOTOGRAVURE.

should be confined in spaces not so large as
to permit of the muslin sinking into them
during its passage over the plate. In etch-
ings and engravings this confinement of the
ink is natural, consequent upon the subject
being expressed in line or stipple, the only
thing to avoid being the running together
of lines placed close together, due in etchings
to the lateral action of the mordant ; while in
mezzotint engravings the same result is
attained by the roughening of the plate, the
rocker producing a cellular surface eminently
suited to the retention of ink.
i^f The etching of a plate in pure half-tone

tone iniajlios. O *

(say a photograph from nature), in which the
tones gradually merge one into another
frequently without any perceptible step
between, and where almost the entire pic-
ture is etched to some extent, would not
yield a surface with this retentive quality
sufficiently pronounced to truthfully render
the tones of the subject. A magnified
section of such a plate would simply show
an undulation of surface corresponding to
the depth to which the etching had been
carried. It will be seen from the accom-
panying sketch of a section of such a plate
(fig. i) that there would be nothing to

A TREATISE ON PHOTOGRAVURE. 17

prevent the ink being removed in the process
of wiping from the whole of the etched por-
tions of the image, except under the
shoulders formed by the margins and by
small patches of high-light at various points
of the subject. This difficulty was met with

^^^^

FlG.l.

AA. The original surface level of the plate. B. The etched portion.

by all the early workers, who found that,
although the roughness of the metal result-
ing from the action of the mordant enabled
light tones to be rendered correctly, it was
insufficient to retain the necessary amount
of ink to produce dark tones.

The difficulty was to some extent sur-
mounted by Fox Talbot, by applying a
resinous dust to the surface of the gelatine
resist ; but this was in connection with the
process in which the plate to be engraved
is coated with the bichromatised gelatine,
exposed behind the transparency, and
etched without washing out the soluble
gelatine.

It is to Klic that we are indebted for the
idea of protecting the metal, before the
transfer thereto of the resist, by an acid-
resisting gum distributed evenly over its
surface in the form of fine particles, which

l8 A TREATISE ON PHOTOGRAVURE.

are caused to adhere to the plate by
heat. This ground, while protecting the
metal, also afforded a surface which would
retain in position a gelatine resist produced
by the carbon process, and transferred to

tff«ct of pain 4

the plate for development. Prior to this,
the carbon process could not be used
because the resist invariably stripped off
the bright metal on drying.

The effect of the grain obtained in this
way is to break up the comparatively large
depression, representing a flat tone in the
subject, into a multitude of minute de-
pressions or cells, each of which is divided
from its neighbours by small patches or
points of somewhat pyramidal form, having
their bases at a depth from the surface
proportionate to the darkness of tone to
be reproduced, and their apices being the

,A s* ,A

''yZFffiff?^^

.

A A The original surface level of the plate. B. The etched nortion
protected by the ground.

original surface of the metal (fig. 2). The
surface of the plate, after etching, will
partake somewhat of the nature of a fine
file, and will be found to retain the ink in
its various parts exactly in proportion to
the depth of the cells.

CHAPTER II.

THE NEGATIVE.

As to the mode of production of the Knowledge or

photograpky

negative from which the photogravure plate
is to be produced, whether one from
nature or from a painting or drawing, it
does not appear necessary in a work deal-
ing with the photogravure process to enter
into details. Anyone unfamiliar with
photography, and desiring to work in photo-
gravure, must necessarily master the first
subject before attempting the second, and
for this such a reader is referred to the
many excellent text-books on the processes
of pure photography. In this work, there-
fore, it will be assumed that the reader is
acquainted with the practice of photo-
graphy, at least up to and including the
making of the negative.

However produced, whether by the wet-
plate process or by gelatine -bromide, it
should possess a good scale of gradation
and be fairly strong, though not hard, with
plenty of detail ; though any negative that

20 A TREATISE ON PHOTOGRAVURE.

will yield a transparency which is satisfac-
tory in point of gradation is suitable for
photogravure.

The amount of detail in a picture is a
question for individual taste. There will,
however, be a slight loss of detail in the
process, consequent upon the " resist,"
which determines the character of the plate,
being a reproduction from a reproduction.
And it is a generally accepted fact that in
no photographic process is all the delicacy
of the original negative quite reproduced in
the print. The effect produced in photo-
gravure might, perhaps, be better described
as the subjection rather than obliteration of
detail, the photogravure on comparison with
a silver or platinum print from the original
negative giving one the idea of a broader
treatment of the subject.

CHAPTER III.

THE TRANSPARENCY.

The first step in the process proper is the Pr°rdau^en°cfy.the
production of a reversed transparency from
the negative selected for reproduction, and
this may be produced in several ways.

If there is to be any enlargement or ^J
reduction in size it will be necessary to
produce the transparency in the camera by
copying the negative ; and it should be
remembered that the transparency must be
reversed, that is, when looking at the film
side the true right hand of the picture
should be on the left, and vice versa. In an
ordinary window transparency the picture
is correctly viewed from the film side.

A moment's consideration will show the
reason for this reversal. The next step is
to obtain a print from this transparency
on carbon tissue. This would bring it
to its correct position, but as it is turned
over on to the copper plate for the purpose
of development, when developed it will
occupy the same position with regard to
right and left hand as the transparency

22 A TREATISE ON PHOTOGRAVURE.

did on its glass plate. The method of
printing from a copper plate again re-
verses the subject; there being thus an
uneven number of reproductions (three)
between the transparency and the print,
if the latter is to be right it is necessary
that the transparency should be reversed,
available. jf the reproduction is required of the same
size as the original negative, there are then
four modes available for the production of
the transparency — wet collodion, gelatine-
bromide, collodio-bromide, and the carbon
process. By the first method, however, it
is necessary to make the transparency in the
camera, and by the second and third the
same necessity arises, unless a reversed
negative is used, whereas in the carbon
process the transparency is in the ordinary
course reversed by being developed on glass.
carbo.most-con. The carbon process is convenient for the
production of the transparency, not only
because it yields naturally the reversed
transparency desired, but also because it
produces in the simplest manner the exact
class of image most suitable for its purpose.
And as, for the production of the resist,
it is absolutely necessary that the worker
should use it, the writer proposes to deal

A TREATISE ON PHOTOGRAVURE. 23

with the carbon process to the exclusion
of the others, merely remarking with regard
to them that the transparency should be
made to resemble one in carbon as closely
as possible.

A point of great importance in the pro-
duction of the transparency is to preserve
as closely as possible the exact scale of
gradation which obtains in the negative,
and the carbon process lends itself readily
to this end. It should be as thin as possible
consistent with the preservation of its scale
of gradation — that is, provided detail is
present in the high lights, any increase of
density in the transparency is not only
unnecessary, but undesirable.

The principle upon which the carbon
process depends is that gelatine, or any
soluble organic body, if treated with bi-
chromate of potassium, becomes sensitive
to light, in so far that the action of the
light renders the gelatine insoluble.

Carbon tissue consists of a stout paper
coated with a film of gelatine, with which
is incorporated a pigment, and has long
been an article of commerce. The practical
difficulties in its manufacture are not such
as need deter any photographer from

Point of chief
importance.

transparency

A TREATISE ON PHOTOGRAVURE.

How tissue is
sensitised.

Effect to exposure
of light.

f tissue.

preparing his own, but it is somewhat
troublesome, and the quantity used in
photogravure is so small that it is recom-
mended to purchase it rather than make it
for one's self.

The tissue is sensitised by being im-
mersed in a bath of bichromate of potassium
in an aqueous solution, dried, and exposed
beneath the negative.

Exposure to light renders the gelatine
insoluble to a greater or less depth in pro-
portion to the amount of light which the
negative has allowed to pass through it, and
on being developed it will be found, if the
exposure has not been carried so far as to
do more than just render insoluble the
entire thickness of gelatine, that the grada-
tion of the negative is accurately preserved
throughout all the tones. Of course, if the
exposure is prolonged after the light has
completed its action on the shadows, so that
it can have no further effect at that point,
the gradation of the transparency will then
be altered by the fact that the action of the
light is still going on in the high-lights and
half-tones, while it is at a standstill in the
shadows. The tissue sold as " special
transparency " tissue is most suitable for

A TREATISE ON PHOTOGRAVURE. 25

transparencies, as it contains a large propor-
tion of pigment, and that in an extremely
fine state of division.

The sensitising bath is prepared in the sensitise bath.
following manner : Take a wide-mouthed
vessel of known capacity, fill it with clean
hot water, and tie loosely over its mouth a
piece of fine muslin in such a way that it
forms a bag reaching into the water. Into
this bag place bichromate of potassium in
the proportion of three ounces to a hundred
ounces of water. After the bichromate has
completely dissolved, liquid ammonia should
be added to the solution gradually until it
distinctly smells of the ammonia. A solu-
tion of the double salt of potassium and
ammonium is thus produced, which has been
found to give better results than the
bichromate of potassium alone.

The muslin may be allowed to remain
over the mouth of the vessel, as it acts as a
strainer when pouring the solution back
after sensitising ; any foreign matter may be
removed by occasionally washing the muslin.

To sensitise tissue, this solution is placed
in a somewhat deep porcelain dish, a little
larger in size than the piece of tissue to
i>e sensitised. The temperature of the

25 A TREATISE ON PHOTOGRAVURE.

sensitising bath must be kept low, say not
higher than 6o°F., otherwise the gelatine
will dissolve instead of merely absorbing
moisture. The tissue is immersed in the
solution with the gelatine surface upwards,
and with a broad camel-hair brush any
air-bubbles are quickly removed, and the
tissue is then turned over on its face, and
the back of the paper likewise brushed over.
The immersion should continue for three
minutes, and it is convenient to use an
egg-boiler as a guide in this operation,
inverting the sand-glass when the immersion
is complete, and removing the tissue from the
bath when the sand has run out. This
length of immersion need not, however, be-
rigidly adhered to, as by sensitising for a
longer or shorter time considerable varia-
tion in the character of the tissue may be
obtained. Thus, an immersion of three
minutes tends to give a quickly printing
tissue yielding an average transparency.
An immersion of two minutes will yield a
tissue producing greater contrast, but
requiring longer exposure ; while more than
three minutes in the sensitising bath will-
give a quick tissue with less contrast, and
the same effect may be obtained by varying

A TREATISE ON PHOTOGRAVURE. 2J

the strength of the bichromate solution,
a weak bath giving a slower tissue and
greater contrasts, and a strong bath giving
a quicker tissue and flatter prints. It is
not desirable, however, to vary the strength
more than one or two per cent.

After sensitising, it is necessary to dry "gj^gj6 aftcr
the tissue, and it is important that this
operation should take as short a time as
possible, consistent with not raising the
temperature of the room in which it is
drying to such an extent as to cause the
gelatine to dissolve. The piece of tissue,
on being taken from the bath, should be
laid face downwards on a clean glass or
zinc plate, and squeegeed. The squeegee
consists of a thin piece of wood, into the
edge of which a strip of strong sheet india-
rubber has been fastened. The rubber
portion of the squeegee is passed over the
back of the tissue quickly, and with only
slight pressure. One stroke in each
direction will suffice to deprive the tissue of
a considerable portion of its moisture, and
too much time must not be taken up by the
squeegeeing, or the tissue will be difficult
to remove from the plate. To dry the Drying cardb
tissue upon, after stripping from the plate,

28 A TREATISE ON PHOTOGRAVURE.

sheets of cardboard should be provided,
somewhat larger than the tissue, and bent
into semi-circular form. A slit is cut in
each end of the card, and a short piece of
string, with a knot at each end, slipped
into the slits, prevents the card flatten-
ing out. The tissue is placed face upwards
on pieces of absorbent paper laid on the
arched backs of the cards, which can
then be suspended on strings to dry.
A little more troublesome, but better, plan
is to squeegee the tissue after sensitising
on to glass or ferrotype plates, and allow
it to remain there until dry. The gelatine
surface is by this means protected from
dust while drying, and a more even surface
is obtained, ensuring closer contact between
tissue and negative in printing. If glass
Gpiast^dfenrotype plates are used, great care must be taken that
they are perfectly clean, and the surface
must be dusted with talc, otherwise the
tissue will not strip when dry. Ferrotype
plates require no previous preparation
beyond sponging over. If the tissue is to be
dried on a support, the squeegeeing must be
more carefully done to ensure the removal
of air-bubbles, first beginning at the middle
and squeegeeing the right-hand half, and

A TREATISE ON PHOTOGRAVURE. 2Q

then changing hands and squeegeeing the
left-hand half, beginning a little past the
middle. By this method any air-bubbles
present are removed by the nearest way,
without having to travel the entire length
of the tissue.

Carbon tissue is practically insensitive
to light while wet, and the sensitising may,
therefore, be carried out in an ordinary
room. But from the drying room actinic
light must be excluded, and if this cannot
be arranged, or even if it can, it will be
found very convenient to employ a drying
cupboard in which the tissue may be
placed.

This can be spimly a large box, having
a hole at the top and bottom through Drying cupboard
which an iron or tin pipe may pass for
the whole of its height, and project out
into the room both above and below.
Holes are pierced in the top and bottom
of the box, and screened against the entry
of light. If an oil lamp be placed so that
its chimney passes a little way up the
iron pipe, the latter will be heated during
its whole length, and will maintain a
temperature inside the box at a point very
suitable for drying the tissue, and the

3o

A TREATISE ON PHOTOGRAVURE

perforations in the top and bottom will
supply the necessary current of air.

The accompanying (fig. 3) sketch shows
an effective, though somewhat more elabo-
rate, form of cupboard.

Fl <3 . 3 .

A. Tin or iron pipe. B. False floors, fitting closely at the outer edges, but
loosely round A. The true floors fit closely round A, but are perforated for
passage of air round the outer edges. The arrows show the direction of the
air current.

Such a drying box will dry tissue that
has been squeegeed on to ferrotype plates
in about six hours, and the tissue will be

A TREATISE ON PHOTOGRAVURE. 3!

found to work well and to keep better than
tissue which has taken longer to dry.

The tissue being dry, the negative should
be prepared for printing by providing what
is known in carbon printing as a "safe edge" ;
that is, strips of opaque paper of about one-
eighth of an inch wide are fastened round
the margin of the negative in order that an
edging of soluble gelatine may surround
the transparency. This is necessary to
prevent the film washing up on develop-
ment, as the unexposed gelatine adheres
more firmly to the support than that which
has been rendered insoluble by the action
of light. Pencil lines should be drawn on
the mask as guides to enable the tissue to
be placed accurately on the negative.

Exposure to light has no visible effect on NO visible ear** on
caibon tissue, consequently it is necessary
that the time during which the exposure is
to continue should be determined by other
than the usual means. The visible action
of light on albumenised silver paper has been

* as guide.

found to proceed at about the same rate as
its invisible action on carbon tissue, or
perhaps it would be more accurate to say
that the ratio of speed between silver paper
and carbon tissue is fairly constant. And

exposure.

32 A TREATISE ON PHOTOGRAVURE.

it is the universal practice to expose along
with the carbon tissue a piece of silver paper
in an actinometer of one form or another,
so that by observing the darkening of the
silver paper the printing of the tissue may
be accurately regulated.

Ammeter; There are a number of actinometers of

different form on the market ; perhaps the

Johnsons. simplest is that known as Johnson's, which

consists of a small box about an inch and
a half square, having a circle of yellow glass
in the lid, into which is fixed a piece of
cardboard of the colour which silver paper
assumes when three parts exposed. There is
a narrow slit in this card, through which the
light may reach the silver paper, a roll of
which is contained in the body of the box.
When the paper beneath the slit becomes
of the same colour as the surrounding card,
the instrument is said to have registered
one tint, and the operation can be repeated
by drawing forward more paper from the
roll until a fresh piece is exposed beneath
the slit, and so on.

A more elaborate and better arrangement

sawyer,. for our purpose is Sawyer's actinometer

(fig. 4). This is an oblong box, having in
its lid a strip of glass upon which has been

A TREATISE ON PHOTOGRAVURE. 33

printed a series of nine tints in carbon.
The tints are numbered, and increase in
opacity from one to nine. A roll of sensitive
silver paper is contained in the body of the
box, and a portion of it is drawn off, so that
it comes beneath the scale. Down each
side of the sensitive paper is a colour guide,
and as the sensitive paper under a given

FIG. 4.

section of the scale reaches the colour of
the side slip, the instrument is said to
register one, two, or more tints according
to the number borne by the section. The
advantage of this actinometer is that the
whole nine tints may be printed without
having to draw out fresh paper. In the
Johnson actinometer it is very easy for
error to creep in through neglect to draw

34 A TREATISE ON PHOTOGRAVURE.

forward a fresh piece of paper at the exact
moment when the tint is reached.

It will be found quite simple after a little
practice to determine how many tints will
require to be registered by the actinometer
before a given negative is sufficiently ex-
posed. The average exposure will be found
to be between six and nine tints on Sawyer's
instrument.
DGvus°spnpfantes as For development it is necessary to use

supports.

glass plates as a support, and these should be
prepared by coating one side with a solution
of gelatine containing bichromate of potas-
subsuatum. sium, and afterwards allowing them to dry
in a strong light. The gelatine solution is
prepared by taking a quantity of Nelson's
photographic gelatine, and placing it in a
wide-mouthed bottle with sufficient water to
cover it ; it is allowed to swell, and the
temperature is then raised by means of a
water bath until the gelatine dissolves.
Sufficient bichromate of potash is then added
to give it a lemon colour, and the solution is
filtered to remove foreign matter. The
plate is flowed over with this solution while
hot, and it will be found to assist the opera-
tion if the plate is dipped in hot water and
coated while still wet. This bichromated

A TREATISE ON PHOTOGRAVURE.

35

so*mg printed

gelatine will keep for a considerable time
if protected from the air.

The tissue, after exposure under the
negative, is immersed in cold water in a
dish, which already contains one of the
gelatinised plates prepared side upwards.
The tissue is immersed with the gelatine
side upwards, and all air-bubbles are care-
fully removed from its surface with a soft
brush. This being done, the tissue is turned
over, and the paper side freed from bubbles
also. When the tendency in the tissue to
curl film inwards has ceased, and it begins
to flatten out, the tissue and plate should be
brought into contact under water, and
removed together to a level surface, which
may be either a table or a squeegee board

J .

covered with thin sheet zinc, and there
squeegeed into close contact as before
described. The surplus moisture is removed
from the back of the tissue with absorbent
paper, and the plate set aside in a hori-
zontal position for about ten minutes,
though a longer time will not do any harm.

The development of the tissue should be DiveloplnK tank.
carried on in a deep tin or zinc vessel of
considerable size, which should be filled to
about one-third of its depth with water at a

A TREATISE ON PHOTOGRAVURE,

Temperature of
water.

Over-exposure.

Under-exposure.

temperature of about 100° Fahrenheit. After
a short immersion in this, the pigment will
be seen oozing out from beneath the edges
of the paper backing, and the latter may
be removed by lifting up one corner, and
drawing it back (under water) steadily from
the gelatine, which will remain adhering to
the glass plate. The warm water should now
be quickly dashed over the surface to
remove any bubbles which may be present,
and then the plate may be allowed to soak
for a few minutes to soften the gelatine,
while the next plate is proceeded with.

By laving the plate with warm water
applied by the hand, in the course of a few
minutes the whole of the soluble gelatine
will be removed from the plate, leaving a
transparency consisting of pigmented gela-
tine, which has been rendered insoluble by
the action of light.

If, on examination, the transparency
should be found over-exposed, the tempera-
ture of the water may be raised up to
120° F., or the addition of a little bi-
carbonate of soda to the water used for
developing will enable development to be
carried further. A transparency which is
too thin — though this does not often occur

A TREATISE ON PHOTOGRAVURE. 37

with the special transparency tissue — may
be intensified by staining it in a solution of
permanganate of potash, and rinsing under
the tap until the desired degree of intensity
is obtained.

On completion of development, the plate AIum>
should receive a final rinse in cold water,
and be soaked in a five per cent, solution
of alum for a few minutes, to remove the
last traces of bichromate, and again rinsed
and set aside to dry.

It is then in a condition to be varnished, ^n't1.'1™'
finished, and worked upon in the same
manner as a transparency on a gelatino-
bromide plate.

In working from a hard negative, or one
in which the contrasts are too great, it is
sometimes an advantage to employ ordinary
tissue instead of the special transparency.
That known as ''standard brown" will
generally be found the most suitable, and
the manipulations in the production of the
transparency are, of course, the same.

CHAPTER IV.

THE GELATINE RESIST.

The resist. ^TQ now come to the preparation of the

gelatine film, by means of which the actual
etching of the plate is to be regulated. This
consists simply of a print from the trans-
parency on carbon tissue, which is trans-
its nature ferred for development to the copper plate.
The development of this print will result
in a film of gelatine of varying thickness
extending over the whole of the plate, and
it is this variation in thickness which regulates
the etching, it being readily understood that,
apart from other considerations, it would
take longer for the mordant to penetrate
and reach the copper through a thick film
E^ch4reslstin than through a thinner one. The dark
tones of the subject being represented by
only a thin film of gelatine, the plate will
be attacked there first, with the result that
the etching will be deeper than in another
tone, where the etching only commences a
minute or two afterwards.

Tissue for the The carbon tissue to be used for the

resist need not be anything like so heavily

resist.

A TREATISE OX PHOTOGRAVURE. 39

charged with pigment as the tissue for the
transparency, the pigment playing no part
in the result beyond enabling the operator to
see before he begins etching whether or not
he has got a correctly-exposed print. At
one time it was customary to use "standard

J ' Standard brown"

brown" tissue almost exclusively for the resist.

But as the progress of the etching has to be

observed through the tissue (the etching as

it proceeds darkening the copper), unless

the film was a thin one all over, it became

very difficult to see exactly what was going

on. There is, however, now on the market

a carbon tissue made by the Autotype Co. "Aut"*ra'ure

expressly for photogravure resists. It is

made in two colours, red and brown. In

each case the tissue is but lightly pigmented ;

in fact, it has the appearance rather of a

stained gelatine than one to which pigment

has been added. Both colours may be relied

upon ; the red, being the lighter colour,

permits of the etching being watched with

less effort ; but the brown more readily

enables the operator to judge whether or

not the exposure has been correct, as the

colour of the red tissue, when seen in a very

thin film, is practically only yellow, and

very slightly contrasts with the copper plate

tissue.

4o

A TREATISE ON PHOTOGRAVURE.

Sensitising the
resist tissue.

Masking

to which it is attached, Practice will in
either case enable work to be judged with
certainty, but it is desirable to select one
of the two kinds, and adhere to it, rather
than change about from one colour to
the other.

The sensitising of the tissue for the resist is
the same as for the transparency, and it is
well to dry the tissue on the glass or ferrotype
plates as before described, in order to avoid
dust falling on the surface. This is more im-
portant when dealing with the resist tissue
than in the case of the tissue for the trans-
parency, because any little pinholes or other
marks can, in the transparency, be retouched,
but such defects cannot be remedied in the
resist without using varnish, which prevents
the etching entirely, and leaves a blank spot
on the etched plate, which would have to
be filled in by hand. The tissue, being
perfectly dry, can readily be separated from
the ferrotype plates by raising one corner with
the point of a penknife, and it will be found
to possess a brilliant, even surface.

It is necessary in printing from the trans-
parency, as from the negative, to mask the
subject round with strips of opaque paper,
and care should be taken that the sides are

A TREATISE ON PHOTOGRAVURE. 41

kept parallel, and the angles right angles ; Guide.tmes.
and as it is necessary that the piece of tissue
should be larger than the opening in the mask,
pencil lines must be drawn on the top and left-
hand side of the mask one-eighth of an inch
from the inner edge. The angle made by
these two lines must be kept perfectly true,
otherwise it will be impossible to ensure that
the subject occupies the exact position
required on the copper. If a slight error has
been made in masking the subject, it can,
within certain limits, be rectified when draw-
ing these lines on the mask.

The size of the transparency between the
inner edges of the mask should be carefully
measured, adding a quarter of an inch for the
safe edge to each dimension, and the piece of
tissue must then be cut exactly to size. If
this has been properly done, it will be found
that, upon placing the tissue on the trans-
parency with the end and one side close to
the lines on the mask, the tissue will extend
on all sides one-eighth of an inch beyond
the mask opening.

A printing frame with pressure screws, Printingframe.
instead of the ordinary springs, is the best to
use, and it should be furnished with a plate
glass front and a sheet of soft rubber to

42 A TREATISE ON PHOTOGRAVURE.

place over the tissue. The mask being on
the film side of the transparency, soft pack-
ing and considerable pressure are necessary
to secure proper contact between the tissue
and the transparency.

The printing frame, containing the trans-
parency with the tissue behind it, is placed
in diffused light, and the exposure made, the
actinometer being exposed at the same time,
and care being taken that the same amount
of light falls upon both the printing frame
and the actinometer. The Sawyer actino-
meter will do for this purpose, but, as the
exposure is considerably less than is
required for the transparency, this in-
strument is scarcely so sensitive as might
be desired. A more delicate instrument is
AVS2Sliyphoto" known as the Woodbury photometer, which
is an arrangement of a series of tints round
a circular opening, beneath which is a piece
of sensitised silver paper. Nothing but
plain glass comes between the paper and
the light, so that the tint is more quickly
obtained. Really, no specially-made actino-
meter is needed. The operator can easily,
with water or oil colour, or by the carbon
process, make for himself a standard tint,
and by exposing a slip of silver paper

A TREATISE ON PHOTOGRAVURE. 43

alongside the standard tint in a frame, the
exposure can be quite accurately gauged. Lengthol
For a medium transparency, it will be found
that when the silver paper has reached its
darkest shade before bronzing, the resist
will be fully exposed.

There is always some uncertainty, if the Trial resist.
transparency is being printed from for the
first time, as to whether or not the correct
exposure has been given, and as it is of su-
preme importance that the resist film shall be
perfect — neither over-exposed, which would
give too thick a resist, nor under-exposed,
which would result in absence of detail in
the shadows — it is advisable to use the first
print as a trial, and develop it, not upon the
copper, but upon the smoothed side of a
piece of opal glass. By this means (a note
being, of course, made of the exposure) it
can be absolutely determined whether every-
thing is right, because, being mounted on a
white surface, a yellowish-red image can be
seen far more readily than would be the
case if the resist were judged from its
appearance on the copper.

Correctness in the exposure for the resist
is of the utmost importance. Although a
slight error may be corrected in development

Character of
resist.

Resist too thick.

44 A TREATISE ON PHOTOGRAVURE.

by using water at a higher or lower tempera-
ture, the latitude in this respect is not so
great in the development of the resist as in
the case of the transparency, because it is
necessary in the resist to ensure that the
image consists of insoluble gelatine only,
and also because extremely hot water, say
above 120° F., has a tendency to cause the
film to strip off the plate on drying. The
operator's aim should therefore be to give
such an exposure as will allow of the resist
being properly developed at a temperature
between 100° and 120° F.

When the exposure of the trial resist is
completed, the printing frame is removed
into the developing room, and the develop-
ment proceeds in exactly the same way as
when developing the transparency.

Endeavour should be made to so regu-
late both exposure and development as to
produce the thinnest possible film con-
sistent with full detail in the shadows. A
resist possessing an appreciable thickness
of gelatine in the darkest shadows will
cause the etching to be long in starting,,
which is always undesirable, and it may be
that the first, or even the second, etching
bath will have to be abandoned as incapable-

A TREATISE ON PHOTOGRAVURE. 45

of penetrating such a film at all, thus
shortening the range of baths, or necessitat-
ing making up special weaker ones.

If the exposure of the trial resist is found
to be correct, another piece of tissue is cut
to size, placed in the frame behind the
transparency, and a similar exposure given ;
and when that is completed it is ready for
mounting on the copper plate.

CHAPTER V.

THE COPPER PLATE.

Quality and surface ffa quality and surface of the copper
plate are very important matters. The
copper should be as pure as can be obtained,
and its surface should be highly polished
and quite free from scratches. The best
copper is, I believe, known as of high
conductivity, which, I suppose, merely
indicates that care has been taken in its
manufacture to eliminate foreign substances.
The thickness of the copper I need say very
little about. If the manufacturers are in-
formed that the plates are to be printed
from direct, they will usually see that the
thickness of the plate is in proper propor-
tion to its size. As ordinarily sold, copper
plates have almost square edges, and before
printing it is necessary to bevel them, in
order to prevent the paper being cut.
In this process there is always some risk
of the plate being scratched, and if the
plate has already been etched, when this
is done, the scratches may be !very difficult

A TREATISE ON PHOTOGRAVURE. 47

to remove without injuring the picture. The
cost of bevelling is not great, and I recom-
mend that the plates should be ordered
bevelled to begin with. When the plates
are received from the manufacturer, they
should be perfect in surface, and if scratches
or other defects appear on the surface, it is
better to return the plates, and obtain per-
fect ones, as it is not an easy thing to patch
up a plate, and produce again a polish equal
to the one the makers can offer.

If, however, the defects are only small and scratches.
shallow, they can be removed by the use of
a burnisher, which can be obtained in various
shapes and curves, and is in the form of a
steel rod, with a highly-polished surface from
its blunt point to the handle in which it is
set. In removing a scratch, the burnisher
should be held in the right hand, with the
scratch running away from the operator,
and, beginning at one end of the scratch, the
plate is gently rubbed with the burnisher,
moistened in the mouth, or with a little oil,
until the soft copper is made to fill up the
depression, and so the burnishing is con-
tinued gradually right up from one end of
the scratch to the other. If the defect is a
small pit in the plate, it may be left alone

A TREATISE ON PHOTOGRAVURE,

Cleaning the plate

American potash.

Sulphuric acid.

if it will come in a dark part of the subject,
but, if not, the only remedy is to remove
the copper with a scraper for a little dis-
tance all round the hole until the pit dis-
appears, and then the marks of the scraper
are burnished out as before described. This
will produce a depression in the plate, but
it will not be so sudden a depression as at
first, and will not hold ink in printing.

When the surface is quite perfect, the
next step is to thoroughly clean it, with
a view to removing all grease and tarnish
from the surface. It is placed on the
table with a piece of paper considerably
larger than itself beneath it, so that the
plate may be isolated from all dust and
other foreign matter, and with a little
pad of cotton -wool it is first treated
with a solution of American potash, strength
unimportant — this is a very powerful
alkali, and must be handled with care, as it
has a solvent effect on the skin. The
potash is rinsed off under the tap, and a
fresh piece of cotton-wool is moistened with
sulphuric acid, of a strength of one part to
twenty of water ; the first will remove the
grease, the second the tarnish. The plate
is again rinsed, and with another pad of

A TREATISE ON PHOTOGRAVURE. 49

cotton -wool its surface is gently rubbed WaShcd whiting.
with a circular motion with a paste com-
posed of double-washed whiting moistened
with a three per cent, solution of ammonia.
This should be continued until, on rinsing
the plate, the water is found to run off
evenly, and not stand in drops on its sur-
face. The plate may then be dried with
a clean linen cloth. This will be facilitated
if the last rinsing of the plate has been in
hot water. The plate is now ready to
receive the bitumen ground, which will be
treated of in the next chapter.

CHAPTER VI.

THE GROUND.

F£oS.ofthe The function of the ground is, as already
explained, to give to the plate the tooth
necessary to enable it to hold the ink in
printing. This being so, any means by
which the copper can be protected at minute
points by a substance impervious to the
action of the mordant will answer the pur-

D£oundS!iquid pose. The two broad divisions of dusts
and liquids suggest themselves. In the
case of dust, its particles must be evenly
scattered over the surface of the plate, and
they must be capable of being attached to
the plate by some means or other.
Liquids may be either sprayed -on to the
plate, or the ground may be the result of the
reticulation of a liquid flowed over the
plate. I refer to liquid grounds more by way
of suggestion of possible methods rather
than as methods which I recommend for
ordinary use. The dust ground is very
rapidly laid, and appears to be eminently

A TREATISE ON PHOTOGRAVURE. 51

satisfactory. For special purposes, how-
ever, it may be desirable to use other
methods, and outlines of the principal ones
will therefore be given.

For use with the spray a solution of
resin, or bitumen, and many other gums
in benzole or ether, may be used, the
solution being contained in a bottle into
the cork of which a scent spray is fixed.
The construction of this little appliance
will be familiar to most of my readers ; it
may be actuated by the breath, or by a
pneumatic ball and tube. If the spray is
in good order, the size of the globules of
moisture may be governed to a considerable
extent by bringing the plate nearer to or
removing it further away from the operator.
To produce a fine spray, vigorous blowing
will be required. When the plate has been
sufficiently covered it should be set aside for
the solvent to evaporate. If a strong ground
is required it will probably be desirable to
spray it two or three times, allowing the
solvent to evaporate between the applica-
tions in order to prevent the globules running
together. When quite dry, if the operations
have been properly performed, the plate
should be practical !y in the same condition

52

A TREATISE ON PHOTOGRAVURE.

With dust ground.

Reticulated
ground.

as a plate grained with dust after the dust
has been fixed to the plate.

The air-brush promises to afford a
very excellent means of distributing liquid
grounds; enabling, as it does, the operator
to vary the coarseness of the deposit at
will. This is a very important point in
which dust -grounding is deficient. In
theory, and to a considerable extent also
in practice, the coarseness of the ground
should vary in the different portions of the
subject in the same ratio as the depth of
etching required, and it is not possible to
obtain this in the dusting box.

The air-brush might be usefully employed
in conjunction with the dust ground by
spraying a liquid ground on the parts of
the subject requiring greater strength after
mounting and drying the resist. The
visible image would enable this to be done
with great accuracy.

For a reticulated ground the old aqua-
tint engraving formula may be used. Make
a saturated solution of resin in rectified
spirits of wine, which must be quite free
from water. It will take two or three
days to obtain complete saturation, and the
bottle should be shaken occasionally. In

A TREATISE ON PHOTOGRAVURE. 53

another bottle take two ounces of spirit, and
add to it half an ounce of the resin solution,
and flow the clean copper plate with it as
though one were varnishing a negative, and
set aside in a horizontal position for the
spirit to evaporate.

If, when dry, the ground is not of the
character desired, it must be cleaned off,
and the plate flowed afresh with the resin
solution, after varying the proportions of
resin and spirit, increasing the quantity of
resin to obtain coarseness, and adding
spirit to obtain a finer grain. The addition
of a few drops of methyl ether or benzine
tends, I think, to improve the character of
the grain.

The advantage in the use of liquid
grounds seems to lie in their not requiring
special apparatus, while the dust ground,
on the contrary, necessitates the making
of a special box, but the cost is not great,,
and I consider the dust ground more
under control, and more reliable for general
purposes.

Dust is the principal difficulty to contend
with in laying a liquid ground; it interrupts
the regularitv of the reticulation, and it is

54 A TREATISE CN PHOTOGRAVURE.

very difficult to protect the plate from it
while the resin is being applied.

ustinrb... The apparatus for laying a dust ground
consists of a rectangular box (fig. 5)
measuring on the base i8in. square, and
in height 2ft. 6in. The size, of course,
must depend on the size of plate intended
to be grained ; the box illustrated is
intended for plates up to 12 x 10, but,
whatever reductions are made in the size of
the base, the height of the box should not
be unduly cut down, otherwise the height
of the column of dust will not be found
sufficient to allow of a sufficient deposit
of dust on the plate without a second
insertion.

The box is supported from the middle of
the sides by pivots, which allow of the box
being revolved on its support. An opening
is provided at the bottom of the front of the
box to allow of the insertion of the plate.
The box should be lined throughout with a
glazed paper or thin sheet zinc, preferably
the latter, as it is necessary that the inside
of the box should be perfectly smooth to
prevent the particles of dust sticking to it,

and damp- and falling down at inconvenient times. If

proof lining.

a zinc lining is used, it also materially assists

A TREATISE ON PHOTOGRAVURE. 55

in keeping the dust from damp, which is a
very desirable thiug. The door is another
point of great importance. It is a very
difficult matter to construct a door on the
usual lines, which will not allow the dust to
escape while the box is being revolved.
The best form of door for this purpose that Dust-^ght door.
I have seen is constructed as follows :
Round the opening strips of brass about
half an inch wide are screwed on the inside
of the box to form a perfectly even surface,
against which the door may be pressed,
and the door, which is without hinges, is
provided round the edge of its inner sur-
face with strips a quarter of an inch wide
of sheet indiarubber, so that when the
door is in place, the indiarubber comes in
contact all round with the plates fastened to
the box. An additional protection against
the escape of dust is provided in the shape
of plates of brass screwed to the face of
the door and projecting beyond its edges.
The front of the box rises about two
inches before the door opening begins, in
order that the dust lying at the bottom
may not fall out when the door is removed,
and this lower portion of the front forms
a ledge sufficient for the door to rest

A TREATISE ON PHOTOGRAVURE,

upon while the plate is receiving the ground
without making use of the fastenings. When
the box is being revolved, the necessary
pressure to keep the door in place is
obtained by a couple of strong brass springsr
after the nature of the springs used in
photographic printing frames. Perhaps the
accompanying sketch will enable the arrange-
ment to be better understood.

FIG. 5.

A, pressure springs holding: door
in place; B, strap with which' A en-
gages; C, door, front view ; D, inside
of door ; E, brass plates on inside of
box and outside of door; F, india-
rubber round inside of door; G,
stand on which plate is inserted in
box.

The grain^ dust. Almost any varnish gum may be used for
the process of dusting the plate, but mix-
tures of two kinds of gum are to be avoided,
as any difference in their melting points

Bitumert

A TREATISE ON PHOTOGRAVURE. 57

may lead either to one of them not be-
coming fixed to the plate, or, if sufficient
heat is applied to fix it, the other gum
may be overheated, and the particles run
together on the plate.

Ordinary resin yields a good grain when
used alone, and is a favourite with French
workers. Copal also may be used, but I
have always given the preference to bitumen.
It is very hard, and can readily be reduced
to a fine powder, and the particles remain
quite free, and do not stick together, as is
the case with some other substances, and,
if desired, the resist can, when mounted on
the plate, be dried off with spirit without
destroying the grain, as would be done if
resin were used. Whatever gum may be
decided upon, about one and a half pints will
be necessary for this size of box. It should
be finely ground, and, as this is a very dusty
business, it will be found convenient to buy
it in this form.

In order to lay a ground, the box is Laying the ground.
revolved several times, the sides and top
being beaten during the operation, to dis-
place the grains of dust which may adhere
thereto, and by this means a cloud of dust
is raised within the box. A final beating is

i|8 A TREATISE ON PHOTOGRAVURE.

given, and the box is brought to a standstill
and secured in position by the peg at the
side. The length of time for which the box
is allowed to rest after being revolved is
important in its effect on the character of
the resulting grain. When the box is
brought to rest, many coarse particles of
dust will be in a state of suspension along
with the finer ones ; the former will
naturally fall first, and the longer the rest is
the finer will be the ground, and vice versa.
Vo7£oundharactcr ^ a coarse ground is desired, the plate may
be inserted after a rest of, say, twenty
seconds. After about one and a half or two
minutes all the coarse particles will have
subsided, and very little increase in fineness
of grain will be obtained by waiting longer.
It naturally follows that the longer the box
is allowed to rest the less dust will remain
for deposit on the plate, and it may be
necessary, if a very fine ground is desired,
to insert the plate more than once. When
the box has rested for the time decided
upon, the door is removed, and the plate
inserted on a stand, having supports about
two inches long, which serves to keep the
plate out of the dust lying at the bottom
of the box (see fig. 5, G).

A TREATISE ON PHOTOGRAVURE. 59

One peculiar effect frequently observed U^e0^tfssof
on the plate upon removing it from the box
is that, although the deposit of dust over
the middle of the plate is perfectly regular,
the deposit near the edges is very uneven,
and it has been suggested that probably this
is due to currents of air created by the
particles of dust which descend close to the
edge of, but not touching, the plate, causing
eddies, and drawing the dust particles into
irregular forms. Be this as it may, the
remedy is to place the copper plate in the
middle of a larger one of glass or metal,
and so pass them together into the dusting
box. The ground should then be found to
be regular over the whole surface of the
copper, and the irregularities will be upon
the supporting plate alone. The length
of time the plate should remain in the
box depends upon the quantity of grain
required, and also upon the size of the box.
If the plate is inserted, say, half a minute

J y Quantity of grain

after the box is brought to a standstill, the
dust will be found to have completely
settled at the end of four or five minutes,
and there should then be a sufficient
quantity on the plate. This can be ascer-
tained by holding the plate near the light

6o

A TREATISE ON PHOTOGRAVURE,

Appearance of
dusted plate.

Removing large
particles.

a little below the level of the eye, and in
this position the dust should appear to
be almost a solid coating, having the
appearance of fine fawn-coloured cloth. If
the deposited dust is insufficient, the box
must be again revolved, and the same pro-
cess repeated. For a very fine ground, in a
box of rather smaller dimensions, the writer
has sometimes given as many as four inser-
tions. If by chance any extra large particles
of dust should have fallen on the plate, they
may be removed with a very fine sable pencil,
slightly moistened in the mouth, but great
care is necessary to prevent the ground
being spoilt ; still it is necessary to remove
them, otherwise they may pierce the gela-
tine resist, and cause the mordant to pene-
trate to the copper without undergoing the
process of filtration through the gelatine
resist.

The questions both of quantity and fine-
ness of ground depend upon the character
of the subject to be reproduced. A light
and delicate subject will require a finer
ground and one less in quantity than a
subject with heavy shadows. During the
etching of the image the mordant is con-
stantly undermining the grains of bitumen r

A TREATISE ON PHOTOGRAVURE. 6l

and, to withstand this, if the etching is to
be deep, the dust grains must be corres-
pondingly large.

When a ground that is considered cor- Fixing the ground
rect as to both quantity and fineness has
been obtained, the plate should be taken
from the box and fixed by one edge in
the jaws of a small hand vice, the grained
surface of the plate being protected from
damage by a slip of cardboard or thick
paper. The plate is now held over a small
gas stove of the ordinary circular form, or
over a Bunsen burner, and gently moved
about to obtain an even degree of heat.
In the case of bitumen, after a while the A$aetaerwnln01

ground fixed

dust will be observed first to lose its dul-
ness and become transparent, and afterwards
to assume a bright appearance with a colour
approaching steel blue, and not till then
should the plate be removed from the heat.
To observe this change properly the plate
should be held horizontally just a little below
the level of the eye, with the light coming
from the front, in which position it will be
readily seen when the dust has attained the
right colour.

In the case of resin and copal I have not
noticed this steel blue appearance, but the

Importance of
sufficient heat.

62 A TREATISE ON PHOTOGRAVURE.

dust simply becomes transparent. It is im-
portant that the plate should be sufficiently
heated, otherwise the dust does not become
properly attached, and affords no protection
to the copper. On the other hand, if it is
overheated there is a danger of the particles
running together, in which case the ground
would be too coarse, or in an extreme case
would extend over the whole plate like a
varnish. When using bitumen for the
ground the heat necessary to produce the
steel colour is so great that there is not
much danger of overheating, but in the
case of resin or copal great care should be
exercised. After the plate is cool the
ground can be examined with a magnifying
glass, and it is still possible to increase the
amount of grain, if desired, by a further
dusting, followed by heating, and so on,
and when cool the plate is ready to receive
the gelatine resist.

CHAPTER VII.

MOUNTING AND DEVELOPING THE
RESIST.

The copper plate having been properly
cleaned, the ground laid in the manner
indicated, and the resist printed, the copper
plate is placed in a dish of clean cold Filtering w^r.
water. It is desirable that the water should
be filtered in order to remove any small
particles which may be suspended in it,
and which might get between the plate
and the resist. This can readily be done
through fine cotton stretched over a light
framework of wood.

With the same object of removing foreign Avoidance Or dust,
matter the plate before immersion in the
water should be carefully freed from all
hairs and dust which may be found adher-
ing to either the grained surface or the
back. Any particles which may be im-
prisoned between the plate and the resist
may cause mischief, either by preventing
the mordant from reaching the copper, or,
if they are grains of dust somewhat large
and pointed, they may perforate the resist,

64

A TREATISE ON PHOTOGRAVURE,

Transferee plate.

Sue of plate.

and so allow the mordant free access to
the copper, which would result in deeper
etching than would be the case if the
mordant had first had to pass through the
gelatine film.

The plate then being in the dish of water,
the exposed resist tissue is removed from the
printing frame, and carefully dusted with a
camel-hair brush, and immersed in the water
face upward.

When removing the tissue from the print-
ing frame, the top of the picture should be
indicated by a pencil mark on the back, as
a guide to placing it in position on the copper
plate, as, although it is possible on first im-
mersing the tissue to see on looking at it
with the light at a certain angle something
of the image owing to the different rates at
which the exposed and unexposed portions
absorb moisture, still it is better to have a
definite mark to go by. When using red
autogravure tissue, a slight image may be
seen, the result of the darkening action of
the light.

The size of the plate for a given picture is
a matter of taste, but it is customary in in-
taglio work to allow equal margins on the
two sides and at the top, with a somewhat

A TREATISE ON PHOTOGRAVURE. 65

larger space at the bottom to allow either of
the signature of the artist or the title of the
subject.

It is possible with a lead pencil to mark M
the grained surface of the plate so as to
show the position in which the tissue is to
be placed, and it is well to do so in the case
of a plate having wide margins, but where
the margin at the top and sides is only
about a quarter of an inch, it is quite easy
to adjust the tissue upon the plate while in
the water, merely using the edges as guides.

On first immersion in the water the tissue soaking the tissue.
will curl with the gelatine side inwards, and
at this stage a clean camel-hair brush
should be passed over the gelatine surface
in order to remove air-bells, and the tissue is
then turned over on its face, and air-bells on
the back are also removed.

By the time this has been done the Austin* in

J position.

tissue will begin to straighten out, and just
before the curl of the tissue begins to
reverse, that is, before the paper backing
becomes concave, showing that the gelatine
has absorbed its fill of water, the tissue
must be rapidly adjusted on the plate, and
this being done, the plate and tissue to-
gether are removed from the dish, movement

66 A TREATISE ON PHOTOGRAVURE.

of the tissue being prevented by pressure of
the fingers.

The plate is placed upon a flat level sur-
face, and the squeegee applied to the paper
backing. The fingers of the left hand are
placed on the junction of the plate and the

f. left-hand edge of the tissue to prevent
movement, and with the right hand the
squeegee is drawn over the paper backing
of the tissue, beginning a little nearer the
left hand than the middle, and drawing the
squeegee, not too quickly or with too much
pressure, from left to right, taking care that
the pressure on the whole length of the
squeegee is equal. The same procedure is
gone through for the other half of the
tissue, and then the superfluous moisture is
removed with blotting-paper, and the plate
set aside in a horizontal position for about
ten minutes. This is in order to allow
of the gelatine thoroughly attaching itself
to the copper.

bath. While this is going on the developing
bath should be prepared. It is desirable
that the vessel should be large, and capable
of holding a good depth of water. For
plates up to whole-plate, 24 x 18 x 4l is a
suitable size for the dish.

A TREATISE ON PHOTOGRAVURE. 6j

The development of the resist does not
differ in any way from the development of
the transparency, except that after the paper
backing has been stripped the temperature
should not be raised above 100° F. if it can
be avoided ; though if it be found that the
resist is over-exposed the temperature may
be raised as high as 120°. I have previ-
ously explained why a medium temperature
is desirable. Particular care should be
taken that all the soluble gelatine is
removed.

After the development is completed the Drying off.
plate is rinsed in cold water, and may then
be set aside to dry in an upright position
with its edge resting upon a piece of
blotting paper. It is recommended that
when possible the plate should be allowed
to dry spontaneously in a place free from
dust, but if for special reasons it is desired
to proceed with the etching at once the
resist may be quickly dried by taking a
small quantity of methylated spirit in a
measure, and adding to it an equal quantity
of water, and flowing this over the plate in
an even wave. As the spirit passes over
the film it will be observed to take with it a
slight scum, which is no doubt composed of

68 A TREATISE ON PHOTOGRAVURE.

soluble gelatine. When the spirit reaches
the end of the plate it should be allowed to
flow off, and a further portion of the spirit
is then flowed over the plate and allowed
to drain off, whilst a small quantity of
strong spirit is added to the mixture of
spirit and water. The plate is then again
flowed with the spirit, the mixture being
strengthened at each application until the
main portion of the moisture has been
expelled ; the plate may be placed in a dish
and allowed to soak in spirit without added
water for a few minutes, after which it may be
taken out and allowed to stand until dry.
The use of a whirler will materially assist the
drying of the film, but if that is not at hand, it
is desirable to fan the plate after treatment
with the spirit in order to dry it as quickly
as possible. The evaporation of the spirit
so reduces the temperature of the plate that
the moisture in the air has a tendency to
condense upon it. The plate should stand
for about half-an-hour after becoming
apparently dry, in order to ensure that no
moisture remains in the film.

If theplateis allowed to dry spontaneously,
which will take some hours, it is desirable
that this should take place in a cool room,

A TREATISE ON PHOTOGRAVURE. 69

and that after becoming dry it should not be
subjected to much variation in temperature.
It has often occurred in the writer's experi-
ence that when the tissue has not been
quite freshly sensitised, the film has
stripped off the plate entirely on being
brought into a warm room.

The margins of the plate must now be
protected with varnish, which may be com-
posed of one part of bitumen dissolved in
five parts of benzole. The varnish should
be somewhat thin, as in that state it dries
more quickly and thoroughly, and affords a
better protection to the copper. The varnish
is applied with a small camel-hair brush,
but it will be found best, first of all, to draw
a line all round, and just within the edge of
the resist, with a draughtsman's ruling pen,
charged with the varnish, using as a rule
a steel straight-edge. The straight-edge
should be supported above the copper-plate,
in order to avoid damage to the resist
(which is very susceptible to injury), or a
piece of soft paper may be placed between
the rule and the film. These lines having
been drawn, it is quite easy to work up to
them with the brush, and so secure straight
and even margins to the picture. The back
of the plate should also be varnished, and,
when dry, the plate is ready for etching.

CHAPTER VIII.

THE MORDANT.

perchiorideofiron. The most suitable mordant for etching the
plate is neutral perchloride of iron. It is
procurable as an article of commerce, as a
solid body, yellow in colour, and very deli-
quescent. It is also sold in liquid form, but
this is unsuitable for our purpose, being
much more acid than the solid.

solution. To prepare the solutions, take seven

pounds of the perchloride, and boil it in an
enamelled iron pan with five pints of water.
When the perchloride has completely dis-
solved, shown by the solution becoming

Testing. transparent, take out a little in a test tube,

and add to it a small quantity of freshly pre-
cipitated hydrate of iron. If the hydrate is
not taken up by the perchiorideofiron solu-
tion, it will be evident that the latter
contains no free acid, and is in a suitable

Neutralising. condition for our purpose. If, however,
the hydrate is taken up by the per-
chloride, it will be necessary to add hydrate
to the bulk of the solution until neutrality

A TREATISE ON PHOTOGRAVURE.

is reached. Some idea of the quantity re-
quired can be formed by the amount used in
the test ; but the quantity added is not
important, because any excess of hydrate
beyond what is necessary to obtain neutrality
will simply remain unchanged, and eventu-
ally settle to the bottom.

Fresh hydrate of iron is readily prepared Hydrate of iron.
by stirring liquid ammonia into a small quan-
tity of the solution of perchloride of iron,
when the hydrate will be precipitated. The
hydrate is filtered out and washed until
freed from ammonia, which may be ascer-
tained by testing the droppings from the
filter with red litmus paper, and is then
ready for addition to the solution of per-
chloride of iron.

After boiling with the hydrate the per-
chloride is allowed to stand for some hours,
and the clear portion can then be poured off,
and the remainder filtered and added to it.
It is not absolutely necessary to filter the
whole of the solution, but I think it is worth
while to take the trouble of doing so.

The strength of the solution should now T«;i,ntf0^rengthcf
be tested by pouring a quantity into a tall
glass jar, using a Beaume's hydrometer for
heavy liquids. At 70° F. the solution will

72 A TREATISE ON PHOTOGRAVURE.

probably show a strength of 43° ; if so, a
twenty-ounce bottle may be nearly filled with
it and duly labelled " 43°," and the remainder
may be boiled until at the same tempera-
ture of 70° F. the strength is raised to 45°,
when a further quantity is taken out and
stored in another bottle. Water is then
added until 40° Beaume is indicated, when
a further quantity is bottled off, and so on,
Range of solutions. until further solutions of 38°, 36°, and 33°
Beaume are obtained, the complete range
being six solutions of 45°, 43°, 40°, 38°, 36°,
and 33° respectively, as indicated by
Beaume's hydrometer at a temperature of
70° F.

The water used in reducing the strength
of the perchloride solution should be warm
in order that the complete solution of the
perchloride may not be disturbed.

The above quantity of perchloride (7lbs.)
will yield about seventeen ounces fluid
each of the range of six solutions.

These solutions improve with use, and it
is as well before etching the first plate to put
a strip of copper into each bottle for about
a quarter of an hour, to take the first edge
off the mordant.
A±rda°nft!ha The solutions are given in the order in

A TREATISE ON PHOTOGRAVURE. 73

which they are to be applied to the plate,
and it will be observed that the first is the
strongest.

A peculiar feature of the process is that a
strong solution of perchloride has less corro-
sive action on copper covered with a resist
than has a weaker one, because it has less
penetrative power on the gelatine film. A
saturated solution will not penetrate even the
thinnest gelatine film. This is no doubt due,
in great measure, to the viscosity of the mor-
dant, and probably to some slight extent
to the tanning action which it has upon the
gelatine. The result of this peculiarity is
that the 45° solution will only penetrate the
thinnest portion of the resist, and when it
encounters a thicker portion its action stops,
and to continue the etching it is necessary to
transfer the plate to a weaker solution. In
this solution, 43°, the etching proceeds with
the portions of the film next in thickness
until it in turn encounters gelatine of a
thickness which will not allow of its pene-
trating. The plate must then again be
transferred to a weaker solution, and so on
until the whole of the image is etched.

A strong solution of perchloride of iron is
somewhat slow in filtering, without the use

74

A TREATISE ON PHOTOGRAVURE.

of special appliances. A simple, yet effici-
ent, apparatus is, however, easily arranged
and fitted up. The materials required are
a cheap form of Springel's pump made of
glass, a wide-mouthed bottle, and some small
sized rubber tubing. The bottle must be

FIG. 6.

fitted with a good cork, which is perforated
in two places to take the neck of the funnel
and a short length of glass tubing, as in the
accompanying sketch (fig. 6). The side
and top tubes of the pump are connected
respectively with the bent glass tube and a
water tap by means of rubber tubing.

The action of the apparatus, when the tap
is turned on, is to extract air from the bottle
by means of the partial vacuum created in
the bulb of the pump. And the liquid in

A TREATISE ON PHOTOGRAVURE. 75

the funnel is caused to pass more quickly
through the filtering medium and into the
bottle in order to supply the place of the air
withdrawn.

There are other mordants which it is pos-
sible to use in place of the perchloride of
iron, but they have almost universally given
place to the latter, and as it is my desire
to indicate the most reliable methods of
working, rather than to confuse the
reader with alternative formulae which offer
no advantages, I have confined myself to
the mordant described in this chapter.

CHAPTER IX.

ETCHING THE IMAGE.

TSS3?S.reof Before beginning the etching the different
solutions should be raised to an even tem-
perature of 70° F. It is convenient to set
the solutions out in order in dishes either of
porcelain or celluloid of a size suitable to
the plate to be etched. Two dishes only,
however, may be used, if preferred, for the
whole of the solutions, the next bath being
prepared while the plate is etching in the
previous one, but it is better to devote one's
whole attention to the progress of the etch-
ing ; and there is the objection that the
strength of the various solutions is altered
to some slight extent by the small quantity
of the preceding solution left in the dish,
though, perhaps, the alteration is not suffi-
ciently great to be of importance.

The etching of the plate is a portion
of the process about which it is difficult
to lay down fixed rules. The conditions
under which the etching takes place
are rarely on different occasions identical,.

A TREATISE ON PHOTOGRAVURE. 77

even in resists printed from the same
negative. A very slight variation in
the thickness of the resist will require the
etching to be proceeded with in a different
manner, and, again, the humidity of the at-
mosphere has a considerable effect on the
resist, dampness causing the film to allow
the mordant to pass through it much more
readily than when the film is absolutely dry.
It must, therefore, of necessity be a matter
for experience to teach how the etching is
progressing, and what strength of mordant
to use.

Bearing in mind what has been said Guides to etchin*
as to the principle upon which the etching
proceeds, the best guide to the etcher is the
appearance of the plate and the stoppage
of the etching. Theoretically, the strongest
solution, 45°, should commence to etch the
shadows within a minute after the plate is im-
mersed in it, a nd the plate should be continued
in this solution until the etching appears
to stop. There may perhaps be three tones
in that portion of the film which this first
solution will attack. The action shown by
discolouration of the copper will first be seen
in the thinnest part, and shortly afterwards
the next tone will begin to darken, and finally

78 A TREATISE ON PHOTOGRAVURE.

the action will spread to the third tone, and
beyond this it will not go, and it is this
ceasing to spread which is meant by the
expression " stoppage of the etching." As
a matter of fact, the etching does not stop,
because in those parts where etching has
begun it still continues, but nowhere else.
When this stoppage occurs, it indicates that
the plate should be transferred to the next
weaker solution, which will take up the etch-
ing where the preceding solution left off, and
if this is not done the etching will, of course,,
go on where it is already at work, and
when the plate is eventually transferred
to the weaker solution, there will be a
distinct step in the gradation between
the tones etched respectively by the two
solutions. To give an idea merely of
the time which may be occupied in the
FTa|Lpiofe: different etching-baths, the following table is
given showing the time for which the plate
forming the frontispiece was etched :

Solution. Time of Etching. Solution. Time of Etching.

Beaume 45° No effect. 38° 4 mins.

»» 43° 2 mins. 36° 3 ,,

» 40° 4 » 33° 2 „

Total time, 15 mins,

Solution 45° began to act two minutes
after immersion of the plate.

This table must not be taken as an

A TREATISE ON PHOTOGRAVURE. 79

infallible guide in etching other plates, be-
cause it is impossible to accurately describe
the conditions as to state of atmosphere,
thickness of resist, etc., under which the
etching took place, but for a trial plate this
example may well be followed.

Usually, five etching baths will be found Number Or baths.
sufficient to complete the etching of a
plate. If the resist be a thin one the 45°
bath will etch the deep shadows, and 36°
will be sufficiently weak to penetrate the
highest lights if the contrast be normal.

If, on the other hand, the resist be some- Thick r^t.
what over-printed, 45° will not penetrate
at all, and the 33° bath will probably be
found necessary to complete the etching.

It is not desirable that the 45° bath, or
the 43° if that be the first solution to
attack the copper, should be allowed to
act for too long a time. Its action is very
slow in spreading to thicker portions of the
resist, and as the effect of each succeeding
bath is cumulative, the portions of the plate
affected by 45° may, if it be allowed to
work too long, be over-etched by the time
the lighter portions are etched sufficiently
deep.

80 A TREATISE ON PHOTOGRAVURE.

It will be remembered that the capacity
of the plate to yield dark tones depends
not only on the depth of the etching, but
on the presence in the shadows of the
unetched points protected by the ground.
By over-etching, these points are gradually
undermined until they do not suffice to
imprison the ink, and the depth of the tone
is reduced instead of being strengthened
as might be expected.

It may be taken as a general rule that
the first etching bath which attacks the
copper — whether it be 45° or a weaker one
— should not be allowed to act longer than
two minutes before the plate is transferred
to the next weaker bath. The second
bath, for similar reasons, should be stopped
rather before than after it has ceased to
attack fresh portions of the plate; while
the third and fourth baths, which do the
greater portion of the work, should be used
well up to their limit, and the last one
until the etching is completed.

There is considerable control over result
in the way in which the plate is treated in
the etching : If it is desired in the repro-
duction to reduce the contrast present in the
original negatives, solution 45° may be

A TREATISE ON PHOTOGRAVURE. 8l

omitted altogether, as that would act only
upon the shadows, and so increase their
depth. Solution 43° may be allowed to
act for one minute only, the remaining
solutions being used as usual.

A subject lacking in contrast may be
improved at slight expense as to the original
scale of gradation by working solution 45°
right up to its limit, and following with
special solutions, made up by mixtures of
the standard solutions, of more widely
differing strengths, e.g., beginning with 45°,
and continuing successively with 41°, 38°,
34°, 30°, and 28°, if necessary.

In the case of some subjects with a very
delicate scale of gradation, the ordinary
method of etching may be abandoned with
advantage, and the etching be begun with
a small quantity of the strongest solution
that will touch the copper. This solution
is diluted from time to time with a few
drops of water, until the whole of the image
is etched. The water must be added in
very small quantities frequently, and in the
same way in which one would an accelerator
in developing a photographic negative, i.e.,
first pouring the water into a measure,
adding the etching solution, mixing together,

82 A TREATISE ON PHOTOGRAVURE.

and returning to the dish. Care should be
taken that the added water is not of a
lower temperature than the solution, other-
wise the perchloride may be precipitated.

By this method nothing of the gradation
is lost if the etching is properly managed,
but it requires some experience to carry on
the etching at the proper speed by diluting
the solution so that the high lights are
attacked neither sooner nor later than the
moment when the shadows have attained
their proper strength.

When using the red autogravure tissue
there is no difficulty in observing the pro-
gress of the etching, as discolouration of
the copper takes place wherever the mor-
dant attacks it, and the transparency of
the resist readily permits of this being
observed.

It may not be necessary to employ the
whole range of solutions to complete the
etching of the plate ; when the discoloura-
tion of the copper has extended to the
whole of the image, it is unnecessary to
use a weaker solution, but the action of
the mordant should be allowed to proceed
in the solution then in use for about half a
minute after the whole of the detail has been

A TREATISE ON PHOTOGRAVURE. 83

obliterated, in order to get proper printing
strength in the higher tones. For instance,
in a subject showing clouds, the whole of
the sky should be allowed to blacken before
the plate is removed from the mordant.

When etching is completed, the plate is Removing resist.
quickly removed from the mordant, and
held under a strong stream of water, whilst
the film is removed by gentle rubbing with
the fingers. If the tap is not conveniently
near, a small quantity of American potash
or other strong alkali may be poured on
the plate, and rubbed over it with a pad
of cotton-wool. This, by neutralising the
mordant, will prevent further action, and the
film can then be removed with less haste
by friction in water.

The plate is dried, and may now be A^aesceerof
examined. The bitumen grain should still
be present all over the plate. The only
place where it is likely to have given way,
owing to the lateral as well as vertical
action of the mordant, will be in the shadows,
and if it has given way here to only a slight
extent, the printing qualities of the plate
will not be seriously interfered with.

The appearance of the plate at this stage
will be very disappointing, and to the novice

84 A TREATISE ON PHOTOGRAVURE.

may seem to indicate failure, which im-
pression may, however, be far from correct.
Rc"eaS|fLtn.: The grain is removed along with the
varnish on the margins and back with a
pad of cotton-wool moistened with benzole,
and, when this has been done, the plate
may be flowed with American potash, and
vigorously rubbed with another pad of
cotton-wool. After rinsing, this should be
followed with weak sulphuric acid, about
one part to twenty, which will remove the
blackness from the etched portions. If
the plate is not now thoroughly clean, weak
nitric acid should be applied in the same
way, and it may finally be polished with
the oil rubber.

After this, the plate will present a much
more satisfactory appearance, and, on ex-
amination with a magnifying glass, it will
be seen that the etching corresponds in
depth to the tones of the picture, and
throughout the subject, from the shadows
to the high lights, will be seen the small
specks of bright copper, portions of the
original surface, which have been protected
by the grains of bitumen, and which will
serve to imprison the ink in the depressions
caused by the etching.

CHAPTER X.

PHOTOGRAVURE IN LINE.

The procedure in the case of a line sub-
ject may be identical with the foregoing,
except as to the etching, but special atten-
tion should be given to the preparation of
the negative. The production of a perfect
line negative on a gelatino-bromide plate is Line
an art in itself; the principal points to
observe are the proper lighting of the draw-
ing or engraving, the use of slow plates with
accurate exposure and careful development
with a weak and well-restrained developer.
The lines of the subject must be represented
by perfectly clear glass on a black ground,
otherwise success in the after processes will
not be attained. With whatever care the
gelatine negative may be prepared it will
scarcely equal a negative produced by the
wet-plate process, and if the latter can be
obtained, by all means use it. I have,
however, prepared satisfactory negatives on
various slow plates, amongst which the slow
isochromatics can well hold their own.

86 A TREATISE ON PHOTOGRAVURE.

The ferrous - oxalate developer can be
recommended as giving good results with
correct exposure. Or a hydroquinone de-
veloper of about half the usual strength, with
twice the normal quantity of citric acid, will
be found reliable, and perhaps more con-
venient, by the general worker.

The negative will require to be intensified,
which may be done by any of the mercuric
methods, and particular care should be
taken in thoroughly fixing the negative,
clearing away all fog, and washing thoroughly
both after fixing and between the two opera-
tions of bleaching and blackening the image.

The best method of producing the line
transparency is by contact on a slow
gelatino-bromide plate, and the same de-
veloper may be used as is recommended for
the negative. If this method is adopted,
however, a reversed negative will be re-
quired. Reversal of the transparency in
the camera is not available, because of the
tendency to a widening of the lines by
halation from the clear glass of the negative.

The carbon process, however, is fairly
satisfactory for line subjects if the negative
be a strong one, care being taken in the
-exposure of the tissue, so that the greatest

A TREATISE ON PHOTOGRAVURE. 87

possible strength of line may be obtained,
consistent with a ground of clear glass, in
order that a thick film of gelatine may be
obtained in the resist in the parts repre-
senting white paper.

If there is little contrast between the lines
and the ground, the mordant may etch
through in places where the copper should
remain untouched. A line transparency is
readily intensified with a solution of per-
manganate of potash. I have found it a
good plan in the case of line subjects to
develop the transparency on finely-ground
glass ; the roughened surface readily retains
the pigment in position without the use of a
substratum, and the subsequent intensifica-
tion with permanganate of potash is more
effective because of the absence of the stain
which spreads over the white ground of the
subject when a gelatine substratum is used,
and to some extent neutralises the effect of
the intensification. And if the transparency
is, when dry, collodionised or varnished,
the granular appearance of the glass is
obliterated.

When developing the transparency, if a
slight veil should extend over the whites, a
wisp of cotton-wool may be trailed over

Intensification.

88 A TREATISE ON PHOTOGRAVURE.

it while it remains in the hot water, but no
pressure must be employed, otherwise the
lines will be displaced. After development,
the transparency should be hardened with
alum, and, when dry, protected with a film
of plain collodion or varnish.

If the subject is in pure line, i.e., without
blotches of ink undivided into line, the
copper plate should, theoretically, only
require to be grained for the purpose of
affording a surface for the resist to adhere
to ; the separation of the lines by spaces
of unetched copper might be expected of
itself, as in etchings, to afford sufficient
inkholding power to enable printing to be
carried out. The lines in a photogravure
plate, however, differ very considerably
from the lines in an etching. The former
are shallow and broad in comparison with
the etched line, and in order to obtain the
full value of a broad line, or the crossing
of one line over another, the ground is
essential. The ground for a line subject
should be fine in character, and not so
abundant as for a half-tone plate unless
the lines are not clearly separated, in
which case the plate will require to be
grained, on the same principle as in the

A TREATISE ON PHOTOGRAVURE. 89

case of a half-tone subject, i.e., if the
subject is strong and dark, a coarser and
more abundant grain will be necessary than
if the subject were light and delicate.

The development and mounting of the Etching.
resist on the copper present no variations in
procedure. In etching the plate, as there
is only one tone to produce, and that tone is
represented by what should be practically
bare copper, one etching bath, or at most
two, will be required. The solution 40°
Beaume is generally most suitable, and at a
temperature of 70° F. etching should com-
mence all over the subject about the same
time, and be complete, if black lines are
desired, in eight to ten minutes. If, owing
to a slight film of gelatine over the lines, the
etching should not commence shortly after
immersion of the plate in the mordant, and
so should not attack the plate evenly all over
the subject, a weaker mordant should be
used ; but the fault of unevenness can only
occur through faulty manipulation in de-
velopment of the resist, in cleaning the
copper-plate, or through defects in the
negative or transparency.

CHAPTER XI.

PRINTING FROM THE PLATE.

The plate having been cleaned after
etching, a proof should be taken from it or
" pulled," as it is called, technically. Up
to this point the expense incurred to enable
one equipped for ordinary photography to
work the process of photogravure, has been
small — some ^3 only — and many who do not
intend to embark commercially in process
work will, no doubt, hesitate to incur the
expense of setting up a small printing
establishment in their homes. But I can
assure them from personal experience that
a great amount of pleasure may be derived
from the possession of a copper plate print-
ing press, and I have no hesitation in saying
that the interest attaching to the production
of one's own prints is well worth the outlay.

The actual printing of the plate presents
no difficulties beyond such as must neces-
sarily be present in any work that is under-
taken by a person of intelligence, if it is to
afford him pleasure.

A TREATISE ON PHOTOGRAVURE. QI

Beyond the fact that the work is pleasant,
there is a great advantage in having the
means and the ability to prove one's own
plates ; one gets a better grasp of the whole
subject of photogravure, and understands
what qualities in the print must be derived
entirely from the plate, and what the
printer's art may be relied on to confer.

There is considerable art in the printing
of an intaglio plate, and its full extent can
scarcely be realised without personal expe-
rience. Two printers of equal ability, if
they were asked to print the same plate
independently of each other would produce
widely differing results, especially if the
plate were an etching, although the work of
each man might be excellent. This is due
to the fact that there is a wide field for the
expression of the printer's individuality, and
their interpretation of the subject may differ,
while each interpretation may be truthful.

The variation in results to be obtained
from a photogravure plate is considerably
less than in the case of a line subject,
whether the subject be a photograph from
nature or a reproduction of a picture,
because the intention of the author or artist
is now fully expressed on the plate, and

Q2 A TREATISE ON PHOTOGRAVURE.

less is left to be expressed in the printing
of it. Still to a certain extent the power
of expression remains, and, even if the
printing is not to be done by himself, it is
desirable that the photograveur should pull
a proof as a pattern for the printer, and,
for the same reason that an etcher often
proves his own plates — that he may finish
what he has begun by impressing upon
the print the intention present in his mind
when he produced the original.

Having said so much as to the desirability
of pulling one's own proofs, let me add that
the courtesy generally met with at the
hands of plate printers prevents the desir-
ability becoming a necessity. They will
usually, at any rate by appointment, arrange
to prove the plate in one's own presence,
and the writer has found them most pains-
taking in carrying out suggestions, pulling
proof after proof until one satisfactory in all
respects is obtained.

I propose now to describe, as well as in
words I am able, the method of pulling a
proof, but no amount of writing will produce
a skilful plate printer, and I can only hope
to save the beginner some trouble by indi-
cating the way in which he should go about

A TREATISE ON PHOTOGRAVURE.

93

the work. First as to appliances and
materials :

1HK PRINTING PKEbS.

The rollers are of iron ; the top one is re-
volved by means of the " cross," as the
handle is called. The press shown in the
cut is of a larger size than is necessary for
an amateur printer, and is furnished with
geared wheels, a great advantage when large
plates are being printed. The bed plate is of
iron, its surfaces are planed up true, and the

g4 A TREATISE ON PHOTOGRAVURE.

motion given to the top roller causes the
plate to travel by means of friction, obtained
by pressure applied by screws to the top
roller, and in travelling, motion is commu-
nicated to the lower roller upon which the
bed plate rests. The rollers and bed plate are
not geared together in any way. The pres-
sure may be varied by means of the screws,
and the packing between the pressure
screws and the bush in which the axle of
the top roller revolves should be partly of
wood or millboard, in order to allow of a
certain amount of spring in the pressure.
To complete the equipment of the press
" blankets " are required, somewhat larger
than the largest size of paper intended to be
printed on. These consist of two kinds,
which are specially made for the purpose —
" fronts," or the kind which is to come next
to the paper, are of very closely woven
woollen material resembling " melton " cloth
of great substance ; and " middles," a
coarser and more open material. Two fronts
will be required next the paper with one,
two, or three middles on the top of them,
according to the character of the plate being
printed. It is convenient to attach a string
to the blankets, pass it over the pulley, and
hang to it a weight sufficient to lift the

A TREATISE ON PHOTOGRAVURE. 95

blankets clear of the paper as the latter,
with the plate beneath, emerges from be-
tween the rollers.

The paper suitable for plate printing is of a Plate Papers-
special kind, almost, if not quite, free from
size. It should absorb water readily, and it
is prepared for use by dipping each sheet, cut
to the desired size, separately in clean cold
water, and stacking the sheets one on top of
the other in a pile with a plate of glass on
the top, and leaving them under a weight
for some hours, in order that they may get
thoroughly damp. The length of time paper
will require to stand before attaining the
right condition will depend on the amount
of size it contains, the effect of the size being
to render the paper less absorptive. If time
is of importance the paper may be brought
into condition more quickly by using hot
instead of cold water to dip the sheets in.

For trial proofs a Dutch plate paper,
either "laid" or " wove," is recommended.
It is cheap, and quite good enough for that
purpose, or for practising on. For higher
class prints there are several kinds of
Japanese paper of excellent quality and
colour which yield prints of a character
well suited to some subjects. The plates in
this book are printed on a Japanese paper.

96

A TREATISE ON PHOTOGRAVURE.

Copper-plate inks.

Materials for Inks.

There is no difficulty in obtaining a range
of other plate papers from the merchants,
differing so widely in character that all tastes
and subjects may be suited.

Copper-plate inks are quite distinct from
ordinary printer's inks, and these latter are
quite useless for our purpose.

The ink can be purchased ready ground
with oil in a very stiff paste, and it only
requires letting down slightly with oil to make
it ready for use. Plate printers prepare
their ink freshly day by day, and say that it
deteriorates very fast, losing its brilliancy
and richness, even when kept from the air.
This may be so, but it is convenient to keep
a little ink always handy, so that a single
proof may be pulled at any time without the
troublesome preliminary of grinding fresh
ink. The best way of keeping it is in a
collapsible tube, such as oil colours are sold
in, only larger. A half-pound tube will last
a very long time if it is used only for trial
proofs. If an edition is to be printed, it is
better to grind fresh ink, because the colour
may be varied until one exactly suiting the
subject is obtained. The principal pig-
ments used in the preparation of the ink are
Frankfort black or drop black ; umber, raw

A TREATISE ON PHOTOGRAVURE. 97

and burnt ; sienna, raw and burnt ; and
Vandyke brown.

The black is the chief ingredient, the
other pigments being used to vary its shade ;
Frankfort black with a little carmine added
gives a very rich black. A warm black or
rich brown may be obtained by varying the
proportions of black and burnt umber.

A slab of marble or an old lithographic
stone will be required to grind the ink upon,
and a piece of marble, similar in shape to
an inverted cup, but solid, and called a
11 muller," to grind it with.

The pigments are obtainable in powder
form from any printer's furnisher, and he
will probably be able to supply the burnt
linseed oil used for grinding them in.
Two strengths of oil, thin and medium,
should be obtained, so that the character
of the ink may be varied.

To prepare the ink, take some of the dry Grinding the ink.
colour, and with a palette-knife mix it on the
ink slab with a little of the thin oil, then
take the muller, and, by vigorous grinding,
mix the colour with the oil, from time to
time adding more colour or more oil as may
be required, until on taking a quantity of the
ink on the palette-knife it can only be pre-

A TREATISE ON PHOTOGRAVURE.

Plate-heater.

Wiping muslins.

vented from dropping off by keeping turning
the knife. This is the best guide I can give
as to consistency. If a stronger ink is re-
quired, that is, one which gives a darker
print, especially in the deeper tones, the
medium oil may be used, as it is of a more
clinging nature, and adheres more strongly
to the plate during wiping. The grinding
must be continued until all grittiness is
removed and the pigment is thoroughly in-
corporated with the oil, otherwise it will
not stand.

The heater is a plate of iron standing on
four legs, and beneath is a perforated gas-
pipe in the form of a ring. A heater may
be improvised with an ordinary circular
gas stove and a piece of stout sheet iron.
A photogravure plate requires very little
heating, and the heater may be entirely
dispensed with without much inconvenience,
as the plate can be warmed over the gas.

The cloths for wiping the plate after ink-
ing are of muslin of different degrees of
coarseness ; old and well washed plain mus-
lin curtains answer very well for the finer
cloths. The coarse muslin used first to
remove the bulk of the ink from the surface
is very open in texture and somewhat stiff;

A TREATISE ON PHOTOGRAVURE. 99

the proper material should be obtained from
a printer's furnisher.

The wiping muslins should be kept to-
gether away from dust and dirt ; they are
generally kept in the " jigger," a box of a
suitable size having a polished mahogany
lid upon which the plate is inked and wiped.
Of course, the lid need not be mahogany, but
it should be of smooth hard wood, to which
dust, which might scratch the plate, will not
readily adhere. A box about ten inches
high will, when placed upon an ordinary
bench or table, bring the plate to a conveni-
ent height for the inking and wiping
operations.

The inking dabber is a roll of woollen cloth
or flannel used for applying the ink to the
plate. A dabber may be purchased from the
printer's furnisher for a small sum, but if it is
preferred to make it, take a long strip of
woollen material, not too closely woven,
about five inches wide, and out of one side of
it cut narrow v-shaped pieces about three
inches long at varying intervals now roll the
flannel up tightly until the base is about
four inches in diameter, and stitch the end
fast. Some cord may be wound round the
neck of the dabber, which will be smaller than

100 A TREATISE ON PHOTOGRAVURE.

the base, and of a convenient shape for holding
in the hand. If the surface at the base is un-
even, take a slice off it with a sharp knife
and then cover it with a piece of the " front "
blanket, which can be stitched fast to the
cone of the dabber. This outer covering
can readily be replaced when it gets stiff
with old ink dried on. If the dabber were
not covered, a slice would have to be cut off
it whenever it got hard with the old ink
remaining on it, and so it would gradually be
destroyed.

The printer's requisites being at hand, we
will proceed to pull a proof from the plate
which has already been cleaned after etching
in the manner described.

If the dabber is a new one, the ink must
be worked into it by rocking it about in the
ink on the slab until it is well charged,
otherwise it will not communicate sufficient
ink to the plate.

Now warm the plate on the heater until
it is nearly as warm as the hand can bear,

Inking: the plate.

and remove it to the jigger for inking. Take
a little ink up on the dabber, and, holding
the plate by one corner, work the ink into
the depressions by a rocking motion of the
dabber, making the latter at the same time

A TREATISE ON PHOTOGRAVURE. IO.I

travel gently forward. The object is to
force the ink into the depressions, and avoid
lifting it out again with the dabber, and the
forward rocking motion is best calculated
to effect this. The plate must not be
" dabbed," that is, pressed on the plate and
lifted straight up again, as the name
" dabber " might lead one to infer ; the ink
would by so doing be lifted, partially at any
rate, out of the depressions, instead of being
left there.

In inking a plate for the first time the
dabber should be worked freely in all direc-
tions, in order to insure that the plate has
taken the ink thoroughly. Afterwards a
certain amount of ink will remain in the
plate after it has passed through the press —
as can be proved by passing it through a
second time with a clean piece of paper —
and going over the plate once will be found
sufficient to ink it thoroughly.

It will be understood that in the process
of inking the whole surface of the plate will
be blackened, and it is now necessary to
remove the surface ink while leaving that in
the etched portions. To do this, take a

C i • r YvT>i v& the plate.

piece of coarse muslin, say two feet square,
and gather it together loosely, turning the

102 A TREATISE ON PHOTOGRAVURE.

edges inwards so that they form a soft pack-
ing for the centre, which should be free from
creases. The mode of folding is the same as
that employed when preparing a duster for
use ; its size and shape when folded should
be that of the hand that is to use it, when
open. Take this folded muslin in the ex-
tended right hand with the smooth centre
outwards, and with a circular motion of the
hand wipe the plate towards you, turning
the plate round from time to time until the
greater portion of the ink has been removed
from the surface. Holding the plate in the
hand, run a rag round the margins to remove
the bulk of the ink, so that it is not again
drawn on to the picture when continuing
the wiping ; then take a piece of the finer
rag folded in the same way, and repeat the
process of wiping. It will be found that to
take up the ink evenly, the rag must be
slightly charged with ink to begin with, and
it will continue to wipe satisfactorily long
after it has become quite black with the ink
taken up.

The plate will have cooled considerably
during the process of inking, and usually it
should not be more than lukewarm when
the wiping is done. The ink becomes more

A TREATISE ON PHOTOGRAVURE. 103

adhesive on cooling, and is better retained
in the depressions, while the surface ink is
softened by warming the rag on the heater
occasionally during wiping.

The principal points in the wiping are to points to observe
keep the rag moving — never letting it stop
while on the plate; not to use too much
pressure with a view to removing the ink
quickly, but to work gently and regularly
over the plate until only a slight film of ink
remains.

The wiping is finished with the ball of the
hand, working it lightly, but smartly, over
the plate with the same circular motion,
and turning the plate round from time to
time until the surface appears bright and
free from streaks. I say appears bright,
because there will really still be a tint left
over the whole plate. If this is not desired,
the ball of the hand should be passed over a
lump of washed whiting, and, after lightly
wiping off the surplus whiting on the apron—
which should always be worn — the wiping is
continued until the surface of the plate is
polished quite clean, in which state it will
yield what is called a " natural " print.

The margins are now cleaned with a cleaning margins.
piece of slightly damped washleather, which

104 A TREATISE ON PHOTOGRAVURE.

should be attached to the apron, and
whiting. A fold of the washleather is
thrown over the thumb, a little whiting
taken up on it, and, using the first finger as
a guide to run along the edge of the plate,
it is applied briskly to the margin, taking
care not to encroach on the subject. The
plate during this operation should occupy a
position on the lower right-hand corner of
the jigger, and the right hand margin is
then cleaned, drawing the thumb from top
to bottom towards the operator, the plate
being prevented from slipping off by the
thumb of the left hand applied to the bottom
edge. The plate is turned round from time
to time from left to right, so that the
margin being cleaned is always the right-
hand one, and, finally, the plate is sup-
ported in the hand, while any marks made
by the left-hand thumb are carefully re-
moved.

The plate is now ready for the press. It
is well to have a thin sheet of zinc some-
what larger than the paper upon which the
print is to be made to put the plate on
when passing through the press, because
the photogravure plate being smaller than
the paper, it is necessary to have some guide

A TREATISE ON PHOTOGRAVURE. IO5

to ensure the print being in the middle of
the paper. A piece of clean paper will do
equally well, but it requires frequent re-
newal, while the zinc plate is easily cleaned
and always ready.

Place the plate face upwards in the Pumng the proof.
middle of the zinc plate or paper guide
on the iron bed of the press — there must
be no soft material between the plate and
the bed of the press, or the plate will be
bent — take up a piece of the damp print-
ing paper, remove any surface moisture
with a sheet of clean tissue paper, and
brush it over lightly with a soft flat brush,
to remove loose hairs, etc., and lay the
paper face downwards on the plate, using
the edges of the zinc plate as a guide. Lay
three or four thicknesses of blanket on the
top of the paper, the fine fronts next the
paper, and revolve the cross so that the
whole pass under the roller. When the
plate emerges on the other side raise the
blanket and carefully remove the paper ; if
it sticks very closely, the plate may be
slightly warmed.

The first proof from a plate is often un- variations in

printing.

satisfactory, and a second should be taken
before judgment is passed upon it. The

106 A TREATISE ON PHOTOGRAVURE.

first is often mealy and granular in the
shadows, owing to the plate having taken
the ink imperfectly. If the second proof
is weak in the shadows, the pressure on the
rollers should be increased, or another
thickness of blanket may be added, and if
the print is still unsatisfactory in this
respect a stiffer ink must be used, and the
plate be allowed to become quite cold
before wiping.

A different result may be obtained by
varying the foregoing manipulations. If
the plate is too strong generally, and yields
too dark a print, the ink may be thinned
down with oil ; or a weaker colour may be
used in preparing the ink — some colours are
much stronger than others, although the ink
be of the same consistency — or the plate
may be kept warm during wiping. And the
converse holds good in the case of a weak
plate.

In the case of a plate too strong in parts
only, the particular parts may be wiped
with a softer rag, with more pressure and
wiping more slowly — if the rag is dragged
over the plate, more ink will be removed than
by a quicker motion.

Having pulled a few proofs and humoured

A TREATISE ON PHOTOGRAVURE. 107

the plate as each succeeding print appears
to require, you will then be able to determine
in what respects the plate is defective ;
and if the defects are capable of being
remedied, you may work upon it in many
ways on the lines laid down in the succeed-
ing chapter. Proofs should, however, be
frequently pulled, in order to see that the
work is having the desired effect.

CHAPTER XII.

AFTERWORK ON THE PLATE.

One of the chief difficulties in retouch-
ing the plates is to make the aftervvork
harmonise with the original. In many
published photogravures, this point has not
been sufficiently regarded, and otherwise
fine pictures have been spoilt by injudicious
handwork. It is far better to discard a
faulty transparency or resist than to trust
to retouching on the plate to cover up faults
resulting from careless work ; and if the
negative is not perfect and another cannot
be obtained, the work should be done with
brush and pencil on that and on the trans-
parency in preference to working on the
plate itself. The process is quite capable
of yielding a sufficient scale of gradation,
without after manipulation in strengthening
shadows and burnishing high lights if full
advantage be taken of its resources.

If a photogravure plate be carefully
examined, it will be seen that the image,
split up as it is by some thousands of
hillocks to the square inch, and each valley

A TREATISE ON PHOTOGRAVURE. IOQ

differing in depth from its neighbour, could
not possibly be imitated by toolvvork, and
if tools are employed, the best that can be
done is to assimilate their work to the
original general character as nearly as
possible. Having said these few words by
way of preliminary, I propose to describe
various means by which a plate may be
retouched. Which method should be used
in the case of any particular plate can only
be decided after seeing the plate itself.

A plate may be strengthened as a whole,
or in any particular portion, by re-immersing
it in the mordant after having again covered
over with a protecting medium the tiny
specks of the surface, which were originally
protected by the bitumen grain. This is
accomplished by rolling the plate up with a
greasy ink applied with a leather or hardened
gelatine roller. The ink is composed of the
following ingredients :

Asphaltum .... .... ij ounces.

White wax .... .... 3 ,,

Stearine .... .... 3J ,,

Spermaceti ... .... 7 ,,

First melt the asphaltum in a water-bath,
and gradually add the other ingredients,

110 A TREATISE ON PHOTOGRAVURE.

stirring the while, until thoroughly incor-
porated. The ink may be run into cakes
for purposes of storage. I believe this or a
similar ink is sold under the name of " finish-
ing ink."

The roller should be purchased from a
dealer in process materials. Its surface
must be perfectly even and true, and it
would prove a delicate task for one to
attempt to make it for himself. I think the
leather-covered rollers are to be recom-
mended, but gelatine rollers, the surface of
which has been hardened by treatment with
bichromate of potash and exposure to light,
are cheaper, and can be used for the purpose.
When not in use, the roller should be hung
up, and not left resting on its surface, or a
flat place will be the result, and, if of leather,
should be greased with tallow to keep it in
condition.

To ink or "roll up" the plate, dilute a little
of the ink with turpentine, working it up with
a palette knife on a sheet of plate glass, or
a lithographic stone. Now pass the roller
over the stone several times, and in different
directions, until evenly charged with the
ink. There will, however, be so much ink
on the roller at this stage that, if applied to

A TREATISE ON PHOTOGRAVURE. Ill

the plate, the depressions, as well as the
surface, would be covered. To remove the
surplus, clean up the ink on the stone, or,
better still, take a second stone, and pass
the roller several times over this until the
roller has on it only the thinnest film of ink.
If the ink is of the right consistency, it
should be quite tacky at this stage, and the
passage of the roller over the stone should
be quite audible. If the ink is too thin, a
little time should be allowed until the tur-
pentine evaporates.

When the roller is properly charged with
ink, place the plate, which must be thoroughly
cleaned, as when originally preparing it for
etching, on the jigger or bench, and pass the
roller over its surface backwards and for-
wards, with very slight pressure, and turn
the plate round from time to time, so that
the roller passes over it in all directions.

The extent to which the rolling up is to
be carried depends upon the portion of the
plate it is desired to strengthen. If the
rolling is continued long enough, more ink
being taken up as required, the whole of the
image will be obliterated ; or the rolling
up may be stopped a little short of this,
so that only the deepest shadows are

112 A TREATISE ON PHOTOGRAVURE.

uncovered, and so on. If it is wished to
strengthen the whole plate, it must be rolled
up only until the bright specks of the original
surface have been covered ; further inking
will gradually obliterate the image begin-
ning with the parts least deeply etched, and
continuing from tone to tone until the ink
extends to the deepest shadows.

After rolling up, the plate is thickly dusted
with finely powdered bitumen, and the
powder not taken up by the ink is lightly
brushed off with a soft brush ; the plate is
heated until the bitumen becomes incorpor-
ated with the ink, and the image becomes
distinctly visible. If the rolling up has been
properly done, a marked change will take
place in the appearance of the plate at this
stage, which cannot be mistaken. The
image, which up to now has been almost
obliterated, will start out quite brilliantly.

When cool, the plate is ready for etching
after having its back and edges protected
with varnish. Any portions of the image
may be stopped out with varnish, and the
etching proceeds for such time as the plate
may require in the perchloride of iron bath
at 40° Beaume.

Where it can be employed, the re-etching

A TREATISE ON PHOTOGRAVURE. 113

method is undoubtedly the best method of
retouching, as the character of its work is
identical with that of the original etching.

In aquatinting, the plate is regrained in the Aquatint.
dusting box, and the dust fixed by heat-
exactly as in preparing the plate before etch-
ing ; and, when the plate is cool, the parts
desired to be strengthened are painted over
with a small brush dipped in a weak solution
of perchloride of iron. The strength of the
solution depends upon how long it will take
the operator to apply the mordant, and
whether he desires to produce a flat or a
graduated tint. Generally it will be found
convenient to dilute a small quantity of the
solution 33° Beaume with an equal bulk of
water, and with it to work on a small por-
tion of the plate at a time, frequently rinsing
the mordant off under a strong stream of
water, drying with a clean linen rag, and
applying the mordant again if required. If
the subject is a very delicate one, and there
is a good deal of work to do, it will be
desirable to stop out the lighter portions
with black varnish, to prevent their being
degraded by the mordant spreading over
them in rinsing it off.

The brush used should be mounted in

114 A TREATISE ON PHOTOGRAVURE.

quill, not metal, but the mordant will be
found to affect the hair in course of time.
Weak nitric acid, i — 20, or the Dutch or
other mordant, may be used if preferred,
but they will be found more destructive to
brushes than the perchloride of iron.

Aquatinting, as above described, har-
monises perfectly with the original biting,
the principles being the same in each case,
and it should be used in preference to tools
in all possible cases. There is, however, a
certain loss of detail, as the mordant acts
to an equal extent on the whole of the
surface unprotected by the grain, not being
restrained, as in the original etching, by the
varying thickness of the resist film.
Roulettes. A roulette consists of a handle resemb-
ling a penholder, with a small steel wheel
fixed in one end in such a way as to
permit of the wheel revolving when it is
drawn over the copper. The wheel has a
serrated edge, and its sharp points indent
the copper to a greater or less extent, accord-
ing to the pressure employed in using the
tool. Roulettes vary considerably in the
width of wheel, from a single line of points
to about half a dozen ; in the broader kinds
the surface is similar to that of a fine file.

A TREATISE ON PHOTOGRAVURE. 1 15

With the single-lined roulette the finer
passages are put in, and lines drawn, while
the broader tools may be employed for
strengthening broad shadows or other work
where the area to be worked upon is com-
paratively large. The wheel should be kept
well oiled, so that it may revolve readily,
otherwise scratches may be made instead of
indentations.

In using the roulette, it should be re-
membered that the actual printing value of
its work is increased by the fact that a
slight burr is raised round each indentation.
It is often desirable to remove this burr
with charcoal. The work of the roulette is
well suited to photogravure plates, and is
seldom obtrusively apparent unless used to
a great extent, or in the lighter tones of
the subject.

There are occasions when the etching Etchin(r point
point may be used with advantage in con-
junction with photogravure, but they are
few ; and it requires great judgment to
know when and how to employ it. There
is nothing in common between the line of
the etching point and the pure half-tone of
photogravure. I have a little mezzotint of
Semour Hayden's that, I think, strikingly

Il6 A TREATISE ON PHOTOGRAVURE.

demonstrates this clashing of line and half-
tone. The little plate is a gem in every way,
except for the etched lines, which, for me,
quite take away the charm of the subject.
Still, the operator may on occasion desire
to use it in some dark corner of a plate
where strength is required, and the lines
may not be obtrusive. It will be necessary
first to prepare the plate by covering it
with an etching ground ; wrap up a small
ball of etching ground in a piece of fine
taffeta silk — the ground is composed of
asphaltum, wax, and tallow, but it will save
much trouble to purchase it ready prepared
— heat the plate slightly, and rub it over
with the silk-covered ball until a sufficient
quantity of the ground has exuded through
the silk on to the plate. To distribute the
ground evenly, pat it gently with a silk-
covered dabber while the plate is still warm.
In this way it will be found quite easy to
get an even thickness all over the plate.
The dabber consists of a disc of cardboard
some two inches in diameter, upon which is
laid a little pile of curled horsehair, and
upon the top of that a thin layer of cotton
wool, and the whole is then covered with
fine taffeta silk, which is tied at the back

A TREATISE ON PHOTOGRAVURE. 1 17

of the disc, not so tightly as to lose the
spring of the hair.

With the etching point the desired lines
are drawn on the plate, taking care that the
point penetrates through the ground right
to the metal. The work should be done
from left to right of the plate, so that the
hand does not travel over lines already
drawn, and, as the ground is delicate, a
pad of soft paper should be interposed
between the hand and the plate.

When the lines are all drawn, the margins
and back of the plate are protected with
varnish, and the plate immersed in per-
chloride of iron, or any other mordant, and
left there, meanwhile removing with a
feather any bubbles which may be formed,
until the desired depth is obtained. The
plate may be removed from time to time,
rinsed and dried, and lines sufficiently bitten
stopped out with varnish, and the etching
be continued until complete.

The etching point may also be used as a
" dry point" for drawing lines without the
aid of etching ground and mordant. If the
point is held in the hand in a sloping
position, it will raise a burr in drawing the
line, and the strength of the line will be

Il8 A TREATISE ON PHOTOGRAVURE.

proportionately greater unless the burr is
removed. The burr raised will be con-
siderably less if the lines are drawn with
the point held vertically.

sandpaper. Sandpaper can sometimes be usefully

employed for strengthening a plate by
pressing the rough surface into the metal.
The coarseness of the sandpaper will
naturally have a great effect on the result.

A plain tint may be given to a sky or
stretch of water without detail by spreading
flour of sulphur mixed with oil over the
cleaned plate. The effect is not, however,
very durable, and is lost after a few im-
pressions have been taken.

There are various means also of reducing
over-bitten passages.

The burnisher is the chief of these, and
it has been previously described. It is as
well to have a variety of shapes to choose
from, and great care should be taken to
keep them free from rust. Before using a
burnisher that has been laid by for any
length of time, it should be cleaned and
polished. This is readily done by cutting
a V-shaped groove in the end of a board,
sprinkling a little flour emery on it, and
rubbing the burnisher up and down in it,

A TREATISE ON PHOTOGRAVURE. I tQ

finishing off in a second groove, using
whiting as the polishing medium.

In order to reduce a passage evenly, dip
the burnisher in oil, or moisten it in the
mouth, and rub it backwards and forwards
with little more pressure than its own
weight, each stroke just clearing the previous
one, and, when the whole area has been
covered, turn the plate round and repeat
the process with the lines in a different
direction, and continue turning the plate
round and burnishing again until the re-
duction is sufficient. It is better to work
in this tentative manner than to endeavour
by each stroke to reduce the printing quali-
ties of the plate to the point desired. This
may, of course, be done where the part to
be reduced is quite small, but for a large
area, such a course would result in great
unevenness.

A stick of willow charcoal may also be
used for reducing any large portion of a
plate that has been over-bitten. The bark
should be carefully removed, or it will
scratch the plate, and one end should be
ground flat, a piece of roughly ground
glass is useful for this purpose. The char-
.coal is then soaked in water, which gives it

120 A TREATISE ON PHOTOGRAVURE.

a stronger tooth, and the plate is gently and
evenly rubbed down with it with a circular
motion, using oil as a lubricant.

Charcoal is preferable to the burnisher in
many cases, because the latter does not
remove the copper, but merely crushes the
little hillocks, more or less, into the depres-
sions, thereby destroying detail to a certain
extent. Charcoal, however, wears down
the tops of the hillocks, and so reduces the
ink-holding capacity of the plate without
otherwise affecting it.

When using charcoal the plate should be
frequently rinsed, to free it from the loose
particles, which form a paste, and would
otherwise wear down the bottom of the
depressions.

The scraper is principally of use in photo-
gravure for removing small defects in the
etching, or the burr caused by the use of
the dry point. As to the former, the method
of using it has been described in Chapter V.
The scraper consists of a triangular blader
having three cutting edges, set into a
handle. To remove the burr from a dry
point line, hold the blade of the scraper
with one side flat to the plate, and make
the cutting stroke in the opposite direction

A TREATISE ON PHOTOGRAVURE. 121

to that in which the line was drawn. The
cutting edge should be held obliquely to
the line, so that the cut becomes a slice
instead of a straight cut through. If the
scraper is properly ground and sharp, there
is no need to fear injury to the plate, as
only the portion standing above the surface
will be removed.

CHAPTER XIII.

STEEL-FACING THE PLATE.

A photogravure plate should yield fifty
prints without much sign of deterioration.
Some plates may stand more work than this,
and others not so much, according to the
depth to which the etching has been carried
and the delicacy of the subject. If a large
edition is required, it will be necessary to
have recourse to steel-facing or acierage
This consists in depositing on the compara-
tively soft surface of the copper plate a
coating of iron by electrolytic action. A
plate so protected will yield an almost un-
limited number of prints, as, on the iron face
showing the least sign of wear, it can be
removed and replaced with a new coating.

The steel-facing, so called (it is really iron
only), of engraved plates was invented in
I^55 by Messrs. Salmon and Gamier, and
to this invention is due much of the popu-
larity of intaglio work, and consequently of
the excellence attained to in its various
branches. The original cost of intaglio
copper plates resulting from handwork only
in conjunction with the limited number of
prints to be obtained from them without loss-

A TREATISE ON PHOTOGRAVURE.

I23

of quality when not steel-faced must of
necessity either place prints beyond the
reach of the many, or result in their being
printed beyond their capabilities.

The process of steel-facing is simple with
the proper apparatus at hand, but, if pre-
ferred, the work may be entrusted to one of
the many firms who make a specialty of
steel-facing.

FIG. 6.

The apparatus required consists — first, of
a trough made of wood, and lined with
guttapercha, or with a thick coating of
pitch, applied hot. The size of the box
should be considerably larger than the
largest plate to be steel-faced. For plates
up to 1 2m. by loin., a box of the measure-
ments given in the accompanying sketch
will be found suitable.

Steel-facing-
trough.

Anode.

124 A TREATISE ON PHOTOGRAVURE.

Two brass rods extend from end to end
of the trough, at a distance apart of eight
inches ; one end of each rod should pro-
trude somewhat beyond the end of the box,
and be furnished with a pinching-screw for
attaching the wire from the battery.

A piece of sheet iron, 22in. by i8in., and
a quarter of an inch thick, forms the anode,
and is suspended from one of the rods by
brass hooks soldered to the back of the
plate. The junctions of the hooks with the
plates are varnished with several coats of
bitumen varnish, but the rest of the plate
remains uncovered.

cathoae. From the second rod is hung the plate to

be steel-faced, so that the surface bearing
the image is opposite to the front of the
anode.

ESffif.!c The solution for the trough is composed

of one pound of sal ammoniac to a gallon of
water.

Any constant current battery will answer
this purpose, but I have found the one made
by Messrs. Reynolds and Branson most
suitable. This consists of a porous pot
filled with an acid solution containing a salt
of mercury, in which the zinc is inserted

A TREATISE ON PHOTOGRAVURE. 125

(the presence of this salt renders re-amalga-
mation of the zincs unnecessary). This pot
is surrounded by three carbons, which are
inserted in the outer stoneware jar contain-
ing a mixture of chromic and sulphuric acids.
This battery is perfectly steady and fume-
less. Two two-quart cells of this form will
produce a sufficient current for the deposi-
tion of the iron.

The positive pole (or carbon element) of
the battery is connected by means of copper
wire with the rod bearing the anode, and the
negative pole (or zinc element) with that
bearing the plate to be steel-faced.

The battery should be coupled up with
the trough, and the current allowed to pass
through the solution for two days before
attempting to steel-face a plate, as the
solution must first be saturated with iron.
For this purpose a large sheet of unpolished
copper must be suspended in the solution
from the rod not occupied by the anode, to
form a cathode, or receiving plate.

After a lapse of two days, test the bath resting.
with a clean plate. If a bright clear coating
is obtained, the steel-facing may be pro-
ceeded with ; but if the coating is porous,
or if gas is given off during the operation,

126 A TREATISE ON PHOTOGRAVURE.

continue the saturating as before. The
coating may also present a spongy appear-
ance through oz^r-saturation, in which case
some of the sal ammoniac should be removed
and replaced with fresh.

When the solution in the trough and the
current are found to be in order, the photo-
gravure plate may be prepared for steel-
facing. A piece of copper wire must first
be soldered to the back of the plate of a
length sufficient to allow of the plate being
suspended in the solution in the trough
opposite to the anode. The junction of the
wire with the plate should be covered with
bitumen varnish, but otherwise the back of
the plate need not be protected, as the
deposit only takes place on the surface next
to the anode.

The process of cleaning the plate is
somewhat tedious, as it is absolutely neces-
sary that the surface should be entirely
freed from all grease and tarnish or other
foreign matter.

After removing all ink from the plate with
turpentine, well brushed over with a some-
what soft nailbrush, the turpentine should
be removed with benzole, and the plate
rinsed and immersed for half an hour in a

A TREATISE ON PHOTOGRAVURE. 127

solution of caustic potash one part to twelve
parts of water. Then brush with a soft
clean brush or a piece of stick covered with
several thicknesses of rag, again rinse, and
pour over nitric acid of a strength of one
part acid to twenty parts of water, rinse
and scrub with cotton wool and a paste of
whiting, rinse once more, and pour on the
acid again, and so alternate the acid and
whiting until water will run off the plate
quite evenly without signs of greasiness.

When the plate is quite clean, attach the
copper wire to a brass hook, and lower the
plate gently into the trough, blowing on the
surface of the solution at the same time to
drive away any scum which may be present,
and which might otherwise become attached
to the plate, and with the same object move
the plate up and down for a few moments,
and then hang the hook on the rod. The
plate may be lifted out from time to time
and examined, and if the process is going
on rightly, it should present the appearance
of being coated with matt silver.

An immersion in the trough of half an
hour will give a coating that should stand
printing for 1,000 or 1,500 copies.

128 A TREATISE ON PHOTOGRAVURE.

If the coating is in anywise defective, it

deposit.

may be removed in sulphuric acid one part
to ten parts of water, and in the same way
a steel-faced plate may, on becoming worn,
have the coating removed, and a fresh
deposit may be made in the manner already
described, as though it were being done for
the first time.

CHAPTER XIV.

HISTORICAL NOTES.

The first experiments of Nicephore Niepce
in connection with photography appear to
have been made with a view to obtaining
intaglio engraving on pewter, for the print-
ing of music, and there is evidence that as
far back as 1813 he made sensitive
varnishes, which he spread upon litho-
graphic stones and pewter plates. As an
original for copying photographically, he
appears first to have used a writing made
translucent by waxing ; and in 1816 he
constructed a camera, or, as he described it
in writing to his brother Claude, " a sort of
artificial eye, consisting of a square box
fitted with an adjustable tube containing a
lens." Other letters written during 1816
give his various experiences and his trials of
such lens as were available. Although, in
writing of his experience with this camera
(May 22nd, 1816), he points out that it is
possible to obtain results in diffused light,
or when the sun is not shining — a ground,
he contended, for using the word " photo-
graphic " instead of " heliographic " — it is

130 A TREATISE ON PHOTOGRAVURE.

probable that he was then referring to
experiments on chloride of silver paper,
and not his work upon metal plates.
The earliest recorded success of Niepce in
heliographic etching on metal is a portrait
of Cardinal d'Amboise, made in 1824 from
a print on paper, and now in the Municipal
Museum of Chalons-sur-Saone, the native
place of this pioneer in photogravure.
Particulars and references to original docu-
ments will be found in Victor Fouque's
" Verite sur FInvention de la Photographic "
(Paris, 1867). Schiendl, in his " Geschichte
der Photographic" (Hartleben,Vienna,i8gi),
gives a reproduction of this interesting early
specimen. As regards its production, Isidor
Niepce writes : "I was a witness of the pro-
duction of the Cardinal d'Amboise. My
father spread upon a polished pewter plate a
varnish consisting of Judean pitch dissolved
in Dippels oil." The original used in this
case was a print which appears to have been
rendered transparent by means of wax, and
Rafter exposure the bitumen which remained
soluble was dissolved away, and the plate
was etched. Niepce struggled hard to
bring his methods into notice, and in 1827
he brought specimens to England, and

A TREATISE ON PHOTOGRAVURE. 13!

fruitlessly endeavoured to bring the matter
before the Royal Society. In 1829 he
entered into a partnership for experimental
work with Daguerre, but he died two years
before the publication of results in 1839,
and as Daguerre apparently took but little
interest in photo-etching, he gave but little
prominence to the experiments of Niepce in
this direction.

The daguerreotype image on its silver
plate (backed with copper) is of the nature
of a weak resist to solvents of the metal, so
if the daguerreotype plate is made the
anode in an electrolytic cell, or is treated
cautiously with a fluid capable of attacking
the silver, a shallow but beautifully delicate
etched image may be obtained ; but from
the point of view of making such methods
available for the production of printing
surfaces, little else but disappointment
attended the efforts of Grove, Fizeau,
Donne, and others who worked in the
direction between 1840 and 1843. Equally or
even more beautiful were Charles Chevalier's
electrotype casts of the daguerreotype plate,
but, like the etchings, they had neither such
depth nor ink-holding roughness as to make
them serviceable as printing plates.

IJ2 A TREATISE ON PHOTOGRAVURE.

A. J. F. Claudet, in the specification of
his English patent, No. 9957 of the year
1843, comes nearest to describing a practic-
able method of etching the daguerreotype
plate into an intaglio printing surface. The
first etching having been effected, he
indicates a method of rebiting, calculated to-
be specially useful in the case of such
shallow plates. The hollows having been
filled with a siccative ink, the smooth parts
are rubbed clean and electro-gilded. The
ink being now removed, the film of gold
forms the resist. Claudet, in the same
specification (9957, of 1843), indicates the
principle of a renewable wearing film, so
important in printing from shallow plates.
He coated his silver-faced intaglio with a
thin film of electrically deposited copper,
and when they became worn through in
printing, he removed it by diluting nitric
acid, or by ammonia.

The founder of that photo - engraving;
method which has become notably im-
portant in recent times is W. H. Fox-
Talbot, and in his first patent relating to
photo-engraving, No. 565 of the year 1852,
he describes a process in which a metal
(steel) plate is coated with a thin film of

A TREATISE ON PHOTOGRAVURE. 133

bichromated gelatine, and when dry the plate
is exposed under a transparency. After ex-
posure, the bichromate must be soaked out
of the film, which now shows a light brown
negative image, and, after drying to lighter
parts of the film, will be readily permeable
by aqueous liquids, while the shaded parts
will be impermeable in proportion to their
depth of tint.

Talbot first used a somewhat acid solu-
tion of platinic chloride for etching, the per-
cloride of iron (with resinous grain) having
been used by him subsequently. The etching
fluid was spread over the film by a brush,
which in rapidly penetrating the unexposed
parts, etched the plate. It is noticeable that
although in the specification under notice,
Talbot makes no mention of a resinous dust
for producing grain, he mentions the lined
screen in the form of a piece of folded
gauze, the image of which is impressed on
the gelatine prior to the image of the object
required. A subsequent patent of Talbot's,
No. 875 of the year of 1858, brings photo-
gravure quite within the range of easy
practice, and Talbot himself produced
remarkably five specimens of work. The
principal points of difference between the

134 A TREATISE ON PHOTOGRAVURE.

method of working here described and the
method referred to above is that the film is
not washed, but as soon as taken from the
copying frame is covered with a resinous
powder, e.g., copal, this powder being melted
by heating the plate. When cold, the
plate is etched by a strong solution of per-
chloride of iron, which readily penetrates
those parts of the film which have been
protected from light, but fails to penetrate
those parts upon which light has fully acted.
The same specification describes other
methods, one in which the exposed gelatine
is partly washed away with warm water, and
another in which the plate is first engraved
or roughened all over, so that it will print
a uniform tint, and upon this is developed
a gelatinous relief. The plate now forms
an original, from which a mould is taken for
electrotypic reproduction.

Talbot in his later work adopted a method
of producing a grain by dissolving common
resin and camphor in chloroform, and some
of this solution being poured over the
exposed film, the chloroform evaporates,
leaving a film of mixed resin and camphor^
when a gentle heat is applied, which causes
the camphor to evaporate, and leaves the
resin in minute particles.

A TREATISE ON PHOTOGRAVURE. 135

In the Talbot methods, we have the
parent of the method introduced as a secret
process about fourteen years ago by the
Austrian painter, Klic, and I believe the
first specimen of his work shown in this
country was a print (portrait of Mungo
Ponton) issued with the " Year Book of
Photography" for 1882 (published in Decem-
ber, 1881). Although secrecy was imposed
upon those instructed by the inventor, details
gradually leaked out, and a publication of
details in the Photographische Mitarbeiter, of
Vienna, during 1886, is often referred to as
the first printed account given of the
method. It is, however, interesting to note
that an account of all the essentials of the
process appeared on page 67 of the Photo-
graphic News for 1884, while in the same
paper for 1887, page 49, there appeared full
and sufficient working details in illustrations
of the appliances used, also in the "Year
Book of Photography " for 1888, page 171.

The production of intaglio plates by
electrotyping from a photographically made
mould, or original, has been the basis
of numerous processes, and in Charles,
Chevalier's electrotyping of the daguerreo-
type image already mentioned we have a

136 A TREATISE ON PHOTOGRAVURE.

first step in this class of work. It was,
however, Paul Pretsch, in Vienna, and
A. L. Poitevin, in Paris, about 1853 or
1854, who first successfully made intaglio
printing plates by electrotyping on a film
of swelled and reticulated bichromated
gelatine. Pretsch gave up his appointment
in the Austrian Imperial Printing Office in
order to exploit his method in England, but
his English patent specification of 1854,
No, 2373, dated Nov. gth, is not sufficiently
clear in its instructions to be a useful
guide to the worker. Pretsch, in works
established at Holloway, produced some
very fine results, marred, however, by very
extensive retouching, which, at that time,
was considered necessary to adapt the
work to the requirements of the market.

The Photogalvanographic Co. failed com-
mercially, being before its time, and Pretsch
returned to Vienna in 1863, a disappointed
man, broken down in health, and in 1873
he died.

A portrait of Paul Pretsch, taken by
Paul Luckhardt, forms the frontispiece of
Ottomar Volkmar's book on "Photogalvano-
graphie " (published by W. Knapp, of Halle
,a/S., in 1894, price 6m.), a work which

A TREATISE ON PHOTOGRAVURE. 137

gives historical and practical details of
the most important photogalvanographic
methods based upon the use of bichromated
gelatine, and which may be divided into two
classes. The Pretsch methods in which the
gelatine is swelled and reticulated by the
action of liquids, and methods in which a
carbon print or gelatine film developed by hot
water on the non-exposed side, are the basis
for moulding and electrotyping. Poitevin,
of Paris, and Mariot, of Vienna, appear to
have been the earliest experimenters in this
direction, and, about 1869, portions of a map
of Austria-Hungary were produced by such
such a method in the Military Survey Depart-
ment at Vienna. After this the method in
its various forms became very general for
ordnance map making. A map of Central
Europe, consisting of 380 plates, was pro-
duced by Mariot's method at Vienna,
between 1872 and 1879, and another on a
larger scale, of Bosnia and Herzegovina,
included 720 sheets, and was in hand
between 1872 and 1886. Modifications of
Mariot's method have also been extensively
used in the survey departments of Prussia,
Great Britain, India, Belgium, and other
countries. The Mariot method consists in

1C

138 A TREATISE ON PHOTOGRAVURE.

developing the carbon print upon a silvered
copper plate. When dry the surface of the
gelatine is made conductive by suitable
means, and an electrotype cast is made, this
cast being the printing plate.

Major Waterhouse has very materially
improved the Mariot process in making it
better suited for completely rendering half-
tone. As far back as 1878, he published a
method of producing grain on the wet carbon
print, by treating it — while on the silvered
copper plate — with a solution of five parts
of tannin in one hundred parts of alcohol,
after which it is rinsed, dried, and slightly
waterproofed by the application of wax dis-
solved in turpentine. Plumbago or silver
bronze powder is used to make the film
conductive (Photographic News, 1878, page
380).

Other improvements on this method (a
method worked upon by Geymet, Placet,
Andra, and others) are due to Waterhouse,
and special mention may be made of his plan
of graining the wet carbon image by sifting
upon it fine sand (slightly waxed on the
surface to prevent adhesion), this sand
being brushed off when the carbon print is
dry (British Journal of Photography, 1889,

A TREATISE ON PHOTOGRAVURE. 139

page 570; Photographic News, 1880, page

'

A photogalvanographic method which
yielded excellent results in the hands of
Messrs. Goupil, of Paris, under the direction
of M. Rousselou, is said to be based upon a
suggestion of Mr. Walter B. Woodbury to
prepare a thick carbon print or Woodbury
relief from a gelatinous mixture containing
powdered glass or other rough inert powder.
This relief is moulded by pressure against
a leaden plate, a reproduction of this leaden
plate by electrotyping being the printing
surface (British Journal of Photography, 1879,
page 603).

Numerous processes have been based
upon covering the copper plate with an
extremely thin layer of bichromated gum,
albumen, or other easily soluble substance,
which rapidly become insoluble on exposure
to light. After exposure under a positive,
the etching can be readily effected by a
solution of perchloride of iron, whether the
non-exposed parts of the film have been
previously washed away or not. In recent
times, this method has-been exemplified in
the so-called enameline or " fish glue "
process of making relief blocks, and an

I40 A TREATISE ON PHOTOGRAVURE.

original form of it, available for half-tone
work on intaglio plates, is that of Mariot,
described on page 193 of the Photographische
Correspondent for 1881. Sixty-three parts
of gum arabic, nine of grape sugar, and
twenty-one of bichromate potassium are dis-
solved in 630 of water, and a copper plate
is coated twice, the excess being whirled off
by means of the turntable. Exposure is
made under a positive, after which the plate
is gently warmed, and, when cool, it is
etched with perchloride of iron.

A method which stands almost isolated is
the photograving method of Obernetter, in
which a silver print, the metallic image of
which has been converted into chloride of
silver, is laid against a copper plate, when
the chloride of silver acts on the adjacent
copper, while itself reduced to the metallic
state (Photographic News, 1884, page 67).

There are many methods and modifica-
tions not touched upon in this historical
summary, but as recent applications of
interesting general principles reference may
be made to M. Villon's mercurographic
methods, and Herr Muller-Jacob's etching
methods with resinate colour resists (Photo-
graphy Annual for 1891, page 156-158).

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