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A MANUAL
PHorijiXC RAVING
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A MANUAL
OF
PHOTOENGRAVING
CONTAINING
PRACTICAL INSTRUCTIONS FOR PRODUCING
PHOTOENGRAVED PLATES IN RELIEF-
LINE; AND, HALF-TONE.
• J •* •»
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• • •
• • • .. • •
* ^ -' • \
WITH SUPPLEMENTXI^ 'CHi^P'PEkSo* 6& ^HE 'THEORY AND
PRACTICE OF HALF-TONE COLOR WORK ,
BY
Frederic E. Ives and Stephen H. Horgan.
Second JEDttion*
CHICAGO: /
The Inland Printer Company.
1902.
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• • ••
• • • ••
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• •••••• •^
BY
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• • ••• .•
* • • • • •
• * • • • *
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• • •
Inland Press,
Chicago.
^ XUy^ ^ ^ ' '•^.' ^
PREFACE.
THIS work is a revision of the " Manual " which
appeared several years ago. While retaining
the features of the first edition that hold good to-day,
it presents a number of new formulae and more com-
plete descriptions of the processes involved.
My purpose has been to provide a practical guide
that might be an aid to the beginner, and a useful book
of reference for the more advanced worker. With this
object in view I have, therefore, entered fully into the
description of the details of the various operations, and
have presented an outline of the chemical principles
underlying the methods considered.
The importance of a study of the scientific laws
upon which the practical work is based can not be too
strongly emphasized. It is the possession of this
4
knowledge that makes the difference between the intel-
ligent investigator and the " rule-of-thumb " work-
man, and the student is urged to give ample attention
to these fundamental principles.
The methods given in the following pages are those
in use by regular engraving houses, and are the results
(3)
4 PREFACE.
of the practical development of the art of process
engraving. By carefully following the instructions,
therefore, the beginner should be able to obtain cred-
itable results.
In addition to the chapters devoted to the subject
of the volume, those on the development of the gelatin
dry plate and the printing of half-tones will be of
interest.
H. JENKINS.
Chicago, September i, 1902.
PUBLISHER'S NOTE.
The first edition of the " Manual of Photoengraving " being
exhausted, the publishers arranged for the present work, which
offers the latest and most approved methods of practice in this
important art.
The chapters which have been added by Mr. Ives and Mr.
Horgan present the three-color process in its scientific and
practical aspects, and will be of great value to those who wish
to enter upon investigations in this interesting field.
«*r.
CONTENTS.
PAGE
Chapter I. The Scope of Photoengraving — The Appa-
ratus Required 7
Chapter II. Shop Arrangement 21
Chapter III. Negative Making — General Principles.. 26
Chapter IV. Negative Making — Preparation of Chem-
icals S3
Chapter V. Negative Making — Linework 39
Chapter VI. Negative Making — Half-tone Work 48
Chapter VII. Negative Making — Causes of Defects in
Collodion Negatives — Care of the Silver Bath. 62
Chapter VIII. Negative Making — Reversing Negatives 66
Chapter IX. Etching — Linework 70
Chapter X. Etching — Half-tone Work 81
Chapter XL Finishing and Mounting Plates 90
(5)
6 CONTENTS.
PAGE
Chapter XII. Drawings — Lithogravure 93
Chapter XIII. Development of Gelatin Dry Plates. . . .100
Chapter XIV. Printing Half-tone Plates no
The Half-tone and Trichromatic Process Theories, by
Frederic E. Ives 119
Three-color Process Work, by S. H. Horgan 135
Appendix. Tables of Weights and Measures 159
Valuable Formulae — Proving Color Plates — To Change
Reading of Thermometer Scales — Resist for Line
Etchings — Whirler for Coating Half-tone Plates —
Enamel for Zinc — Intensifying Negatives — Dry
Enamel Process — Printing Methods — Other Useful
Information.
MANUAL OF PHOTOENGRAVING.
CHAPTER I.
THE SCOPE OF PHOTOENGRAVING — THE
APPARATUS REQUIRED.
BY the term photoengraving is meant the produc-
tion of printing plates having images in relief
upon the surface of metal, these images being obtained
by a series of photographic operations.
There are two general classes of these engravings
known respectively as line plates and half-tone plates —
the former b.eing reproductions of subjects formed only
of lines, or masses of solid black and white, the latter
those of subjects having intermediate tones.
In both classes, three general stages of work are
involved as follows:
Negative making.
Etching.
Finishing and mounting.
Each of these includes a number of details which
will be described under the proper heads.
THE APPARATUS REQUIRED.
The apparatus required for making photoengrav-
ings will vary in completeness with the amount of work
to be turned out. For the experimenter or the estab-
(7)
8 MANUAL OF PHOTOENGRAVING.
lishment which devotes but a small department to the
work, an equipment of high grade and large capacity
would be out of the question. For shops, established
with a view to commanding a large patronage,
however, where rapidity of production and a uni-
formly excellent quality of work are important matters
of consideration, it is essential that the apparatus be
of the most approved pattern, and that each depart-
ment be fully equipped.
The capacity of the apparatus must depend upon
the conditions governing in the special case. In gen-
eral, however, provision should be made for producing
line negatives as large as 14 by 17 inches and half-tones
not smaller than 10 by 12 or 11 by 14 inches and as
much larger as the capital available will permit. The
demand is usually for plates smaller than these dimen-
sions, but the professional engraver should be prepared
to fill exceptional as well as regular orders.
THE LENS.
The best lenses for photoengraving purposes are
those known as anastigmats, of which the Goerz ( Series
IV), the Zeiss and the Cooke may be considered as
approved types for this special use.
These lenses are rectilinear (that is, they reproduce
straight lines without distortion), they are practically
without Cttrvature of field and cover a much larger
plate area than the older types of the same focal lengths.
THE PRISM.
In making half-tone negatives, it is generally most
desirable to secure reversal (see Chapter VIII) by
I ,ll^
MANUAL OF PHOTOENGRAVING. 9
using a glass prism silvered on one side and mounted
so that it may be screwed to the hood of the lens.
THE CAMERA.
In selecting the camera it is advisable to obtain
the form known as the enlarging, copying and reduc-
ing camera, as its construction presents several ad-
vantages over the ordinary copying camera.
For half-tone work it should be provided with an
adjustable screen plateholder, which enables the kit to
be dispensed with for holding the screen and sensitive
plate. This holder is so constructed that the separation
of screen and plate can be adjusted accurately and
easily to any desired degree, and to allow different sizes
of plates to be used with any screen.
It has displaced the kit in all leading shops, but
for those who may desire to use the latter, details of
its construction will be given below.
CAMERA STAND.
The camera should be provided with a stand, which
may be in the form of a long table or bench to stand
on the floor, or it may be swung from the ceiling, this
condition being necessary if the building is subject to
vibrations from the running of machinery or other
causes. It consists essentially of an oblong frame upon
which the camera will slide readily, the frame being
suspended from a beam of the same length, ropes or
strips of metal running from the ends of the beam and
attached to each end of the frame in an inverted V
shape. The beam being suspended from the ceiling,
carries the frame upon which the camera is placed. At
lO
MANUAL OF PHOTOENGRAVING.
one end of the frame is fastened the copy board, which
should be in a position perpendicular to the bed, and
arranged to slide to the right or left when desired.
The length of bed should suit the capacity of the
camera. For a lo by 12 camera, ten feet; 11 by 14,
twelve feet; and for a 14 by 17 camera fourteen feet
CAMERA AND SWING.
are good proportions. The camera stand can be easily
constructed of ordinary planed scantling, or can be
purchased from dealers in photoengravers' supplies.
SILVER BATH.
The silver bath is almost invariably kept in a glass
vessel of special form, which, when holding the bath
for use, should be kept in a " light-tight " box with a
cover. It is important that a bath of ample capacity
be provided, as it will require less attention than a small
one and save the operator annoying delays. In all well
equipped shops two or more baths are provided for
MANUAL OF PHOTOENGRAVING.
II
each operator, that one may be used while another is
being rectified.
SILVER BATH.
EVAPORATING DISH.
For evaporating the alcohol from the bath, a porce-
lain evaporating dish is required. It should be large
enough to hold the solution, with room to spare. As
an accessory, it is well to have an iron dish to hold sand
in which the porcelain dish can rest while heating.
TRAYS.
For line etching there should be one or more large
trays or " tubs " arranged to rock at the will of the
TRAY.
etcher. These " tubs " are made of wood, sealed water-
tight and are usually protected by a coating of asphalt
12 MANUAL OF PHOTOENGitAVING.
varnish. For developing prints on zinc, any ordinary
sheet metal tray will serve the purpose. For half-tone
etching, porcelain or rubber trays may be used.
PRINTING-FRAMES.
For printing on metal
there are special frames so
constructed that equal con-
tact with the negatives can
be obtained for all parts of
the metal plates. For
making silver prints as a
J■KlHTiK^;-^HAMB, basis for drawings, the
ordinary photographer's printing-frame is used.
GLASSWARE.
For measuring solutions,
several graduates of a capac-
ity of from eight to sixteen
ounces each should be pur-
chased; also a large funnel
for filtering the baths and
several smaller ones for col-
lodion, printing solutions, etc.
An important article is
the " act i no-hydrometer " for
testing the strength of the sil-
ver baths.
Various sizes of plate
glass should be provided for negative-making and for
turning negatives upon. For the latter purpose the
MANUAL OF PHOTOENGRAVING. I3
glass is usually obtained of about one-fourth inch in
thickness, to stand the pressure in the printing-frame.
Vials for holding collodion, large bottles for filter-
ing the bath into, and smaller ones for other solutions
are also necessities.
For inking line plates, composition rollers are used.
These should be of the kind known as " hard " rollers,
as they distribute the ink in a more even manner than
soft rollers.
An excellent roller for this purpose can be made
from white rubber, such as used for clothes wringers.
For inking the plate after etching, a leather-covered
roller is often used.
14 MANUAL OF PHOTOENGRAVING.
MISCELLANEOUS ARTICLES.
Besides the articles described above, there are other
essentials, as follows: Gas stoves, for heating and
drying plates ; squeegees, for smoothing down negative
films — these are simply strips of white rubber fastened
to a strip of wood ; scales, for weighing dry chemicals ;
negative racks; brushes for etching — bristle for line
NEGATIVE RACK.
etching, and soft for half-tone ; inking-slab for rolling
ink upon — a smooth sheet of stone, zinc or glass will
answer the purpose; pincers, for holding plates while
burning in ; " hooks," for cutting zinc plates ; small
camel's-hair brushes, for spotting and painting o\\
plates ; egg beater ; hammers ; nails ; scraping tools, for
cleaning spaces on zinc; engravers' tools, for finishing
plates after etching ; files, for smoothing edges of metal ;
calipers, punches, etc.
MACHINERY FOR FINISHING.
For a well-equipped shop there are several machines
which are essential. Small concerns are often operated
MANUAL OF PHOTOENGRAVING. 1 5
with only a small equipment of machinery, but for
large establishments the outfit is usually very extensive.
The routing machine is used for deepening and
cleaning out the spaces in zinc etchings, and sometimes
for making a bevel around half-tones, etc. These ma-
chines can be obtained in various sizes according to
the dimensions of plates to be routed.
A circular saw is also an essential piece of ma-
chinery, for sawing metal plates, blocks, etc.
The trimmer, as its name indicates, is used for
trimming the edges of blocks after the plates are
mounted.
The shoot-board is used for a similar purpose and,
in small shops, is generally substituted for the trimmer.
The Daniels planer is used for making mounted
blocks type-high. It is an expensive machine, and
for small establishments the shaving machine operated
by hand can be used instead.
A drill is often of use for various purposes, and is
necessary in " anchoring " or mounting half-tone plates
from the back.
The beveling machine is used for beveling the edges
of plates.
The buffing machine is used for polishing metaL
As a rule, it is not found in small shops, as the metal
can be polished by hand.
For taking proofs, a printing-press is required, and
for the engraving establishment that known as the
" Washington " hand press is best.
The mounting slab is simply a smooth-surfaced
block of iron upon which the cuts are placed when
being mounted.
i6
MANUAL OF PHOTOENGRAVING.
A detailed description of the above-mentioned ma-
chinery is not given here, c«i account of the various
designs on the market, and as manufacturers are always
ready to send specific descriptions to inquirers*
THE WHIRLER.
In coating plates for half-tones with the enamel
solution it is necessary, in order to obtain, an even coat-
I B
WHIRLER.
ing, that a rapid whirling motion be given while the
solution is in the fluid condition on the plate.
A number of devices can be used for this purpose.
A common form consists of a handwheel mounted in a
horizontal position on a board and connected by means
of a belt with a table similarly mounted at the other
f^
MANUAL OF PHOTOENGRAVING. 1/
end of the board, the table being provided with damps
to fasten the plate. Upon revolving the handwheel the
table is caused to revolve also, thus spreading the solu-
tion evenly over the plate.
A good whirler can be constructed, however, as
follows: To the bottom of a shelf, or at the end
of a bracket placed at a convenient height, fasten
a drill stock as shown in Fig. A. Then at a machine
shop obtain a strip of iron about three-fourths of
an inch or an inch in width, one-sixteenth of an
inch in thickness, and twelve or fifteen inches long,
and to its center fasten a round stem as shown in Fig.
B. Also have two strips made about four or five inches
long with apertures cut at each end, those at one end
of a size and shape to admit the ends of strip B. Have
one of the ends of each of the latter strips bent over,
and a hole drilled to admit a thumb-screw, as shown in
the cut. Fig C.
The long strip is fastened in the chuck of the drill
by means of the stem, and the two short strips are
slipped over the ends, as shown in Fig. C. A gas stove
should be placed under the whirler to warm the plate
and accelerate the drying of the coating.
The use of this whirler will be explained in Chap-
ter X.
THE KIT.
Before the advent of the plateholder mentioned in
a preceding paragraph, the kit was used by operators
to hold the screen and sensitized plate during exposure.
It is simply a rectangular frame so constructed
that when placed in the plateholder of the camera the
negative plate will occupy the position of the ground
2
i8
MANUAL OF PHOTOENGRAVING.
glass, the screen being held in front of it. Its construc-
tion can be understood by an examination of the illus-
tration. A is a frame made of strips of cherry, walnut or
other suitable wood, about one inch wide, one-eighth
i
B
(
;
J
KIT.
inch thick and of lengths required by the size of the
screen. The ends should be mortised and glued
strongly together. On the opposite side of this frame
is fastened a second frame of strips, one-half inch wide
and one-fourth inch thick, placed so that the inner
edges of this frame will be flush with the inner edges
of the other. The ends of this second frame should
MANUAL OF PHOTOENGRAVING. IQ
be fastened in a similar manner to those of the first.
To the longest sides of this second frame should be
fastened springs, which may consist simply of elastic
curved strips of brass or steel, the springs being fast-
ened at one end so that they can be moved to allow
the loose end to press upon the screen when in position.
These sides of the second frame should be thin in the
center so that the springs will not interfere with the
slide. Across the corners of the kit between the frames
of which it is composed are placed four comer pieces
to separate screen and plate. These are often of silver
but may also be made of wood, and should be no thicker
than to prevent contact of screen and plate, and should
be set into the first frame to be flush with the side next
the second frame. When a greater separation is de-
sired small pieces of cardboard can be inserted between
the comer pieces and the screen.
In the diagram, A represents the first frame; B,
the second, with a view of one edge of the sides con-
taining the springs ; C, the complete kit.
The kit should be made of a size to readily admit
the screen used, negative glass of the same size being
used also. It should be thoroughly covered with shellac
varnish, to prevent the silver solution destroying the
wood.
The use of the kit is indicated by the description of
its construction.
THE SCREEN PLATE.
The screen plate is, of course, absolutely necessary
in half-tone negative making. The size obtained should
be governed by the size of the half-tone plates which
the establishment expects to make.
20
MANUAL OF PHOTOENGRAVING.
The description of the screen and its uses will be
given in chapter VI.
CHEMICALS.
The chemicals required for making the collodion
negatives and for the etching operations are as follows :
Alcohol (grain).
Alcohol (wood).
Ether (sulphuric).
Gun cotton.
Ammonium iodide.
Ammonium bromide.
Cadmium bromide.
Cadmium iodide.
Potassium iodide.
Potassium bromide.
Potassium cyanide (fused).
Ammonium bichromate.
Strontium chloride.
Iron sulphate (ferrous).
Iron perchloride.
Potassium permanganate.
Iodine.
Silver nitrate.
Turpentine.
Castor oil.
Ammonium sulphide.
Eosine.
Le Page's liquid glue.
Calcium chloride.
Mercuric chloride.
Ammonium chloride.
Acetic acid.
Nitric acid (Com.)
Nitric acid (C. P.)
Chromic acid.
Copper sulphate.
Rubber cement.
Transfer etching ink.
Lye.
Dragon's-blood.
Sodium bicarbonate.
Absorbent cotton.
Charcoal blocks.
Ammonia (strong).
Ordinary charcoal will not answer for polishing
the metal. The most suitable is that used by jewelers
for soldering purposes, and is obtained in blocks of
about 3 by 4 inches.
To insure success most of the chemicals mentioned
above should be chemically pure. They should be
kept in bottles corked or stoppered to prevent evapora-
tion or deterioration. The bottles should be plainly
labeled to prevent errors when the contents are wanted
for use.
MANUAL OF PHOTOENGRAVING.
21
CHAPTER II.
SHOP ARRANGEMENT.
IT is a difficult matter to prescribe a set plan for
the arrangement of a photoengraving establish-
ment, as there is great variation in the size and relative
positions of rooms which may be selected for occupa-
tion, and as large shops require more extensive accom-
u^
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SHOP ARRANGEMENT.
modations and special features which need not enter
into the equipment of smaller concerns.
There are general principles, however, which can
be applied in fitting up any shop, and the accompany-
ing diagram is given to represent an arrangement for a
shop of moderate size.
22 MANUAL OF PHOTOENGRAVING.
THE OPERATING ROOMS.
A is the room for the half-tone, and B for the line
operating. One room is often used for two or more
cameras, but it is advisable, if possible, to provide
separate apartments for the cameras, to avoid interfer-
ence of one operator with another, i and 4 are the
darkrooms. These may be constructed with walls of
seasoned flooring joined to be light-tight. They should
contain sinks 3 and 5, over each of which should be
placed a tap for washing the negatives. At the right
of the sink there should be a shelf for holding the bottles
of developer and other solutions. Other shelves should
also be provided for holding stock solutions and other
accessories. Above the sink there should be a window
containing a light of orange glass, arranged to slide
upon readily at the will of the operator. If dry plates
are to be developed, an arrangement should be pro-
vided to close up the yellow light and substitute the
ruby light required for dry-plate work.
The silver baths should be placed in receptacles at
the back of the darkroom, the bath holders being placed
at such a level as to permit the convenient lowering
of the plates into them. Above, or at one side of the
silver baths, a shelf should be located upon which the
plateholder can rest.
The darkroom should be large enough to give ample
room, and should be free from cracks and openings
through which light might pass. 2 and 6 are benches
for holding negative racks and other articles.
The cameras should be placed near the darkroom,
and swung at a height most convenient for the oper-
ators to manipulate.
MANUAL OF PHOTOENGRAVING. 23
The illumination of the copy is an important factor
in producing negatives, and provision should be made
for obtaining the best facilities. The light can be
obtained either from a skylight, or by means of electric
lamps. In many shops both methods are used, the
light being obtained from the skylight during the
bright hours of the day, and from the lamps at other
times. The skylight should, of course, be large enough
to furnish an ample volume of light. The lamps
should be arc lamps, and one should be swung on each
side of the camera stand, near the copy board, in such
a manner as to be readily raised or lowered. They
may, if desired, be arranged with movable stands, in-
stead of being swung. Two lamps should be used, as
a more uniform illumination can be obtained from two
than from one, and reflections are then avoided. The
lamps should be wired to burn independently of each
other, and the current furnished should be uniform, to
prevent, as far as possible, flickering and variation in
the intensity of the light. Reflectors should be used
to concentrate the light on the copy.
A shelf should be built outside of one of the win-
dows to give facilities for sunning the silver baths. A
gas stove should be placed on one of the benches, for
evaporating the baths, heating negatives, etc.
ETCHING ROOM.
C is the etching room, which for convenience is
located next to the operating rooms. 7 is a sink of
ample capacity where the metal may be polished, glass
washed, and negatives turned. 8 is a shelf for holding
glass and other articles. 9 and 10 are rooms for sen-
24 MANUAL OF PHOTOENGRAVINa
sitizing metal, one being designed for line and one for
half-tone work. They should be furnished with
benches, shelving, and gas stoves. The illumination
should be subdued, to prevent the action of light on the
plates before printing, but not to the extent necessary
in the darkrooms for negative-making. It is not neces-
sary to provide sinks for these rooms, although they
add greatly to convenience.
The construction, arrangement, and care of these
rooms should be such as to prevent the accumulation
of dust, which would cause spots in the coating of the
plates. This remark will also apply to the darkrooms,
I and 4.
In the room used for coating the line plates a bench
and slab may be provided for rolling up the plates. 1 1
is a bench for general purposes, such as cutting zinc
upon, holding negatives for printing, etc. 12 is the
powder box to contain the dragon's-blood for the line
etchings. In some shops an open box is used, but it
is better to have a closet built around it to prevent the
powder from being carried about the room. 13 is a
bench for a gas stove for burning in the plates. 14 and
16 are etching tubs, placed near the windows, to obtain
ample light. 15 is a sink or a bench to hold a tray of
water to rinse the plates after etching. 17 is a shelf
placed outside of the window for printing by daylight.
An electric lamp should also be provided for use in
printing.
THE FINISHING ROOM.
D is the finishing room in which numbers 18 to 23
represent the several machines. 24 and 25 are benches
MANUAL OF PHOTOENGRAVING. 2$
for mounting the plates upon, and for holding tools,
material, etc.
The machinery should be operated from a line of
shafting which should be provided with belt shifters,
that any machine may be started or stopped as desired.
If the building is equipped with a power plant the
shafting may be operated by a belt running from some
other line. If the place is not thus equipped the power
may be obtained from a gas engine or an electric motor.
E represents the office.
In large establishments the half-tone etching is
often done in a room separate from that used for line
etching, but such an arrangement need not be con-
sidered necessary.
In selecting a location for a shop it is important
to obtain one where there will be an ample supply of
running water at all times, and where there is a num-
ber of windows, as it is desirable to have plenty of
light.
In fitting up the shop, economy in expense should
often be sacrificed to completeness and convenience, as
future results may at times justify an outlay which at
first might seem to be extravagant.
The above description is intended to give only gen-
eral directions for the shop arrangement. Special
situations will require various departures from this
plan.
26 MANUAL OF PHOTOENGRAVING,
CHAPTER III.
NEGATIVE MAKING — GENERAL PRIN-
CIPLES.
THE ACTION OF LIGHT ON SENSITIVE SALTS.
THAT light produces changes in most substances is
a fact established by daily experience, the
changes most readily observed naturally being those of
color.
In considering the subject in hand we are concerned
with the transformations that take place when light
acts upon certain salts of silver, and further, with the
chemical operations by which results of practical value
are obtained.
We shall begin with the established proposition that
when light is absorbed by any substance it does some
kind of work which, it is readily conceived, must be
necessary to produce the changes. This work is under-
stood to be the tearing apart of the molecules* of the
substance, the result being a change in its chemical
composition.
White light is not elementary in nature, but is the
•A molecule may be defined as the smallest particle of matter that
can exist without its chemical character being changed. Molecules are
made up of atoms which are alike in elementary and different from
each other in compound substances. When matter is so acted upon
that its molecular structure is changed, a reaction is said to occur.
MANUAL OF PHOTOENGRAVING. 2"]
effect produced by a combination of colored rays readily
detected by the common experiment of passing a
beam of white light through a prism to obtain the solar
spectrum, in which the only pure colors in nature can be
observed — the term pure meaning unmixed. From
the spectrum also we obtain the three primary colors —
the least number that can be combined to give white
light — and these are found in the red, green and blue-
violet.
The silver salts as ordinarily prepared are acted
upon most largely by the blue-violet rays, because the
color of the salts is such as to absorb these rays to a
much greater extent than the others. In practical pho-
tography, however, other colors usually have a greater
or less effect on account of the fact that they are not
" pure," but contain some of the blue element and also
reflect more or less of the white light that falls upon
them.
By using certain dyes upon the silver salts, how-
ever, a much greater range of color sensitiveness is
secured, as the absorptive powers of the salts are thus
extended. The practical application of this method
will be found in a later chapter.
To illustrate the principles stated above, if silver
chloride is exposed to light it becomes darkened, indi-
cating that some change in its nature has taken place.
Just what transformation has taken place has for many
years been a matter of speculation and dispute, but the
most eminent authorities assert that the probability is
that a part of the chlorine has been separated from the
molecule (which is composed of silver and chlorine —
two atoms of each), there being left a molecule con-
28 MANUAL OF PHOTOENGRAVING.
sisting of two silver atoms and one chlorine atom, form-
ing silver subchloride.
Similar action is supposed to occur when either bro-
mide or iodide of silver is exposed, and it has been
found that in any case the action is accelerated if there
is in contact with the silver salt some substance that
readily absorbs the element supposed to be liberated.
In the case of the iodide, in fact, no change will take
place unless such a substance is present.
The chemist expresses such transformations in
symbols, as follows :
Silver Chloride. Silver Subchloride. Chlorine.
Aga Cla (acted upon by light) = Ag, CI + CI
in which Ag represents an atom of silver and CI one of
chlorine, the number of atoms in the molecules being
indicated by the small numbers attached.
It must not be understood that change in color
always occurs with a change in the character of matter
acted upon by light. Some colorless compounds split
up into others which are also colorless, and others under
certain conditions exist in such minute quantities that
any color change is not perceptible. By acting upon
the new compounds with certain chemicals, however,
we may produce reactions bringing colored substances
into existence. The making of negatives depends upon
these principles..
In practice, the sensitive salt is mixed, or rather, it
is formed, in some solution which can be spread in a
film upon a plate. The plate is then exposed in the
camera and afterward treated with chemicals which
cause the image to appear. The two methods used in
modern practice are the wet collodion process and the
MANUAL OF PHOTOENGRAVING. 29
emulsion, the latter being usually made with gelatin as
a vehicle for the salts, although collodion was originally
employed and for some purposes is used to-day.
THE WET COLLODION METHOD.
The collodion is made by dissolving gun cotton in a
mixture of alcohol and ether, and certain salts contain-
ing bromine, iodine or chlorine, or combinations of
these salts, are dissolved in it, the solution being then
spread upon a glass plate and allowed to " set." The
plate is then placed in a solution of silver nitrate, which
reacts upon the salts and forms the corresponding
silver salt and a nitrate of the metal. This may be
expressed in the following symbols or equation :
Potassium Silver Silver Potassium
Bromide. Nitrate. Bromide. Nitrate.
K Br + Ag NOg = Ag Br + K No,
The silver bromide is sensitive to light. The potas-
sium nitrate is a by-product of the reaction so far as our
operations are concerned, and may be disregarded.
Some of the silver nitrate is left upon the surface of
the plate and this acts as an absorbent of the chlorine
which is freed during exposure. Exposure in the cam-
era does not produce a visible image, but this is
obtained by "development."
If a solution of ferrous sulphate is flowed over the
surface it precipitates metallic silver from the free
silver nitrate remaining, and this silver is deposited on
the light-affected portions of the film, in proportions
corresponding to or approximating the intensity with
which the light has acted on the different parts. We
thus obtain a visible image in silver, reproducing the
30 MANUAL OF PHOTOENGRAVING.
original object, except that the light and dark portions
are reversed. In practice, the action of the nitrate is
restrained by acetic acid in the solution. Otherwise the
action would be too strong and fog the image.
It is supposed that the ** invisible image " — that is,
the portions affected by the light — possesses an attrac-
tive force which acts upon the particles of silver, vary-
ing in intensity as the light varies, and as the action of
the developer continues more silver is precipitated and
deposited upon the plate in similar proportions, so that
the visible image increases in intensity.
The next operation is to remove the unaffected por-
tions of the film, or as it is technically called, to " fix "
the negative. This is done, after washing the plate, by
applying a solution which forms soluble compounds
with these portions, which are then washed out. In
fixing wet collodion plates, cyanide of potassium is
generally used, and the reaction is as follows with a
bromized collodion :
Silver Potassium Silver Potassium Potassium
Bromide. Cyanide. Cyanide. Bromide.
Ag Br + 2 K C N = Ag K (C N)2 + K Br
In photoengraving, the image after developing and
fixing is never dense enough, and we therefore render it
heavier and blacker. The most satisfactory means for
doing this is by two operations, the first being to pro-
duce, with one solution, compounds in the film which,
when acted upon by the second solution, will give the
required intensity.
If we first apply a solution of copper (cupric) bro-
mide, the reaction produces silver bromide and cuprous
bromide, according to the following reaction :
MANUAL OF PHOTOENGRAVING. 3I
Silver Cupric Silver Cuprous
(in the film). Bromide. Bromide. Bromide.
Ag + Cu Bra = Ag Br + Cu Br
The film is now white and is blackened by the appli-
cation of silver nitrate solution.
Silver Cuprous Silver Silver Silver Copper
Bromide. Bromide. Nitrate. Bromide. Subbromide. Nitrate. "
Ag Br + Cu Br + 2 Ag Noj = Ag Br + Agj Br + Cu (Noa)a
Intensification, therefore, renders the ground of the
negative dense and black but leaves the clear spaces
transparent.
When it is necessary to " clear " any of these spaces,
solutions are applied which will dissolve the compounds
adhering to them.
THE EMULSION METHOD.
In making emulsions, instead of first making an
insensitive film and then treating it with silver nitrate,
the nitrate is added directly to the solution, forming the
sensitive compounds at once within the collodion or
gelatin. The by-products are then removed by washing
or precipitation, and the collodion is *' ripened," that is,
brought to a state of maximum sensitiveness.
In using collodion emulsion, it is generally coated
before exposure with some substance that will act as a
halogen absorbent, although with certain methods of
preparation the silver salt may be sufficiently sensitive
without it. This is always unnecessary with gelatin,
however, as the gelatin itself is capable of absorbing the
element set free.
In the development of emulsion plates, the chemical
action involves different conditions than those which
take place with the wet collodion. Instead of the silver
32 MANUAL OF PHOTOENGRAVING.
being deposited from a solution to form the visible
image, it is freed from the molecules of the silver salt
which were altered by the light, and a subsequent action
takes place by which the unaltered particles of the sen-
sitive compound in contact with the changed molecules
also yield silver to add to the intensity of the image.
The solution to be used for developing emulsions there-
fore must be capable of reducing silver from the trans-
formed salts, while in the wet collodion method it is, as
stated above, necessary to use one that can precipitate
the silver from the solution of the nitrate. In develop-
ing an emulsion the image is built from below the
surface, while in operations with the wet collodion it is
built up from above.
The fixing and intensifying processes depend upon
similar reactions in both methods.
MANUAL OF PHOTOENGRAVING. 33
CHAPTER IV.
NEGATIVE MAKING — PREPARATION OF
CHEMICALS.
COLLODIONS.
FOR line work or half-tone negatives in which con-
trast is desired.
Alcohol 8 ounces
Ether 10 ounces
Gun cotton 80 grains
Iodide of ammonium 30 grains
Iodide of cadmium 50 grains
Chloride of calcium 10 grains
For regular half-tone work :
Alcohol 8 ounces
Ether 10 ounces
Gun cotton 80 grains
Iodide of ammonium 48 grains
Iodide of cadmium 24 grains
Bromide of cadmium 16 grains
The amount of gun cotton may be increased if a
thicker film is desired.
To prepare the collodion dissolve the gun cotton in
the ether and six ounces of the alcohol. Then put the
remaining two ounces of the alcohol in a clean mortar
and add each salt separately, and grind with the pestle
until dissolved. After all of the salts have been added
3
34 MANUAL OF PHOTOENGRAVING.
and dissolved, pour this solution into the solution of
gun cotton and shake well. The collodion will usually
be found to work well in a few hours after making,
but should it fail to work clearly add a few flakes of
iodine to turn toward a red color. Before using, the
collodion should be filtered through a tuft of absorbent
cotton placed in the neck of a clean, dry funnel which
should be provided for this purpose alone. The col-
lodion bottle should be kept tightly corked, as the
ether rapidly evaporates, leaving the collodion thick.
THE SILVER BATH.
To prepare the silver bath, dissolve crystals of silver
nitrate in water until the actino-hydrometer will, when
floated in it, register 40. Distilled or clean rain water
should be used if obtainable, but ordinary water as
obtained from the faucets can generally be used. In
any case the bath after mixing should be placed in the
sun for a day or two until it becomes perfectly clear.
After sunning, the bath should be carefully filtered,
and, in order that it may give clear images, a few
drops of pure nitric acid added until blue litmus paper
will be turned red if placed in the solution. Too
much acid, however, will cause weak images.
The bath is now placed in its holder, but must be
" iodized " before good results can be obtained with
it. If a collodionized plate is sensitized in it when first
prepared, the plate when taken from the bath will look
thin and be of a light bluish color, and will give a
weak, thin image. This is due to the fact that in a fresh
bath the silver salts when formed in the film are largely
dissolved out by the silver solution. To prevent this
MANUAL OF PHOTOENGRAVING. 35
silver iodide must be formed in the bath. The best
method is to place a coUodionized plate in it as large
as the holder will take and let it remain until the salts
are dissolved out of its film into the bath. If necessary,
this operation should be repeated, until the plates when
taken from the bath will have a rich, creamy appear-
ance, and give images of the desired strength. The
methods for caring for the bath solution will be given
in Chapter VII.
THE DEVELOPER.
The developer for these plates is a solution of
ferrous sulphate, which may be dissolved in various
proportions. The following will be found to give
good general results :
Ferrous sulphate 4>4 ounces
Acetic acid 3 to 3^ ounces
Water 48 ounces
Alcohol 2^ ounces or q. s.
The crystals of iron should be finely ground in
a mortar and then thoroughly dissolved and the other
constituents added.
The developer may also be made up by measuring
its strength by the hydrometer, in which case it should
register 20, and to each 20 ounces there may be added
i^ ounces acetic acid, and alcohol in sufficient quan-
tity to make the solution flow readily. The action of
the sulphate is to reduce the silver, as explained in
the preceding chapter, the acid being used to retard
its action and keep the image clear. Were the iron
allowed to act alone it would cause a rapid reduction
over the entire plate and veil the image. The alcohol
is used to cause the developer to flow readily over the
36 MANUAL OF PHOTOENGRAVING.
plate, for after the bath has been used for a time it
takes alcohol from the films, causing the developer
to flow in streaks, but the addition of alcohol to the
developer causes it to flow in an even sheet. If the
baths are boiled at short intervals to prevent the
alcohol from accumulating in them, it will not be
necessary, however, to use alcohol in the developer.
FIXING SOLUTION.
Cyanide of potassium.
Water.
Make a solution strong enough to dissolve the un-
reduced salts. If made too strong it will have a
tendency to cut out detail in the negative.
Hyposulphite of soda may be used instead, but the
cyanide is preferable.
INTENSIFYING SOLUTIONS.
There are several methods for intensifying nega-
tives, but those most commonly used are with the cop-
per and silver and the mercury intensifiers. The
former is generally favored.
COPPER AND SILVER METHOD.
I. Make a saturated solution of copper sulphate,
and also one of bromide of potassium.
Place some of the copper solution in a wide-mouthed
bottle, and add some of the bromide solution. Exact
proportions are not necessary. One part of the bromide
solution to six or eight parts of the copper will be
about right. In making the saturated solutions, it is
MANUAL OF PHOTOENGRAVING. 37
well to use warm water to more readily dissolve the
salts.
2. Nitrate of silver. Water.
Make a solution about 25 grains of the silver to the
ounce of water. It is not necessary in practice, how-
ever, to measure the quantities exactly. The operator
"will generally place a few crystals in the bottle and
dissolve in some water, adding a few more crystals
if the solution acts too slowly.
3. Nitric acid. Water.
Make a weak solution. About one part acid to
eight or nine parts water.
4. Ammonium sulphide. Water.
One part of the sulphide to about five or six parts
of water, to which a few drops of ammonia may be
added. This solution should be renewed whenever it
begins to cause yellowness in the negatives.
MERCURY METHOD.
Mercuric chloride'. Water.
Make a saturated solution. Some ammonium
chloride is usually added to cause greater saturation.
In connection with this solution, solutions 3 and 4
given above are used.
CLEARING SOLUTION.
I. Place some iodine crystals in a bottle with a few
crystals of iodide of potassium and add enough water
to make a deep red solution. The quantity of iodide
should not be as great as the quantity of iodine used.
Only a few crystals will be necessary.
38 MANUAL OF PHOTOENGRAVING.
2. Cyanide of potassium. Water.
Make a very weak solution.
This solution is most readily prepared by taking
a small quantity of the fixing solution, and diluting it
largely with water.
The iodine solution can be made weak and the
cyanide strong or some of the cyanide can be added to
the iodine until the red color is bleached and the re-
sulting mixture diluted to the desired degree. In the
latter case, of course, this single solution is applied to
the negative instead of the two solutions being used
separately.
MANUAL OF PHOTOENGRAVING. 39
CHAPTER V.
NEGATIVE MAKING — LINE WORK.
IN making negatives the operator must bear in mind
that absolute cleanHness and care in manipulation
must be observed in every detail of the work if success
is to be attained. This remark will also apply to all
other departments.
CLEANING THE GLASS.
The glass upon which the negative is to be made
must be free from all dirt, grit or scum. To provide
for this, two tubs, large trays, or jars should be pro-
vided, into one of which a strong solution of lye
should be placed, and into the other a quantity of nitric
acid diluted with water. The glass should first be
soaked in the lye until any particles of matter adhering
to it are destroyed or loosened. It should then be
washed well to remove the lye and dirt, and placed to
soak in the acid. When removed from the acid it
should be washed again and placed in a negative rack
to drain, or if desired for immediate use it may be
dried by rubbing with a clean towel, and afterward with
a piece of soft cotton cloth. Before collodionizing, it
should be carefully dusted with a camel's-hair brush, to
remove any specks which might enter the bath or cause
spots in the film. A number of plates should be cleaned
40 MANUAL OF MIOTOENGRAVlNa
at a time and kept in a negative rack for use. Some
operators albumcnize the glass by flowing over it, after
washing, a solution of i ounce of albumen in 8 or lo
ounces of water, acidified with nitric acid. After drying
in the rack the glass is put away with the albumenized
sides all facing in one direction. Such glass does not
require an edging of rubber before collodionizing.
FOCUSING.
In focusing, care should be exercised to obtain
absolute sharpness of the image on the ground glass,
as any blurring of the lines will render the negative
practically useless. Fasten the copy to the board so
that the image will occupy the center of the ground
glass, put a large stop in the lens, and move the camera
until the image, when perfectly sharp on the ground
glass, is of the size desired. In general, the focusing
should be done upon that part of the copy about mid-
way between the center and the edge, particularly if the
copy is one of large dimensions.
The lights should be placed so that the illumination
of the copy will be as uniformly distributed as possible.
In photographing large copies by the electric light, it
is sometimes advantageous to move the lights during
exposure, to obtain an even illumination over the whole.
In photographing tracings or line drawings on thin
paper, a sheet of white paper should be placed back of
the copy. Copy which is crumpled, or which can not be
made to He flat on the copy board, may be placed in an
ordinary printing-frame and photographed through the
glass. The cover glass in such a case should be clear
and well cleaned.
MANUAL OF PHOTOENGRAVING. 4I
A small magnifying glass is often of service in
focusing to examine the lines of the image, especially
if the ground glass is of coarse grain, or if the reduc-
tion is great, or the lines of the copy indistinct. With
indistinct lines it often facilitates accurate focusing to
place a piece of newspaper or other printed matter
across the face of the copy, and focus on that, removing
it afterward, of course. After the focus is obtained,
fasten the camera in position by means of the set-screws
at the back, take out the ground glass, remove the large
stop and substitute a small one. Having the copy
focused, the next operation is the
COLLODION IZING AND SENSITIZING.
Having cleaned and dusted the plate, if it has not
been albumenized, dip a small brush (or a small stick,
around one end of which a tuft of cotton has been
wrapped) into a solution of rubber in benzine (see
Chapter VHI), and run a narrow strip of this around
the edge of the plate. The solvent will evaporate, leav-
ing the rubber around the edge, which will prevent the
film slipping from the plate. Now hold the plate by one
corner in a horizontal position in the left hand, and
pour the collodion from the phial in a pool near the
upper right-hand comer D, as shown in the diagram.
Use sufficient collodion to cover the plate and move
the plate so that it will run first up to D, then to C,
then to A, and finally to B, from which it is to be
drained into the phial. It is recommended to have a
second phial into which to drain the collodion, as this
prevents chance specks of dust getting into the clean
solution. While draining, the plate must be carefully
42
MANUAL OF PHOTOENGRAVING.
rockcfl to obtain an even coating. When the collodion
has become set, invert the plate, place it on the dipper
and lower steadily into the silver bath. Close the cover
to the bath and let the plate remain for several minutes
and it will then be ready for exposure.
EXPOSURE.
Close the darkroom door and have the plateholder
resting on its shelf in an upright position and open to
receive the plate. Then draw the dipper holding the
plate from the bath. If properly coUodionized and sen-
sitized, the film will be free from any spots or streaks
and will have a creamy appearance, with the silver
solution on the surface in an even sheet. If the solution
lies over the surface in greasy-looking streaks, return
the plate to the bath at once, moving it around for a
moment in the solution, and let remain for several
minutes longer. When the plate is found ready to ex-
pose, let it drain for a minute or two, wipe the back
with a rag or tuft of cotton, then place in the holder
so that the film side will be toward the copy when
placed in the camera, close the back of the holder and
MANUAL OF PHOTOENGRAVING. 43
place it in the position of the ground glass in the
camera.
Having the cap on the lens and the lights prop-
erly placed, draw the slide from the holder, then re-
move the cap from the lens. The time of exposure must
be a matter of experience, as it will vary with the in-
tensity of illumination, the amount of reduction of the
copy, etc. Short exposure gives broad lines, with lack
of intensity in the negative, and the resulting print will
be lacking in detail. Long exposure gives fine lines,
detail and density, but tends to fill the fine lines. For
blue or weak lines give as short an exposure as prac-
ticable, for such lines tend to affect the sensitive film,
and if the exposure is lengthened, the lines in the image
will fill. Light blue lines can not be reproduced on the
ordinary plate. When the ground of the drawing is
yellowish, give ample exposure, as such a color does
not readily affect the film. Shorten the exposure time
in proportion as the image is reduced in size. If the
copy is brightly illuminated it will require less time
than when the light is weak.
When the exposure has been considered sufficient,
replace the cap on the lens, return the slide to the
holder, and take the holder to the darkroom. The
plate is now ready for development.
DEVELOPMENT.
This must of course be done by the non-actinic light
in the darkroom. To develop the image, hold the plate
horizontally in the left hand and flow the developer
from a graduate or an ordinary tumbler over the film
in an even wave ; then holding the solution on the plate,
44 MANUAL OF PHOTOENGRAVING.
keep moving the plate gently to cause the developer
to flow from side to side. The negative image will
soon appear, and the time of its appearance will in-
dicate whether the exposure was properly timed. If
the right exposure was given, the image will appear
in a few seconds, the white ground taking a dark ap-
pearance and the lines retaining the color of the film
before the developer was applied. If, however, the
image flashes up at once and some or all of the lines
become darkened, it indicates overexposure and the
lines will be filled, as the whole surface has been im-
pressed and the silver will be deposited to a greater or
less extent on those parts which should remain clear.
If, on the other hand, the image is slow in ap-
pearing, and the details are brought up with difficulty,
the plate has been underexposed. If one portion of
the image appears before another, it indicates uneven
lighting of the copy, and when that portion which ap-
pears first is sufficiently developed, it should be washed
under the tap while the developer is allowed to act upon
the other portions of the plate. Otherwise the fine lines
in one part might fill by the time the other parts were
sufficiently developed. When the whole image has at-
tained the proper intensity, which must be determined
by experience, and the details are visible, the plate
should be immediately washed under the tap to entirely
remove the developer and unreduced silver solution.
The remaining operations can be performed by day-
light.
FIXING.
Now flow the fixing solution over the film until
the unaffected portions are entirely dissolved, when the
MANUAL OF PHOTOENGRAVING. 45
lines should appear as clear glass. Then wash the
plate well again, and examine it carefully to determine
if the film has proper density, if the lines are fine
enough, and if all are clear. Some experience will be
required to detect these qualities. If any of the lines
are filled they will have a hazy appearance, quite readily
detected, but if not too badly filled they can be cleared
by a subsequent operation explained below. If the
plate is satisfactory thus far, it must be intensified to
make the ground opaque, for in its present condition
the light would pass through the ground so readily as
to render the negative useless for obtaining a print upon
the metal.
INTENSIFICATION.
Intensification may be done with either the cop-
per and silver or the mercury intensifier. To inten-
sify with the former, flow the copper solution over
the fixed and washed negative until the film becomes
white, then wash well and flow with the silver solution
until it is blackened throughout, then wash well again.
It will usually be necessary to repeat the process a
second time, and sometimes even three or four times,
if the exposure has been short, but twice will, as a rule,
be sufficient if the exposure has been rightly timed.
If any portion of the ground should still appear thin,
after the other portions have become sufficiently dense,
repeat the operation on that part alone, to increase its
density.
If, after the entire ground has acquired the proper
density, the lines all appear sharp and clear, additional
blackness may be given to the film by flowing it with
the ammonium sulphide solution No. 4. Before using
46 MANUAL OF PHOTOENGRAVING.
the solution No. 4, flow with the dilute nitric acid
solution No. 3, and rinse. This will preserve clear-
ness. Wash thoroughly after blackening with the
sulphide solution. If the lines are at all veiled, the
sulphide is liable to turn them yellow, and in such a
case it should be omitted. Additional density in the in-
tensification may be obtained by treating the film with
a dilute solution of iodide of potassium, after the cop-
per and before the silver is used. This turns the film
a lemon-yellow color. This treatment will, however,
sometimes cause a stain if the bath and other chemicals
are not in a clean condition. The solution is made by
dissolving a few crystals of iodide of potassium in
water.
CLEARING.
If, after intensifying with the copper and silver
solutions, any of the lines are filled, they must be
cleared. To do this, flow over the filled portions the
dark red solution of iodine and iodide of potassium,
and rinse the plate. Then follow carefully with the
very dilute solution of cyanide, applying it until the
filled portions are cleared. If the cyanide solution is too
strong it will dissolve the film also and ruin the nega-
tive. During the operation the water should be kept
running from the tap and immediately applied if the
action shows any tendency to proceed too far; and it
is often to advantage to let the water run over the plate,
while the cyanide is being applied, to cause the action
to proceed slowly. This treatment of the film will
cause it to become whitened. To blacken it, the am-
monium sulphide solution must be used as directed
above.
MANUAL OF PHOTOENGRAVING. 47
Instead of using the iodine solution strong and the
cyanide solution weak, some operators prefer to dilute
the former and use the latter strong, intensifying again
after the clearing. Instead of using the solutions
separately, they may be mixed by adding cyanide to
the iodine solution until the color disappears, and dilut-
ing with water. The solution is then applied until the
lines are cleared. If the lines are very much filled it
will be impossible to clear them, and the negative will
be worthless.
THE MERCURY METHOD.
Have the mercury solution in a tray and allow the
fixed negative to remain in it until bleached. Then
flow with the acid and sulphide solutions to blacken.
For greater density, place in the mercury again until of
a grayish color, and repeat with the sulphide solution,
washing well after each operation. The sulphide solu-
tion tends to weaken the film, and in washing the nega-
tive after its use the water should not be allowed to run
on it with much force. Having obtained a negative
with clear lines and opaque ground, it may be dried
spontaneously or over heat and is then ready for revers-
ing, the operations for which are described in Chapter
VIII.
48 MANUAL OF PHOTOENGRAVING.
CHAPTER VI.
NEGATIVE MAKING — HALF-TONE WORK.
THE SCREEN PLATE.
IN making half-tone negatives we encounter condi-
tions which do not exist in the production of line
negatives. In line work we have no gradations between
black and white, but in half-tone operations we are
required to reproduce intermediate tones.
To obtain a negative suitable to render these grada-
tions upon the metal plate we cause an image to be
formed, which consists of a great many little black dots
and clear spaces, the sizes of these elements varying
to accord with. the variation in the tones of the original.
This result is obtained by having in front of the
sensitive plate, during exposure, a glass plate ruled so
as to have alternating parallel opaque lines and clear
spaces. This ** screen plate," or " half-tone screen,"
may have lines ruled in only one direction or in several,
but ordinarily we use one which has rulings in two
directions, the two sets of lines crossing at a right
angle and forming clear spaces between the intersec-
tions. The light passing through the spaces produces
the desired effect.
A *' single-lined " screen, that is one having lines
ruled in only one direction, was formerly used, but
MANUAL OF PHOTOENGRAVING. 49
this necessitated turning the screen after half the
exposure had been given, and for greater convenience,
as well as to obtain more certain results, the cross-
lined screen has been adopted.
These screens are usually made with equal widths of
black lines and clear spaces, and for regular work these
relations may be considered as giving the best results.
The number of lines per inch should be selected with
consideration for the class of printing to be done from
the plates. For newspaper work a ruling of eighty-five
lines is generally preferred, for regular use one hun-
dred and thirty-three, and for fine printing and high-
grade magazines one hundred and fifty to one hundred
and seventy-five. Screens having as many as three
hundred lines per inch are occasionally used for special
work, but the plates require exceptional facilities and
skill in printing.
THE HALF-TONE NEGATIVE.
A negative properly made by exposing the sensitive
plate through the screen will have the largest dots in
the portions corresponding to the white parts of the
copy, and the next in size will be those representing the
tone next in intensity to the whites. The dimensions
of the dots will therefore decrease as the tints in the
original grow darker until they almost or quite disap-
pear in the solid blacks.
In order that a negative may give the most satisfac-
tory results, certain relations must, in general, exist
between the size of the clear spaces and the opaque
dots. What may be termed a standard negative (that
is, one properly made from a good original) will have
4
50 MANUAL OF PHOTOENGRAVING.
square opaque dots in the high lights, the corners of
each of these dots being joined to a certain extent to the
corners of the neighboring ones. The opaque dots in
the next tone will either be more slightly joined or not
quite uniting, and in the deeper shades we find the black
dots surrounded by clear glass, those in the parts repre-
senting the solid blacks of the original being reduced
to points, or perhaps absent.
A print made from such a negative will have sepa-
rate black dots (corresponding to the clear spaces) in
the high lights, and the dots will increase in size as the
shadows deepen until they run into solid lines. The
details in the shadows will be formed of open dots
(corresponding to the separate opaque dots in the
negative), these open dots decreasing in size as the
shades increase in intensity until they are almost or
quite absent in the blacks. There is, therefore, a simple
gradation corresponding to the tones of the original,
each shade being composed of elements of a certain
size.
It is readily seen, therefore, that the character of
the print will depend largely upon the relative sizes of
the elements composing the negative and the extent to
which the dots in the high lights are joined. If we
have a negative in which these dots are but slightly
united, it is evident that the high-light dots in the print
will be large and will probably give an effect too dark.
On the other hand, if the clear spaces in the negative
are very small the corresponding dots in the print may
not have sufficient strength to be sufficiently etched. It
must also be considered that if the dots in the other
portions of the negative do not bear the correct rela-
MANUAL OF PHOTOENGRAVING. 5I
tions in size we will not have a correct reproduction of
the original.
There are certain conditions to be fulfilled in the
operations of making the negative if results most
nearly approaching the ideal are to be attained. Prin-
cipal among these are the adjustment of the distance
between the screen and the sensitive plate and the size
and shape of the aperture of the diaphragm. The forma-
tion of the dots in their relative proportions most
largely depend upon the manner in which these rela-
tions are adjusted to each other. We will now consider
these and other factors entering into the operations of
half-tone negative making.
CHARACTER OF THE COPY.
It is evident that the nature of the object to be
reproduced will determine to a greater or less extent
the character of the results, and also that subjects of
different characteristics will require variations in the
methods of work to suit the different cases.
Some photographs and wash drawings have com-
paratively little gradation or detail and are too sharp in
contrasts to have pleasing effects. Others are so defi-
cient in contrast that they present a " flat " appearance.
The former class, of course, requires treatment that will
produce detail in the half-tone negative where it is defi-
cient in the copy and the latter will require manipula-
tion to obtain brilliancy in the resulting print. The sur-
face upon which the drawing or photograph is made
also has an effect in forming the results. The grain of
rough surfaces usually causes an unpleasant effect in
the half-tone, and smooth surfaces are therefore to be
52 MANUAL OF PHOTOENGRAVING.
preferred. The color of the original must also be con-
sidered in this connection. As a rule chocolate brown
and black give the best effects, while bluish or lilac
tones tend to give " flat " negatives.
ILLUMINATION OF THE COPY.
Uniform illumination is essential to insure success
in making half-tone negatives. Flickering of the lights
and variation in their intensity make it difficult to judge
the exposure time accurately and to obtain the effects
that the operator may desire. The lamps should be
placed so that reflections on the copy may be avoided,
and it will at times be found desirable to illuminate
very large subjects by means of daylight rather than by
the electric lamps.
SEPARATION OF SCREEN AND PLATE.
If, during exposure, the sensitive plate and the
screen were in contact it is evident that the dots on
the negative would be practically of the same size ; that
is, we would have little or no variation in the dimen-
sions of the elements. The image would simply be cut
up by a network reproducing the lines of the screen.
If, however, the screen and plate are separated to
permit the light to spread or be diffracted between
them, we find that the dots vary in size, and at a certain
distance we obtain a negative image in which their
relative proportions are at least approximate to those
described in a preceding paragraph. The effect of such
separation upon the relative size of the dots varies, of
course, with the distance between the plates. The
nearer they are together the less will be the variation,
MANUAL OF PHOTOENGRAVING. 53
the Stronger will be the clots in the shadows, and the
less the contrast in the negative. By varying the
amount of separation we can, therefore, obtain detail
or contrast as the case may require. When using
coarse screens the distance must be greater than with
fine screens to obtain similar results, as a less distance
with the fine ruling gives the same ratio between the
diameter of the screen openings and the distance of
separation as a greater distance does with a coarser
ruling. With the same stop, the necessary exposure
time will be less as the separation is increased, and vice
versa.
AREA OF THE DIAPHRAGM APERTURE.
Whether the half-tone negative shall have detail
or contrast depends in a great degree upon the area of
the aperture in the diaphragm used during exposure.
If the exposure is made with a small aperture the
resulting negative will be found to have the dots in the
high lights separated from each other and those in
the shadows strong and approaching in size to the dots
in the high lights. The negative will therefore be made
up of a network of clear lines and a print on metal
made from it would be formed of lines corresponding.
An etching made from such a print would have the
high-light portions too dark, and as a whole it would
be top " flat " and dark, that is, lacking in brilliancy.
If, on the contrary, a very large aperture is used, the
high lights in the negative will be formed of large dots
uniting to make a network of dark lines with clear
spaces between the intersections. The opaque dots will
rapidly decrease in size as the shadows increase in
54 MANUAL OF PHOTOENGRAVING.
intensity, and some portions may be without dots to
render the detail necessary to give the correct effect.
A print made from such a negative would have
its high lights made up of separate dots, the middle
tints would be formed of dark lines varying in
thickness, and the shadows would consist of solid
masses. An etching made from such a print would
give proofs with insufficient gradations, and if the dots
in the high lights of the negative have been too much
closed up, the corresponding dots in the print will not
be large enough to allow a deep etch, rendering the
plate liable to smudge in printing.
There is evidently a mean between the two
extremes, it being possible to find a diaphragm having
an aperture which, in conjunction with the right degree
of separation between screen and plate, will give a neg-
ative the print from which will have the dots in the
" whites " of sufficient size to allow a sufficiently deep
etch and yet so separated that these high lights will
appear of the requisite clearness, the dots and lines in
other portions being of such dimensions that in the
resulting print we will have a proper correspondence to
the gradations in the original. Instead of using one
diaphragm for the entire exposure, however, it will
generally be found conducive to the best results to
employ two — one having a small aperture, being used
during part of the exposure, to obtain detail in the
shadows, and another having a larger aperture for the
balance of the time, to close up the dots in the high
lights. When the original has the proper relations
between detail and contrast, one size of aperture may
give the desired effect, it being assumed that the screen
MANUAL OF PHOTOENGRAVING. 55
distance has been properly adjusted. In using two sizes
of aperture during exposure the proportion of time to
be allowed each must, of course, be determined by the
character of the copy, and only experience can develop
judgment in this regard. •
SHAPE OF THE DIAPHRAGM APERTURE.
During exposure each transparent space in the screen
acts in a manner similar to that of a lens and causes
an image having the shape of the diaphragm aperture
to be formed upon the sensitive plate. It is possible,
therefore, to determine the form of the dots in the nega-
tive by using an aperture of a certain shape. We are
also able in this way to secure dots that will most
readily join in the high lights. It is evident, then, that
a round aperture will cause round dots to be formed,
and that a square one will give square dots, etc. If an
aperture is used in the form of a narrow slit parallel to
the lines of the screen, the negative will be formed of
parallel lines, as the action of the light passing through
such an opening will be to form a series of elongated
dots which will join end to end. It is plain that square
dots will more readily join than round ones, and are
therefore to be preferred in operating to secure clear
high-light effects. In using a square aperture, more-
over, the action of the light at the corners may be inten-
sified by extending the corners of the aperture, and this
is, of course, particularly desirable when photographing
" flat " subjects. To obtain still greater action on the
high lights a stop may be used during part of the
exposure, having four small openings, the center being
closed. The light, passing through these openings, has
56
MANUAL OF PHOTOENGRAVING.
an action similar to that shown when the comers of the
diaphragm are extended, but the closing of the center
allows the action to take place only between the inter-
sections of the cross lines and therefore the high lights
are alone affected.
The diaphragms suggested by Max Levy and illus-
trated below represent the apertures described above,
and the conditions presented by the character of the
copy will determine whether one or two or three shall
be used during exposure. For copy having normal
relations as to contrast and detail, the square opening
alone may give correct rendering, but if necessary to
join the high-light dots properly, the aperture with
extended corners may be used during part of the expo-
sure, and if the original is " flat," the multiple aperture
may finally be used.
As a rule, however, the stop with the multiple aper-
ture is not used in practical work, as it is seldom that
desirable results can not be obtained by the proper
manipulation of two diaphragms. Mr. Morgan has
1^ ''\
6D-liT>e. Ss-llne. loo-Iinc.
* ^ ^
ISO-line. 175-line- aoo-line.
CUTS SHOWING HALF-TONE SCREENS MOST GENERALLY IN USE.
MANUAL OF PHOTOENGRAVING.
57
devised those illustrated below and they are recom-
mended as fulfilling practical requirements to the best
advantage.
The diamond-shaped opening is used during part
of the exposure to obtain dots for detail in the shadows,
and the one with extended corners is used to close up
the dots in the high lights.
From the foregoing it will be observed that the size
and shape of the diaphragm openings and the relative
time given with each when two different apertures are
used must be determined by the nature of the copy and
the effect to be produced.
EXPOSURE TIME.
The time of exposure will vary, of course, according
to the conditions enumerated in the preceding para-
graphs. Insufficient exposure, all other elements being
properly adjusted, will result in the formation of dots
that are not sufficiently joined in the high lights and not
large enough in the shadows. If the time given has
been too long the union in the high lights will probably
be so excessive as to produce clear spaces too small to
58 MANUAL OF PHOTOENGRAVING.
allow the print to be etched to the required depth. It is
well to remember that under the same conditions an
aperture of a given diameter will require four times the
exposure of one of similar form having twice this
diameter. (Similar areas are to each other as the
squares of their like dimensions, and therefore the
larger opening will admit four times the light that
would pass through the smaller one in the same time.)
MANIPULATIONS.
First see that the screen is clean. It should be
rubbed with a soft, clean cotton cloth until any spots or
streaks are removed from the surface or they will be
reproduced on the negative. Breathing on the surface
while rubbing will assist in cleaning it. When clean,
insert the screen in the rack in the plateholder designed
for it so that it will be in front of the sensitive plate
when all is ready for exposure. The copy must be
studied to determine the extent of separation to be
allowed between screen and plate and also whether one
diaphragm shall be used or two, and if the latter, what
sizes of apertures shall be employed and the exposure to
be allowed with each. These factors can usually be
pretty accurately judged by the experienced operator,
but in the appendix we give suggestions by Count Tur-
ati and Max Levy for use by those who may wish to
make experimental determinations.
The operations preliminary to exposure are the same
as described in the preceding chapter. The exposure is
made in accordance with the conditions involved, the
principles stated above being observed. If the copy is
harsh in contrasts, with heavy black shadows, it is often
MANUAL OF PHOTOENGRAVING. 59
of great assistance in obtaining detail to hold a piece of
white cardboard in front of it during a part of the
exposure. This card should be kept moving to insure
imiformity of light action on the plate. If, on the other
hand, the copy is '' flat,'' a reading glass may be used
to concentrate the light from one of the lamps on the
high-light portions, thus increasing action from these
parts. This method may sometimes also be used to
bring any parts up lighter that may be too dark in the
copy to make good effects, although skill in manipula-
tion is necessary to obtain satisfactory results. The
plate is developed in the same way as a line negative
by flowing the developer over it, flooding with water
as soon as the image appears of the required intensity,
and fixing and washing again. The negative is then
examined to determine whether it has the qualities that
will give the best rendering of the copy. As stated
above, if the opaque dots are widely separated in the
high lights and the shadows are filled with strong dots,
the resulting print will be gray and " flat." If the dots
in the high lights are very much closed the print may
not have strong enough dots to etch deeply, and if suffi-
cient detail is not present in the shadows the contrasts
might be too harsh. In either case, the exposure
should be repeated, varying the conditions to secure
more or less brilliancy, or gradation, as required.
If the negative is satisfactory it must be intensified
and the operations are carried out as with line negatives.
It will be observed that intensification enlarges the dots,
and allowance for this should be made in adjusting the
conditions during exposure. Two applications of the
intensifiers will generally be sufficient and sometimes
6o MANUAL OF PHOTOENGRAVING.
only one, although three may be necessary in certain
cases.
The clearing solutions can often be used to advan-
tage in " brightening " the entire image of a half-tone
negative or in " cutting out " certain portions. In the
former case the iodine and cyanide are used over the
surface of the entire plate (after intensifying) in the
same manner as described for line negatives, great care
being taken to avoid any excess that would make the
negative too " open." In local " cutting," the solutions
can be applied to the portions only that are to be acted
upon, although the iodine can usually be allowed to first
act on the entire surface, then the cyanide on the parts
to be cut out, one wash of the latter being finally given
over the whole before applying the ammonium sulphide.
The local application of the cyanide may be given by
dropping it from a bottle upon the negative while water
is allowed to flow over it to prevent too rapid action,
but it is often best done by using a medicine dropper,
and this is particularly advisable when the part to be
cut out is quite small. Such clearing, of course, is not
always necessary. Many negatives require only inten-
sification to complete the work.
In making coarse-screen negatives for newspaper
work, the best effects are generally obtained by working
for contrast with the screen separation and diaphragms,
and then, if necessary, '' cutting out " the entire nega-
tive until the clear spaces in the high lights are large
enough, using local reduction on the other parts after-
ward if required. This also applies, of course, when
exceptionally brilliant negatives are required in any
other class of work. If properly done, the high lights
MANUAL OF PHOTOENGRAVING. 6l
in the print will be clear and the etching from it will
have a character necessary for the best results upon soft
paper. " Flat " negatives, that is, those having too
great uniformity of size in the constituent dots, can
nearly always be improved by this local treatment on
the shadows.
In making half-tone negatives, a small magnifying
glass, such as used by jewelers, is of great assistance in
examining the dots. In deciding upon the quality of
the results consideration must be given to obtaining
effects which will appear best for the class of printing
for which the plate is to be used.
After a satisfactory negative has been obtained it
should be varnished or reversed, and is then ready for
the printer.
62 MANUAL OF PHOTOENGRAVING.
CHAPTER VII.
NEGATIVE MAKING — CAUSES OF DEFECTS
IN COLLODION NEGATIVES — CARE
OF THE SILVER BATH.
THERE are various defects liable to occur in the
making of collodion negatives, which may be
due to faults in the chemicals, or lack of care in manip-
ulation. The following are the most common :
Pog, by which is meant a filling up or deposit in
those portions of the image which should remain clear.
It may be caused by:
Actinic light entering camera, plateholder or dark-
room, and striking the sensitive plate.
Insufficient acid in developer or in bath.
An un ripened collodion.
Overexposure.
Overdevelopment.
Developer too strong or too warm.
Fumes of chemicals.
Transparent spots in the film may be caused by:
Dust in the collodion, in the bath, or on the plate.
Excess of iodides in the bath.
Undissolved salts in the collodion.
Streaks in the Him may be due to:
Improper flowing of the collodion.
Scum on surface of bath.
MANUAL OF PHOTOENGRAVING. 63
Bubbles or specks of dust floating in collodion.
Removing plate from bath too soon.
Alcohol in the bath, in which case the streaks will
be rather broad and wavy, and run in the direction of
the dip.
Developer containing insufficient alcohol.
Developer striking film with too much force.
Developer too strong.
Collodion too thick, or overiodized.
Dirty plates.
Dirty plateholder, which will sometimes cause
blotches like " oyster shells."
Thin images may be caused by:
A weak or insufficiently iodized bath.
Excess of acid in the bath.
Underexposure.
Poor lighting of copy.
Blurred images may be caused by:
Improper focusing.
Camera being jarred during exposure.
Uneven density of film may be caused by:
Uneven lighting of copy.
Uneven coating of collodion.
CARE OF THE SILVER BATH.
If uniformly good negatives are to be obtained, the
silver baths must be kept in a proper condition. Every
well-regulated establishment has several baths,' so that
when one needs rectifying another can be used with-
out causing delay. The following rules will, if fol-
lowed, keep the bath in proper order:
64 MANUAL OF PHOTOENGRAVING.
1. Be sure that all vessels in which the bath may be
kept are perfectly clean and free from any traces of
other solutions.
2. Keep it covered.
3. Isolate it from other chemicals.
4. Keep the hands clean while dipping plates or
handling the bath.
5. Skim the top every morning with a strip of clean
paper.
6. Filter often through absorbent cotton.
7. Keep the strength up. It does not waste silver
to do so. Some clean saturated solution can be added
to the bath occasionally when it is in use.
8. When the bath becomes charged with alcohol
boil it down. By putting some water in the vessel in
which it is boiled, and pouring the bath into it, some
of the iodide will be precipitated, and aid in keeping
the bath from becoming overiodized. Then place on
the gas stove and let it steam until the odor of alcohol
is entirely gone. It is generally best to let it boil down
to a small volume. Then test with the hydrometer,
and if necessary add clean water to make it register 50.
Then filter well, and it is ready for use again. If it
fails to work clearly, add a few drops of nitric acid
C. P.
9. To remove organic impurities and matter in
suspension, add some bicarbonate of soda to the bath
and set it in the sun for a day or two. The silver
nitrate will form dark-colored inscrfuble compounds
with the impurities which will be precipitated.
Then filter the bath and if necessary add fresh,
strong solution to bring it to required strength. The
HALF-TONE— 8S-L1NE SCKEEN.
*
HALF-TONE.
Border Obulncd by HalC-tonlDK Ihe Gray Card Mount, and Culline
White Lin«.
MANUAL OF PHOTOENGRAVING. 65
bath must also be acidified again by the addition of
nitric acid C. P.
10. If the bath becomes overiodized, pour it into
some clean water to precipitate the iodide, filter, and
boil down to required strength. If the bath is evapo-
rated at proper intervals, and the iodide removed as
directed in paragraph 7, it will not become overiodized.
66 MANUAL OF PHOTOENGRAVING.
CHAPTER VIII.
REVERSING NEGATIVES.
IN order that the proof from the etching may appear
unreversed as regards right and left, it is necessary
to " turn '' the negative film before obtaining the print
from it. There are four methods by which this may be
done, as follows:
1. The sensitive plate may be placed in the holder
so that the glass side will be turned toward the copy,
allowance being made in focusing for the thickness of
the glass. The springs of the plateholder must be
specially arranged to hold the plate when this method
is used.
2. The image may be taken from the reflection of
the copy in a mirror, or, what amounts to the same
thing —
3. By having a glass prism with silvered hypot-
enuse arranged to fasten to the front of the lens,
the rays of light being reflected from it through the
lens and onto the sensitive plate. A modification of
this arrangement has the prism as a fixed part of the
lens.
4. By stripping the film from the glass support and
placing it in a reversed position. The two methods
last mentioned are those usually employed. The con-
struction of the prism suggests its method of use.
MANUAL OF PHOTOENGRAVING. 67
For turning the collodion film it must be coated with
the following solutions:
RUBBER SOLUTION.
Rubber cement.
Benzine, naphtha, or benzole.
Add sufficient of the solvent to the cement to make
a thin solution.
PLAIN COLLODION.
Alcohol 6 ounces
Ether 6 ounces
Gun cotton 120 grains
Castor oil i^ to 2 drams
When the film of the negative is dry and cold,
flow the rubber solution over it, and place in the nega-
tive rack until dry. When the rubber is dry, flow the
collodion over the film, and let it dry also.
Instead of being allowed to dry spontaneously, the
collodion may be ignited and burned. This gives the
same result as the slower method and is often done
with line negatives in newspaper shops where it is nec-
essary to turn work out in the shortest time possible.
After the collodion is dry, cut the film to the desired
size around the image. If the cut is to be rectangular,
the negative should be placed on a board or a table
with a straight edge, and a T-square and triangle may
be used in cutting the lines. If the board has two
edges at right angles to each other, the T-square alone
will answer the purpose. After the film is cut let the
negative rest in a tray of water until the fihn is loosened,
then lift one comer with a knife until it can be taken
between the thumb and finger of one hand, raise from
68 MANUAL OF PHOTOENGRAVING.
the glass, take hold of the adjacent corner also, and
strip the entire film from the glass and lay it in
reverse upon a second sheet of clean glass wet with
water. Then lay a sheet of wet paper upon the film
and rub the squeegee over it in various directions to
remove all of the water. After this is done, hold face
down over the gas stove until the paper begins to dry,
then remove it and heat the film, to thoroughly dry it,
and place in a rack to cool. It is not necessary to use
the paper if the film is tough and the squeegee free
from grit.
If the film refuses to strip from the glass after
soaking in the water, or if an albumen substratum has
been used under the original collodion film, place the
plate to soak in a solution of acetic acid. Curling of
the film after transfer is sometimes caused by insuffi-
cient oil in the collodion. Should the film fail to
adhere to the glass after stripping, flow a thin solu-
tion of gum-arabic under it, squeegee and dry as usual.
Flowing the collodion or rubber over the plate while
warm will cause bubbling. The collodion will some-
times bubble also on a cold plate. This may usually
be remedied by flowing some ether over it after it has
just set. It is customary in engraving establishments
to turn several negatives upon one sheet of glass and
print all together on the same sheet of metal. As a
rule, however, it is best to print half-tones separately.
Negatives made with the prism will require varnishing
before being used to print from. A thin solution of
gum arabic flowed over the plate while the film is wet
will answer this purpose.
It is often required to combine a line and a half-
MANUAL OF PHOTOENGRAVING. 69
tone negative for printing upon one plate. This is
readily done by stripping the respective films from the
original negatives and mounting them together on one
glass, in the positions desired.
70 MANUAL OF PHOTOENGRAVING.
CHAPTER IX.
ETCHING — LINE WORK.
THE etching processes described hereafter depend
upon this principle —
If certain chromic salts are dissolved in solutions of
organic matter and the solutions are then dried and
exposed to light, the action of the light will be to render
the matter insoluble.
In our practical applications, we coat a metal plate
with the sensitized solution and, after drying, expose
it under a negative. The light passes through the clear
spaces and hardens the parts of the coating under them,
but the other parts, being protected by the opaque por-
tions of the negative, remain soluble.
By washing away these soluble parts, we have left
an image corresponding to that on the negative, and,
having by further operations rendered it resistant to
the etching fluid, we etch away the exposed ground of
the plate, leaving the image in relief.
PREPARATION OF THE METAL.
Zinc is almost invariably used for line etching on
account of its comparative cheapness and its special
adaptability for this class of work.
The metal may be polished by machine or by hand,
the latter method being used in most establishments of
MANUAL OF PHOTOENGRAVING. "Jl
moderate size. To polish the metal by hand a board
should be fitted in an inclined position in a sink so that
water from the tap can run upon it when desired, a
couple of nails being driven at the lower portion to hold
the metal in position when lying upon the board.
If the metal is obtained polished from the dealers,
it will be necessary to use the charcoal only to prepare
the surface for coating. If it is unpolished, it should
first be rubbed with pumice stone or Scotch hone until
the roughness is removed, and then finished with the
charcoal. If the pumice stone is used, its polishing
surface should first be ground flat and smooth, other-
wise it will scratch the metal. While being polished,
the metal should be kept wet from the tap, being rubbed
in one direction only with the pumice stone or a hone
and in the transverse direction with the charcoal, the
end of the charcoal being used. If any flaws are
detected in the surface of the metal, they must be
removed by punching from the back as follows — place
a pair of calipers so that one point shall be directly over
the flaw, the other, of course, being directly under it.
Press the latter against the back of the plate so as to
leave a scratch, the end of which will indicate the
location of the flaw. Then turn the plate face down
upon a smooth iron slab, place the end of a punch over
the flaw as indicated and strike the other end of the
punch with a hammer, which will bring the flaw up
to the surface. Then polish again until the surface of
the plate is free from scratches and pits. The condi-
tion of the finished surface will depend largely upon
the charcoal. Some charcoal is gritty and leaves.
scratches which, if deep enough, would show in the
^2 MANUAL OF PHOTOENGRAVING.
etching. Such grittiness can often be removed by
soaking the charcoal in water or the jar of dilute acid.
LINE ETCHING.
SENSITIZING SOLUTION.
Albumen from fresh t%% i ounce
Water 8 ounces
Bichromate of ammonium 15 to 20 grains
Dissolve the bichromate in the water, add to the
albumen and beat up well with the egg-beater in a
bowl or mortar. Filter until clean. Some etchers
add a few drops of ammonia to the solution.
COATING THE PLATE.
Having polished the plate, file the roughness from
the edges, wash it, let some water remain on the sur-
face, and carry it to the room used for coating and drain
the water off. Then pour some of the sensitizing
solution to cover the plate and drain it off at one cor-
ner, repeating two or three times, draining at different
comers to equalize the coating. Specks of dirt or
bubbles should be removed.
Then hold the plate over the gas stove and warm
until dry, keeping it slightly inclined to allow any
surplus fluid to drain. A little practice will enable an
even coating to be obtained. When the plate is dry,
allow it to cool in the dark and it is then ready for
printing.
PRINTING.
See that the heavy glass which is used for the bed
plate in the printing-frame is clean, and also the back
of the negative. Any grit between the two will some-
MANUAL OF PHOTOENGRAVING, 73
times cause them to crack when the pressure is brought
to bear. Also see that there is no grit in the rabbet
of the frame. Then place the negative, film side up,
upon the bed plate, and carefully place the coated plate
face down upon it. Place the back of the frame upon
the metal (usually with a pad of felt or some folded
papers between), lay the bars across and fasten at the
ends, and turn the screws until sufficient pressure is
obtained to make contact between the plate and nega-
tive. Then place the plate in the light to print. If in
sunlight, support the frame so that the rays will strike
directly upon the face. If the electric light is used, give
half of the exposure while the frame rests upon one
side, then turn it to rest upon the opposite side,
and give it the balance of the exposure. If the nega-
tive is a large one, keep the light swinging, to equally
illuminate the whole surface. Do not allow the print-
ing-frame glass to become too hot, or it will crack. The
exposure time will vary from one to three minutes in
the sunlight and from three to ten minutes in the elec-
tric light. It will require but little experience to judge
of it properly.
ROLLING UP AND DEVELOPING.
After the plate has been sufficiently printed, it must
be rolled up with the special ink to obtain the image.
Upon the slab provided for the purpose, place a little
of the ink and with a knife spread it in a line across
one end ; then with the composition roller distribute it
in an even coating over the slab. (Lifting the roller
from the slab while rolling will aid in obtaining an even
coating.) If any particles of hardened ink or other
74 MANUAL OF J^HOTOEN GRAVING.
matter cling to the roller, remove them with turpentine
and a rag. When the roller has an even coating of the
ink on it, roll it over the face of the zinc until it also
is evenly coated. The ink on the zinc should not be too
thick ; the metal should appear faintly through it. If
the ink should be too thick on the metal, clean the roller
with turpentine, and when dry roll it over the zinc and
it will remove a good deal of the ink. The ink coating
should be heavy enough, of course, to absorb enough
dragon's-blood to form sufficient resist to the acid,
when burned in.
In cold weather the ink will sometimes refuse to dis-
tribute properly under the roller. In such a case wet
it with a few drops of turpentine, or warm the slab,
and this difficulty will be removed. The roller should
be kept free from dirt, and in starting work for the day
the slab and roller should be cleaned with turpentine
and fresh ink used. A little experience will enable the
worker to judge when the plate is properly rolled up.
When the proper coating of ink is obtained upon the
metal, place the plate in a tray of clean water (or hold
it under the tap) and rub the surface carefully with a
tuft of wet absorbent cotton. The parts of the coating
which were not affected by the light will rub away,
leaving the image in black lines. If the exposure has
been properly timed, the lines will all remain unbroken
upon a clean ground of metal. If the plate was under-
exposed, many of the lines will rub away, and if over-
exposed, the ink will cling to parts from which it should
separate. In such a case a few drops of ammonia added
to the water in the tray will often enable it to be
removed. Rub the image with the cotton until all of
? PHOTOENGRAVING.
75
the lines are clean and sharp, being careful to see that
the spaces are free from any adhering ink. Then dry
the plate by draining and warming over the gas stove.
By patting it before warming with a piece of damp
chamois skin, rolled into a pad, the surplus water can be
readily removed.
With a camel's-hair brush paint in with the transfer
ink, wet with turpentine, any parts of the lines which
may be broken, and also the largest open spaces as
shown in the cut at the left. The one at the right shows
the appearance after routing and finishing.
The painting in of these spaces supports the roller
and prevents smudging in the subsequent rolling.
POWDERING AND ETCHING.
After the plate has been painted, it is ready for
powdering. Have some dragon's-blood in the powder
box and dump it upon the surface of the plate, and then
brush off the surplus with a broad soft brush, finishing
with a tuft of dry cotton until the metal spaces are
"](> MANUAL OF PHOTOENGRAVING.
clean. The dragon's-blood will adhere to the ink.
The plate should now be held over the gas stove and
heated until the powder incorporates with the ink, as
shown by its turning a rather glossy black. There are
two grades of dragon's-blood, one a dark red color, the
other lighter in color. The latter will burn in more
readily than the other, and form a strong resist. After
the plate is thus heated, paint the back with asphalt
varnish, cool, and the image being now able to resist
the acid, the plate is ready for the first " bite.''
The acid used for this bite should not be very strong.
The proportions are not arbitrary. The beginner, how-
ever, may take about two and one-half parts of the
commercial nitric acid to thirty-two parts of water,
for the first etch. Place this solution in the etching tub
and immerse the plate in it. The action of the acid is
to combine with the metal, forming zinc nitrate and
hydrogen gas, the former being deposited on the plate
and the latter passing off into the atmosphere. Then
rock the " tub," and as the action of the acid proceeds,
keep the plate clean by brushing with the bristle brush
used for the purpose. This bite need not be deep.
Three to five minutes will be sufficient, when the metal
will be found so etched away as to leave a line in slight
relief. Then remove the plate from the acid, rinse,
dry off the surplus water with a towel or the damp
chamois, and wann over the stove. Before continuing
the etching the sides of the lines must be protected
to prevent the acid attacking them and causing
breaks. This is usually done by " powdering four
ways," as follows : Take the plate to the powder box
and dump some of the dragon's-blood on it; then,
MANUAL OF PHOTOENGRAVING.
77
beginning at one edge of the plate, pass the brusH over
it from that side to the side opposite, so that the pow-
der will be brushed against the sides of the lines.
For instance, as shown in the diagram, if the brush
is started at the side D, brush in direction indicated by
the arrow A toward side B. Hold the brush upright,
and move in even sweeps without lifting from one
extreme edge to the other. When the spaces between
the lines are clean, and the lines all " covered," heat the
plate again to cause the powder to adhere to the lines,
and, when cool, powder in a similar manner in the
direction of arrow B, moving the brush from A to C,
and heat again. Repeat the powdering in the remaining
two directions, heating after each, and if properly done
the powder will adhere so as to protect the lines on all
sides.
When cool, the plate is ready for the second bite.
The etching is done in the same manner as at first, the
78 MANUAL OF PHOTOENGRAVING.
time being increased somewhat, and when it has been
carried far enough the plate is again rinsed, dried and
powdered as before, and placed in the bath to etch
again, the strength of bath and time being increased.
When the action has again proceeded sufficiently, it is
removed from the acid and prepared for the fourth bite.
This may be done by simply powdering again as for the
other bites, but it is customary with many etchers to
roll the plate up again to form a thick coating of ink
over the top of the lines before powdering for the
fourth bite, so that the ink will run down the sides of
the lines during the heating and form a heavier coating.
This is best done with the leather-covered roller. After
this " rolling up," the plate is powdered again and
given the fourth bite. The four bites will, as a rule,
be all that are necessary for ordinary work, and the
plate can be cleaned, routed and mounted.
A *' clean bite,'' however, may be given to remove
the " shoulder " from the lines, although it need not
be considered necessary in general work. During the
operations of powdering and etching, the lines are not
always etched straight down, but are formed in steps
which, if prominent, will print up and make a broad
line in the resulting proof. To remove this "shoulder"
to a certain extent the ink and powder are first removed
from the plate after heating and flowing with lye or
alcohol, using a stiff scrubbing brush. A coating of ink
is then rolled over the top of the lines and powdered
and heated so that while the top will be protected, the
sides will remain bare. The plate is then placed in a
weak solution of acid and etched for a few moments,
the effect being to etch away some of the shoulder and
MANUAL OF PHOTOENGRAVING. 79
give a sharper line* This must be done with great
care. After cleaning, the plate is ready for the finisher.
While etching, the plate should be turned so that the
action of the acid may be even on all sides. If the
plate becomes heated during the etching, remove it and
cool with water or put some ice in the bath. Heat has
a tendency to soften the ink and cause the lines to
break.
The strength of acid and time of etching for each
bite can not be stated arbitrarily. They depend largely
upon the character of the etching, some lines not being
able to stand the action as long as others, and it requires
some experience to judge when the biting has pro-
ceeded far enough, the object being to allow the acid
to act as far as possible without undercutting or break-
ing the lines. As a rule, the experienced etcher does
not measure the acid, and judges by the appearance of
the lines when the operation must cease. The beginner,
however, may commence by using the following pro-
portions for the solution and times for biting :
First bite — 2 J4 parts acid to 32 parts water. Etch
two to three minutes.
Second bite — 2j4 parts acid to 32 parts water.
Etch five to six minutes.
Third bite — 3 J4 parts acid to 32 parts water. Etch
eight to ten minutes.
Fourth bite — 5 to S parts acid to 32 parts water.
Etch ten to twelve minutes.
The beginner should start with subjects having
strong lines, and should carefully watch the actictfi until
he has acquired such experience that he can etch with-
out timing the bites. For regular work four bites are
8o MANUAL OF PHOTOENGRAVING.
usually sufficient, but some plates may be given five and
others will require only three, the latter being the case
when the lines are close together. In many establish-
ments the clean bite is omitted, care being taken to
powder the plate clean, so that no excess of powder
will cling to the lines and form a large shoulder. For
a clean, deep job the plate may have the spaces routed
before the last bite.
In powdering the plate, the brushing need not be
confined to only the four directions. Some etchers
apply it in various ways until the lines are sufficiently
protected. No powder should be allowed to remain on
the open spaces, and to prevent excessive shoulder
no more than enough to protect the lines should be left
adhering to them. However, where an extra strong
bite is to be given, it is sometimes well to powder twice
around the plate. After the second or third bite the
small spaces will fill with the powder, but the lines
being close together, great depth is not required as in
the wider spaces. Should any of the powder adhere to
the open spaces, causing roughness, a knife or scraper
can be used to clean them. After the finishing etch has
been given, the coating should bef removed from the
plate by scrubbing with lye, and the plate delivered to
the router. Alcohol will also remove the coating, but is
more expensive than lye.
VIGNETTED HALF-TONE, HIGH-LIGHT EFFECT —
iw-LlNE SCREEN.
From Wash Drawing by W. L. Wells.
MANUAL OF PHOTOENGRAVING. 8l
CHAPTER X.
ETCHING — HALF-TONE WORK.
HALF-TONE etching may be done upon either zinc
or copper, but the latter is now almost univer-
sally employed on account of its superior printing and
wearing qualities.
The metal is prepared in the same manner as
described in Chapter IX, and although the same sensi-
tizing solution may be used, it has been practically
superseded by that known as the " enamel " process,
so called because it forms a hard coating on the plate
and remains after the etching has been completed.
SENSITIZING SOLUTIONS.
NO. I.
Make three solutions, as follows :
A. Albumen from fresh eggs 5 ounces
Water 2 ounces
B. Le Page's Liquid Glue 4 ounces
Water 4 ounces
C. Bichromate ammonia 140 grains
Water 2 ounces
Ammonia A few drops
Beat the eggs up well with the water, add solutions
B and C, and mix thoroughly. Filter the resulting
solution several times through a glass funnel, in the
6
82 MANUAL OF PHOTOENGRAVING.
neck of which a clean piece of fine sponge or wet
absorbent cotton has been placed. Be sure that all
specks of dirt are removed.
NO. 2.
Water ..." 4 ounces
Le Page's Liquid Glue 2 ounces
Bichromate ammonia 60 grains
Ammonia A few drops
Dissolve the bichromate and ammonia in the water ;
add to the glue, mix well and filter.
COLORING SOLUTION.
Dissolve some eosine (red shade) in warm water;
let it cool and keep in a tray for use.
COATING THE PLATE.
For the purpose of illustration we will assume that
the drill stock whirler described in Chapter I is to be
used. The manipulations with any other kind will,
of course, be similar.
Having the copper polished and a film of water
upon the surface, take it to the darkroom, drain off the
water and flow the plate with some of the enamel solu-
tion, draining the surplus off at one corner ; then flow
once or twice again and drain, removing any specks or
bubbles with a small brush or a stick. The solution
being clean, put the plate in the whirler face down,
having one corner in the opening in one of the clamps
and the opposite corner in the opening of the other, the
clamps being so placed that the plate will be centered.
Then turn the hand wheel of the drill so that the plate
will be given a rapid whirling motion which will spread
MANUAL OF PHOTOENGRAVING. 83
the solution evenly over the surface. The gas stove
under the whirler should be burning so as to warm the
plate and dry the coating. The plate need not be heated
excessively. Enough to dry it will be sufficient. If it
is not convenient to have a stove under the whirler, the
plate may be whirled cold until the solution is partially
dried, and then removed from the whirler and heated
to dry.
EXPOSURE.
If the coating upon examination now appears clean
upon the plate, let the plate remain in the dark until
cold, and then expose under a half-tone negative as
directed for exposing line plates. (In placing the plate
on the negative be sure that it is not moved after the
two are in contact or the negative will probably be
injured.) It is always well to examine the negative
before printing to see whether the clear spaces in the
high lights are comparatively large or small and
whether the dots in the middle tints and shadows are
strong or weak. Some negatives will require less
exposure than others, but a little experience will enable
it to be pretty accurately determined. Sometimes it will
be found that the high lights are a little too much closed
to give a large enough dot by the time the shadows are
completely printed, and in such a case a good print may
often be obtained by shading the shadow parts with a
card and exposing the denser portions of the negative
longer, keeping the card moving slightly to let the tints
grade into each other. The same method may be used
if the high-light dots happen to be normal and the
shadow dots weak. The object should be to obtain a
print having separate dots in the high lights strong
84 MANUAL OF PHOTOENGRAVING.
enough to etch deeply and give clear results, and
enough detail in the shadows to give the best reproduc-
tion of the original.
DEVELOPMENT.
After the exposure has been considered sufficient,
remove the plate from the negative by carefully lifting
it by one edge. Then dip it in the eosine solution for a
moment and hold it under water running from the tap.
The image will appear of a brilliant red color, and
should be washed until the details are all clear. The
eosine solution is simply to color the image to render it
clearly visible during development. Some etchers omit
it, but its use enables the development of the details to
be more readily watched. If the plate has been properly
exposed, the dots and lines of the image will correspond
with the clear spaces in the negative, and if the negative
is one of good quality the details will be open and the
high lights will be clear with dots strong enough to
allow sufficient depth in etching.
If the plate has been overexposed, the dots in the
high lights will be too large and probably joined
together and the shadows may be filled where there
should be detail. If, on the other hand, the exposure
has been insufficient, the print will be weak, with dots
too small, and parts of the image may wash away. In
either case, the coating should be removed and the plate
resensitized and printed again.
Imperfect contact between the negative and plate
will sometimes cause some of the parts to fill up, and
when this defect is discovered a new print should be
made, using a piece of metal that is flat enough to give
MANUAL OF PHOTOENGRAVING. 85
perfect contact. Slightly filled portions may occasion-
ally be cleared during development by passing a tuft
of wet absorbent cotton over them, although it is gen-
erally more satisfactory to make a new print.
The film may be given additional hardness if the
plate, after development and before the alcohol is
applied, is dipped in a dilute solution of chromic acid
and rinsed. This is not an essential operation, but is
often of advantage when enamel etchings are to be
made upon zinc.
BURNING IN AND " SPOTTING."
When a properly exposed print has been obtained
and developed it should be flowed several times, after
being taken from the tap, with grain or wood alcohol
to remove the water, and then dried spontaneously, or
the alcohol may be ignited and burned off.
The print must then be burned in, which is done by
holding the plate by means of a pair of pincers over a
strong, steady heat until the coating becomes of a
dark brown or black color. Keep the plate moving to
secure uniform action of the heat. Then let it cool and
rub with a dilute solution of chromic acid, which will
clean the copper and enable any spots to be readily
detected. The plate must now be " spotted," that is, any
stipple which is missing must be replaced by some sub-
stance which resists the etching fluid. Either asphalt
varnish or the transfer ink may be used for this pur-
pose. A small camel's-hair brush should be obtained,
and some of the asphalt being placed upon it, the brush
is drawn to a point and touched to the spots from which
86 MANUAL OF PHOTOENGRAVING.
the Stipple is missing, and any portions of the image
which it is desired shall appear solid black are also
painted in. If the ink is used, the plate is powdered
with dragon's-blood, which is brushed off with cotton,
and the plate then heated enough to burn in the powder
adhering to the spots of ink. The back is then painted
with asphalt varnish, the plate is cooled and is ready
to etch.
If, during the burning, the coating turns a grayish
color and will not change with continued heating, the
enamel is too thin and would not hold in etching. In
such a case remove it and coat the plate again.
ETCHING.
For the etching fluid, prepare a strong solution of
perchloride of iron, place it in a tray, immerse the plate
in it and brush the face of the plate with the etching
brush. The plate can now be allowed to rest in the
solution, being brushed occasionally to clean the face
from the sediment which results from the chemical
action. The tray may be rocked, if desired, but this is
not necessary and is not generally to be recommended.
Examine the plate at intervals, and when the dots in the
high lights appear to have had as much etching as they
will stand, brush the plate and wash immediately under
the tap. If upon further examination the dots appear
large enough to stand more, return the plate to the
solution and continue the etching. In etching, avoid
excessive brushing. Use the brush only occasionally
to clean the plate, unles^ it is desired to etch out some
part especially light. To obtain a better idea of the
MANUAL OF PPIOTOENGRAVING. 87
actual depth of the etching than can be determined by
the appearance of the stipple, scratch off with a knife
some of the enamel on the margin of the plate. The
scratch will etch down and the depth can be felt with
the finger nail. When, finally, the action has proceeded
far enough, rinse the plate, clean with solution of
chromic acid, rinse again, clean the asphalt from the
back with turpentine, dry and prove.
The result is what is technically termed a " flat
etching." To bring the high lights up more clearly
and to add brilliancy to the print it is usually necessary
to " reetch " the plate.
RE-ETCHING AND VIGNETTING.
After the plate has been proved to determine what
results it would give in its present condition, the print-
er's ink should be removed by washing thoroughly with
benzole. The portions in the shadows and middle tints
that are considered sufficiently etched may then be
painted in with asphalt varnish and the plate returned
to the etching solution for further treatment. After
this second etching has proceeded sufficiently, the plate
is proved again, other portions are painted in, and the
plate is again etched, these operations being continued
until the desired results are obtained. Care should be
observed to paint in and etch in such a manner as to
avoid the formation of lines where one tint should
grade into the next. Reetching is often done in the
second and following stages and often altogether by
omitting the painting and applying the etching solution
locally to the parts to be reducea. The operator fills a
88 MANUAL OF PHOTOENGRAVING.
camers-hair brush with the etching fluid, holding in his
left hand a Wad of wet absorbent cotton. He applies
the brush to the parts that need lightening and as the
action proceeds he removes the fluid from the plate with
the cotton, examining the dots with a magnifying glass
and repeating the operations until the dots are small
enough.
Vignettes, which are wavy or irregular edges, may
be etched around the image in the following manner:
After the plate has been etched to a printing depth the
center is painted in solid with the asphalt, the edge of
the paint being allowed to make a line marking what is
to be the inner edge of the vignette, the portions beyond
this being left unprotected. A short etch is then given
to the plate, which is then washed, dried and painted
again, the asphalt being carried this time beyond the
edge of the first painting. These operations can be
carried on until several tints are etched around the
border.
The next operation is to paint in to the edge of the
vignetted image and etch away all the stipple outside,
the paint being then removed from the face of the plate
with turpentine and the border deepened with the
router or hand tool. If the edges of the tints are too
sharply defined, local applications may be made to blend
them together.
When it is desired to have certain portions of an
etching free from stipple so as to show pure white in the
printing, the plate is painted in, leaving these portions
unprotected, and it is etched until the stipple in these
parts break away, further deepening, if necessary, being
done with a tool.
MANUAL OF PHOTOENGRAVING. 89
BURNISHING.
After the plate has been finally etched, it is some-
times desirable to have certain parts appear darker, and
such portions are rubbed with a tool known as a bur-
nisher, the depth of tone depending upon the extent to
which this action is carried.
90 MANUAL OF PHOTOENGRAVING.
CHAPTER XI.
FINISHING AND MOUNTING PLATES.
AFTER the etching of the line plate is finished, it
L is tacked to a board and placed in the routing
machine, and all the larger open spaces deepened with
the routing tool. If several negatives have been printed
on one sheet of zinc, each image is cut out, a thin bor-
der of zinc being left around it. The cut is then fas-
tened to a block by tacks driven through the routed
spaces and around the edge, and the block is planed
type-high. Any burr remaining on the lines is then
removed with a hand tool, and the plate is ready for
proving.
In mounting a half-tone cut, a beveled edge may be
formed around the cut with the routing or beveling
machines, and the plate fastened to the block by tacks
driven through this edge. Another method is to mount
the plate from the back as follows : Saw the margin of
metal from around the image, leaving enough for a
black line (if the line is wanted), and bevel the edge
with a file, removing the burr from both sides. Clean
the back of the plate and scrape the surface bright in
several places, leaving several deep scratches in the
places thus brightened, then upon each place drop some
hydrochloric acid, and lay a thin piece of solder upon it.
Upon the solder set a small screw, and, holding it in
MANUAL OF PHOTOENGRAVING. 9I
position with a piece of wire or any convenient tool,
direct the flame of a blowpipe upon the solder until it
melts and forms around the head of the screw. The
solder should not be too large or it will form too
large a mass when melted. Having thus soldered
screws to the several points, which should be evenly
distributed over the plate, set the plate with the
screws down, upon the wood block, length of the
plate with the grain of the wood, lay another block
upon the face of the plate and strike it with the
hammer, so that the screw will leave marks upon
the face of the first block. Then, with a one-fourth
inch drill, drill holes through the block at these
points, after which insert a countersink drill in the
chuck and with it drill from each side of the block into
the holes made by the one-fourth drill, letting the coun-
tersink go below the surface of the block on each side.
Sandpaper the face of the block and place the plate on
it so that the screws will sink into the corresponding
holes, allowing the plate to rest upon the surface of the
block. Then, protecting the face of the plate with
another block, clamp it tight and with a small ladle pour
melted type metal into the holes on the opposite side,
not allowing it to come to the surface of the block.
When it is cool, the plate will be firmly fastened to the
block.
Saw the block around the metal, leaving a small
margin of wood, and then it is ready to trim. Place
the block on the trimmer, having the gauge set so that
the knives will just catch one edge, and pass the table
back and forth, giving the gauge screw a slight turn
each time until the wood is trimmed up to the metal.
92 MANUAL OF PHOTOENGRAVING.
If the plate is so placed that the wood will not trim
parallel to the edge of the plate, place a piece of folded
paper between the block and gauge to cause the part at
which the wood is thickest to be moved farther toward
the knives. Trim each edge, running the block through
slowly when making the last cuts, and then make it
type-high in the planer. If the type metal should be
found to come to the surface of the block, it should be
routed down. In mounting line and half-tone cuts
together, if the plates are not of the same thickness, the
thinner ones must be underlaid to bring their surfaces
to the level of the thickest plate. Cherry wood is usu-
ally used for blocking plates, metal blocks being used
for those from which stereotypes are to be made, such
as line plates for newspaper work.
The first proofs from half-tone plates will often
show black spots. In such a case the plate is given to
the engraver, who tools them out. The half-tone may
often be improved also by having certain parts bur-
nished to make those parts in the proof appear darker.
For fine magazine work it has become customary to use
the tool very extensively upon half-tone plates, many
of them being given the appearance of fine wood
engravings. The tool is also often used to vignette
the plates and to clear away the stipple in places where
it is desired to have clear whites in the proof.
MANUAL OF PHOTOENGRAVING. 93
CHAPTER XII.
DRAWINGS — LITHOGRAVURE.
LINE DRAWINGS.
IN making line drawings for reproduction, the lines
should be made with india ink and should be per-
fectly black. They should also be heavy enough to
stand the necessary reduction and still be sufficiently
strong to etch without breaking. The best results are
obtained in the cut when the drawing is made larger
than the reduction is to be, and it is customary to draw
the original two or three times the size of the finished
plate.
It is often necessary to translate a photograph or
wash drawing into a line drawing or to make changes
in a piece of linework. In such cases, it is a saving of
time to draw over a silver print and then bleach out
the photographic image, leaving the black lines upon
a white ground.
The method is as follows: Obtain some plain
salted paper and sensitize it by brushing the surface
with a tuft of absorbent cotton wet with a solution of
silver nitrate. Dry in the dark and expose under an
ordinary negative made from the copy to be reproduced
until the image shows a dark red or purple. Wash,
then place in a dilute solution of acetic acid for several
94 MANUAL OF PHOTOENGRAVING.
minutes until the image is fixed. Wash again, then dry
and make the drawing over it with Higgins' waterproof
ink. When this is dry, flow over the print a saturated
solution of mercuric chloride in alcohol. The red image
will be removed, leaving the drawing, after which the
paper should be rinsed and dried, being then ready for
the photographer. Those who prefer to " salt " the
paper also will find a formula in the appendix.
Instead of the " printing-out paper " described
above, bromide paper may be used, the bleaching being
done by means of the iodine and hyposulphite of soda
solutions.
When it is desired to make tracings of a drawing or
any portion of it, the back can be .rubbed with a
pigment (such as a blue pencil) and then laid back
down on another sheet of paper or a card and the lines
traced over to transfer them. The work is then finished
by drawing the black ink over the lines thus obtained.
Guide lines, notations, etc., that are not to appear in
the cut should be made in blue, as they need not be
erased, the ordinary plate, as stated in a previous
chapter, not being acted upon by this color.
In making symmetrical designs (that is, drawings
of which one half is duplicated in form in the other), it
is necessary to draw only one half. Two negatives can
be made and joined to form the complete plate. To
judge how the result will appear in the finished condi-
tion, place a piece of mirror glass along the edge of the
drawing and the reflection combined with the lines of
the drawing will show the results.
The card stock k-nown as " scratch-board '' is gen-
erally preferred for drawings, as it has a smooth sur-
MANUAL OF PHOTOENGRAVING. 95
face, takes ink readily and permits alterations to be
made without materially changing the character of the
surface.
DRAWINGS FOR HALF-TONE.
Drawings for half-tone reproduction are technic-
ally known as " wash drawings," from the method of
producing them with the brush and india ink or other
pigment in solution. The " air brush," with which air
is used to blow a fine spray of the pigment upon the
surface of the drawing is used to a great extent on
certain classes of work, such as making vignetted back-
grounds and softening tones.
Photographs can usually be much improved for
reproduction by having certain portions painted over by
the artist, the colors and strength of the pigments being
determined by the results required. Combinations of
photographs and " wash " work are also commonly
used for various illustrative purposes. Photographic
figures can be combined with backgrounds made
with the brush, and fashion drawings are frequently
made with faces taken from photographs and the
bodies drawn in.
TINT-BLOCKS.
" Tint-blocks " are plates from which colors are
printed, and each is usually only a part of the image,
the entire reproduction being formed of a combination
of printings from such plates. Usually a " key plate,"
which is a complete etching from the original drawing,
is printed in black over the colors. These " tint blocks "
are obtained by making as many separate prints, with
transfer ink and dragon's-blood upon zinc, as there
MANUAL OF i'UUTOICN GRAVING.
'h^ 3
HALF-TONE.
m Wash Drawing by N. J. Quiik.
— OUTLENEl) AND HAND-TOOUED,
MANUAL OF PHOTOENGRAVING. 97
are to be color-plates. The artist scrapes out the por-
tions of the image on each plate that are not to appear
in the color to be printed from that block and paints in
solids where required. The plates are then etched,
routed and mounted. Tints can also be inserted with
the Ben Day machine described below. This method
of making colors-blocks direct on the zinc insures more
perfect register than can be obtained by making sepa-
rate drawings for the different colors. The term
" register " is used to define the relative position of the
colors when the plates are printed. Perfect register
means that each tint falls exactly in the place intended
for it.
LITHOGRAVURE.
By the term lithogravure is meant the production of
plates containing tints of lines or dots, or both, the
effect being similar to that obtained by lithographic
processes.
These tints are usually inserted upon drawings
by means of the Ben Day machine.
The apparatus consists of a film of gelatin compo-
sition mounted in a frame, the form of the tints being
so placed in relief upon it that when rolled up with ink
they can be readily transferred to the copy by placing
the film above it and pressing upon it with a burnisher
or other convenient instrument. Similar results, how-
ever, may be obtained by the following method :
The necessary apparatus is simply several plates
ruled to form tints of lines or dots, some examples of
which are shown on the following page.
These rulings are made upon plates of stereo-metal
mounted on blocks of wood to be type-high.
7
98 MANUAL OF PHOTOENGRAVING.
The outlines of the drawing are made and then a
sheet of tissue-paper is stretched tig-htly over it and
pasted at three of the edges, after which the outline of
the tint first to be inserted is drawn on the tissue in
pencil. After this is done, a card is slipped under the
tissue and the tissue cut out with a sharp knife on the
lines just drawn, the card heing then removed, leaving
the space on the drawing bare where the tint is to be
placed. The dra\Mng li, then placed on the bed of a
hand press, the tint-block being rolled up with ink and
placed face down upon it. The pressure being brought
to bear, leaves the dots on the face of the drawing in
the open space, the other parts of the drawing being
protected by the tissue. This sheet of tissue being
removed, another one is put on, the outlines for another
tint drawn and cut out, the tint-block being rolled up
and the impression being taken as before, leaving
another tint on the drawing, and so on for the remain-
ing tints.
To get the cross-line tints, two impressions are
taken from a single-lined plate, the position of the plate
for the second impression being at the angle desired
to the first position. In making a shade line around
letters, where it is desired to have a white space between
MANUAL OF PHOTOENGRAVING. 99
the letter and the shading, the tint may be allowed to
run up to the letter when the impression is made, the
white space being scraped out afterward. When let-
ters which are to appear white are to be protected while
the impression is being made, tissue cut out to fit the
letters are pasted on them at two or three points, the
tissue and paste being afterward removed. When the
tints are all inserted in the drawings, the reproduc-
tion is made in the camera as usual. This process
gives results similar to those obtained in lithograph-
ing, and very handsome effects can be obtained by run-
ning the tints in colors.
Hand-stippling is also often used to give character-
istic effects upon drawings.
lOO MANUAL OF PHOTOENGRAVING.
CHAPTER XIII.
DEVELOPMENT OF GELATIN DRY PLATES.
IN Chapter III it has been observed that the develop-
ment of emulsion plates depends upon the action of
a solution that will decompose the molecules of silver
compound that have been acted upon by the light, the
subsequent action being to attract from the neighboring
particles of unaltered salt more silver to add to the
intensity of the image thus formed. In practical work
we not only apply the solution to reduce the silver from
its compound, but we mix with it other solutions to
modify its action.
There are a number of compounds suitable for
developing emulsion plates, but as an example we will
take pyrogallol (commonly known as pyrogallic acid).
To the solution of pyro, as it is called for abbreviation,
we add one of an alkali, as sal soda, one of sulphite of
sodium, and often a small quantity of bromide of potas-
sium. The sal soda softens the film on the plate, allow-
ing the developer to readily penetrate it. The sulphite
helps to keep the pyro from absorbing oxygen from the
air and thus deteriorating, and also to a considerable
extent governs the color of the negative, a matter of
considerable importance. The bromide is used to
restrain the action of the pyro sufficiently to prevent too
r ,
MANUAL OF PHOTOENGRAVING. lOI
rapid action and consequent " flatness '' or fog in case
of overexposure or possible excess of the alkali. It
thus tends to give clearness and contrast. With rightly
timed exposures and a properly proportioned developer
it is not a necessary constituent, although a few drops
is usually added to the solution.
In using the developer, therefore, the following
facts should be kept in view :
The alkali tends to give detail and if used in excess
will produce a negative that is too much lacking in con-
trast or perhaps " fogged." If the negative has been
underexposed a little excess of alkali helps to bring out
necessary detail.
Excess of sulphite gives the negative a bluish-black
color which tends to give " flat " prints. The quantity
should be adjusted to produce a color which may be
described as an olive-black.
Excess of bromide restrains the formation of detail
and tends to give " hard " negatives.
Excess of pyro also has an action to give negatives
with contrast and lack of detail.
It is evident that we may mix the developer in pro-
portions to promote detail or contrast. There are,
however, certain proportions of the constituents enter-
ing into the composition which may make what we may
term a normal developer, that is, a developer which
when applied to a properly exposed plate will bring out
the gradations and intensity in proper order, producing
a negative of the best technical quality.
The time of exposure, of course, is a matter of no
less importance than the development of the negative,
for while with skilful manipulation good results may be
102 MANUAL OF PHOTOENGRAVING.
obtained from the plate slightly under or over exposed,
it is only with correct exposure that the best effects are
produced.
The exposure time of the gelatin plate is much
shorter than for the collodion, varying from a small
fraction of a second to several seconds (or perhaps
under special conditions to an extended time).
A correct exposure properly developed will yield a
negative having gradations to render the details in the
subject, but will preserve the contrasts sufficiently to
avoid flatness in the resulting print.
Overexposure* tends to produce negatives full of
detail, yielding prints without brilliancy.
Underexposure tends to produce negatives with
strong contrasts, lacking in detail, the resulting print
being " hard."
PYRO DEVELOPER.
Prepare stock solutions as follows :
A. Sodium sulphite, 40 by actino-hydrometer.
B. Sal soda, 20 by actino-hydrometer.
C. Mix A and B in equal quantities.
D. Bromide of potassium, i part to 9 or 10 parts water.
For convenience these solutions may be made up in
quantities, but the sulphite solution should be kept as
well as possible from the action of the atmosphere.
Yellow, foggy negatives are often caused by using sul-
phite solution which has become changed by absorption
of oxygen.
To prepare the solution for practical use, a certain
*The terms overexposure and underexposure should be considered as
comparative. While under most conditions what we may define as nor-
mal exposure and development give the best results, there are some cases
where it may be desirable to vary from it to produce a special effect.
MANUAL OF PHOTOENGRAVING. IO3
amount of solution C is mixed with water, and for each
ounce of the resulting solution two grains of dry pyro
are added, and, if necessary, a few drops of D. (In
practice it is more convenient to measure the pyro than
to weigh it every time. A mustard spoon that will con-
tain a certain quantity may be used as a measure, and
enough spoonfuls added to make approximately the
amount required.)
Just what proportion of C that is best to use depends
upon the temperature of the atmosphere and the brand
of plate. In warm weather 2^ or 3 parts of C will
usually be sufficient for a total of 16 ounces of the
developer. In cold weather a greater amount of C may
be taken. A few trials will determine the proper pro-
portions to use in general, according to the way the
negatives appear.
FIXING SOLUTION.
Plates may be fixed by immersion in a plain solution
of hyposulphite of soda (about one part of the salt to
four parts of water), but this plain bath soon deterio-
rates and the acid solution is best for fixing a number
of plates and for continuous use. The following is a
good formula :
FIXING BATH.
Water 64 ounces
Hyposulphite soda 12 ounces
Sulphite soda i ounce
Powdered alum i^ ounces
Acetic acid iH ounces
Renew the solution when it becomes weak or shows
any tendency to discolor the negatives.
104 MANUAL OF PHOTOENGRAVING.
DEVELOPMENT.
In the development of the plate, the points to be
considered are: First, the tirhe in which the image
appears; second, the contrasts; third, the detail;
fourth, the intensity. An intelligent judgment of these
will enable the operator to determine whether the expo-
sure has been of the proper duration, and to conduct the
development accordingly.
Place the plates in a clean tray, which should be kept
for this purpose alone, and flow the developer over them
in an even wave, using enough to cover the plates.
Then rock the tray to cause the developer to flow from
side to side. If the exposure has been properly timed
the high lights of the image will appear first, then the
gradations in the middle tones, those corresponding to
the lighter shades first, being followed by the darker
shades, then the details in the shadows. When all the
gradations have thus appeared in proper order, the
development is continued until the proper intensity is
reached, which is determined by the appearance of the
plate when held up to the red light. Only experience
will enable the intensity to be properly judged.
If the exposure time has been too short, the image
will be late in appearing as compared to the normal, and
the details in the half-tones and shadows will hang
back, and if the development is carried on as for proper
exposures the high lights will gain the desired intensity
before the details will come out, thus producing a nega-
tive devoid of detail. In such a case simply place the
plate in a tray containing developer diluted with water.
The development will then take place slowly, the details
having time to appear before the high lights assume any
MANUAL OF PHOTOENGRAVING. I05
great intensity. When the details have properly
appeared, the plate can be returned to the normal devel-
oper until the proper intensity is obtained. The under-
exposed negative may often better be placed for a time
in a tray of water until the details appear, and then
returned to the developer to bring out the intensity.
Some operators place undertimed plates in a devel-
oper to which an excess of alkali has been added, but
such forcing of detail will seldom yield a good negative,
and there is great liability to fog.
If there is any detail which can be brought out the
method given above will do it. A badly undertimed
plate will, of course, never produce a good negative.
If the plate has been overexposed, the image rapidly
appears, the details coming up with the high lights, and
the negative will be " flat." In such a case it should be
placed at once in a tray containing normal developer to
which there has been added more of the bromide solu-
tion. The restrainer will cause the reduction in the
portions least affected by the light to be retarded, while
the high lights will gain in intensity, thus producing
contrasts.
When a number of plates are developed in succes-
sion the developer will deteriorate, and should be
replaced by fresh as occasion may require.
During development, the plate should be examined
from time to time by holding it between the eye and the
red light, and when the proper intensity has been
obtained it should be rinsed for a moment under the tap
and placed in the fixing bath, in which it should remain
for ten or fifteen minutes after the white color has left
the film.
I06 MANUAL OF PHOTOENGRAVING.
In developing orthochromatic plates they should be
exposed as little as possible to the red light, particularly
at the beginning of operations.
After fixing, the plates should be washed in running
water for an hour or two to remove the hypo from the
film.
When taken from the water the hand may be passed
over the face of the negative to remove any sediment
from the water, the plate being then placed in the rack
to dry.
INTENSIFICATION.
If the negative is found to be too thin to give satis-
factory prints, it should be intensified. This operation
requires great care to avoid streaks and stains. It is
best to have a glass tray to hold the solution, and this
tray should be kept clean and for this purpose alone.
There are many formulae for intensifying solutions,
but the mercury method is very generally used.
NO I.
Mercuric chloride i% ounce
Water 20 ounces
Have the negative thoroughly fixed and all hypo
washed out of the film and bleach it in the above solu-
tion. Then wash well again in running water and
blacken to the desired degree in a solution of
Sodium sulphite .^ i^ ounce
Water 15 ounces
Wash again in running water for half or three-
quarters of an hour.
MANUAL OF PHOTOENGRAVING. I07
NO. 2.
Dissolve 2^ ounces of iodide of potassium in 12
ounces of water and pour into it gradually a saturated
solution of bichloride of mercury. A red precipitate of
mercuric iodide will be formed. The mercury solution
must be added until this precipitate can not be dissolved
by shaking. Avoid adding any more mercury, how-
ever, than will make the solution very slightly turbid.
Then add 2^/4 ounces hyposulphite of soda, and when
dissolved add water to make up to 40 ounces.
For use, take one part of the above solution to three
parts of water and immerse the negative after fixing
and washing until sufficient density is obtained. If the
hypo has not been thoroughly washed from the film
the intensifier will cause stains. If over-intensified, the
density may be reduced by leaving the negative in the
fixing bath for a short time.
With the mercury intensifiers it is best to use dis-
tilled or rain water if obtainable. Hard water is liable
to cause markings in the negative.
URANIUM INTENSIFIER.
A. Nitrate uranium 30 grains
Water 8 ounces
B. Ferricyanide potass 30 grains
Water 8 ounces
For use mix 6 ounces of A with 6 ounces of B and
add 2 ounces glacial acetic acid.
Have the plate thoroughly washed and flow the
solution over it and keep the tray in motion until the
required density is reached. Then wash for fifteen or
Io8 MANUAL OF PHOTOENGRAVING.
twenty minutes. Prolonged washing reduces the inten-
sity and if the intensification has been carried too far,
the remedy is obvious.
REDUCTION.
Negatives which are too dense may be reduced by a
dilute solution of hyposulphite of soda to which a little
of a solution of ferricyanide of potassium has been
added.
The solutions may be made up in the proportion of
J/2 ounce of salt to 8 ounces of water. Add a little of
the potassium solution to the hypo solution and immerse
the negative until sufficiently reduced. Finally wash
well.
CAUSES OF DEFECTS IN GELATIN NEGATIVES.
Fog. — White light entering darkroom or camera,
overexposure, excess of alkali in developer, hypo or
other chemicals in developer, developer too warm.
Negative too thin. — If the shadows lack detail,
underdevelopment; if the shadows have detail, weak
developer, or exposure too great.
Intensity too great. — Overdevelopment, reagent in
excess in developer, or warm developer.
Abnormal contrasts. — Underexposure or developer
too strong.
Frilling. — Solutions too warm, insufficient alum in
fixing bath or prolonged washing.
Flatness. — Overexposure or too much alkali in
developer.
Spots. — Dust or bubbles in developer.
MANUAL OF PHOTOENGRAVING. IO9
Stains. — Developer oxidized, impure cHemicals or
not enough sulphite in developer, deteriorated fixing
solution or insufficient fixing.
Streaks. — Developer allowed to flow unevenly over
plate when first applied, or fixing bath acid.
Crystals on negative, — Hypo not all removed from
film.
no MANUAL OF PHOTOENGRAVING.
CHAPTER XIV.
PRINTING HALF-TONE PLATES.
PHOTO-MECHANICAL engraved printing-plates
have largely revolutionized pressroom theories,
and owing to the shallowness of the engraving and to
the greater necessity of dependence on the qualities of
paper and ink, the judgment and skill of the pressman
is more than ever before required to give life and bril-
liancy to cutwork. Unevenness in half-tone plates is
a source of much annoyance to the pressman. All
plates should be made perfectly level before etching
and the greatest uniformity should be observed in the
grinding and polishing.
The following instructions for preparing half-tone
plates for printing obtains in one of the large estab-
lishments of America noted for the quality of the half-
tone work produced. Obtain all the cuts on a certain
piece of work from the composing-room before they
are made up in the forms, and of each cut have proofs
taken on three different weights of paper — 24 by 36,
60, 70 and 80 pounds — and then proceed to make cut
underlays. Taking one of the proofs on the 70-pound
stock, carefully trim it all around, leaving a margin of
one-sixteenth of an inch of blank all around the print.
Then cut out of the sheet all of the extreme high lights,
being careful to cut a little of the surrounding shadows
MANUAL OF PHOTOENGRAVING. Ill
with them, the purpose of this being to prevent too
much impression on the point of division, which would
have a tendency to bring up the shallows. Then take a
proof on the 8o-pound stock and remove from it the
extreme blacks and solids — always cutting a little
inside the line — and paste them on the 70-pound sheet
already treated, using common flour paste or mucilage.
Then take one of the proofs on 60-pound stock and
cut out all of the intermediate shades such as should
appear lighter or softer in the finished print. Take
these several proofs and paste them together, and this
would be called a four-ply cut overlay, excepting that
all of the pieces comprising it are ciit a trifle inside of
the line. If the cut has more shade in it than can be
properly treated with three sheets, take a 50-pound
paper in place of the 60-pound and add one sheet to the
underlay, treating it in the same way as the second
sheet, with the exception that instead of cutting out the
extreme solids remove all the semi-dark shades as well
and paste them on. Having made the underlays in the
manner described, proceed to unmount the cuts from
their bases. In order to do this without injuring or
scratching them, great care is required. The tools
which will be found to be the most advantageous are a
small hammer, a pair of pliers, and a small chisel —
this last should be about a quarter of an inch in diam-
eter at the shank and should have a long, tapering
blade, and be about half an inch wide at the extremity
of the blade. Some small wire brads, such as are com-
monly used for mounting the plates, a prick punch, a
small nail set, an electrotyper's iron finishing plate, and
a pair of plate calipers such as are used by electro-
112 MANUAL OF PHOTOENGRAVING.
typers, are the other requisites. Having removed the
plate from the block, take the calipers and mark at
least two distinct points on the back of the plate in
order to be able to paste the underlay accurately in
position. This done, lay the cut face up on the iron
plate and with a small boxwood planer go over the
entire surface, taking care to strike only a moderate
blow. Take the block thereafter and examine it care-
fully to see that it is free from lumps and rough places
and mount the cut on the opposite side to that from
which it was taken and send it to the composing-room.
This method saves a great deal of time in the final
make-ready of the form, as it is only necessary to even
up the impression on the cut, and the underlay will
throw the lights and shades where they should be with-
out any further care on the part of the pressman, and
for long runs will preserve the cut much better than if
a plan of overlaying was followed. It holds up to the
rollers the dark parts of the cut, properly supplying
them with ink and protecting the lighter and more
delicate shades from receiving unnecessary pressure.
The practice of many pressmen who obtain good
results is to even up the cut by underlays, and then
proceed to make such overlays as the character of the
work will indicate to be the most suitable. To be suc-
cessful in making any kind of an overlay, as little paste
as possible should be used, only sufficient to compactly
bind together the different portions of the overlay, and
to register each piece of paper over the other with
positive accuracy. For work of differing character the
papers used in overlays vary. Impressions of the cuts
are taken, for instance, on three grades of stock : One
HALF-TONE.
Hand-tooled Cost-
ackground — Heavy Border.
MANUAL OF PHOTOENGRAVING. II3
sheet, say, of lo-pound folio, one of double that thick-
ness of supercalendered, and one sheet of the stock
upon which the cut is to be printed. Sometimes the
last sheet mentioned is selected for the first treatment,
which consists in cutting away from it any large, light
backgrounds, and scraping down and slitting off many
of the light and medium tones, so as to throw up the
stronger ones and the solids. A sharp knife and some
degree of skill is necessary to handle a sheet of paper
in this way, but it is worth one's while to acquire it, for
it saves time and much pasting on of parts of overlays,
besides giving a firmer basis.
The sheet of supercalendered stock may now be
taken, and from it should be cut all the light tints as
well as some of the stronger ones. The sheet is also
used as the foundation on which to paste the cut-out
portions of the two other sheets.
The third sheet of thin folio should be used to make
overlays for such portions of strong solids and shades
as require them. These should be pasted accurately in
place on the supercalendered sheet, and over them
should be fastened the first sheet treated. From this
arrangement it will be apparent that the first sheet, the
folio and the supercalendered sheets press on the form
in the order named, and in their relative degree of
pressures.
VIGNETTED HALF-TONES AND PHANTOM EDGES.
To obtain the best results in printing half-tones the
edges of which are designed to fade into the white or
color of the stock without showing the line of demarka-
8
114 MANUAL OF PHOTOENGRAVING.
tion, it IS necessary that the cut shall be lower than
type-high. The cuts must be made absolutely true and
level; any inequality permitting them to rock will be
fatal to good work. If the cuts are too high or type-
high, the most convenient means of lowering them is to
sandpaper the backs until they are reduced slightly
below type-high. The make-ready, overlay, etc., do
not vary from that given in the preceding pages.
WHY PLATES FILL UP WITH PICKS.
This comes from several causes, usually unsuitable
rollers or rollers not set light enough to properly roll
the delicate plate surfaces and rollers not cast true in
the stocks. Inks that are too stiff or too thin, or not
sufficiently ground, or ground in inferior oil or var-
nish, will also cause this trouble. Washing the plates
with either woolen or cotton rags forces into the sharp
openings of the half-tone the flock from the rags, and
this also causes " picks." Half-tone work should be
washed with a good brush of medium fineness, and a
clean cotton rag should be used to lightly sponge up
the washing fluid — be it benzine, astral oil or turpen-
tine. In no case should rags alone be used to clean
these plates, nor should anything be carelessly, harshly
or hurriedly rubbed over their surfaces.
Defective coating on enameled paper, or what is
known as surfaced wood-cut paper, will produce picks
and fiU-ups on half-tone plates; and in such cases an
ink with a very slight tack should be used to get fair
working results; but the form should be washed off
oftener than when better stock is running. After
making ready, and between long stops, half-tone plates
MANUAL OF PHOTOENGRAVING. II5
should be thoroughly cleaned off, as by so doing clearer
and more satisfactory work can be turned out.
COLORS FOR HALF-TONE PRINTING.*
In every child's storehouse are treasured many bits
of color. This love of color, inborn, may always be
made of strong appeal. The profusion of illustration
constitutes one of the greatest influences in every grade
of publication — commercial, scientific and literary.
The form and detail being fixed by the subjects con-
cerned, it remains only to print them in such quality
and strength of color as shall be best. Since the
greater portion of printing is confined to one color, this
article is limited to printing in monotones.
Fitness to the subjects themselves controls the
choice of some colors. Figures, particularly nudes,
require warm tones. It is not customary, however, to
be restricted to such monotones as approach flesh tints.
Browns, deep reds and rich olives are all good.
Marines are the most limited in range of color, greens
and blues being generally used. Landscapes allow
more license in color, all of the autumnal tints being
possibilities.
Next to the subjects, the purposes and uses of the
print must be regarded. For permanent value, sim-
plicity of effect is of more importance than any strik-
ing contrasts which will, in time, prove a detraction.
The plain catalogue page is made attractive by some
monotone which is at once decorative and an approach
•From an article by Mr. Henry Lewis Johnson in The Inland Printer
the above suggestive notes on colors for half-tone printing are taken by
special permission.
Il6 MANUAL OF PHOTOENGRAVING.
to the true color of the subject. Commercial printing,
such as catalogues and placards, admits of stronger
colors than are used in bound volumes, purely illustra-
tive. The practical value of a catalogue illustration
often requires that all of the details be clearly shown,
and dark colors are necessary for this. In art cata-
logues the reverse is found ; everything is sacrificed to
effect.
Black always shows the full strength and brilliancy
of an engraving. Colors which approach black in
density possess most brilliancy and detail. Browns,
although good, are open to some prejudice, since for
many years they have been used on every fine program,
catalogue and specimen print. An order for a " fancy
job " has been synonymous with brown ink. This
color has one practical advantage. Where the same
plates are used year after year in catalogues they
become necessarily somewhat worn and battered.
These defects are largely obscured by this neutral
color.
Blues are not much used in half-tone printing. In
their use all of the lights, which give contrast and bril-
liancy to a picture, are lost. It is naturally a color
seldom used for landscapes. The slow drying qualities
of the ink are an objection to its use on programs or
any work which has to be bound soon after printing.
Blue-black, of the darkest shades, is being largely
used, giving marked brilliancy to the print.
Reds, in the richer carmine shades, are effective but
somewhat costly. They are difficult colors to handle
well, requiring very exact gradations to avoid being
crude. Yellow has some important uses. Deep corn
MANUAL OF PHOTOENGRAVING. II7
yellow IS preferable to the canary shade. Greens are
good and are in favor at present. Particularly rich
effects are obtained in deep shades of olive, yielding
strength and warmth. Such prints closely approach
photogravures in effect, having strength yet obscuring
the half-tone lines. Instead of primary browns, blues '
and greens, each one is better for ordinary purposes as
it approaches black.
For the printer there is a practical, and indeed,
economical side to the use of colored inks. By using
the engraver's proof in black in making ready, the
print may be brought up to its proper condition. The
element of " rush " usually enters in at this stage.
Justice can not be done to the cuts in black in long,
hurried runs, as it is difficult to maintain the color. A
slight variation in the brilliancy of the print in. an
olive or brown does not constitute the defect which it
would in black. In place of strained effects in descrip-
tive lines and text the monotone is the desired decora-
tion.
The use of monotones is an interesting and a crit-
ical part of the work. For the simplest print the
requirements of color are exacting, and, successfully
handled, constitute a step in advance in the art of
printing.
The
Half-tone and Trichromatic Process
Theories.
By FREDERIC E. IVES.
MANUAL OF PHOTOENGRAVING. 121
HALF-TONE PROCESS THEORY.
THE idea of breaking a photograph up into lines by
interposing a line-screen when printing it, as a
means of converting it into a half-tone engraving, is
very -old in photographic history. To people who
thought that such a breaking up of the photographic
image was all that was required to make it like an
engraving, the use of a screen was obvious. It natu-
rally occurred to a great many, at different times, but
in as many instances nothing of practical value resulted,
for the simple reason that the problem is not to add lines
to a photographic image, but to translate the body
shading of a photograph into line shading, which is a
very different proposition.
Therefore it was natural that the first true solution
of the problem should not be by the application of a
screen, but mechanically, by the regular application of
an engraver's V-shaped tool, in a planing machine, to
the irregular surface of a cast from a photo-gelatin or
" Woodbury " relief plate. The depth of cut, varying
with the height of the relief, resulted in the production
of lines graduated in size like those of a wood engrav-
ing, but which, when inked, reproduced the shading of
the photograph with a degree of precision which the
most skilful hand engraving could not rival. The first
commercially successful half-tone engraving process,
which was introduced in 1881, was a practical modifica-
122 MANUAL OF t>HOTOENGRAVlNC.
tion of this procedure, involving precisely the same
fundamental conception. It consisted in pressing a
fully inked surface of V-shaped elastic lines against a
plaster cast of a photo-gelatin relief, thus producing by
a single rectilinear movement a result similar to that
obtained in the planing machine by many passages of
the tool; and this photo-mechanical graduated line-
print on plaster was used like a pen drawing as copy
for a photoengraved printing-plate.
The more direct and now practically universal proc-
ess by means of a cross-line sealed screen used in front
of the sensitive plate in the camera, is merely a more or
less perfect optical equivalent for the mechanical proc-
ess, grew out of it, and is successful in proportion as it
constitutes a successful application of the same funda-
mental principle.
In the mechanical process, the impact of the
V-shaped elastic line, varying with the height of the
relief, graduated the surface width of the lines.
In the optical process, when employing a single-line
screen, with an air space between it and the sensitive
plate, the wedge of rays reaching the plate through each
clear line of the screen, is (or may be) so distributed
laterally as to constitute an optical V-line, which corre-
sponds to the mechanical V-line, and the impact of the
dioptric image formed by the camera lens, varying
according to its light and shade, corresponds to the
photo-gelatin relief, and similarly varies the width of
developable line by varying the depth of photographic
penetration of the optical V.
All this involves a conception of the function of the
process screen which should make it evident that rela-
MANUAL OF PHOTOENGRAVING. 123
tive width of clear spaces, distance of screen from sensi-
tive plate, and form and diameter of lens aperture, are
all working factors, and that their relations should be
adjusted with the same care and precision as the
mechanical relation of a V-tool to the surface of a
photo-gelatin relief.
Even the mechanical process, however, was not
quite so simple as the foregoing statement would make
it appear, because it was necessary to provide means
for producing cross-line effects, with white dots in the
shadows, and black dots or points in the lights. It is
not necessary to detail the means by which this was
effected ; suffice it to say that it is effected in the screen
process by employing a black cross-line screen in place
of a single-line screen, and that the character of this
screen enables us to consider the matter from a new and
simpler point of view, not losing sight of the fact that
it does not negative anything that has been said about
the essential relation of the optical to the mechanical
process.
Each aperture of the cross-line screen may be regard-
ed as a pinhole, forming upon the surface of the sensi-
tive plate a pinhole image of the diaphragm aperture of
the camera lens, the image round if the diaphragm aper-
ture is round, but graduated in illumination from a
bright point in the middle down to a dimly illuminated
edge, so that it is equivalent to a V-cone stipple instead
of a V-line, and the depth of its photographic impact,
and consequent ultimate surface extension, is controlled
by the relative intensity of that part of the dioptric
image which illuminates it. Thus we secure a transla-
tion of body shades into dots which at their smallest (in
124 MANUAL OF PHOTOENGRAVING.
the negative) represent the deeper shades of the pho-
tograph, but growing larger in the lighter parts of the
image, finally overlap and leave small transparent dots
to represent the high lights, as is required for the pro-
duction of the best printing-plates.
On a sufficiently large scale, i. e., with sufficiently
coarse screens, all this works out as a simple problem
in optics, the understanding of which will provide
the operator with means to perfectly control the opera-
tion of the process, to produce every possible effect, by
change of screen distance and size and shape of dia-
phragm aperture. With finer screens, diffraction intro-
duces a disturbing element, which may be made either
helpful or embarrassing, so far as regards the gradua-
tion and sharpness of line or dot, according as the
adjustment of screen distance is favorable or otherwise ;
but always necessarily at the expense of microscopically
sharp definition of outline, because every ray that is
diffracted is bent away from its true defining path. If
this were sufficient to very seriously affect the results,
means would be found for entirely eliminating this
factor; but commercial exigencies demand that we
shall be content with the very sirnplest possible " good
enough " process, and from that point of view nothing
more can now be offered.
MANUAL OF PHOTOENGRAVING. I25
TRICHROMATIC PROCESS THEORY.
A TRUE theory is a logical scheme founded on
inferences drawn from established principles.
A false theory may be a logical scheme based upon false
premises, or an illogical scheme based upon true prem-
ises. Even a false theory may lead to valuable results ;
but it seldom leads to more than partial success, and
oftener to failure and discouragement. A true theory
will indicate correct practice and insure ultimate suc-
cess.
The theory that red, yellow and blue are the primary
colors of light will not serve as a basis for the most
successful trichromatic process photography, because it
is a false theory. If it were true, a mixture of yellow
and blue spectrum rays would make a bright, pure
green ; but they do not — the mixture appears almost
white to the eye. A single proved fact that contradicts
a theory proves that theory to be false.
The theory that spectrum red, green and blue-violet
rays may be taken as the primary colors of light is not
open to this objection, because every color can be
reproduced to the eye by mixing these spectrum rays.
Why this is so, we need not here inquire, because our
object is merely to make a photographic color analysis
in terms of the three most suitable colors, which are
afterward to effect the synthesis in a triple color print.
Just here, those whose knowledge of the subject is
126 MANUAL OF PHOTOENGRAVING.
but superficial may say, " But we do not use red, green
and blue- violet in our color print synthesis ; we use red,
yellow and blue." As a matter of fact, if you get good
results without much " faking '' you use bright, trans-
parent crimson (not true red* ), bright, transparent pea-
cock blue (not true blue), and light yellow (all of the
spectrum except blue-violet) inks, which are the com-
plementary or shadow colors of spectrum green, red and
blue- violet; and that is equivalent to working with
green, red and blue-violet light colors. More about this
later.
We have already stated that red, green and blue-
violet spectrum rays can be so mixed as to reproduce
all other colors. Would any other three colors of light
serve this purpose? It has been asserted that "Any
three colors farthest apart in the chromatic circle may
be taken as the primaries." If we were to accept this
theory and carry it to its logical conclusion, we would
expect to succeed with spectrum yellow, spectrum
green-blue, and a compound of spectrum blue-violet and
red ; but if we try the experiment of mixing these colors
of light to represent spectrum red, green, and blue, we
shall find that, at best, there is a degradation of purity
amounting to about fifty per cent. We must keep as
close as possible to spectrum red, green, and blue-violet
if we would avoid serious degradation of color.
Having settled upon our primary colors, we have to
determine what relation these bear to the photographic
process by which we get our analysis of all colors in
three monochrome images. One might suppose that it
* Almost a magenta pink ; it is difficult to find a nomenclature that means
the same to ever>-body. A physicist would call this color " purple."
MANUAL OF PHOTOENGRAVING. I27
would be sufficient to make one negative image by the
exclusive action of spectrum red rays, another exclu-
sively by spectrum green rays, and another exclusively
by spectrum blue-violet rays. This would be the case
if all the colors in nature were actually mixtures of red,
green, and blue- violet spectrum rays; but they are
not — they include also orange, yellow, yellow-green
and blue-green spectrum rays, and all of these must be
recorded in terms of the primaries in order to make an
analysis which insures the preservation of all hue and
luminosity values.
The key to the situation is Maxwell's celebrated
color-curve diagram, which has been available for this
purpose for more than forty years ; but its bearing
upon this problem was long overlooked.
Professor Clerk-Maxwell, the eminent English sci-
entist, opposing Brewster's theory of red, yellow, and
blue primary colors, devised an ingenious " color-box,"
with which he was able to prove, by measured mixtures
of spectrum rays, that red, green, and blue-violet are
the spectrum colors most competent to reproduce all
others by mixture, and plotted curves upon a diagram
of the spectrum, showing the proportions in which these
" primaries " must be mixed to reproduce all other
spectrum hues — and not only hues, but luminosity
values. This diagram, first published in 1861, is repro-
duced on next page.
Reference to this diagram will show that all spec-
trum colors intermediate between the chosen primaries
in the spectrum are covered by two curves, which, by
their relative height at any given point, show the per-
centages of the two primaries which, by mixture, repro-
128
MANUAL OF PHOTOENGRAVING.
duce not only the spectrum hue at that point, but also
the relative luminosity value.
As Maxwell pointed out at that time, it would be
possible to obtain a colored representation of the spec-
trum with three photographic transparencies shaded in
accordance with these three curves and projected upon
a screen by means of three magic lanterns with red,
green and blue lights. This he could not then do except
by an artifice, because color- sensitive photographic
plates were then unknown ; but it can now be readily
done with suitable combinations of orthochromatic
plaies and color screens.
Now, how does this apply to the reproduction of the
colors of nature by trichromatic process? The answer
is, that because all the infinite variety of colors are
mixtures of spectrum rays, a method that will reproduce
the hue and relative luminosity of all of these spectrum
^
MANUAL OF PHOTOENGRAVING. I29
rays separately must therefore necessarily reproduce
them in every possible mixture.
This is not only a logical conclusion from a consid-
eration of the facts, but works out in practice so per-
fectly that people who have seen such reproductioas in
the stereoscopic photochromoscope have frequently sus-
pected a trick, and have even openly charged that the
original objects which were shown for comparison were
being directly reflected to the eye through the instru-
ment.
So far, we have introduced no unnecessary compli-
cations either in the theory or the practice of trichro-
matic process reproduction. Such complications come
when we extend the principle to synthesis by printing-
inks instead of direct mixtures of light rays, and
although equally clear to the mind when once really
understood, have proved very puzzling to the majority
of inquirers, even leading many to the conclusion that
we have to deal with two quite distinct problems and
methods.
It should be evident, however, from what has
already been said, that, in the production of the nega-
tives, no other procedure than the one described can be
competent to yield a triple record which perfectly differ-
entiates all hue and luminosity values; and if these
subtle differences do not exist in the record, they can
not appear in the result.
We should therefore seek to understand the relation
of the printing colors in printmaking to the colored
lights in triple lantern projection, and see if the two
methods will not work out to the same result with the
same negatives,
9
139 MANUAL OF PHOTOENGRAVING.
The key to the situation will be found to be a recog-
nition of the fact that synthesis by triple lantern projec-
tion is a plus color synthesis, and synthesis by color
prints is a mimAS color synthesis. In one case we com-
mence with a darkened screen and build up to white by
adding together three light colors, and in the other case
we commence with a white surface and build up to
blacks by adding three sJiadozv colors.
The writer demonstrated this relation in lectures
delivered some years ago, as follows : " Fixed pictures
in color can be produced by a further extension and
complication of the method, employing the same nega-
tives to make three-color prints, which are mounted in
contact between glasses, like a lantern slide, or super-
posed on paper. In this case, inasmuch as the super-
position of color prints adds shade to shade, instead of
light to light, the colors of the prints are complementary
to the colors of light used in projection and in the pho-
tochromoscope. The print from the negative to repre-
sent red is peacock blue ; the print from the negative to
represent green is pink or crimson, and the print from
the negative to represent blue- violet is a light yellow.
Although I have already stated the reason for this, I
may make it clearer by an experiment with the triple
lantern. When there is no slide in the lantern, and the
blending of the red, green and blue-violet disks makes
white, we shall find that placing the positive of the red
sensation in the red light produces a peacock-blue pic-
ture on the white ground. It is the function of the
shades in this positive to take away red light from the
white of the disk, making what looks like a peacock-
blue photograph, and corresponds to the " blue " print
MANUAL OF PHOTOENGRAVING. I3I
in three-color printmaking. In the same way, the posi-
tive of the green sensation throws pink or crimson shad-
ows on the white disk, corresponding to the " red '' print
in three-color printmaking, and the positive of the
blue-violet sensation throws yellow shadows on the
white disk, corresponding to the yellow print in three-
color printmaking. The mixture of the primary light
colors in equal parts makes white, and the super-
position of the primary shadow colors in equal parts
makes black. Therefore, commencing with a darkened
screen, we add light to light, red, green, and blue-violet ;
but, commencing with the white disk on the screen, or
with white paper, we add shade to shade by our posi-
tives, peacock-blue, crimson and yellow."
It is thus proved that the correct printing colors are
not " red, yellow, and blue,'* but a certain pink or crim-
son, a certain yellow, and a certain " peacock " blue. In
fact, in order to reproduce all the colors in nature by a
trichromatic printing process, it is as important to use
these hues in printing-inks as it is to take red, green,
and blue-violet spectrum colors as the basis of color
analysis.
. This also, besides being logical theory, works out
successfully in practice, although the fact that the white
of a color print is ordinarily a full spectrum white
instead of a white made by mixing red, green and blue-
violet spectrum rays, introduces a new factor, which
must be taken into account, and its effect upon the result
understood.
Given the condition that our whites are made up of
all of the spectrum rays, it follows that our printing
colors, taken together, should absorb all of the spectrum
132 MANUAL OF PHOTOENGRAVING.
rays, and that is equivalent to making our triple lantern
projections with three groups of spectrum rays which,
taken together, constitute the whole spectrum, instead of
three isolated groups of the pure " primary '* colors. It
is quite easy to show what is the effect of doing this, by
actual experiment with the triple lantern; but as this
can not be done in the pages of a book, it may be stated
that if the hue of the primaries is matched by the group
mixtures, as it should be, the result is a slight loss of
purity of color, but without any falsification of hue and
luminosity values, and therefore without notable loss of
" naturalness." Knowing that our synthesis was to be
made with such group mixtures instead of " pure "
colors, we could calculate an analysis that would yield
somewhat less degradation of purity of color, but it
would necessarily be at the expense of differentiation of
hue, the relative importance of which is indicated in a
recent statement by Sir William Abney that " it is much
more important to obtain by means of the negatives a
correct hue, and if the proportions of density are correct
the admixture of white will not be observed detrimen-
tally, so long as it is kept within reasonable limits
. . . the appearance of color will appear to give a
true representation."
It is possible to have three kinds of printing colors
which fulfill the necessary conditions of collectively
absorbing the entire spectrum, yet being correct in hue.
They may either absorb evenly and exclusively the
spectrum from A to D, from D to F, and from F to H,
or the absorption bands may be a little wider but
still abruptly defined, so that collectively the strongest
absorption is on the D and F lines, or the absorptions,
MANUAL OF PHOTOENGRAVING. 1 33
Strongest over the " primary " spectrum colors, may
overlap in a falling ratio, so that they must be mixed or
superposed to fully absorb every intermediate spectrum
color. To the eye, these inks will appear almost identi-
cal, but they will not act exactly alike in forming the
compound colors. The specific merits of each kind are
capable of mathematical demonstration, but space not
permitting of more definite treatment, the writer will
merely express his preference for the second kind for
half-tone trichromatic printing, and the third kind for
color printmaking in gelatin transparencies.
From all that has gone before, it may be gathered
that the half-tone trichromatic process is theoretically
capable of correctly reproducing hues and relative lum-
inosities, with some little dilution by white or black.
This dilution, which would generally be negligible if it
were not intensified by imperfections in the inks and
printing, may be partly eliminated by employing a sim-
pler analysis, which would be represented by color
curves not overlapping to the same extent as in Max-
well's diagram, with some sacrifice of accuracy in the
rendering of hue and luminosity values. The shorter
and steeper the analysis curves, the greater the tendency
to fail in the differentiation of hues, and so to produce
crude color effects ; but some compromise in this direc-
tion is justifiable in doing certain classes of commercial
work, where accuracy of hue and gradation is less
valued than vividness of color. In either case, in prac-
tice, the worst defects will usually be those due to errors
in exposure and density ratios when the elements of the
color record are made by separate operations, as is the
usual practice. With the latter source of error elimi-
134 MANUAL OF PHOTOENGRAVING.
nated, the half-tone trichromatic process, carried out in
accordance with the theory here set forth, can be made
to yield, with very little reetching (and often with
none) results generally far more satisfactory to the
critical eye than the most elaborately reetched produc-
tions have averaged up to this time.
Three-Color Processwork.
A. BRIEF OUTLINE OF THE KNOWLEDGE A PHOTOENGRAVEK
MUST POSSESS TO UNDERTAKE THREE-COLOR
BLOCK MAKING.
By S. H. HORGAN.
r t
^
^
INTRODUCTORY.
AN effort has been made in these pages to compress
-^^^ in the shortest possible space the information
necessary for the photographer, engraver, or even the
beginner at either of these occupations, to learn prac-
tical three-color negative making.
To maintain brevity all theories on the subject have
been eliminated, as also the reasons for each operation.
To avoid confusion to the reader, all mention of proper
scientific terms, such as the solar spectrum, color sensa-
tions, density curves, etc., have been avoided.
Information regarding the operations of photo-
graphing, the making of the positives, half-tone nega-
tive making, sensitizing the metal plates, printing on
them, developing, etching and proving is given by
Mr. Jenkins, and is consequently omitted here. So also
instructions to the printer about underlays and the
selection and use of the three-color inks are not consid-
ered within the province of this book.
The manufacturers of lenses, sensitive plates, color
filters, colored inks and other requisites in three-color
processwork are making it easier each year to produce
(137)
138 MANUAL OF PHOTOENGRAVING.
three-color blocks, still the exact procedure in color
photography has not as yet been definitely settled upon.
Later developments, as they come to light, will be given
among the " Process Notes " of The Inland Printer.
This is written by a process man for his brother
process men, to whom he wishes all possible success in
the most fascinating of photographic operations —
Three-color Processwork.
S. H.HORGAN.
MANUAL OF PHOTOENGRAVING. I39
THREE-COLOR PROCESSWORK.
COLOR BLINDNESS.
THE person contemplating three-color photog-
raphy should not trust his own judgment as to
whether his color vision is normal, but have his eyes
tested for color blindness. Some eyes lack entirely
any appreciation of the sensation of red, others fail to
distinguish green, while a few are blind to the violet
sensation. There are degrees in the defectiveness of
eyes to the color sensations, perfect color vision being
rare. The nearer perfect color vision is the better will
its possessor succeed at three-color photography.
THE THEORY OF THE THREE-COLOR PROCESS.
All three-color photography is based on the theory
that there are but three primary colors, and that all the
other colors or hues are mixtures of these three in
varying proportions.
Tints in three-color block printing are obtained by
allowing the white surface, on which the three colors
are printed, to be exposed in varying degrees. Shades
are the result of superimposing the three colored inks
in dots on and between each other, until black is
reached by printing the three colors solidly over each
other.
For clearness sake the three colors used in the print-
ing-inks will be called yellow, red and blue, according
to Prang's standard colors.
140
MANUAL OF PHOTOENGRAVING.
Let it be remembered that in making a negative of
a black-and-white subject, for ordinary photoengraving
and printing in black ink, the black in the copy does not
affect the sensitive plate ; it is the transparent part of
the negative. It is the same in three-color negative-
making. The theory is that when making the negative
blue:
ye:li-0>a/
RED
IF THIS WAS THE COPY IN COLORS FOR THREE-COLOR RECORD NEGATIVES.
THE YELLOW RECORD NEGATIVE SHOULD SHOW TRANSPARENCY
AND OPACITY AS ABOVE ;
THIS SHOULD BE THE TRANSPARENCY AND OPACITY OF THE
RED RECORD NEGATIVE,
AND THE BLUE RECORD NEGATIVE SHOULD POSSESS TRANSPARENCY
AND OPACITY LIKE THIS.
for the yellow printing-block the yellow in the copy
should not affect the sensitive plate, but should be the
transparent part of the negative. In making the nega-
tive for the red printing-block the red in the copy
should not affect the sensitive plate and should be the
transparent part of the negative. In making the nega-
tive for the blue printing-block the blue in the copy
should not affect the sensitive plate, but should be rep-
resented by transparency in the negative. The nega-
MANUAL OF PHOTOENGRAVING. I4I
tives in three-color work have no color in themselves,
but record the amount of each of the three primary
colors found in that which is photographed. Hence
they should be properly tenned color record negatives.
THEORETICAL SENSITIVE PLATES FOR THREE-COLOR
WORK.
To make three-color negatives the yellow negative
should be made on a plate that is sensitive to red and
blue, and insensitive to yellow ; the red negative should
be made on a sensitive plate that is sensitive to yellow
and blue, and insensitive to red ; while the blue nega-
tive should be made on a plate that is sensitive to red
and yellow, and insensitive to blue.
THE THEORY OF THE COLOR FILTERS OR SCREENS.
To aid in carrying out this theory, colored screens,
or filters, are used, so that rays of light from the copy
are screened or filtered before reaching the sensitive
plate. In making the yellow negative a color filter
should be used to shut out the yellow rays, and allow
only the red and blue rays to pass through. For the
red negative a color filter should shut out the red rays
and permit the yellow and blue rays to pass ; and for
the blue negative a color filter should shut out the blue
rays and permit the passage of the yellow and red rays
of light from the copy. So much for the theory
PRACTICE VERSUS THEORY IN THREE-COLOR PHOTOG-
RAPHY.
In practice it will be found that neither color fil-
ters, sensitive plates or three-color inks are available
14-2 MANUAL OF PHOTOENGRAVING.
to carry on three-color block-making precisely as laid
down theoretically in the previous paragraphs. Why
this is so is too long a story to be told here. By numer-
ous compromises and skilful manipulation, difficulties
are overcome so that in practice three-color blocks can
be produced which will be quite satisfactory.
THE LIGHT.
Daylight in or near large cities and in changeable
weather is too variable to furnish the best illumination
for three-color negative making. The color of the
light from a clear sky, it will be understood, is bluer
than from a clouded sky. So also is the light from the
sun yellower as it sinks in the west. These variations
in the color of the light alter the color of the copy,
besides rendering it almost impossible to calculate cor-
rectly the time of exposure for the three negatives.
Electric arc focusing lamps of a good make, with
proper carbons and a steady supply of electric current,
furnish the most reliable light for three-color photog-
raphy.
Instead of using color filters between the copy and
the sensitive plate, the copy itself can be illuminated
with colored light. For instance, the illuminant may
be a powerful electric light, between which and the
copy color filters can be introduced. Just as great
care, however, will be required to have these large light
filters properly adjusted and maintained, as if they
were the smaller ones.
MANUAL OF PHOTOENGRAVING. I43
THE LENS AND CAMERA.
The special feature of the lens should be its cor-
rection for chromatic aberration, so that all colored
rays passing through the lens may come to a similar
focus on the ground glass. Non-achromatic lenses
focused the violet rays nearer the lens than the yellow
rays. The violet rays were not visible, but were the
ones which acted first on the sensitive plate. The yel-
low rays were visible and were consequently the ones
focused. Hence, in using a non-achromatic lens it
was necessary after focusing to move the ground
glass forward to a point where the violet rays would
be in focus. When the photographic dry plates came
into use sensitive to the yellow rays, then lenses were
constructed so as to bring the violet and yellow rays to
the same focus, and such lenses were termed "achro-
matic." For three-color photography it is essential
that the lens be corrected still further, so that the red
rays are also brought to the same focus as the violet
and yellow ones. With some " achromatic '' lenses the
image will have to be focused through each color filter
used, or three times. The difficulty of keeping the
images the same size and maintaining perfect register
under such circumstances need not be pointed out. A
lens properly corrected for chromatic aberration, at the
same time quick working, is essential in three-color
work.
If dry plates and wet plates are to be used it is bet-
ter to have a separate camera and holders for the dry
plates, or at least a special back to the camera adapted
to take dry-plate holders and a ground glass frame.
144
MANUAL OF PHOTOENGRAVING.
TO TEST A LENS FOR ACHROMATISM.
A chart should be carefully drawn, consisting of
outline squares, as shown in the diagram :
B
Y
R
B
Y
R
B
Y
R
Y
R
B
Y
R
B
Y
R
B
R
B
Y
R
B
Y
R
B
Y
B
Y
R
B
Y
R
B
Y
R
Y
R
B
Y
R
B
Y
R
B
R
B
Y
R
B
Y
R
B
Y
B
Y
R
B
Y
R
B
Y
R
Y
R
B
Y
R
B
Y
R
B
R
B
Y
R
B
Y
R
B
Y
CHART FOR TESTING A LKNS FOR ACHROMATISM.
These squares are drawn in outline in the colors
indicated by the letter in the center of each square.
The lines should be made with a ruling pen, the lines
in the different colors being precisely the same width,
with the squares the same distance apart. The red ink
can be used dilute, but should be free from any trace
of blue. The chart should be one and one-half times
larger than the largest plate it is intended to make with
the lens, and should be focused on the blue squares.
A negative of this chart taken on a Cramer slow
isochromatic, a Carbutt polychromatic, a Cadett spec-
trum, or a Lumiere panchromatic plate, will give an
HALF-TONE,
i) Shape, wilh Vignetted El
^MJh^.^^
K^
^
r
1
b3' H^^^^
^l3'''i«^.^^^V>^
<^
MANUAL OF PHOTOENGRAVING. I45
idea of the achromatic property of the lens. If any
squares are out of focus, or if the outer edges of the
squares do not form a perfectly straight line, as in the
drawing, then the lens is not suitable for three-color
negative making.
THREE-COLOR FILTERS OR SCREENS.
The practical three-color worker should not attempt
to make his own three-color filters. The makers of
color-sensitive plates have studied out scientifically the
color filters best adapted to their own make of plates.
It will be a great saving of time and money on the part
of the beginner, at least, if he adopt the color filters
recommended by the maker of the sensitive plates he
intends using.
Color filters are made in several forms. In all cases
the glass used in them must be optically flat. The most
scientific form of filter is the glass cell, filled with an
aniline dye. These can be purchased with a pipette for
filling and emptying them. In another form of color
filter two optically flat glasses are coated with gelatin
first, then stained with the proper dye, and when dry
cemented together with Canada balsam. In another
make of filter collodion is substituted for gelatin as a
medium for holding the dye.
Three-color filters can be purchased from John
Carbutt, of Philadelphia; Lumiere, of France and the
United States; Sanger Shepherd & Co., of England,
and others.
The three-color filters should be used in grooved
slides inside the camera, and immediately behind the
back combination of the lens.
10
14^ MANUAL OF PHOTOENGRAVING.
THE COLOR-SENSITIVE PLATES.
To make the color-record negatives, it is best theo-
retically to use color-sensitive plates sensitive to the
whole spectrum. They should also be developed in the
same kind of developer, its strength and temperature
being maintained the same. Mr. Frederic E. Ives has
invented — United States Patent No. 668,980, Febru-
ary 26, 1 90 1 — an ingenious way of accomplishing this
by securing with a single achromatic lens the three-
color records on a single sensitive plate. If the color
filters are properly balanced this single plate should
contain the three-color record negatives of the same
gradation of density.
John Carbutt's Polychromatic plates, used in com-
bination with a set of three-color filters by the same
maker, is one of the many brands of dry plates that can
be used for the three-color record negatives.
Cadett's Spectrum plates, together with a set of
color filters made by Sanger Shepherd, are used by
some three-color workers.
The Messrs. Lumiere recommend these screens
and plates of their manufacture. With their blue filter
use their Extra Rapid Blue Label plates; with the
green filter, their Orthochromatic, Series A, and with
their orange filter their Orthochromatic, Series B. The
exposures through the orange and green filters are
twelve times longer than the exposure through the blue
filter.
Different plates of the same maker can be used.
For instance, Cramer's " Banner '' plates may be used
for photographing through the blue filter ; the Medium
MANUAL OF PHOTOENGRAVING. I47
Isochromatic for photographing through the green
screen, and " Banner " plates, or Instantaneous Iso-
chromatic, bathed in cyanine, for photographing
through the red screen. The method of resensitizing
dry plates with cyanine will be given later.
ISOCHROMATIC COLLODION EMULSION.
Dr. E. Albert, of Munich, supplies a collodion emul-
sion called " Eos " which can be used in all kinds of
processwork and is made isochromatic for three-color
photography by the addition of sensitizing dyes which
he also furnishes. This emulsion is flowed, in a dark-
room, on the glass plate in the same manner as ordi-
nary collodion, and is then ready for exposure in the
camera. Under favorable conditions it will remain
without drying for almost a half-hour. Emulsion
dispenses with the silver bath. It is used without a
sensitizer when photographing through the blue-violet
screen; with a sensitizer marked "A'' when photo-
graphing through the green screen, and a dye marked
" R. P.'' for use with the red screen. The development
is with hydroquinon, but the other operations of fix-
ing, intensification, " cutting," drying and turning are
the same as in making ordinary wet-plate negatives.
Strong illumination is required for the copy, as the
collodion emulsion is not as sensitive as gelatin dry
plates.
HALATION IN THREE-COLOR RECORD NEGATIVES.
Halation, or reflections from the back surface of
the glass on which the color record negative is made,
must be guarded against, particularly in the negative
148 MANUAL OF PHOTOENGRAVING.
made through the red screen. The makers of color
sensitive plates can furnish them possessing non-hala-
tion properties if so ordered, and as all color-sensitive
plates should be. There are various non-halation
backings in the market, and they should be used as
directed.
RESENSITIZING DRY PLATES.
This is the procedure for rendering a good quality
of dry plate sensitive to the red, for use with the red
screen.
Make the following stock solution and keep it in a
darkroom :
Gruber's or other C. P. cyanine 6 grains.
Absolute alcohol 10 ounces.
The sensitizing bath as wanted is made as follows :
Of the above stock solution 2 ounces.
Alcohol (ninety-five per cent) 2 ounces.
Distilled water 20 ounces.
This sensitizing solution is filtered perfectly into a
porcelain tray, and in an absolutely dark room dry
plates are allowed to soak in this bath for about five
minutes, when they are removed and stood up on
chemically pure blotting paper for fifteen minutes to
drain, after which these plates are bathed in the fol-
lowing bath :
Distilled water 20 ounces.
Alcohol (ninety-five per cent) 2 ounces.
Aqua ammonia Yi ounce.
After rinsing in this bath for a minute they are
placed in an absolutely light-tight drying closet. The
carbonic acid in this closet should be absorbed by a tray
of quicklime.
MANUAL OF PHOTOENGRAVING. I49
The dyeing and washing operations are best carried
out by using one of the makes of cages found in the
market for holding a dozen or more dry plates and
lowering them into an upright bath, which should
contain the resensitizing solutions.
It is customary to perform these resensitizing
operations in the evening or the last thing in the after-
noon so that the plates may be dry by morning. It is
better also to resensitize only sufficient plates for use
the following day.
The important points to remember in resensitizing
dry plates are : the cyanine must be pure, and absolute
alcohol be used to dissolve it in; the same proportion
of alcohol must be used in the washing bath as is used
in the dyeing bath ; that these cyanine plates will not
keep long and that they must be developed in the dark
at first, for a minute or so, and then in a safe light.
To determine if the darkroom light is safe for
resensitized plates, in absolute darkness put a cyanine
dyed plate into a plateholder, pull the slide of the plate-
holder half way out and expose the plate to the light
used in the darkroom for from three to five minutes.
Develop this plate first in the dark as before instructed
and see if there is not a trace of exposure on the half
which was uncovered to the darkroom light.
THE EXPOSURE.
The relative exposures can only be found by experi-
ment, for they depend on the illumination, the lens, the
diaphragms, the density of the color filters and the
sensitiveness of the plates used.
It is recommended that the photographer making
150 MANUAL OF PHOTOENGRAVING.
three-color record negatives keep a day-book in which
is registered for every exposure, the subject, the reduc-
tion or enlargement, lens, color filter, kind and size
of diaphragm, time of day and length of exposure,
together with any other data affecting the negative.
Later, the kind of developer, its temperature, time of
development and comments on the resulting negative
should be added. This daily register will become one
of the most valuable books of reference to the photog-
rapher; it will save much needless experimenting and
waste of material.
Strips of paper containing three patches of color
made from the three colors used in printing the three-
color blocks, together with a patch of black, should be
attached to each piece of copy so that these patches of
color be included in every color-record negative made.
These patches of color are of the utmost value in
development. In fact, without them it is impossible
to determine the correctness of exposure or develop-
ment. These color patches serve afterward to distin-
guish the color-record negatives one from the other.
THE HALF-TONE DIAPHRAGM.
• If from a single half-tone three impressions were
made, one in yellow ink, the second in red ink and the
third in blue ink; if, also, the register was so perfect
that these impressions were exactly over each other,
the result of the three superimposed printings would
appear like a single impression in black ink. If these
printings were repeated and the impressions be out of
register, as they are most likely to be anyhow, then
varying color effects will occur in the proofs.
MANUAL OF PHOTOENGRAVING.
iSi
To prevent, as far as necessary, the different inks
from printing over each other, and to avoid these acci-
dental color effects, it is best to engrave the. half-tones
in lines, so that in printing they can be used at angles
of sixty degrees to each other.
^
o
DIAPHRAGMS WITH ELLIPTICAL APKRTURKS.
To accomplish this with cross-line screens, dia-
phragms with elliptical apertures are used.
These diaphragms should be cut out of printer's
pressboard or ferrotype plate, with the points of the
slits at angles of forty-five degrees to the vertical sides
of the diaphragm.
When used these diaphragms must be exactly in
line with one of the lines of the cross-line screen. To
insure this the plateholder containing the cross-line
screen should be put in its place in the camera, a piece
of ground glass substituted for the sensitive plate, and
the lens turned until the images of the slots in the dia-
phragm make continuous lines on the ground glass.
If the lens is fixed in this position this test as to paral-
lelism of the elliptical stop and one of the lines of the
screen need not be repeated.
152 MANUAL OF PHOTOENGRAVING.
To use these stops more than one-half the exposure
may be given, then the lens capped, the diaphragm
reversed and the remainder of the exposure made. Or
a large elliptical stop may be used to close up the high-
light dots in the negative, and a small elliptical stop,
turned in the opposite direction to the large one, to fur-
nish the small dots in the shadows of the negative.
Another plan is to use these elliptical diaphragms
without reversing, the effect in the half-tone being the
same as if a single-line screen were used.
TO PREVENT PATTERN IN PRINTING.
In Richmond's " Grammar of Lithography," pages
1 70- 1 71, ninth edition, 1886, will be found instructions
for laying down line tints, for color printing in three
colors, in which it is stated : *' The direction of this
second series of lines is very important, and must make
an angle of sixty degrees with those first transferred.
The third transferring is then done, and the result
should be that the lines coincide in direction with the
three sides of an equilateral triangle. The reasons for
putting the lines so exactly in this direction is that the
production of any set pattern is thus avoided."
Ives used this disposition of lines in his three-color
block printing of 1881. Without apparently knowing
this, Albert, in Germany, patented the use of lines at
sixty degrees in 1891. Du Hauron, unaware of its
having been used before, received a patent on it in
France in 1892, and Kurtz, thinking it an original dis-
covery with himself, obtained a United States patent
on it in 1893.
So the angle of sixty degrees, which lithographers
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F-TONE FROM WASH DKAWI\G.
MANUAL OF PHOTOENGRAVING.
153
found generations ago for laying down tints, is the
proper one for the three-color block maker to-day.
To do this a single cross-line screen can be used if
means are provided for rotating either the copy, the
positives or the sensitive plate.
A disadvantage of rotating either the copy or the
positives is that the size of the half-tones it is possible
to make is so much smaller than the screen used.
The makers of screens furnish two cross-line
screens for three-color half-tones that it is best to
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CHART SHOWING THE ANGLES AT WHICH THE HALF-TONE SCREENS IN THE
THREE-COLOR PRINTING BLOCKS SHOULD CROSS EACH OTHER.
adopt. One is the ordinary cross-line screen ruled with
lines at angles of forty-five to its sides. The other is
a special screen made to match the first one both as to
thickness of lines and the spaces between the lines.
154 MANUAL OF PHOTOENGRAVING.
The lines of the second screen are ruled at angles of
seventy-five and one hundred and five degrees to its
sides. This screen can be used one way for the yellow
printing-block and reversed for the red printing-block
negative. Owing to this reversal the two glasses of
which the screen is composed should be of the same
thickness.
THE PROCEDURE IN THREE-COLOR BLOCK MAKING.
The reader is presumed to be familiar with the
half-tone process; it is only necessary to notice here
the additional operations in the making of three-color
blocks.
The previous chapters have told the necessity of
an achromatic lens to bring the red, yellow and blue
rays to precisely the same focus. It has been recom-
mended to purchase the color filters, darkroom lights
and color sensitive plates. It is also better to depend,
for instructions in the development and handling of
whichever brand of plate that is used, on the dry-plate
maker. Just how to resensitize dry plates for special
sensitiveness to the red has been carefully described.
The danger of halation, the necessity of a reliable
source of illumination for the copy, and the value of
a register of the exposures and after treatment has
been urged. How to make the diaphragms and the
kind of half-tone screens to use has been pointed out.
Having all these requisites we will now go over the
operations in making three-color blocks.
We will assume that a water-color sketch is to be
reproduced in color. Fasten the sketch securely to the
copy board. Everything about the camera must be
MANUAL OF PHOTOENGRAVING. I5S
fixed solidly so that there shall be no change in the
relative position of either copy, lens or sensitive plates
during the making of either negatives or positives.
Remember always to have patches of the three-colored
inks, to be afterward used in the printing, attached to
the copy, so as to be phot<^raphed in each negative.
Also have registry marks, one at each side of the copy.
The blue-violet color filter is polished clean and
inserted in its slide behind the lens, and the copy
focused to its proper size. Diaphragm the lens down
until the image is sharp on the ground glass at every
point. Cap the lens and insert the holder containing
the blue sensitive dry plate, draw the slide one-third
the distance, and expose the plate for what might be
considered one-third the time required for the whole
exposure. Cap the lens again, draw the slide out two-
thirds of the way, and expose for the same length of
time as at first, draw the slide out entirely, and expose
once more for the same time. Do not fail to make a
156 MANUAL OF PHOTOENGRAVING.
record of all this in the daily register. Development
of this test plate will determine the proper exposure for
future plates. Repeat this time of exposure test with
the green filter on the green-sensitive plate and on the
red-sensitive plate with the red filter.
The exposure through the green screen is liable to
be from three to twelve times longer than through the
blue-violet screen, while the exposure through the red
screen may be from twelve to twenty times longer than
the exposure through the blue-violet screen.
The relations of the exposures vary with the illumi-
nation of the copy, its reduction or enlargement, the-
density of the color filters, the brands of plates used
and their development, so that the operator must deter-
mine for himself through these time tests the proper
exposures to be given.
DEVELOPMENT.
It is not necessary to go over the method of dry-
plate development. Sufficient is it to caution against
the danger of fogging the green and red sensitive
plates by light in the darkroom. It is best to flow the
developer on these plates in absolute darkness, and
allow the development to proceed for at least a minute
before turning up the light that is considered safe. A
record should be kept of the time taken in development.
REDUCTION OR INTENSIFICATION.
After perfect fixing and a good washing, should
the negatives not correspond in density, this can be
remedied by intensifying the weak negative or reducing
the strong one.
MANUAL OF PHOTOENGRAVING. 1 57
THE POSITIVES.
Positives are made from the three negatives, either
on dry or wet plates, as the operator prefers. Equally
good positives can be produced by either method. The
positives represent in their shadows just how much ink
of each color will be used in the printing. One with a
well-trained eye for color can determine by comparing
them with the original copy whether they possess the
proper color balance — that is, whether, when printed
over each other, the colors will be in the proportion they
are in the copy. The proper color balance can be
restored by careful reduction or intensification of the
positives, either locally or over the whole plates.
THE HALF-TONE NEGATIVES.
The positives are placed in a rotatory holder in the
copy board and turned to the proper angles before
making the half-tone negatives, or, better still, fixed
one after the other in exactly the same position in the
positive holder, and the half-tone screen changed as
explained in the chapter on how " To Prevent Pattern
in Printing."
ETCHING THREE-COLOR BLOCKS.
There is no difference in etching plates for three-
color and etching plates for black printing, only that it
is better to etch all three plates together so that the
color balance may be preserved. The registry marks
having been preserved on the half-tone plates the plates
are turned over to the printer to prove them. If, after
proving, it is found that one color overbalances the
158 MANUAL OF PHOTOENGRAVING.
Other by being too strong, the strong plate can be given
a further etching, or either of the plates can be reetched
locally where necessary.
PRINTING THREE-COLOR BLOCKS.
It is within the power of the printer, by skilful
underlaying of the plate, to modify the result in any
way he pleases, so that corrections can be made in many
ways. There should not be any corrections for the
printer to make after he receives the final proof from
the maker of the plates. The inks should correspond
with the color patches photographed with the copy.
The best inks to use are the ones now used by almost
all the three-color printers.
It was not intended to give in these few chapters
instructions in presswork or the presses to use. Press-
work is a business entirely distinct from three-color
block making, and it is only the latter the writer has
tried to the best of his ability, though briefly, to
explain.
MANUAL OF PHOTOENGRAVING.
159
APPENDIX.
TABLES OF WEIGHTS AND MEASURES
INFORMATION FROM VARIOUS
SOURCES.
MEASURES.
LINEAL.
Mile. Rods. Yards.
Feet.
Inches.
I — 320 — 1760 —
5280
— 63360
I - 5>^ -
I6>^
— 198
I
3
- 36
I
12
SURFACE.
Acre. Roods. Sq. Rods. Sq. Yds.
Sq. Ft.
I — 2560 — 102400 — 3097600
— 27878400
I 160
4840
— 43560
I —
30X
— 2-J2%
I
— 9
VOLUME.
Gallon. Quarts. Pints.
Gills.
Cubic Inches.
I — 4 — 8 —
32 =
= 231
I 2
16
I —
4
FLUIDS.
Gallon. Pints. Ounces. Drams.
Minims.
Cubic Centim's.
I 8 128 1024
6l/|/Io
— 3785435
I — 16 — 128 —
7680
— 473179
I — 8 —
480
— ^574
I —
60
— 3697
i6o
MANUAL OF PHOTOENGRAVING.
Pound.
I
WEIGHTS.
TROY.
Pound. Ounces. Pennyweight. Grains.
I = 12 = 240 = 5760
I = 20 = 480
I = 24
apothecaries'.
Drams. Scruples.
= 96 =
Grams.
373.24
31.10
1.56
Ounces.
12
I
8 =
I =
288
24
3
I
Grains.
5760
480
60
20
I
Grams.
373-24
31-10
3.89
1.30
.06
AVOIRDUPOIS.
Pound. Ounces. Drams. Grams.
I = 16 = 256 = 453-60
I = 16 = 28.35
I = 1.77
I gram = 15.43 grains = .03215 troy ounces = .03527 avoir-
dupois ounces.
I grain = .0648 grams.
I pound avoirdupois = lyVj pounds troy = i^V pounds
apothecaries'.
I ounce avoirdupois = i^/^ ounces troy = i^^^ ounces
apothecaries'.
I pound troy = i pound apothecaries'.
I ounce ** =1 ounce **
I grain
I pennyweight
((
= I gram
= f dram
((
PROVING COLOR PLATES.
Mr. J. H. Siedenburg, of New York, says The Inland
Printer, has devised the following method of proving color
plates : In a worthless piece of zinc, say 10 by 12 in size, ^32"
inch holes are drilled in diagonal corners. Short pieces of a
steel needle are driven into these holes and soldered there.
HALF-TONE FROM RETOUCHED PHOTOGRAPH.
M**
MANUAL OF PHOTOENGRAVING. l6l
after which the upper ends of the needles are filed to sharp
points. This he calls the " ground plate." After photographing
and etching the color plates, one of them is taken and clamped
securely to the center of the ground plate; ^/^^-inch holes are
drilled through the regular registry points, which were, of
course, on the copy and photographed on each plate. These
holes are bored through both the color plate and the ground
plate. Now two blocking brads about ^/„„ inch thick are driven
through the ground plate holes from the back and cut off to
height of thickness of color plate. With nail set, punch the
metal around the brads to hold them rigid. When ^/,_-inch
holes are bored in the center of the registry points in the other
color plates they are all ready for proving. When the first color
plate is proved the needle points in the ground plate puncture
holes in the proof, which are used to register the paper in the
subsequent printings, while the steel brads keep the plates in
register.
TO CHANGE THE READING OF ONE THERMOM-
ETER SCALE TO THAT OF ANOTHER.
Fahrenheit to Centigrade. — Subtract 32 from the Fahrenheit
reading and multiply the result by ^/g.
Fahrenheit to Reaumur. — Subtract 32 from Fahrenheit
reading and multiply result by */q.
Centigrade to Fahrenheit. — Multiply Centigrade reading by
^/g and add 32 to the result.
Centigrade to Reaumur. — Multiply the Centigrade reading
by Vy
Reaumur to Fahrenheit. — Multiply the Reaumur reading by
^'/^ and add 32.
Reaumur to Centigrade. — Multiply the Reaumur reading
by v.-
RESIST FOR LINE ETCHINGS.
Instead of using dragon's-blood to form a resist for the
first bite in line etching, some etchers prefer rosin and graphite,
in a very finely powdered form. After the plate is dried the
rosin is applied and all surplus carefully dusted from the plate,
11
l62 MANUAL OF PHOTOENGRAVING.
which is then heated just enough to cause that which adheres
to the ink to be burned into it. Then. the graphite is applied
and treated in a similar manner. After the first etch, dragon's-
blood is used, as described in the chapter on line etching.
A WHIRLER FOR COATING HALF-TONE PLATES.
A very convenient whirler, especially adapted for plates of
not very large dimensions, may be made as follows :
Remove the handle from a plumber's force cup. Onto the
stem of a small drill stock screw a nut, then slip a washer on,
insert the stem through the hole in the cup, then slip on another
washer, and finally screw another nut down to make the joint
^
air tight. (If the drill stock has not a stem with a threaded
end, but is provided with a chuck, fasten a threaded bolt of
proper diameter into the chuck.) To use the whirler, wet the
back of the plate, also the rim of the cup, and press it down
upon the plate until it adheres. Then flow the face of the plate
as usual, invert and v/hirl over the gas stove until the coating is
dry. The illustration below will indicate the construction and
use of this whirler.
ENAMEL FOR ZINC.
A contributor to The Inland Printer recommends the fol-
lowing :
Water i6 ounces
Glue 8 ounces
Bichromate ammonia 350 grains
Citrate of iron and ammonia 50 grains
MANUAL OF PHOTOENGRAVING. 1 63
After printing develop as usual and burn into a golden yellow
or brown color. This formula is said to print very quickly.
INTENSIFYING NEGATIVES.
Instead of using ammonium sulphide to blacken the nega-
tive after intensifying with the copper and silver solutions,
some operators use ferrous oxalate. The solution may be pre-
pared as follows :
Make a saturated solution ferrous sulphate and a saturated
solution potassium oxalate. Keep in separate bottles, but when
ready to use mix one part of the first with three parts of the
second, by pouring the iron into the oxalate solution. Wash
the negative very thoroughly after blackening.
A DRY ENAMEL PROCESS.
The following formula appears in The Inland Printer for
March, 1902:
Water 15 ounces
Albumen 7 ounces
White rock candy ^ ounce
Bichromate ammonia ^ ounce
Chromic acid 35 grains
Aqua ammonia J4 ounce
Mix in order given and filter thoroughly. Coat and dry
plate as usual. Before printing rub the negative with a little
lard on a piece of cotton, to prevent sticking, and have negative
and metal of same temperature. Expose two to three minutes
in sunlight, or five to eight minutes by electric light. To
develop rub over the image powdered washing soda that has
been sifted through cheese-cloth. The powder will adhere to
the unexposed parts. The development should be done in the
darkroom, and the atmosphere should not be too dry. If
necessary, moisten it by sprinkling the floor with water. When
the image appears completely developed, burn into a deep
cherry color, and while plate is hot plunge it into cold water
and rub away the. powder with wet cotton. If the powder
164 MANUAL OF PHOTOENGRAVING.
should stick to any portion of the image finely powdered salt
applied to that part will remove the powder.
A German authority, Herr Tschorner, gives the following
formulae :
Sugar 250 grains
Gum arabic 30 grains
Ammonium bichromate 155 grains
Water 8 ounces, 2 drams
Chromic acid (35 per cent sol.) 35 minims
Very even films on a zinc plate are given by this formula.
After developing with magnesium carbonate, burning in is
done at 380° Fahr., and a fine, hard enamel obtained, which
resists even strong nitric acid etching. When using a mixture
of gum arabic and grape sugar, development is still easier.
The formula is :
Grape sugar 185 grains
Gum arabic 31 grains
Ammonium bichromate 154 grains
Water 7 ounces, 3 drams
Chromic acid (10 per cent sol.) 35 minims
The film burns in at 380° Fahr., and gives a very hard enamel.
Grape sugar and dextrin is another good formula, as follows :
Grape sugar 154 grains
Dextrin 31 grains
Ammonium bichromate 154 grains
Water 7 ounces, 3 drams
Chromic acid (10 per cent sol.) I5 to 35 minims
The print develops well, burns in at 380° Fahr., and gives a
hard enamel. Likewise excellent is a mixture of grape sugar
and albumen, like this :
Grape sugar 185 grains
Dry egg albumen 31 grains
Ammonium bichromate 154 grains
Water 4 ounces, 2 drams
Either of the above enamels is poured as usual on a carefully
cleaned zinc plate and dried over heat. The plate must be
MANUAL OF PHOTOENGRAVING. 165
fairly warm, or the negative is apt to stick to the sensitive
film when printing. Exposure in bright sunlight runs to about
three or four minutes under a line or half-tone negative; it is
then dusted over (developed) with finely powdered magnesium
carbonate by means of a brush or tuft of cotton. After burn-
ing in it is ready for etching in a five per cent nitric acid bath,
to which some thick gum arabic, dextrin or glue has been
added.
TO PREPARE PERCENTAGE SOLUTIONS.
For each fluid ounce of water take of the salt 4.557 grains
to make a i per cent solution, twice the amount for a 2 per cent
solution, etc.
When stated in parts per 1,000, etc., for each fluid ounce
of water take of the salt 0.4557 to make i part in 1,000, twice
the amount to make i part in 500, ten times the amount to
make i part in 100, etc.
FINDING SCREEN DISTANCES BY FOCUSING.
Count Turati suggests the following method for deter-
mining the correct separation of the screen and sensitive plate :
With Canada balsam cement a thin piece of microscope
glass to the center of the inside surface of the ground glass.
Focus the image sharply, insert a stop with square aperture,
in the lens, and gradually move the screen by means of the
gear, closely examining the center of the ground glass with a
magnifier. As the screen approaches dark dots will be noticed,
gradually becoming more distinct and larger, and if the size
of the aperture is correct they will join at the corners in the
high lights and appear of the dimensions required in a good
negative. They will not be very sharply defined, but if the
correct distance is passed and the screen brought too near to
the ground glass, the dots will disappear and be replaced by
the image of the screen lines. If at all positions that the screen
may be placed the dots are blurred, and if the lines are indis-
tinct when the distance is at a minimum, it indicates that the
aperture is too large, and a stop with smaller one should be
l66 MANUAL OF PHOTOENGRAVING.
tried. A stop that ts too small will require a screen distance
too great.
Mr. Levy offers the following suggestion for determining
the distance to correctly render the shadows:
Insert a round stop of a size from f-22 to f-32, and focus
the screen until a small black cross appears sharp in the center
of each dot. The distance is then correct, and the greater part
of the exposure should be given with this stop, and the balance
with a stop having a square aperture of proper size to close up
the high lights.
PRINTING METHODS.
BLUE PRINTS — WHITE LINES ON BLUE GROUND.
1. Citrate of iron and ammonia i ounce
Water 4 ounces
2. Red prussiate of potassium i ounce
Water 4 ounces
Dissolve and mix the two solutions, coat the paper with
sponge or absorbent cotton wet with solution, dry in dark and
print under negative until details are visible. Then develop by
washing under tap.
It is stated that blue-prints may be bleached by a very dilute
solution of potassium carbonate and potassium hydrate, after
which they should be flowed with dilute hydrochloric acid and
washed. This being the case, they may be used similar to silver
prints, as described in Chapter XIII.
BLUE LINES ON WHITE GROUND.
Gum arabic 385 grains
Sodium chlorid 46 grains
Tartaric acid 62 grains
Perchlorid iron 123 grains
Water 3H grains
Coat paper and dry in dark. After exposure, develop in sat-
urated solution of potassium ferrocyanide. Fix in i to 20
solution of hydrochloric acid. Wash.
MANUAL OF PHOTOENGRAVING. 167
BLACK LINES ON WHITE GROUND.
Oxalic acid 5 grains
Ferric chlorid 10 grains
Water 3 ounces
After printing, develop in 15 per cent solution of ferrocyanide
of potassium ; wash and fix in 10 per cent solution of hydro-
chloric acid. Wash.
ANOTHER PROCESS.
Water 300 cu. centimes
Gelatin 10 grams
Ferric chlorid, in thick solution. . 20 cu. centimes
Tartaric acid 10 grams
Ferric sulphate 10 grams
When paper is dry, expose under negative and develop in
Gallic acid 20 grams
Alcohol 200 cu. centimes
Water i liter
and wash.
A SUBSTITUTE FOR GROUND GLASS.
There is scarcely any accident more aggravating to the photo-
engraver than the breaking of the camera ground glass. As
it is of frequent occurrence and it is difficult to obtain glass
ground fine enough for the purpose, it behooves the photog-
rapher to be provided with the following varnish, which fur-
nishes an excellent substitute for ground glass :
Sulphuric ether 4 ounces
Benzole 2 ounces
Alcohol Yi ounce
Gum sandarac or dammar 100 to 150 grains
If too much alcohol is used it will give a transparent instead of
a ground glass effect. Flow this varnish on a sheet of plain
glass, like collodion. It dries quickly and without heat, and
1 68 MANUAL OF PHOTOENGRAVING.
should give an excellent imitation of ground glass. In passing
it might be said that if a little glycerin is rubbed into the grain
of an ordinary ground glass it renders it much easier to focus
on. It is best to rub it over but a portion of the ground glass,
•say a strip from the center to one edge.
PLAIN PHOTOGRAPHIC PAPER.
It is an easy matter to prepare one's own paper and it will
keep for any length of time. All that is necessary is to use a
good quality linen paper and soak it in a weak sizing of gelatin
containing a chlorid salt, so that when applying nitrate of
silver afterward to this paper a chlorid of silver will be
formed. The following is an excellent formula : Take a smooth
linen paper, if it is to be used for pen-and-ink work, or a rough
paper like Whatman's drawing paper if for washwork, and
immerse it in a warm solution of the following :
Water i ounce
Gelatin 12 grains
Chlorid of ammonium 8 grains
When the paper is soaked with this liquid hang it up to dry.
It will keep indefinitely. To sensitize this paper use :
Water i ounce
Nitrate of silver 50 grains
Nitric acid 15 grains
VARNISHES.
VARNISH FOR COLLODION NEGATIVES.
Water 30 ounces
Borax i]^ ounces
White shellac 4 ounces
Glycerin ^ ounce
Dissolve the borax in the water, then add the shellac and warm
the water, keeping it so until the shellac is dissolved, then add
the glycerin.
HALF-TONE FROM RETOUCHED PHOTOGRAPH.
HALF-TONE FROM RETOUCHED PHOTOGRAPH.
MANUAL OF PHOTOENGRAVING. 169
DEAD BLACK VARNISH.
Gum lac 30 grams
Alcohol 200 cu. centim's
Dissolve.
Lampblack 60 grams
Alcohol 40 cu. centim's
Dissolve and add to the gum solution.
PERCHLORID OF IRON SOLUTION FROM LUMPS
OF THE SALT.
Process Work gives the following directions for reducing
perchlorid of iron in lumps to a solution for etching: Take
seven pounds of perchlorid and boil in an enameled iron pan
in five pints of water; when the perchlorid has completely-
dissolved the solution will be transparent. Take out a couple
of ounces and stir into this portion strong liquid ammonia; the
result will be a thick, pasty precipitate of ferric hydrate, which
should be turned into a filter paper in a funnel and be washed
free from ammonia by letting water filter through it. When
the drippings from the filter no longer give a blue tinge to red
litmus paper, the washing is complete. Take an ounce of per-
chlorid from the boiled solution and add a small quantity of
the pasty hydrate to it. If all the hydrate is dissolved more
will be required, and when it is seen that the hydrate is no
longer taken up with the solution it will be evident that the
latter contains no longer any free acid, and is in a suitable
condition for etching. Having noted the quantity used in the
test you will know how much is required by the bulk. It will
not matter if a bit too much is put in, as it will filter out. It is
best to filter the liquid. A solution prepared in this way will
be transparent, and will not become muddy and green as that
which contains free acid. It will also be ready for use at once,
and will not be likely t^^. depo.sit the green scum of oxide on
the plate, which is so difficult t^p rerpove.; The solution should
be diluted to 35 degrees Beauriiel
•> > i"
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Contains 86 pages.
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