on the boards they are to occupy when mounted, and, as it is impossible
to remove a print for readjustment once it is laid down for final
mounting, the wisest course is to indicate by faint pencil marks on the
mount the exact position the print is to occupy; then it may be laid
down accurately and without any indecision. A small gas or oil stove is
required on the mounting table to keep the glue liquid, but maintaining
the solution in a constant state of ebullition throughout the operation
is unnecessary and harmful to the glue; the flame should be regulated
so that the mountant is kept just at the melting point. Place the
drawing board beside the gas stove and with a house-painter’s brush
of good quality and size spread the glue over an area considerably
exceeding the dimensions of the print to be mounted. A thin coating of
glue evenly applied to the board is the end to aim at, to accomplish
which the brush should be worked in horizontal strokes, crossing these
with others at right angles. Have at hand a small pile of paper cut
into pieces somewhat larger than the print to be mounted (old newspaper
answers admirably for these pieces), lay one down on the glued patch
and press it well into contact by passing the closed hand across it in
all directions. Raise one corner of the paper, and slowly but firmly
strip it from the board. Repeat the operations of gluing the board
(in the same place) and stripping the newspaper 2 or 3 times, when a
beautifully even cushion of glue will remain on the board.
Mounting the prints is the next step. The cushion of glue obtained on
the board has to be coated with glue for, say, every second print, but
the amount applied must be as small as possible. After applying the
glue the print is laid down upon it, a square of the waste newspaper
laid over the print, which has then to be rubbed well into contact with
the glue. Raise a corner of the print with the point of a penknife
and strip it from the board, as in the case of the newspaper. Care
must be taken when handling the print in its glued condition to keep
the fingers well beyond the edges of the print, in order that no glue
may be abstracted from the edges. Lay the print quickly down upon
its mount; with a clean, soft linen duster smooth it everywhere into
contact, place upon it a square of photographic drying board, and with
the bone burnisher go over it in all directions, using considerable
pressure. The finished result is a mounted print that shows no signs of
buckling, and which adheres to the mount with perfect tenacity.
II.—Gelatin 2 parts
Water 4 parts
Alcohol 8 parts
The alcohol is added slowly as soon as the gelatin is well dissolved in
the water, and the vessel turned continually to obtain a homogeneous
mixture. The solution must be kept hot during the operation on a water
bath, and should be applied quickly, as it soon dries; the print must
be placed exactly the first time, as it adheres at once. The solution
keeps for a long time in well-corked bottles.
«TRANSPARENT PHOTOGRAPHS:»
I.—The following mixture may be employed at 176° F., to render
photographs transparent. It consists of 4 parts paraffine and 1 part
linseed oil. After immersion the photographs are at once {546} dried
between blotting paper. For fastening these photographs to glass, glue
or gelatin solution alone cannot be employed. This is possible only
when one-fourth of its weight of sugar has been added to the glue
before dissolving. The glasses for applying the photographs must be
perfect, because the slightest defects are visible afterwards.
II.—If on albumen paper, soak the print overnight in a mixture of 8
ounces of castor oil and 1 ounce of Canada balsam. Plain paper requires
a much shorter time. When the print is thoroughly soaked, take it from
the oil, drain well, and lay it on the glass face downward, and squeeze
till all is driven out and the print adheres. If a curved glass is
used, prepare a squeegee with edge parallel with the curvature of the
glass. It will take several hours before the print is dry enough to
apply color to it.
«THE GUM - BICHROMATE PHOTO-PRINTING PROCESS.»
Gum bichromate is not a universal printing method. It is not suited
for all subjects or for all negatives, but where there is simplicity
and breadth in sizes of 8 1/2 x 6 1/2 and upward, direct or
enlarged prints by it have a charm altogether their own, and afford an
opportunity for individuality greater than any other method.
While almost any kind of paper will do, there are certain qualities
that the beginner at least should endeavor to secure. It should be
tough enough to stand the necessary handling, which is considerably
more than in either the printing-out or developing methods. It must
not be so hard or smooth as to make coating difficult, nor so porous as
to absorb or let the coating sink in too much; but a few trials will
show just what surface is best. Till that experience is acquired it may
be said that most of Whatman’s or Michallet’s drawing papers, to be had
at any artist’s materials store, will be found all that can be desired;
or, failing these, the sizing of almost any good paper will make it
almost as suitable.
For sizing, a weak solution of gelatin is generally employed, but
arrowroot is better; half an ounce to a pint of water. It should be
beaten into a cream with a little of the water, the rest added, and
brought to the boil. When cold it may be applied with a sponge or
tuft of cotton, going several times, first in one direction and then
in the other, and it saves a little future trouble to pencil mark the
non-sized side.
The quality of the gum is of less importance than is generally
supposed, so long as it is the genuine gum arabic, and in round, clean
“tears.” To make the solution select an 8-ounce, wide-mouthed bottle,
of the tall rather than the squat variety, and place in it 6 ounces of
water. Two ounces of the gum are then tied loosely in a piece of thin
muslin and suspended in the bottle so as to be about two-thirds covered
by the water. Solution begins at once, as may be seen by the heavier
liquid descending, and if kept at the ordinary temperature of the room
may not be complete for 24 or even 48 hours; but the keeping qualities
of the solution will be greater than if the time had been shortened
by heat. When all that will has been dissolved, there will still be a
quantity of gelatinous matter in the muslin, but on no account must it
be squeezed out, as the semi-soluble matter thus added to the solution
would be injurious. With the addition of a few drops of carbolic acid
and a good cork the gum solution will keep for months.
The selection of the pigments is not such a serious matter as some of
the writers would lead us to believe. Tube water colors are convenient
and save the trouble of grinding, but the cheap colors in powder take
a better grip and give richer images. The best prints are made with
mixtures of common lampblack, red ocher, sienna, umber, and Vandyke
brown, the only objection to their employment being the necessity of
rather carefully grinding. This may be done with a stiffish spatula
and a sheet of finely ground glass, the powder mixed with a little gum
solution and rubbed with the spatula till smooth, but better still
is a glass paper weight in the shape of a cone with a base of about
1 1/2 inches in diameter, bought in the stationer’s for 25 cents.
The sensitizer is a 10 per cent solution of potassium bichromate,
and whatever be the pigment or whatever the method of preparing the
coating, it may be useful to keep in mind that the right strength or
proportion, or at least a strength of coating that answers very well,
is equal parts of that and the gum solution.
In preparing the coating measure the gum solution in a cup from a toy
tea set that holds exactly 1 ounce, it being easier to get it all
out of this than out of a conical graduate. From 20 to 30 grains of
the color or mixture of colors in powder is placed on the slab—the
ground surface of an “opal” answers well—and enough of the gum added
to moisten it, and work the paper weight “muller,” aided by the {547}
spatula, as long as any grittiness remains, or till it is perfectly
smooth, adding more and more gum till it is like a thick cream. It
is then transferred to a squat teacup and 1 ounce of the bichromate
solution gradually added, working it in with one of the brushes to
perfect homogeneity. Of course, it will be understood that this mixture
should be used all at once, or rather only as much as is to be used
at once should be made, as notwithstanding what has been said to the
contrary, it will not keep. After each operation, both or all of the
brushes should be thoroughly cleaned before putting them away.
Not the least important are the brushes; one about 2 inches wide and
soft for laying on the coating, the other, unless for small work, twice
that breadth and of what is known as “badger” or a good imitation
thereof, for softening.
The paper can be bought in sheets of about 17 x 22 inches. Cut these
in two, coating pieces of about 17 x 11. The sheet is fastened to a
drawing board by drawing pins, one at each corner. The coating brush—of
camel’s hair, but it is said that hog’s is better—is filled with
the creamy mixture, which has been transferred to a saucer as more
convenient, and with even strokes, first one way and then the other,
drawn all over the paper. It is easier to do than to describe, but all
three joints, wrist, elbow, and shoulder take part, and unless the
surface of the paper is too smooth, there is really no difficulty to
speak of.
By the time the whole surface has been covered the paper will have
expanded to an extent that makes it necessary to remove three of the
pins and tighten it, and then comes the most important and the only
really difficult part of the work, the softening. The softener is
held exactly as one holds the pen in writing, and the motion confined
altogether to the wrist, bringing only the points of the hair in
contact with the coating, more like stippling than painting.
If much of the coating has been laid on, and too much is less of an
evil than too little, the softener will soon have taken up so much as
to require washing. This is done at the tap, drying on a soft cloth,
and repeat the operation, the strokes or touches gradually becoming
lighter and lighter, till the surface is as smooth and free from
markings as if it had been floated.
Just how thick the coating should be is most easily learned by
experience, but as, unlike ordinary carbon, development begins from the
exposed surface, it must be as deep; that is, as dark on the paper as
the deepest shadow on the intended print, and it should not be deeper.
While it is true that the bichromate colloid is not sensitive while
wet, the coating is best done in subdued light, indeed, generally at
night. Hang the sheets to dry in the dark room.
Exposure should be made with some form of actino-meter.
Development may be conducted in various ways, and is modified according
to the extent of the exposure. Float the exposed sheet on water at
the ordinary temperature from the tap. The exposure should admit of
complete, or nearly complete, development in that position in from 5 to
10 minutes; although it should not generally be allowed to go so far.
By turning up a corner from time to time one may see how it goes, and
at the suitable stage depending on what one really wants to do, the
otherwise plain outcome of the negative is modified, gently withdrawn
from the water, and pinned up to dry.
The modifying operation may be done at once, where the exposure has
been long enough to admit it, but generally, and especially when it
has been such as to admit of the best result, the image is too soft,
too easily washed off to make it safe. But after having been dried and
again moistened by immersion in water, the desired modification may be
made with safety.
The moistened print is now placed on a sheet of glass, the lower end
of which rests on the bottom of the developing tray, and supported
by the left hand at a suitable angle; or, better still, in some other
way so as to leave both hands free. In this position, and with water
at various temperatures, camel’s-hair brushes of various sizes, and a
rubber syringe, it is possible to do practically anything.
«TABLES AND SCALES:»
«Comparative Exposures of Various Subjects.»—
Seconds
Open panorama, with fields and trees 1
Snow, ice, marine views 1
Panorama, with houses, etc. 2
Banks of rivers 3
Groups and portraits in open air (diffused light) 6
Underneath open trees 6
Groups under cover 10
Beneath dense trees 10
Ravines, excavations 10
Portraits in light interiors 10
Portraits taken 4 feet from a window, indoors, diffused light 30
{548}
«TABLE SHOWING DISPLACEMENT ON GROUND GLASS OF OBJECTS IN MOTION»
By Henry L. Tolman
_From the Photographic Times_
Lens 6-inch Equivalent Focus, Ground Glass at Principal Focus of Lens
──────+─────────────+─────────────────+─────────+──────────
Miles │ Feet │ Distance on │ Same │ Same
per │ per Second. │ Ground Glass, │ with │ with
Hour. │ │ in inches, with │ Object │ Object
│ │ Object 30 Feet │ 60 Feet │ 120 Feet
│ │ away. │ away. │ away.
──────+─────────────+─────────────────+─────────+──────────
│ │ │ │
1 │ 1 1/2 │ .29 │ .15 │ .073
2 │ 3 │ .59 │ .29 │ .147
3 │ 4 1/2 │ .88 │ .41 │ .220
4 │ 6 │ 1.17 │ .59 │ .293
5 │ 7 1/2 │ 1.47 │ .73 │ .367
6 │ 9 │ 1.76 │ .88 │ .440
7 │ 10 1/2 │ 2.05 │ 1.03 │ .513
8 │ 12 │ 2.35 │ 1.17 │ .587
9 │ 13 │ 2.64 │ 1.32 │ .660
10 │ 14 1/2 │ 2.93 │ 1.47 │ .733
11 │ 16 │ 3.23 │ 1.61 │ .807
12 │ 17 1/2 │ 3.52 │ 1.76 │ .880
13 │ 19 │ 3.81 │ 1.91 │ .953
14 │ 20 1/2 │ 4.11 │ 2.05 │ 1.027
15 │ 22 │ 4.40 │ 2.20 │ 1.100
20 │ 29 │ 5.87 │ 2.93 │ 1.467
25 │ 37 │ 7.33 │ 3.67 │ 1.833
30 │ 44 │ 8.80 │ 4.40 │ 2.200
35 │ 51 │ 10.27 │ 5.13 │ 2.567
40 │ 59 │ 11.73 │ 5.97 │ 2.933
──────+─────────────+─────────────────+─────────+──────────
W. D. Kilbey, in the _American Annual of Photography_, gives still
another table for the exposure that should be given to objects in
motion.
According to his method the table is made out for a distance from the
camera 100 times that of the focus of the lens; that is, for a 6-inch
focus lens at 50 feet, a 7-inch at 58 feet, an 8-inch at 67 feet, a
9-inch at 75 feet, or a 12-inch at 100 feet.
Toward At Right
the Angles to
Camera. the Camera.
Man walking slowly, street scenes 1/15 sec. 1/45 sec.
Cattle grazing 1/15 sec. 1/45 sec.
Boating 1/20 sec. 1/60 sec.
Man walking, children playing, etc. 1/40 sec. 1/120 sec.
Pony and trap, trotting 1/100 sec. 1/300 sec.
Cycling, ordinary 1/100 sec. 1/300 sec.
Man running a race and jumping 1/150 sec. 1/450 sec.
Cycle racing 1/200 sec. 1/600 sec.
Horses galloping 1/200 sec. 1/600 sec.
If the object is twice the distance, the length of allowable exposure
is doubled, and vice versa.
«To Reduce Photographs.»—When one wishes to copy a drawing or
photograph he is usually at a loss to know how high the plate will be
when any particular base is selected. A plan which has the merit of
being simple and reliable has been in use in engravers’ offices for
years.
Here are the details:
[Illustration: Reducing Scale for Copying Photographs.]
Turn the drawing face down and rule a diagonal line from the left
bottom to the right top corner. Then measure from the left, on the
bottom line, the width required. Rule a vertical line from that point
until it meets the diagonal. Rule from that point to the left, and the
resulting figure will have the exact proportions of the reduction.
If the depth wanted is known, and the width is required, the former
should be measured on the left upright line, carried to the diagonal,
and thence to the lower horizon. The accompanying diagram explains the
matter simply.
«COLOR PHOTOGRAPHY:»
«A Three-Color Process.»—Prepare 7 solutions, 4 of which are used for
color screens, the remaining 3 serving as dyes for the plates.
A.—Screen Solutions.—
Blue violet.
By weight
Methylene blue 5 parts
Tetraethyldiamidooxytriphenyl carbinol 2 parts
Or:
By weight
Methyl violet 5 parts
Alcohol 200 parts
Water, distilled 300 parts
Green.
By weight
Malachite green 10 parts
Alcohol 200 parts
Water, distilled 300 parts
{549}
Yellow.
By weight
Acridin yellow N. O. 10 parts
Alcohol 200 parts
Water, distilled 300 parts
Red.
By weight
Congo rubin 10 parts
Alcohol 200 parts
Water, distilled 300 parts
B.—Dyes (Stock Solutions).—
By weight
I.—Acridin yellow or acridin orange, N. O. 1 part
Alcohol 100 parts
Water, distilled 400 parts
By weight
II.—Congo rubin 1 part
Alcohol 100 parts
Water, distilled 400 parts
By weight
III.—Tetraethyldiamidooxytriphenyl carbinol 1 part
Alcohol 100 parts
Water, distilled 400 parts
The screen solutions, after being filtered through paper filters into
clean dishes, are utilized to bathe 6 clean glass plates previously
coated with 2 per cent raw collodion; we require 1 plate for blue
violet, 2 plates for red, 2 plates for yellow, and 1 plate for green,
which in order to obtain the screens are combined in the following
way: Yellow and red plate, yellow and green plate. For special purposes
the other red plate may be combined with the blue violet. Another
method of preparing the screens is to add the saturated solutions drop
by drop to a mixture of Canada balsam and 2 per cent castor oil and
cement the glasses together. Those who consider the screens by the
first method too transparent, coat the glass plates with a mixture of
2 to 3 per cent raw collodion and 1 per cent color solution. Others
prefer gelatin screens, using
By weight
Hard gelatin (Nelson’s) 8 parts
Water 100 parts
Absolute alcohol 10 parts
Pigment 1 part
This is poured over the carefully leveled and heated plate after having
been filtered through flannel.
The collodion screens are cemented together by moistening the edges
with Canada balsam (containing castor oil) and pressing the plates
together in a printing frame, sometimes also binding the edges with
strips of Japanese paper.
On the evening before the day of work, good dry plates of about 18° to
24° W. are dyed in the following solution:
By weight
Stock solution, No. 1 16 parts
Distilled water 100 parts
Alcohol 5 parts
Nitrate of silver (1.500) 50 parts
Ammonia 1–2 parts
This bath sensitizes almost uninterruptedly to line A. The total
sensitiveness is high, and the plate develops cleanly and fine. Blue
sensitiveness is very much reduced, and the blue screen is used for
exposure. As far as the author’s recollection goes, the plate for the
yellow color has never been color-sensitized, many operators using the
commercial Vogel-Obernetter eosin silver plates made by Perutz, of
Munich; others again only use ordinary dry plates with a blue-violet
screen. This is, however, a decided mistake, necessitating an immense
amount of retouching, as otherwise it produces a green shade on
differently colored objects of the print.
For the red color plate the dry plate is dyed in
By weight
Stock solution, No. 2 10 parts
Distilled water 100 parts
Nitrate of silver (1.500) 100 parts
Ammonia 2 parts
The resulting absorption band is closed until E, reaching from violet to
red (over C). This red pigment was examined by Eder, who obtained very
good results, using ammonia in the solution.
The corresponding screen is a combination of malachite green with
acridin yellow or acridin orange N. 0.
For the blue color plate the dye is made up as follows:
By weight
Stock solution, No. 3 0.5–1 part
Distilled water 100 parts
Nitrate of silver (1.500) 100 parts
Ammonia 1–2 parts
This dye yields a strong band, commencing at B, reaching to C 3/4 D;
since the orange screen used herewith necessitates a long exposure, the
action seems to extend into the infra-red (beyond A).
As a rule, cyanine is used instead of the tetraethyldiamidooxytriphenyl
carbinol {550} (HCl salt), but the former is apt to produce fogged
plates. Methyl violet or crystal violet has also been suggested.
Exposures should be made in direct sunlight or with artificial pure
white light (acetylene); electric light is too variable.
The most suitable methods of reproduction are half-tone, and the
prototype methods; also Turati’s Isotypie. The greatest difficulty
in 3-color printing nowadays is presented by the want of accurate
printing. We must use the proper paper and pure fast colors; the inking
rollers should be smooth, not too soft, and free from pores or weals.
The blocks must be firmly fixed typehigh, otherwise they take color
irregularly. A good printing machine is, of course, most essential.
To supplement the above working directions: After having kept the
plates for 2 or 3 minutes (constantly moving the dish) in the dyes,
they are removed into a dish containing filtered alcohol, which
extracts the superfluous pigment. Plates thus treated dry much more
rapidly, develop cleaner, and show no fogging.
Most of the above dyes may be obtained from the “Berliner
Actiengesellschaft für Anilinfabrikation,” the acridin only from the
“Farbwerk Mühlheim, a/Main, vorm. A. Leonhard & Company.”
«Solution for Preparing Color Sensitive Plates.»—H. Vollenbruch
maintains that plates sensitized with erythrosin silver citrate are not
only more sensitive to color impressions, but also have better keeping
qualities than ordinary erythrosin bathed plates.
For depression of the over-active blue rays he recommends the addition
of picric acid to the coloring solution. The picric acid erythrosin
silver citrate ammonia solution is prepared as follows:
_Solution I_
Citrate of potassa 1 gram
Distilled water 10 cubic centimeters
_Solution II_
Silver nitrate 1 gram
Distilled water 10 cubic centimeters
Both solutions are mixed and a white precipitate is formed which
is allowed to subside. The clear supernatant liquid is poured off
carefully, precipitate washed with water, allowed again to subside, and
the wash water again decanted. This process is repeated two or three
times. Finally a large bulk of water (20 cubic centimeters) is added
to the precipitate and well shaken; 5 cubic centimeters of this is
reserved, the remainder is treated to ammonia, drop by drop, until the
precipitate is redissolved. Now add the 5 cubic centimeters of reserved
solution and shake the whole until every particle is dissolved. Then
make up the solution to 50 cubic centimeters and filter; this forms
Solution III.
_Solution IV_
Distilled water 300 cubic centimeters
Pure erythrosin 1 grain
Under lamplight the 50 cubic centimeters of Solution III are poured
slowly with repeated shaking in Solution IV, by which the originally
beautiful red is converted into a dirty turbid bluish red somewhat
viscid fluid; add—
_Solution V_
Picric acid 4 grams
Absolute alcohol 30 cubic centimeters
Shake well, and add to the whole 33 cubic centimeters ammonia (specific
gravity, 0.91), wherewith the beautiful red color is restored.
After the filtration call this Solution VI. This solution keeps well.
The slight deposit formed is redissolved on shaking.
The plates are sensitized as follows: The plate to be sensitized is
first laid in a tray of distilled water for 2 or 3 minutes, then
bathed in a mixture of 1 cubic centimeter ammonia for 1 minute and
finally for 2 minutes in a bath composed of the following:
Color Solution VI 10 cubic centimeters
Distilled water 300 cubic centimeters
The plate is well drained and dried in a perfectly dark room. These
plates keep well for several months.
«MICROPHOTOGRAPHS.»