ENLARGING BY ARTIFICIAL LIGHT
To make enlargements on bromide paper by artificial light with
home-made apparatus demands a certain amount of contrivance and
preparation. Once the apparatus is made and put in working order,
however, its use is as simple as the manipulations employed in
enlarging by daylight. The following description of a home-made
enlarging lantern and its use is peculiarly adapted for home use.
Procure a good, sound box 14 inches square, and another 10 by 10 by 3
inches. Remove the cover of the larger box and hinge it so that it will
serve as a door. At the centre of the opposite end of the box cut an
opening large enough to hold a pair of condensing lenses, such as are
sold for magic lantern work. The diameter of the condenser should be
equal to the diagonal of the negative used; its purpose is to gather
the light and concentrate it upon the negative with uniform intensity
at all points. Now cut a hole in the top of the box and insert an elbow
of speaking-tube (tin), turning the horizontal piece with its opening
toward the rear of the lantern. This will act as a chimney for the
lamp or the illuminant used. Remove the cover from the smaller box and
cut an opening in the bottom of the box a little smaller each way than
the negative used. Around three sides of this opening attach grooved
strips of wood so that the negative may be inserted and held close to
the box. This smaller box is now attached to the larger one so that the
negative comes exactly opposite the centre of the condenser and about
three inches in front of it.
In the larger box place a gas stand fitted with a Welsbach or other
incandescent burner; or we may use any good oil lamp with a silvered
reflector behind the flame. The stronger and purer the light the
shorter the exposure necessary. The gas supply can be secured by
rubber-tube connection with the house supply. The flame of the lamp
or gas fixture should be in line with the centre of the condenser. If
we now light the lamp, close the door of the lantern, and insert the
negative, we will see that the latter is very strongly illuminated all
over. The back of the camera, with the ground glass removed, is fixed
to the front of this lantern so as to enclose the negative completely.
The joints between the boxes and camera are carefully covered by strips
of black paper and the apparatus made practically light-tight.
The conditions at this point are just what they were when we attached
the camera to the opening in the window shutter in enlarging by
daylight. The table and box support for the sheet of bromide paper are
arranged as before; the lantern is placed at one end of the table,
and the support for the enlargement at the other. The enlarged image
is brought to the desired size and carefully focused; the test for
exposure made; the lens capped and the sheet of sensitive paper fixed
to its support facing the lens and exactly at the point of focus.
The lens is uncovered, the exposure made, and the print developed as
already described. It is unnecessary to say that, while the tests for
exposure and the exposure itself are being made, the room must be
absolutely darkened, and the sensitive paper handled with the same care
that we would give to a plate before development.
When film negatives are to be enlarged from, either by daylight or
artificial light, the manipulations are precisely the same as those
employed with glass plates, except that the film must be enclosed
between two pieces of glass free from all blemish.
Where expense is not to be considered as of importance an Ingento
enlarging lantern, or a special daylight enlarging camera offers many
advantages in convenience of manipulation. Among the many varieties of
bromide papers obtainable those known as _Platino-bromide_ and _Royal
bromide_ are perhaps the most desirable for pictorial purposes.
Sometimes, after we have enlarged a picture which in its original
form had given us pleasure, it will be apparent that in the larger
picture we need the interest of color. The cold gray-black tones are
not equally suitable for all subjects. This difficulty can be overcome
by toning the prints according to the subjoined formulae, for which I
am indebted to Mr. E. A. Robins. The most permanent method of toning
bromide prints is that of altering the silver of which the image is
composed to silver sulphide. The substance is of a warm brown or
sepia tint and is quite permanent in air, and it does not yield even
to such a powerful bleaching agent as chloride. The print must be
carried farther in development than is usual, as toning tends to
slightly reduce the intensity of the print. It should also be alumed
after fixing and is then immersed, with or without previous washing,
in the following bath: hypo, 2 ounces; alum (common), ¼ ounce; water,
15 ounces. The bath is heated to about 120° F. before the prints are
immersed, and the operation should be conducted in a current of air or
out-of-doors, as sulphur dioxide is given off and is very unpleasant.
The prints tone slowly and gradually attain a sepia tone, which varies
with the quality of the negative, a brilliant negative giving a richer
sepia than a weak negative. After toning, the prints are washed and
dried, any scum upon the surface being removed by a tuft of cotton wool
and plain water or weak acid. Very fine effects can be produced with
this bath upon “Royal” bromide paper, approaching carbon prints in
quality.
The next most important toning bath is uranium, and although this is
generally tabooed because of its so-called non-permanent qualities,
if reasonable care be taken in the manipulations, no fault can be
found with it in this respect. The bath that has produced excellent
results in my hands is: potassium ferricyanide, 10 grains; water, 10
ounces; add—acetic acid, glacial, 4 drams; uranium nitrate (10 per cent
solution), 2 drams. The mixed solution will not keep more than thirty
minutes. Any tone can be produced from sepia to a Bartolozzi red. The
print is afterward washed until all the yellow stain is removed, any
left in reducing the permanency. Too much washing will remove all
the tone, and as the process is one of intensification, the prints
should not be too dark. If the uranium-toned print be immersed in the
following solution a sea-green tone is produced, which has a very
charming effect for seascapes and moonlight scenes—Ferric chloride, 15
grains; hydrochloric acid, ½ dram; water, 6 ounces.
Bromide prints can be toned to a Bartolozzi red by means of Schlippe’s
salt, or thio-antimoniate of soda. The print is first bleached
by immersion in the following—Potassium bichromate, 20 grains;
hydrochloric acid, 2 drams; water, 10 ounces. It is then washed
until free from all the yellow stain, and flooded with a solution of
Schlippe’s salt, 15 grains to 1 ounce of water; the print at once
assumes a Bartolozzi red tone, and only requires washing to complete
the operation; this is also an intensifying process, and so the print
must be kept fairly light, and all hypo must be washed out before
toning. To obtain a brilliant blue tone the following process is
available, and is quite permanent: To a 10 per cent solution of ferric
chloride add a 10 per cent solution of potassium ferricyanide until no
more precipitate is formed. This precipitate is dissolved by adding a
10 per cent solution of potassium oxalate, giving a deep green solution
quite clear, and in this the prints are immersed until the required
tone is obtained. If the action be too rapid it may be slowed by
diluting with water. The prints are washed and cleared by flooding with
a 2 per cent solution of hydrochloric acid; they may be given a violet
tone by placing in a 1 per cent solution of ammonia.