Contact printing
C Print
Emulsion
Format
Gelatine silver papers
Gum Printing
Hand-made photogravure
Photogravure
Platinum printing
Rotogravure
Silver albumin paper
Toning / Toned Photographs
Contact printing
The photographic negative is placed directly on top of a photo paper and is illuminated. The picture thus becomes exactly the same size as the negative. This method has been used since the infancy of photography until the present day.
C Print
A standard colour print made from a colour negative.
Emulsion
The light sensitive coating on photographic film, plates and printing paper.
The coating is composed of silver salt crystals suspended in a binding agent
such as gelatine.
Format
A term to categorise the type of camera based on the dimensions of the
photographic film. The format may be measured in the metric system, such as
35mm, or in inches as 4x5. The choice of which format a photographer uses
may be aesthetic - as in use of a large format (8 x 10) which produces high
image definition, or very fine detailing. The choice may also be
utilitarian, as in the case of street photographers, who use smaller formats
for enhanced mobility.
Gelatin silver papers
Since the end of the nineteenth century, gelatin silver has been by far the most common photo paper. A light-sensitive emulsion is poured over the paper base and is bound in gelatin.
Gum Printing
Gum printing gives a permanent image since it is made of pigment imbedded in
gum Arabic. The gum/pigment solution is made sensitive to light by the
addition of a dichromate and then paper is coated with the solution by
brush. After drying the paper is put in contact with a negative. Exposure to
a strong light will make the gum/pigment insoluble in water. Beneath the
dense parts of the negative the lack of exposure will leave the gum soluble.
It will dissolve when placed upside down in a tray of water.
Seemingly simple, it takes many coatings of the gum/pigment to get an image
of acceptable contrast. Each time the paper support has to be dried and kept
in good condition so the negative can again be put in contact with the image
in perfect register. It requires a lot of skill and training to get the
tonality right, but the chemistry is easily accessible.
The reward is the possibility to alter the pigment color for each coating,
giving the print any conceivable richness of color. Also the choice of paper
makes it possible to enhance the image by the selection of a smooth surface
for fine details, and a coarse surface for the sensation of softness. Most
work is done in black and white and is recognizable by less fine detail and
a painterly, handmade quality.
Combining platinum printing and gum printing gave one of the finest images
by the photographer Edward Steichen. In an image of a pond, the neutral
black platinum print has a coating of blue/green soft color on top. In
Sweden Lennart Olson has been using the process for many years.
Hand-made photogravure
The hand-pulled or hand-drawn photogravure has been called the "aristocrat
of the photographic processes." Hand-made photogravures were most
appreciated by the romantic pictorialists of the Art Nouveau period. They
were used in Alfred Stieglitz´s periodical Camera Work, 1903-1917. Many of
Stieglitz´s own photographs were printed as photogravures, and he considered
each hand-pulled photogravure print as an individual and original work of
art. Often, the photogravures were finer than the original prints.
Alvin Langdon Coburn, a famous member of the Photo-Secession, also regarded
hand-pulled gravures as original prints. Coburn said: "I think I may claim
that in my hands photogravure produced results which can be con-sidered as
original prints, and which I would not hesitate to sign".
Other recognized photographers who used photogravure were Edward S. Curtis
in his twenty-volume work, the North-American Indian, and Paul Strand in
Photographs of Mexico and The Mexican Portfolio.
There are two kinds of photogravures, hand-pulled and machine photogravures
(rotogravure). You can tell the difference by carefully studying the print
under a magnifying glass. The hand made photogravure has no cross-line
screen and the grain is scattered all over the picture, most obvious in the
lightest part of the picture. There is also an indented mark in the paper,
caused by the pressure of the copper plate.
Photogravure
The photogravure method was invented in 1879. Photogravure is a complicated
and time-consuming engraving process, requiring that the original negative
be reprinted, retouched and processed in several stages.
A positive in the size of the final photogravure is made from the camera
negative. The positive is then contact-printed with light-sensitive
gelatin-coated pigment paper. The negative gelatin layer is transferred to a
prepared copper plate, which has been carefully cleaned and covered with
resin or carbon powder melted with heat to produce the aquatint grain. The
soluble part of the gelatin is washed away and the plate is etched in
ensuing ferric chloride baths.
The plate is sensitive to wear, which means that the number of prints is
limited. Since the silver of the original print has been replaced by colour
pigment powder, which is printed on acid-free copper print paper, the
photogravure is guaranteed a virtually unlimited lifetime.
Copper print paint is being used and therefore the photogravure can be given
any colour whatsoever.
Platinum printing
The permanence of platinum and the soft, rich tonality of these prints made
platinum printing the preferred medium of photographers such as Alfred
Stieglitz, Edward Weston and Fredrick Evans. Until the 1930´s there was a
commercially available platinum paper, but when the price of platinum rose
to prohibitive levels, the manufacturer gave up production. Some
photographers like Fredrik Evans gave up printing; others successfully
managed to make the necessary chemicals in their labs. Contemporary
photographers have since the 1970´s revived the process and the chemicals
are again becoming available.
Platinum salts are made sensitive to light by iron oxalate and then coated
on paper. Along with platinum (potassium chloroplatinate), other metals in
the platinum family such as palladium (sodium palladous chloride) can be
used, giving the prints a warmer and smoother tone. A combination of the two
gives good control of tonality. The addition of small quantities of
potassium chlorate controls the contrast.
The paper coated with the solution of platinum and iron oxalate is, after
drying, placed in contact with the negative and exposed to sunlight or a
strong artificial light source. The exposure can vary between a few minutes
and more than an hour, which makes it a very time consuming process. Due to
the low sensitivity to light, this is a contact printing method. It is
common to enlarge the negative to the desired size of the print.
The platinum metal is embedded in the fibers of the paper, without any
gelatin or other emulsion as in other processes. This gives the prints a
"pure" feeling along with a long tonal scale. The stability of the platinum
metal makes the prints permanent since pollution in the air has no effect on
the image. Only the quality and handling of the paper support will determine
the lifetime of the print.
Rotogravure
The machine-made photogravure (rotogravure) has a regular cross-line screen,
easily discernible in the lightest part of the picture. Printing is done
from a rotating copper cylinder, mechanically inked, and the method is
suitable for fast printing speeds, printing books and magazines.
In Sweden and in Scandinavia, Henry B. Goodwin, 1878-1931, used
photogravures for his three great books, hand-drawn photogravure for
Konstnärsporträtt1 (1917), and rotogravure for Anders de Wahl1 (1919) and
Vårt vackra Stockholm (1920). In Germany, Karl Blossfeldt´s magnificent
work Urformen der Kunst (1928) was printed in rotogravure.
Nowadays there are new printing methods and new materials which make it
difficult to tell the difference between hand-pulled photogravures and
machine made photogravures. The cross-line screen of the rotogravure can be
replaced by an irregular stochastic screen, which looks very similar to
the scattered grain of the hand made photogravure.
Silver albumin paper
The silver albumin print was the most common type of printing paper from the 1850s until about the year 1900. A thin paper was coated with a skin of albumin and made light-sensitive through a solution of silver nitrate. The albumin gave the print a shiny surface, as opposed to its predecessor, the salt paper process (1839-1860), which gave a print a matt finish. The paper was developed in daylight, with the negative lying in direct contact with the prepared photo paper. The print was thus exactly the same size as the negative. After being toned in gold, the print assumed a pretty brown tone of varying nuances, from dark brown to lilac-brown.
Toning / Toned Photographs
Photographs that have been treated with a chemical solution that reacts with
the silver in the emulsion and alters its appearance,
most notably in colour. The image may be treated in its entirety or only in
selected areas. Chemicals such as platinum, sulphur, gold and selenium may
be used to achieve different tonal qualities in the final image.
