drained. Finally, oil-based inks are spread over it,
standing proportionally in the areas with less water
(shadow areas) because of the repulsion of oil and
water. The print can be left like this, direct bromoil,
or used as a matrix against white paper to produce
several bromoil transfers.
In the carbro process, the photographer starts
with a wet gelatin silver print that is put in contact
with a ‘‘carbro tissue’’ (thin paper sensitized with
bichromated gelatin and pigments). Introducing
both in a bleaching bath, the gelatin tissue hardens
proportionally to the amount of silver in each area
of the print. After separating them, the tissue is
applied to good drawing paper so the gelatin sticks
to it and the image is transferred. The silver print
can be redeveloped and used a few more times. Due
to its complexity, this process was developed and
used mostly by pictorialists around the 1920s and
has fallen almost completely out of use.
Subtractive Color Processes
Curiously the pigment processes were among the
first to be used in order to obtain full color images.
The first two decades of the century were dominated
commercially by the Autochrome, the additive pro-
cess invented by the Lumiere brothers. Autochromes
were positives on glass and could not be printed.
Nevertheless, the remarkable advances in color cam-
eras, able to obtain three separation negatives of the
three primary colors simultaneously, promoted
research into printing methods that involved the
overlapping of three layers, each one exposed to a
primary color negative.
One of the first commercially available color
printing process was based on carbro, requiring
three silver prints made from three separation nega-
tives and using a carbro tissue of each primary color
to obtain three colored gelatins that must be per-
fectly aligned and pressed together over the paper to
form the full color image. The dye-transfer process
also uses three gelatin tissues hardened proportion-
ally to the light received, after eliminating the non-
hardened areas with water, each gelatin is immersed
in a dye bath (yellow, magenta, and cyan) and the
three colored gelatins are carefully aligned to obtain
the full color image. Although its origins can be
traced as far back as the 1870s, its peak use was in
the period after World War II. It still is highly
appreciated by photographers selling to museums
and collections; they value its excellent color repro-
duction, high light stability, and the possibility of
using different paper surfaces. To improve the light
stability even more some recent innovations on car-
bon derived processes, such as EverColor have
appeared in the 1990s, combining digital color
separation films and more permanent pigments.
In the 1910s and 1920s, the search continued for
an integrated process with three overlapping layers
that would not require separate treatment for each.
The process that succeeded commercially, and
became the most widely used, is the Chromogenic
or Color Coupler, commonly termed C-Print, in
which each of the three layers is sensitized to a
primary color (blue, red, and green) with complex
molecules that contain light sensitive silver and part
of a dye molecule. After exposure, a latent silver
image is formed. The developing process causes
each light-activated molecule to join with the the
dye molecule, thus forming a color dye. The silver is
removed in the fixer, leaving a final image comple-
tely formed by organic dyes.
It is very difficult to find dye molecules that
fulfill all the complex requirements of this process:
first, to behave according to the needs of the pro-
cess (i.e., to be able to split in two separate mole-
cules that will result in a primary color when joined
in the color developer); second, to show in the print
a good primary color; and third, to be stable to
light, humidity, and other conservation hazards. In
this search, manufacturers have not always chosen
the most balanced solution, but sometimes com-
promise the durability due to the higher costs of
choosing other molecules or processes. Most of the
commercial color prints made before 1970 have
very low color stability and their conservation con-
ditions are very poor. Among the few early com-
mercial products with a good dark color stability
are Kodachrome prints, based on the same process
used for transparencies. Since 1970, most of the
companies have improved significantly in both the
dark and light stability of their chromogenic prints.
A color process frequently used in art photogra-
phy is usually referred by its commercial name,
Cibachrome (presently Ilfochrome). It is a dye
bleach or dye destruction process, based on the
experiments of Arthur Traube (1910s). It uses a
paper covered with three layers containing the col-
ors that are later destroyed in a bleaching bath
proportionally to the amount of light received, so
it gives a direct positive from a color transparency.
It is not hard to identify due to its characteristic
thick polyester base, black margins, high color
saturation, and high contrast. Dye bleach papers
are commercially available in several surfaces and
also in transparent sheets for backlighting. Due to
their relatively good stability in dark storage (accel-
erated aging tests confirm a durability of more than
50 years without appreciable loss of color), dye
bleach has been a process of choice for fine artsPRINT PROCESSES