still consider non-RC papers, now commonly called
‘‘FB’’ or fiber-based papers, to be more archival.
In general the archival quality of modern gelatin
silver papers is good if the processing removes all
signs of sulfur (from the fixer), which can accelerate
the transformation of silver into silver sulfur during
the aging process. One way to avoid sulfuring is to
tone the print, substituting the silver for another
more stable metal (platinum, gold) or by creating a
silver compound (silver sulfur) that forms a chemi-
cal shield to prevent oxidation. Considering the
attraction of silver to sulfur, sulfur toning acts as
a controlled accelerated sulfuring to affect the
whole print, instead of only certain areas as usually
happens over time. DOP prints are much more
stable to light fading and oxidizing agents (ozone,
industrial gases, car pollution, etc.), in comparison
with POP prints because of their bigger filamentary
silver conglomerates.
Monochromatic Iron Processes
Some of these processes are known from the early
days of photography, such as the cyanotype,
invented by Sir William Herschel in 1835, which is
based on the sensitivity to light of iron salts, and
offers the rich deep blue tones that account for its
name. Early in the twentieth century it obtained a
certain popularity among amateur photographers,
due to its simplicity that allowed them to make
contact prints with great ease and very few materi-
als. Sometimes professionals also used it to obtain
fast test proofs, becoming in some way the equiva-
lent to the professional use of Polaroid or digital
cameras in modern studios. Since the 1950s, it
enjoys a certain use among artists and photogra-
phers, who can use it to print on cloth and other
materials instead of a paper base. It proves simple
to identify thanks to its characteristic color, matte
surface, and lack of emulsion that leaves the paper
fibers easily visible, because the light sensitive solu-
tion is directly absorbed.
The platinotype is another process based on the
light sensitivity of iron salts. Invented by William
Willis and commercialized in 1878 through his own
company, it obtained great acceptance by studio
portraitists, although its high price never allowed it
to equal the sales of gelatin silver papers. In order to
identify it often the economic circumstances of the
sitter provide valuable contextual data, because false
platinotypes were made using matte collodion toned
in platinum for less wealthy sitters (see above). After
World War I, platinum prices increased significantly,
and it was generally replaced by palladium that of-
fers similar results. Both have always been greatly
appreciated in artistic photography, due to their
wide tonal range, deep blacks with shadow details,
and excellent conservation. They can be identified by
their matte surfaces with neutral tones (when not
toned), and clearly visible paper fibers as they also
have no emulsion.Monochromatic Pigment Processes
These processes are derived from Louis Poitevin’s
search to find a way of printing more permanent
photographs through the use of the light sensitive
bicromated gelatin. He patented several methods in- In them, a negative is exposed in contact with
an emulsion of bichromated gelatin, that hardens
proportionally to the light received, and later is
‘‘developed’’ by pouring water over the gelatin to
dissolve and remove the non-hardened areas.
Among the most widely used in the early twentieth
century were carbon, bromoil, carbro, and gum
bichromate, which were used by photographers pur-
suing a more pictorial effect in portrait and artistic
photography. In the last decades of the twentieth
century, gum bichromate has experienced a revival
by some graphic artists who want to create photo-
graphic images with limited tones and textural
effects. The Fresson process, derived from carbon,
was patented by the Fresson family who still produce
limited series for art galleries and photographers
from all over the world. The high resistance to light
fading of the pigments, used in all these processes,
guarantees the excellent conservation of these prints,
even those from the nineteenth century.
The carbon process began in the 1860s and takes
its name from the pigments (amongst them carbon
black) introduced in the bichromated gelatin to
obtain the final color of the image. Although their
colors can vary greatly, the most common ones are
similar to those of traditional silver papers (neutral,
warm, or purplish blacks). They are identified by
their dense dark tones, and a certain relief in contours
between high contrast areas is visible in raking light.
A further modification of the carbon process is the
bromoil process developed in England in the 1900s
and widely used by Pictorialist photographers till the
end of the 1930s. Its own name describes the process,
in which a silver bromide gelatin print is used as a
matrix to print with the traditional oily inks of litho-
graphy. This is achieved by immersing the bromide
print in a solution that hardens the emulsion in direct
proportion to the density of silver in each area. Later
the print is introduced in water, so the less hardened
areas (lighter tones) absorb more water, and then
PRINT PROCESSES