Chapter 1
Uncoated Paper and Salt Prints
This chapter describes anthotypes, Breyertypes, calotypes, salt prints, catalysotypes, ceroleins, chromatypes, crysotypes, cyanotypes, energiatypes, Feertypes, fluorotypes, kallitypes, platinotypes, Printing Out Papers (POP), and Developing Out Papers (DOP).
The phenomenon of darkening of silver salts in the presence
of light was known in the 1600's. Silver nitrate is soluble in
water, while silver chloride is water-insoluble. The chloride
occurs in nature as a soft mineral called horn silver, while
silver nitrate does not occur naturally.
Since silver nitrate is water soluble and was observed to
darken when exposed to light either in solution or dried, it
would seem to be the simplest of experiments to dip paper into
a solution and make shadow pictures in the sun. This may have
been done in the 1700's, but the first documented experiment
was performed by Thomas Wedgwood, son of the English potter
Josiah Wedgwood, and was reported in 1802 by the chemist
Humphrey Davy. Wedgwood and Davy also experimented with silver
chloride, called silver muriate, prepared with muriatic
(hydrochloric) acid. They observed that silver chloride was
considerably more light sensitive than silver nitrate, which we
now know to be true. But simple silver nitrate photography was
a technological dead end; photography was to encounter many
such dead ends in the next century.
Because Wedgwood and Davy failed to solve the problem of
fixing the image, all their pictures have faded, and they are
not credited with the invention of photography. Their work is
remembered as the forerunner of Talbot's success.
calotypes (salt prints): 1841 (patent) to the
1860's.
William Henry Fox Talbot patented the positive/negative salted
paper process in 1841 after a public announcement in 1839. He
soaked paper in a solution of common salt (sodium chloride),
then applied a water solution of silver nitrate, thus achieving
a mixed coating of silver nitrate and silver chloride on one
side. He fixed the image by again soaking the light-exposed
paper in a salt solution. The process produced a printing-out
image during exposure, but Talbot also found that the image
could be considerably intensified by developing in a mixture of
silver nitrate and gallic acid. During the same year Sir John
Herschel suggested the use of sodium hyposulfite as a fixer
instead of sodium chloride, and "hypo" has remained to this day
the basis of photographic fixers.
Talbot gave the name 'calotype' to paper negatives or prints
made from them. The term 'salt print' refers to prints that
were made by the salt/nitrate process from various negatives
including calotype negatives and glass negatives (the latter
being superior because of the absence of paper fiber).
According to Lassam [89} he later gave the name 'Talbotype' to
the calotype process at the urging of friends.
The calotype is described in many historical books; a
particularly concise description is found in reference [135] by
Stapp. DuBose [45] has an excellent history and process
description that gives a perception of the results of process
variations, particularly on color. This is discussed in
Appendix III on the Fotofind program.
Ceroleine
Calotype paper negatives were translucent, not transparent.
When the negatives were printed, the paper fiber was imaged
along with the silver image, to the detriment of resolution. As
early as 1841 Talbot had applied melted wax to his negatives
with a hot iron after they were processed and dried; he
included it in one of his patent claims. In 1851 Gustave LeGray
demonstrated better results by waxing the paper before it was
sensitized and processed. Negatives made by his process were
called ceroleines, a more convenient name than "LeGray's
Process". Positives made from good paper negatives showed
excellent resolution and tonal range, but they were soon
superseded by wet-plate glass negatives.
The index of refraction of waxes is closer to that of paper
fibers than is the refractive index of air. Therefore if wax
fills the spaces between fibers, light scattering by the fibers
is significantly reduced. Paper consists of a mixed population
of fiber compositions, some of which are not even transparent,
so a perfect match cannot be attained. Waxes, too, are complex
mixtures, and white wax was recommended over yellow. Towler
[108, 178] gives a procedure for separating the cerolein, or
white component, from bees' wax.
To achieve best results, wax should wet the fibers and
completely displace the air. Application was done with heat in
most cases, with care to avoid scorching. The sizing materials
used in some papers prevented good penetration and wetting, as
did silver salts and processing residues. Talbot's negatives
often showed blotchy and uneven light transmission. LeGray's
process of waxing before processing was inherently better,
provided the most suitable paper and wax was used.
Interesting sidelights on the waxed paper process as practiced
by Roger Fenton are given by Hannavy [70], particularly
regarding pre-exposure and post-exposure waxing.
Oils were tried, since they penetrate and wet without heat.
Unfortunately they tended to soak into storage envelopes and
anything else the negatives contacted, necessitating periodic
reoiling. The process was messy enough without that.
The quality of the paper base was important because trace
impurities caused spots, discoloration, and fading. Individual
photographers tried the available artists' and drawing papers
and usually settled on a favorite. They could buy presized
papers or prepare their own from various recipes.
Reilly [121] has emphasized an important distinction in
nomenclature. Salt prints are made by a two-step process:
salting and sensitizing. The paper may or may not be coated
with an emulsion or binder. Albumen prints are also made by
sensitizing a pre-salted paper and therefore technically are
salt prints, even though they have an albumen coating, unlike
Talbot's earliest prints. Plain salt prints have a surface of
exposed paper fibers; albumen prints are always glossy, but
paper fibers are visible in the highlights through the
transparent albumen because there was no undercoating of white
baryta as in later bromide paper.
POP and DOP Processes
Printing-out papers (POP) are those in which the silver image,
called photolytic silver, appears spontaneously during light
exposure without chemical development (subsequent fixing is
still necessary). There is no negative image produced by the
POP reaction. The production of photolytic silver under the
action of light quanta is related to the simultaneous formation
of a latent image, but the exact relationship is not fully
understood. Photolytic images must be gold-toned because they
are inherently unstable even if fixed in hypo. Photolytic
silver is accompanied by the release of an equivalent amount of
free halogen gas (chlorine, bromine, or iodine), which may then
recombine and reduce the effective rate of darkening. If
recombination is prevented or slowed, a faster rate of
darkening results; one way of accomplishing this is the
inclusion of reducing agents in the emulsion or binder. All
silver papers will eventually darken in daylight; POP papers
are simply those in which the change is fairly rapid and the
tonal range is useful. POP processes, including albumen,
dominated 19th century photography.
In developing-out papers (DOP) light exposure produces an
invisible latent image requiring chemical development to become
visible. The colloidal particles of reduced silver in POP
images are very much smaller than the filamentary particles in
DOP images. Comparison electron micrographs are presented in
Eastman Kodak [47-28], and Reilly [122]; a transmission
electron microscope is necessary because individual particles
in POP images are too small to see in light microscopes. The
small size of these clumped particles is the principal reason
for the characteristic reddish color of POP prints, though
processing variations and toning alter the color. This is
discussed in more detail in Chapters 3 and 11, and in Reilly
[123-3]. According to Reilly [122, 6], the largest class of DOP
prints from 1840 to 1885 were crayon portraits, which continued
to be made into the 20th century (see Appendix II).
These surface characteristics are summarized below because
they are important recognition clues for dating:
1. Exposed paper fibers over entire surface:
POP salt
prints
1841-c1860
kallitypes &
platinotypes
1870's-c1890's
2. Glossy surface, paper fibers visible:
POP
albumen
c1850-c1890
3. No fibers visible, glossy or matte:
POP or DOP, silver chloride or
bromide c1890-present
Cyanotypes: 1842 - present
The cyanotype has not been taken seriously by professional
photographers because the tonal range is poor and the images
are bright blue, an unrealistic color for both portraits and
landscapes. On the other hand cyanotype paper is cheap and easy
to make and process, and the image has good permanence.
However, cyanotypes should not be stored in contact with
buffered or alkaline paper, sometimes called non-acidified
paper and used in archival applications: such paper will fade
cyanotypes. Exposure to light will also fade the images.
Specimens showing family groups and buildings are fairly
common, but the greatest use was in copying text and line
drawings, as blueprints. It has been in continuous use perhaps
longer than any other photographic process.
The original process was discovered in 1842 by the astronomer
Sir John Herschel, motivated by a need to copy his scientific
calculations before the era of copy machines. Herschel's first
process was based on ferric ammonium citrate and potassium
cyanide, which produces a blue image where light strikes it.
The image is fixed by simply washing in water. A positive print
with blue shadows and white highlights is made by printing from
a negative. A contact print against a line drawing makes the
familiar blueprint with white lines on a blue background.
Crawford [38, 163-166] describes the process in detail for home
experimenters. Reference C is a valuable source of process
information.
Less well known is Henri Pellet's patented (U.S.) process for
making direct positives, described in Lietze [84, 65-69].
Poitevin also made direct positives in a violet color (Lietze
[92, 75-78]). In both processes line drawings could be made in
one step with dark lines on a white background, without
reversal.
In all these processes the paper fibers are exposed in all
parts of the image. Often the paper was sized with glue or
starch to reduce penetration into the surface. Because of
toning and process variations the colors were not always bright
blue; they may range from blue-black to purple.
Valuable insight into the cyanotype process is in Ref. C by
Mike Ware.
Platinotypes, Palladiotypes: 1873 (patent) -
1937
The platinum process is classed as a ferric process related to
the cyanotype. William Willis patented platinotypes in 1873 in
England. Crawford describes the full working process [38,
76-78, 167-175]. The chemistry is also discussed in Eder [48,
543-546] and in Lietze [92, 79-90]. According to Crawford,
platinum paper went off the market in 1937, but there have been
revivals, and palladium paper is again commercially available
as of this writing. Platinum paper shows a weak image during
exposure (POP), but developing is necessary for the final
image. Colors range from silver gray (neutral black) to warm
brown, depending on processing and toning. Paper fibers are
visible throughout the picture, and the image appears embedded
in the fiber texture. The image consists of reduced metallic
platinum and is more stable than the underlying paper.
A variation, multiple platinum printing, is described briefly
by Struss [137].
Palladium is chemically similar to platinum but cheaper and
more plentiful and was used both alone and in mixed chemistry.
Willis' patent claims the use of salts of palladium, gold,
iridium, platinum, and mixtures thereof.
Many writers are lyrical about the unique beauty of platinum
prints. It is perhaps the only process whose intrinsic beauty
is a useful (though subjective) identifier; Crawford describes
it very well [38, 77].
Kallitypes: 1843 - 1890's
The kallitype process is chemically similar to the platinotype
process except that the final image contains metallic silver
rather than platinum. Kallitypes resemble platinotypes in their
beauty, and in fact kallitype paper was marketed commercially
as a substitute for the very expensive platinum paper.
Unfortunately people expected the substitute to be as resistant
to fading as platinum, but the stability of silver does not
compare with that of platinum, and kallitypes acquired a bad
name. At about the same time the more convenient gelatin silver
chloride papers became available and kallitypes fell from
favor.
Crawford describes two kallitype processes in detail [38,
177-180]. Pernicano [115] gives a detailed modern recipe.
Kallitypes are also described in the 1908 Library of Practical
Photography [131], in The Photo [116], and in Eder [48, 543].
The paper surface shows exposed paper fibers throughout. The
image becomes visible during exposure (POP) but darkens during
development and fixing. Colors ranged from black to brown;
there were many homemade process variations.
Non-commercial Types of Uncoated Prints
A non-commercial listing does not mean that there are no
surviving specimens. The early days of photography were a
do-it-yourself period; amateurs and professionals eagerly tried
every process that was published. Some, but not all, inventors
tried to license or restrict use of their processes. Robert
Hunt of London freely made public three of his processes: the
catalysotype, energiatype, and fluorotype, and many
publications carried instructions and notes on their
application. It would be of interest to find more authenticated
specimens of these lesser-known types.
Anthotype: 1842
Sir John Herschel discovered in 1842 that water and alcohol
extracts of flower juices coated on paper were light sensitive.
Several workers published recipes: Snelling [133, 37-42,
113-116] has considerable detail. Among the list of recommended
flowers were the violet, red poppy, and wall flower. The images
were "fugitive", and exposures as long as four to five weeks
were needed. The light instability of organic dyes was a
problem of long standing, and Herschel's early attempt to make
a virtue of it is intriguing. Five weeks' exposure time is a
little long for practicality, however.
Breyertype: 1839 - ?
An obscure but historically important process invented by
Albrecht Breyer of Berlin in 1839. It was a silver chloride
facsimile print of text and line drawings made by shining light
through the back of sensitive paper placed in contact with a
printed page. The print was produced by the light reflected
from the page being copied, and was a negative from which
positives could be made.
Breyertypes may be recognized by their subject matter of
printed text or drawings, either positive or negative, whose
color was brownish black with a texture of paper fibers, and
with exposed paper fibers over the entire surface. The same
subject matter may appear in prints made by the various
cyanotype processes described in Lietze [92], but they were
colored blue, purple, or other distinctive colors. Other
photographic processes were capable of copying text, but they
can often be recognized by characteristics such as
coatings.
Catalysotype: 1844 - ?
This printing-out process was invented by Dr. Thomas Woods of
Ireland in 1854, and improved by Robert Hunt in London. The
paper was coated with iron iodide and sensitized with silver
nitrate. The name was derived from catalysis, which was thought
to explain image formation, probably an erroneous concept.
Chrysotype: 1842 - ?
Another of Sir John Herschel's iron processes of 1842, in
which the paper was first coated with ferric ammonium citrate
and dried. After exposure it was developed in gold chloride and
fixed in potassium iodide. The image consists of reduced
metallic gold that is purple in color. It had a limited tonal
range and was used mostly for copying line drawings and text,
producing a negative of white lines on a purple background.
Chemically it is related to the kallitype and cyanotype.
Although the paper was not made commercially, the recipe was
published and widely used by amateurs.
Chromatype: 1843 - ?
Another of Robert Hunt's processes in 1843. The sensitive
material was a mixture of copper sulfate and potassium
dichromate, which produced a direct positive image of an orange
or lilac color; Eder [48, 553] lists variations. If the process
had been more sensitive it might have been successful, because
it produced a direct positive in the camera.
Energiatype: 1840 - ? Also called
Ferrotype.
This process of Robert Hunt's had considerable vogue, with
lengthy articles appearing in books and periodicals. The paper
was coated with a mixture of succinic acid and sodium chloride
in a gum arabic binder, then sensitized with silver nitrate.
After exposure it was developed in iron sulfate (hence the name
ferro-type). According to Snelling [133, 111] the same
developer works well with other salts of silver.
Feertype: 1889 - ?
An early diazo print, 'Diazo' refers to a class of light
sensitive nitrogen-based organic compounds, which can produce a
wide range of colors, mostly broad-band colors low in
saturation. Feertypes were not commercially successful when Dr.
Adolf Feer patented the process in Germany in 1889, but they
were the forerunner of the Ozalid process after World War I
that competed with blueprints for copying line drawings. There
was no pictorial usage then, though today the process is
sometimes used to print on cloth bases, such as tee-shirts.
Fluorotypes: 1844 - ?
Another Robert Hunt process, with little acceptance or
documentation. The name was derived from sodium fluoride, which
was mixed with potassium bromide; it was developed in iron
sulfate.
Summary of Identification of Uncoated Prints