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all. Because the paper support is partially opaque, the
negatives do not need to be viewed through transmitted
light to see an image.
The nineteenth century photographer considered the
paper substrate to be the most important component of
the calotype. It’s physical properties and characteristics
translated directly into the negative’s fi nal appearance,
and thus into any prints made from it. Dimensions var-
ied from 2 × 2" to greater than 15 ×18", the size being
directly proportional to the capacity of the camera. From
exquisitely thin to stout and thick, the photographers
explored a wide range of papers. Wove papers were
preferred to laid and chain papers, and even water
marks were trimmed away, since they would be visible
in the image and print. Thin, uniform papers yielded a
crisper image, while a thick, fi brous paper a softer ef-
fect. Greater or lesser absorption properties in a paper
created denser or more ethereal tones. Sizing affected
the outcome as well, from fi ne gelatin sized English
papers which yielded warmer tones, to the cooler tones
of the starch sized French and German papers. Finally,
the purity of these papers was paramount. Uneven dis-
tribution of the size in the pulp could result in a mottled
image. Any fi llers or impurities such as bits of metal
or other inorganic contaminants could create uneven
results, even spots or stains.
Locating a reliable source for paper of suitable qual-
ity proved diffi cult and troublesome before mid century.
Industrialization of mechanical printing and paper mak-
ing in the 1820s claimed the lion’s share of available
cotton and linen rags, making handmade papers less
available and more expensive. The new photographers
required the greater quantities that mass production pro-
vided, but of a consistently superior quality not readily
available from the average paper mill. Between 1843 and
1853 the three most frequently recommended papers for
the calotype were Whatman, Turner and Canson. After
1852, qualifi ed paper makers were persuaded to create
a “niche market” for photographic papers. An impor-
tant milestone came from the Chafford Mills in Kent
that produced the paper watermarked “RTurner Patent
Talbotytpe.” The paper was highly regarded for it’s even
texture, consistent production quality and longevity and
used by many practitioners such as Benjamin Bracknell
Turner (1815-1894). From 1853 and continuing well
into the 1860s, increasing paper selections were avail-
able by Turner, Whatman, Canson, Sanford, Papier Saxe,
Hollingsworth, Papier Rive and Towgoods. There was
also variety in preparation, from plain to gelatinized to
iodized, in an effort to simplify the steps and encour-
age purchases. Given the demand for such high quality
stock, surviving negatives are often in excellent condi-
tion. Apart from mechanical wear, such as tears, creases
and skinning, the paper remains supple and if properly
processed, will retain clear, bright highlights. Usually
the paper is a natural cream color, although negatives
exist on papers tinted with bluing agents.
Sensitization takes place in two steps. First the paper
is “iodized” by applying a halide salt solution usually
potassium iodide and a smaller proportion of silver
nitrate. In the second step, just before use, the iodized
paper is coated with gallic acid and silver nitrate. If the
solutions are lightly brushed onto the paper, the result-
ing silver image layer may be thin to moderate. Alter-
natively, if the paper is immersed, fl oated or repeatedly
coated, it will absorb a maximum amount of solution
potentially resulting in a dense image, printing through
to the verso from this saturation.
In-camera exposures could range from 30 seconds
to six minutes or longer, depending on conditions.
During exposure, the latent image is created: atom-size
irregularities or fl aws inherent to silver halide crystals
will condense after irradiation from light. Even a brief
exposure is enough for the condensed irregularities to
become sensitivity specks, which in turn become the
points of attack for chemical development. Alternatively,
if the sensitized paper is continually exposed to light,
the latent image will visibly print out and can eventually
completely blacken the paper.
The calotype developer was gallic acid and silver
nitrate. A component found in nutgall, mangoes and
other vegetable matter, gallic acid has a strong chemical
affi nity to the halides. The image development in paper
negatives is different from the image forming in salted
paper prints and albumen prints which are printing-out
processes. It is called physical development, and in it,
the developing agent (gallic acid) donates electrons to
the silver ions in solution (from the silver nitrate) so that
metallic silver is deposited at the site of the latent image.
This coating or plating of the latent image amplifi es until
the image reaches visible size. Its spherical morphology
and size dictates the particle’s refl ective properties and
chemical robustness, and a well-processed image will
appear neutral gray. The temperature and purity of the
developing solution and washing baths were identifi ed as
important variables because the rate of chemical reaction
increases when temperature rises and impurities could
react with the chemistry. Technical diffi culties such as
over- and underexposure were compensated for with
under-and over development, much as they are now.
The image was stabilized by removing unexposed
halides by washing with either potassium bromide or
sodium thiosulphate, then known as “hyposulfi te of
soda.” Talbot initially preferred potassium bromide.
John Herschel discovered the ability of the thiosulphates
to dissolve the insoluble salts of silver chloride in 1819
and was the fi rst to use the compound in photography.
Eventually sodium thiosulphate became the standard
chemical fi xer, although improper use resulted in acute
staining and fading and the loss of many early photo-