368
lens. Daguerre’s original camera used a meniscus, or
simple convex-concave, lens.
In preparation for taking the picture, the camera’s lens
was focused and capped and the plate holder inserted
into the camera. In place of a shutter, the protective
opaque slide was pulled away from the plate and out
of the camera and the lens cap removed to begin the
exposure. The fi rst daguerreotypes could require twenty
minutes or longer of exposure, depending on light condi-
tions. Once the estimated exposure time was reached,
the lens cap and protective slide were replaced and the
plate holder removed from the camera and returned to
a darkroom for development.
In the darkroom, the plate was suspended face-down
in a box containing a small amount of mercury that had
been heated to 120 to 180 degrees Fahrenheit by means
of a spirit lamp to distribute it evenly across the bottom
of the box. Mercury vapors chemically reacted with ar-
eas of the silvered plate that were exposed to light. The
daguerreotypist examined the plate at intervals to check
the progress of the developing latent image.
Once the picture was visible and the contrast in its
light and dark tones deemed satisfactory, it was bathed
in a heated solution of salt or “fi xed” in a bath of sodium
thiosulfate, or “hypo,” for approximately thirty seconds
to remove the sensitized chemicals that remained on
the plate. The hyposulfi te was then rinsed off with
water and the plate carefully dried to avoid spotting.
The fi nished plate was then enclosed behind glass in a
protective frame.
Development of the Daguerreotype Process
In the early nineteenth century, a number of artists,
scientists, and amateurs simultaneously were experi-
menting with various chemicals, surfaces, cameras,
and lenses to fi x a permanent image that was gener-
ated by light instead of by an artist’s hand. In England,
Thomas Wedgwood, Sir Humphry Davy, and William
Henry Fox Talbot were working to print such images on
paper, and in France, Nicéphore Niépce and Daguerre
each were searching for a means of capturing pictures
on metal plates. Daguerre had turned to photographic
experimentation after the popular and profi table exhi-
bition of his diorama paintings in Paris. These large-
scale, semi-translucent canvases featured trompe l’œil
paintings illuminated with various lighting effects to
give the illusion of passing time. Having used a cam-
era obscura to create his paintings, Daguerre became
interested in devising a method to capture the camera’s
projections. In 1826, he learned from the Parisian op-
ticians Charles and Vincent Chevalier that another of
their clients, Niépce, had been using bitumen of Judea
to print images on pewter. Daguerre wrote to Niépce
to inquire about his process, which Niépce had named
heliography. The two began a tentative correspon-
dence, with each reluctant to divulge the extent of his
progress to a rival. In late 1829, after concluding that
their independent work could advance more quickly in
collaboration, Niépce and Daguerre became partners.
When Niépce died three and a half years later, his son
Isidore succeeded him in the partnership; Daguerre
continued experimenting.
By 1837, Daguerre’s progress in stabilizing the
photographic process was such that he revised the
original terms of the partnership that had designated
Niépce as the inventor of the process and Daguerre as
its improver to give himself the primary role. He had
happened upon a combination of common salt, silver,
iodine, and mercury that fi nally succeeded in devel-
oping a latent photographic image and permanently
fi xing its subtle shades on a copper plate. Seeing the
potential profi t in the improved process, Isidore Niépce
acquiesced to Daguerre’s terms. In attempting to sell
his fi ndings to subscribers in France and abroad, Da-
guerre approached François Jean Dominique Arago,
director of the Paris Observatory, permanent secretary
of the French Academy of Science, and a member of
the French Parliament’s Chamber of Deputies. Having
experimented himself with light-sensitive materials
and with means of measuring the effects of light’s in-
tensity, Arago immediately recognized the commercial,
scientifi c, and artistic potential of Daguerre’s process.
At the 7 January 1839 meeting of the Academy, Arago
proposed that “the Government should compensate
M. Daguerre direct, and that France should then nobly
give to the whole world this discovery which could
contribute so much to the progress of art and science”
(qtd. in Gernsheim, 1968, 84). In July 1839, the French
government passed bills awarding Daguerre and Niépce
an annual pension of six thousand and four thousand
francs, respectively, in exchange for a detailed history
and description of the promising daguerreotype process.
For the additional two thousand francs, Daguerre also
was asked to reveal the secrets behind the realistic ef-
fects of his diorama paintings.The Public Introduction and Adoption
of Daguerreotype
In keeping with Arago’s hopes and with Daguerre’s
and Niépce’s agreement with the French Government,
the daguerreotype process was introduced to the public
at a joint open meeting of the Academies of Science and
of the Fine Arts on 19 August 1839. In front of a rapt
crowd that fi lled the Academy’s halls and courtyard,
Arago detailed, but did not demonstrate, the necessary
equipment and procedures on Daguerre’s behalf. The