Dating back to 1839, the daguerreotype is one of the oldest known forms of photography. It was the first process that did not require excessively long exposure times, making it ideal for portrait photography.
Louis Daguerre (1787-1851) had been trying since 1829 to capture the images he viewed through his camera obscura, a wood box that produced an image on a sheet of frosted glass via a lens at one end. In 1839, after a decade of painstaking work, he presented his daguerreotypes to a joint session of the Academic des Sciences and the Academic des Beaux-Arts. The pictures included images of shells, fossils, and a dead spider, photographed through a microscope.
The process for developing the pictures was long and laborious. The plates had to be prepared from a sheet of copper coated with a thin layer of silver. The silver surface had to be polished until it was mirrorlike. It was then exposed to iodine vapors to form a surface of silver halide that would react with light to produce the image. The plate was then exposed in a large, boxlike camera, after which the image was developed using mercury fumes. The resulting picture was fixed using a water and sodium thiosulfate solution.
Finished daguerreotype images are laterally inverted from the original object and are reflective, like a mirror. They are mounted and placed behind glass sealed with paper tape to avoid tarnishing. Daguerreotypes are not reproducible—each image is a one-off; the only way to copy a daguerreotype is to take another daguerreotype of that image.
