The silvered surface, sensitized in fumes of iodine, was placed in a camera for exposure. The plate was developed in mercury vapor. No negative was involved, and the image produced on the plate appears as both negative and positive when turned in the light. The surface of a daguerreotype is extremely fragile, requiring protection behind mat and glass in folding, booklike cases of leather covered wood or plastic. To set off the daguerreotype, most cases also contain linings of dark velvet or silk.
Daguerreotypes are one of a kind.
Copies required additional exposures. No photographic reproduction equals actually viewing such an image. Sizes of daguerreotypes were early standardized. A full or whole plate was the largest size ordinarily available. The salt combined with the silver nitrate to form light sensitive silver chloride.