Daguerreotype

Invented in Paris by L.J.M. Daguerre in 1839, it was the first commercial photographic process. It used a copper plate with a polished silver surface sensitized by iodine fumes which was exposed in a camera, and the image developed over heated mercury vapour. There is no negative but a reversed plate mounted behind protective glass in a decorative case. It became a widely popular process for portraiture as refinements in technique were made and exposure times considerably reduced.