Woman in a bonnet, c 1850.
© National Media Museum / Science & Society Picture Library
A hand-coloured daguerreotype portrait of a rather severe-looking woman in bonnet and shawl, taken by an unknown photographer in about 1855. In 1839, the Daguerreotype, invented by Louis Jacques Mande Daguerre [1787-1851], became the first photographic process to be announced to the public. A highly-polished silver surface on a copper plate was sensitised to light by exposing it to iodine fumes. After exposing the plate in a camera it was developed with mercury vapour. Daguerreotypes are unique images which may appear as a positive or negative depending on how light hits the surface.