Daguerreotype

About

Daguerreotype is a direct positive photograph formed on a copper plate coated with a thin layer of silver.

Portrait de Louis Jacques Mandé Daguerre (1787-1851), inventeur du daguerréotype, Thiesson, E., 1844, 8,9 x 6,8 cm, musée Carnavalet, Histoire de Paris

Historical period of production and use

The daguerreotype was a huge commercial success, dominating the market for photographic processes until the early 1850s, when it began to be supplanted by collodion negatives.

Producing a daguerreotype is a long and painstaking process involving a series of steps. First, the manufacturer applies the silver coating to the plate. After the silver layer is meticulously polished and buffed, the plate is sensitized with iodine vapors. It is now ready for exposure; the exposure time may vary from several minutes to just a few seconds, depending on the lighting conditions and whether other chemicals were added to accelerate the process.

Manufacturing

Producing a daguerreotype is a long and painstaking process involving a series of steps. First, the photographer buys copper plates that have been electroplated with silver. After the silver layer is meticulously polished, the plate is sensitized with iodine and/or brome vapours. The plate should then be exposed immediately afterwards, for a period ranging from several minutes to just a few seconds, depending on the lighting conditions and whether other chemicals were added to accelerate the process. The latent image is then developed using hot mercury vapour. The plate is then fixed with sodium thiosulfate starting in 1841 to fix the image, and then rinsed, eventually gilded, then washed and dried.

Identification

Because the silver-coated plates were extremely physically and chemically fragile, daguerreotypists learned right from the start to protect their images by placing them under glass, in decorated frames or cases inspired by those previously used for miniatures. These are important elements used to authenticate and date these works. The fact that the image can be viewed in both positive and negative, depending on the angle of light reflection, is another important clue to identification (amphitypic character).

Deterioration

The daguerreotype image is very sensitive to friction, which is why it is displayed under glass. It easily tarnished at its outer edges, with a circular alteration that can show iridescent colours, when the framing or mounting system has lost its hermeticity and allows oxygen, humidity and pollutants from the ambient air to penetrate. However, the daguerreotype and its mounting system form a coherent material and historical whole, and we must try to preserve it, even if it is no longer effective.

Enlarged detail x 8 © ARCP / Mairie de Paris

Credits

Visual Glossary of Photographic Processes © ARCP / Mairie de Paris, 2023

Glossary