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Collection Daguerreotypes

Glossary of Terms

  • Brass mat — Used to frame the image and provides a protective space between the daguerreotype plate and the cover glass. Some mats are stamped with the photographer's name and address.
  • Case — Daguerreotype cases are made from a variety of materials. The most common cases are made of wood covered with tooled leather or embossed paper. In 1854, thermal plastic union cases, noted for elaborate designs, came into use.
  • Daguerreotype — A plate of copper, lightly coated with silver. After cleaning and polishing the plate, exposure to iodine vapors created a light-sensitive surface that looked like a mirror. The plate, held in a lightproof holder, was then transferred to the camera and exposed to light. The plate was developed over hot mercury until an image appeared. To fix the image, the plate was immersed in a solution of sodium thiosulfate or salt and then toned with gold chloride.
  • Hallmark — Stamped marks on the daguerreotype plate which identify the plate manufacturer or photographic supply house. Hallmarks usually consist of symbols, initials, and/or numbers. The number indicates the ratio of silver to copper. The most popular number was 40, indicating 1 part silver to 39 parts copper. Lists of hallmarks used by plate manufacturers and the approximate years that they were produced can be used to date images. These lists may be found in reference books, such as Rinhart's The American Daguerreotype.
  • Preserver — A thin brass binding that holds the daguerreotype, brass mat, and cover glass together. Preservers were widely used in the 1850s.