Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by function]
6. photographic materials
7. photographic media
8. photographic plates

Anotations

Scope note:

Initially, the term referred to sheets of glass coated with collodion subsequently sensitized and dried. In 1871 Richard Leach Maddox discovered that an emulsion of gelatin containing a sensitive silver salt could be exposed to the action of light in a dry state. This provided a leap forward in photographic media as it simplified the process of taking photographs, avoiding the necessity of plates being prepared immediately before exposure, and processed immediately after.