dryplate

A dry plate, in photographic terms, refers to a glass plate coated with a gelatin-based emulsion containing silver halide crystals that records an image when exposed to light. Unlike the earlier wet collodion process, the dry plate could be prepared, coated, and stored in a dry state, allowing photographers to load and expose plates in the field without mixing chemicals on site. After exposure, the plate is developed, fixed, and washed to produce a negative.

The dry plate concept emerged in the 1870s. Richard Leach Maddox introduced gelatin-based dry plates in the early 1870s, enabling a practical, portable alternative to wet plates. Over the following decades, improvements by various scientists and manufacturers, notably in the 1880s and 1890s, increased emulsion sensitivity and shortened exposure times. Plates were sold pre-coated and sealed in light-tight packets, ready for use in standard large-format cameras. Common plate sizes included 4x5 inches and larger formats, though smaller sizes existed.

In operation, a dry plate is loaded into a camera, exposed, and then processed in a darkroom. Development converts the latent image into a visible negative, which is then fixed and washed. The technology played a crucial role in the democratization of photography, enabling faster shoots and more portable equipment for amateur and professional photographers alike.

The dry plate ultimately gave way to flexible film in the late 19th and early 20th centuries, as roll film and single-use cassettes offered even greater convenience and rapid development. By the 1920s, gelatin film had largely supplanted glass dry plates, though the latter marked an essential step in the evolution of modern photography.