Definition
The collodion process is a photographic technique that produces a wet-plate negative on a glass plate coated with a solution of collodion (cellulose nitrate dissolved in ether and alcohol) and a soluble photosensitive silver salt. The plate must be exposed and developed while still wet, typically within a few minutes.
Overview
Developed in the early 1850s, the collodion process rapidly supplanted earlier daguerreotype and calotype methods due to its relatively short exposure times, fine detail, and low cost. It enabled the creation of high‑resolution negatives that could be reproduced on multiple prints, most commonly by the albumen paper printing method. The technique dominated commercial and artistic photography from roughly 1851 until the emergence of dry‑plate gelatin processes in the 1870s, though it continued to be used by specialists and revivalists into the 20th and 21st centuries.
Etymology/Origin
The name derives from “collodion,” a viscous, transparent solution originally formulated in the 1840s as a medicinal plaster and wound dressing. The term collodion itself comes from the French colle (“glue”) and the suffix ‑odion, indicating a solution. When combined with silver nitrate, the collodion solution becomes light‑sensitive, giving the process its name.
Characteristics
- Materials: Glass plate, collodion solution, potassium iodide (or bromide), silver nitrate, ether, alcohol, and a portable darkroom.
- Preparation: The glass plate is cleaned, then flooded with the collodion‑silver iodide mixture; excess liquid is drained, leaving a thin, even coating.
- Timing: The plate must remain moist (hence “wet plate”) from preparation through exposure and development, typically within 10–15 minutes.
- Exposure: Compared with earlier processes, exposure times range from a few seconds to a couple of minutes, depending on lighting and lens aperture.
- Image Quality: Produces negatives with excellent resolution, fine grain, and a wide tonal range. Prints derived from collodion negatives exhibit sharp detail and subtle gradations.
- Limitations: Requires immediate on‑site processing, a portable darkroom tent or wagon, and careful handling of volatile chemicals (ether, alcohol, and silver nitrate), posing health and safety concerns.
- Variants: Includes the wet collodion (original), dry collodion (plates stored with a preservative before exposure), and ambrotype (a positive image viewed directly on the glass plate) and Tintype (positive on a thin iron sheet) adaptations.
Related Topics
- Daguerreotype
- Calotype (Talbotype)
- Albumen print
- Dry gelatin silver process
- Ambrotype
- Tintype (ferrotype)
- Photographic emulsions
- Historic photographic chemicals and safety practices
The collodion process remains a subject of interest among photographic historians and contemporary practitioners who value its distinctive aesthetic and hands‑on methodology.