collodión

Collodión is a viscous liquid made by dissolving nitrocellulose in a mixture of alcohol and ether. When the solvent evaporates, the nitrocellulose forms a tough, flexible, and transparent film. This property made it a key component in early photographic processes, most notably the wet-plate collodion process. In photography, collodion served as the binder for light-sensitive silver halide crystals on a glass plate or other substrate. The plate had to be coated, exposed, and developed while the collodion was still wet, hence the name of the process. After development, the image was fixed, typically with sodium thiosulfate. The resulting glass plates, known as ambrotypes or tintypes depending on the substrate, produced sharp and detailed images. Beyond photography, collodion has found applications as a topical antiseptic and in the manufacture of flexible films and coatings due to its adhesive and film-forming qualities. Its historical significance is primarily tied to the revolution it brought to photography in the mid-19th century.