Kollodium

Kollodium, or collodion in English, is a viscous, syrupy solution of nitrocellulose (cellulose nitrate) in a mixture of ether and alcohol. The name reflects the gel-like film it forms as the solvents evaporate. Typical formulations contain a small percentage of nitrocellulose dissolved in ether with a portion of alcohol; the exact composition varies by application. The solvent pair makes the solution highly flammable and volatile, so handling requires good ventilation and avoidance of open flames.

Historically, collodion was central to the wet-plate collodion photographic process introduced in the early 1850s. A glass plate was coated with collodion and then sensitized in a silver nitrate bath to form a light-sensitive emulsion. The plate had to be exposed and developed while still wet, producing high-resolution negatives on glass. Variants included salted collodion and different silver-bath formulations; the method was eventually superseded by dry-plate processes in the late 19th century.

Collodion also found medical and industrial uses. Flexible collodion refers to formulations that dry to a transparent, elastic film and have been used as wound dressings or protective skin sealants, sometimes as carriers for medicaments. It can be applied as a liquid and later peeled or washed away with solvent. In addition to its photographic and medical roles, collodion has served as a film-forming vehicle in coatings and varnishes for various substrates.

Safety considerations are important. The solvents (ether and alcohol) are highly flammable, and vapors can be hazardous if inhaled. Collodion should be stored in tightly closed containers away from heat sources and used in well-ventilated areas.