Collodium

Part of speech: noun

Definitions

1. A clear, viscous liquid made by dissolving nitrocellulose in a mixture of ether and alcohol, used in photography and medicine
2. A flammable solution created by treating cellulose with nitric acid and dissolving it in organic solvents, historically used for coating wounds and photographic plates
3. A sticky fluid composed of nitrated cellulose dissolved in ether and alcohol, formerly applied to skin injuries and employed in early photographic processes

Etymology: Collodium is an older spelling of "collodion", a sticky, clear liquid made by dissolving nitrocellulose in ether and alcohol. The name comes from Medieval Latin "collodium", which in turn goes back to the Ancient Greek adjective "kollōdēs", meaning "sticky" or "gluey". The Greek word itself is built from "kolla", glue, so the name describes the substance's most noticeable quality: once spread on a surface, the liquid dries into a thin, tough film. That tacky, film-forming quality is why the substance proved so useful. Once it dried, it could hold a coating firmly in place, and it became a standard medical dressing for covering small cuts and skin wounds. The same property made it valuable to photographers, who used it to bind light-sensitive chemicals to glass plates. The spelling "collodium" is now dated; "collodion" is the form in current use. Both forms keep the Greek root's original sense of stickiness.

Synonyms: collodion