Collodion was widely used to glue electrodes to the head for Electroencephalography until the 1990s. It has been replaced by water-based gels in most uses to avoid the contact with acetone, which is not only contained in the glue but needed in quantity for electrode removal.
Collodion is also used in theatrical Makeup for various effects, such as simulating old-age wrinkles or scars.
Collodion also finds use in the cleaning of Optics such as Telescope mirrors. The collodion is applied to the surface of the optic, usually in two or more layers. Sometimes a piece of thin cloth is applied between the layers, to hold the collodion together for easy removal. After the collodion dries and forms a solid sheet covering the optic, it is carefully peeled away taking contamination with it.
