REMOVAL OF REM-JET BACKING
The removal of rem jet backing is by immersing the film in an alkali solution, called a Prebath, that softens the binder of the water-soluble backing, and then in Backing Removal removing it by spray jets and rotating buffers.
This solution also contains a high concentration of the salt, sodium sulphate, which is photographically inert but which prevents the emulsion from swelling excessively.
It is important that there are sprays on the emulsion side to prevent the backing from the base creeping round to the emulsion where it can stick and is difficult to remove.
Backing left on the emulsion are seen as smears of very fine particles under a microscope. The only technique that will remove them apart from rewashing, which is sometimes ineffective, is to use a very fine abrasive on the emulsion side and "polish" it off.
Brass polish like "Bluebell" or "Brasso", made of a fine alumina powder was widely used. Rotating buffing rollers, of lamb's wool, plush or foam plastic, are used to ensure the complete removal of the backing.