The Gelatine Silver process is the photographic process used with currently available black and white films and printing papers. A coating of silver salts in gelatine is added to the glass. These light sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many more years after their manufacture.
Gelatine is an animal by product of the hog and cattle industries and is made from animal bone after all minerals elements have been removed.
Its ability to swell allows chemicals to access the silver salts in emulsion and to wash the film free of chemicals once the silver image has been formed.