The image is then made permanent by treatment in a photographic fixer, which removes the remaining light sensitive silver halides.

Photographic fixer is a mix of chemicals used in the final step in the photographic processing of film or paper.

After the formation of dyes is complete, the silver image is removed in processing by a specialty photographic fixer called bleach fix or blix.

The paper that has been exposed is processed, first by immersion in a photographic developer, halting development with a stop bath, and fixing in a photographic fixer.

Silver halides are soluble in solutions of sodium thiosulfate () which is used as a photographic fixer, to remove excess silver halide from photographic emulsions after image development.

A book that reflects both Ms. Brodsky's emphasis on concept and Mr. Hutchins's on the physical is "Fixer," by Berwyn Hung, a worn-looking volume immersed in a narrow tank of photographic fixer.

In this application to photographic processing, discovered by John Herschel and used for both film and photographic paper processing, the sodium thiosulfate is known as a photographic fixer, and is often referred to as hypo, from the original chemical name, hyposulphite of soda.

Ammonium thiosulfate is used in photographic fixers (so called rapid fixers; they work more quickly than sodium thiosulfate fixers) and for leaching of gold and silver (it works with presence of copper as a catalyst here; this process is a nontoxic alternative of the standard cyanide one).

He discovered sodium thiosulfate to be a solvent of silver halides in 1819, and informed Talbot and Daguerre of his discovery that this "hyposulphite of soda" ("hypo") could be used as a photographic fixer, to "fix" pictures and make them permanent, after experimentally applying it thus in early 1839.