What exactly does a clearing bath do?

[Jake S. Del Mastro]

I've been experimenting with B&W reversal developing recently using some DIY chemicals and I was wondering about the clearing bath. What exactly does it do? I've heard that it prevents your film from having a yellow cast (a problem I've been encountering), but how exactly does it do that? Where is the yellow coming from? Is it silver oxide?

I've heard about three different clearing bath chemicals, sodium sulphite, sodium metabisulphite and potassium metabisulphite. Do they all do the the same thing or does it depend on which bleach you use?

[Simon Wyss]

The silver made soluble by the bleach bath is dissolved out of the film in the clearing bath.