Quote Originally Posted by CBG View Post

Wash aids are rather gentle in effect, merely allowing better
diffusion of water and chemicals in and out of the paper base.
Wash aids are invariably alkaline, mildly to quite. As well
as sodium sulfite alone or laced with the bisulfite there is
sodium carbonate. The latter recommended by Agfa.

I believe the mechanism involved is ion exchange.
The hydroxyl ion population being high results in
detachment of the silver bering thiosulfate
ions. Non silver laden thiosulfate, I'd
suppose ditto.

Quite a few chemicals can serve well as hypo
clearing agents. Sodium sulfite is the only
one to be quantified, publicly. Dan