Are all liquid rapid fixers the same?

Ammonnium thiosulfate is always present (I think), thus should the dilution always be the same?

I think that Kodak Flexicolor Fixer needs somewhat LESS dilution, but the others (Ilford's, Heico's, Kodak Rapid Fix, and others) are largely the same. Does anyone disagree?

Also, take Kodak Fixer with Hardner (powder): The formula has about 160g per liter of sodium thiosulfate (anhydrous), but I think that if you simply mix that amount of sodium thiosulfate in water, fixation will be faster. Why? Because the acidic hardener in K Fix powder slows down fixation.

Please comment, exclusive of manufacturer's directives. - David Lyga

Most films today are pre-hardened and the use of a hardening fixer is not needed. The presence of alum as the hardening agent greatly slows down washing rates.

The Kodak Rapid Fixer comes with the hardener in a separate bottle.

A waste if you don't need the hardener, but really useful if you tone prints and prefer to use hardener at the end of that process.

Michael R 1974: I don't know, I just thought that fixers made for the same purpose were largely the same in concentration. Perhaps there are minor deviations. And, yes, pH does affect fix time. - David Lyga