SP-FastFix is a hybrid fixer that contains both sodium and ammonium ions. This allows us to package it as a powder in our Mylar pouch. Easier to ship, easier to mix than tradition powders.
Just add 450 ml of water (95°F/35°C) and wait for it to dissolve.
We call it FastFix since the fixing time is about half way between a traditional fixer and a true rapid fix. Capacity is about 20% greater than most other fixers (about 60 sheets of 4x5); shelf life (after mixing) is at least a year.
More detail on our blog: Fixing the Fixer Problem
Click here for the data sheet.