Ilford Rapid Fixer is Ammonium Thiosulfate based and is incompatible with hardener. If you want hardening, then you want Hypam, which as mixed is non-hardening, although it is hardener compatible, I haven't seen a jug of the hardener in years. Ilford says their films do not need hardening unless machine processed in a machine that requires it, and doesn't recommend it for their papers either.....