Well, at least the stability of the permanganate bleach can be improved easily.
Add about 20g Calgon per liter and the result should be much better.
Look for this agfa link for further explanation. www.google.com/patents/EP1006408A1?cl=en
The final formulation will look this way. The text is quite promising, but I must admit that I haven’t used it till now…
Water 700 ml
M 19 (Natriumkaliumhexametaphosphat) 20 g
Potassium permanganate 2 g
Sulfuric acid (20 wt -%) 27 ml
Fill with water to 1000 ml (pH = 1.4)
In this movie forum is roughly the same formulation, just slightly different sulfuric acid concentration.