A compound that reductively reacts with a colored substance rendering it colorless and/or soluble. Reducing bleaches are considered less destructive to fibers than oxidative bleaches. However, compounds bleached reductively can oxidize in air thus reverting to their prebleach color.
Examples of reducing bleaches include:
Sodium borohydride, Tetramethylammonium borohydride, tetraethylammonium borohydride, Sodium dithionite (sodium hydrosulfite); Sodium bisulfite, Sodium thiosulfate (Blankit), Sodium formaldehydesulfoxylate (Rongalite), Titanium trichloride, Titanium sulfate