Abstract: An electrochemical reactor suitable for reducing dye to leucodye, comprises at least four electrolytic cells, wherein the electrolytic cells are provided in the form of at least two stacks of at least two electrolytic cells each such that one stack at a time can be separated for cathode or anode regeneration during suspension preparation.

Abstract: An electrolytic dye reduction method comprises preparing a catholyte by dispersing a dye in a leucodye comprising electrolyte. In a preferred method the leucodye like leucoindigo is the sole dispersing aid.

Abstract: An electrolytic reactor comprises at least one electrolytic cell with an anode compartment and a cathode compartment separated by a separator, in particular a semipermeable membrane. The anode compartment comprises an inlet and an outlet for anolyte at opposed ends, said inlet and outlet being connected with each other via an anolyte circulation pipe equipped with a storage means for anolyte, an anolyte vessel and at least one adsorption filter for adsorbing molecular impurities. When molecular impurities comes from the cathode compartment through the separator, the electrolytic reactor acts also as a cleaning device for the catholyte.