The present invention is related to an electrochemical processor, which comprises two electrodes of different electrochemical potential, which are bridged via an electrolyte. Upon, completion of the electric circuit between the two electrodes, the second electrode is oxidized and therefore changed in at least one physical parameter, e.g. the second electrode becomes transparent. The electrochemical processor is characterized in that the surface of the second electrode, which is in contact with the electrolyte, is partially covered with an electrically insulating material, wherein this material is adjacent to the electrolyte. Moreover, the present invention relates to the use of this electrochemical processor and a method of composing such electrochemical processor.