Yes Mrs.Lightning it could be the copper of wires I used ,but realy I dont know its real make ,possibly copper and this could be accumulation of copper oxidised ions on one of the electrodes (red end for sure) Your suggestion of using wrist bands to cover the plate is interesting but you need conductivity to close the circut ,how to do that ,when you use it on your body the body conduct electricity ,but on plastic dish it wont work,besides our zapper ..super delux 2003 is so sensitive to this ,if it detects the slightist poor conductivity ,it beebs and shuts off.

Any how the bottom line is the mere observation of this electrophoretic tendency and both success and my self experienced rash and red marks when using salt water mostly on red end wrist strap contact point with our hands/ankles.

One observation ,when we checked the wires (black end) on experiment-1 after 24 hours of 4.5 v dc voltage use, we found its end (exposed wire end) cut and snapped up ,or now we know for sure it was disolved completlty and all that stuff that disappeared has migrated to the other side of the plate (blueish color).
thanks Yes Mrs.Lightning for pinpointing that ,possibly copper and this could be accumulation of copper oxidise on one of the electrodes (red end for sure) .