Electrolysis occurs when electricity passes between two electrodes immersed in water. When using electrodes made of silver, this process produces Colloidal Silver , otherwise known as silver ions or more technically ionic Colloidal Silver , but there are some other things produced along the way.... think of these as side effects :) The electrolysis will cause molecules of silver to be freed from the silver electrode, and these silver ions are then floating in the water. The elecrolyis action also causes some of the water molecules to separate (oxygen and hydrogen freed from each other). Eventually, some of the silver ions will hook up with some of the oxygen ions. This forms silver oxide that then tends to be drawn towards the negative silver electrode IE> the cathode. Once the process has been going on long enough, you will visibly be able to tell which of the two silver electrodes is the negative, it will be the one that has grown more visibly black with accumulated stuff than the other electrode. This stuff may be the crud you have noticed.