The rate at which these develop varies as the electrolysis proceeds. Bubbles formed at one electrode may stream through the electrolyte towards the other electrode. The colour of the solution tends to fade, more quickly at the cathode side of the drop of solution. When a growth of metal from the cathode reaches a grain of copper oxide, it grows very rapidly through or around the grain. Fine drops of liquid form under the lid of the petri dish, mainly just above the anode.
Bubbles appear first at the anode, and much later at the cathode.
Bubbles may be seen earlier at the cathode at higher voltages. Sharp noises are heard when a lit match is held near the bubbles formed towards the end of the reaction process. This list of possible observations is not complete.