After heating do not lift the metal rods by hand they ... or dull. It can be filled with hot water or heated on an electrical hot plate so that all four sides are at the same temperature.

A small amount of water is added to an aluminum soda can and brought to boiling on a hot plate or with a Bunsen burner ... then immediately remove the can from the heat and place in the ice water bath ...

Eventually, the metal foil will oxidize, and the entire hotplate will stop working. Repairs can be done with copper tape, but by the time that repair is needed, the heating element is already on ...