CAST IRON has a melting point of 2,190 ° F
  POT METAL - is the primary component of pot metal is zinc and has a low melting point: 786 ° F. Because of a lot lower meltaing point, Pot Metal
is chaeper and a lot easier to mold than Cast Iron.
  SPELTER is sometimes used merely as a synonym for zinc. It doesn't hold details as well as bronze