A launder is used to transport molten metal. The basic construction of a launder is a steel trough lined with refractory material to insulate the molten metal from the steel. (Insulating both thermally and chemically.) The molten metal will lose heat as gravity draws it down the launder. If the heat is lost too quickly, the metal will freeze in the launder. There are a number of factors that influence the rate of heat loss including: