Hollow cylinder made of moldable, exothermic riser material which is inserted into the sand mold and forms a sheath around the cylindrically designed, open riser.
The exothermic reaction (ignition of the material) is initiated by the liquid metal.
The effect of the exothermic sheathes is not to transfer heat to the metal, as is often assumed, but mainly to provide an additional insulating effect on the ignited, hot, glowing inserted sheath. Exothermic sleeves can be adjusted to suit the corresponding castings and are often combined with breaker cores.
Insulating riser sleeve