In distinction to heat-releasing compounds (exothermic mixtures) that self-heat as a results of an heat evolving reaction, heat insulation compounds 1st absorb heat from the liquid metal wont to fill the mold till reaching equilibrium temperature; from this moment on, they shield the liquid casting metal against more heat losses for a definite time. Therefore, riser sleeves product of insulating compounds delay the start of hardening, promote seal-feeding and increase yields.
Insulating compounds may be used as a powder to hide risers. they’re spread over the open risers, covering the metal contained within the riser against heat emission.
