Kast-O-lite 30 Kast-O-lite 30 insulating castable refractory poured in a 1/2” thick layer gives a large measure of thermal protection, along with mechanical armoring, incase you are moving crucible tongs in and out of your equipment, and for general shop safety; it is use rated to 3000 F, is alumina based for flux tolerance, contains glass mini spheres for insulation, and is very resistant to thermal shock; it ways 90 lbs. per cubic foot (compared to 146 for regular refractory). Kast-O-lit