Many thanks.... I have a large box of lightweight firebricks from 1970 or so. We made a quicky kiln with them by stringing nichrome wire inside. Held down by nails or two prong wall fasteners
McMaster Carr sells somehting close to it, alumina based, if you ever want to build another one.
Temperature Range: 0° to 2300° F
Heat Flow Rate (K-factor): 0.85 Btu/hr. x in./sq. ft. @ 1112° F
Density: 19-20 lbs./cu. ft.
Thick. Size Each Each
1" 24" x 36" Stock #93595K73 $110.35