This article discusses the creation of a porous mullite ceramic through the incorporation of fly ash cenospheres (FAC) into mullite powder through the gelcasting process. Sintering temperature and the amount of FAC added were investigated as factors affecting density and strength. The authors found that the porous mullite ceramics had a high strength, and high porosity (48.1-72.2%) Thermal conductivity was measured and was determined to be 0.16-0.22 W/mK....