A high temperature ceramic filter is produced from a composition containing efractory cement, aggregate, pore forming additives, and sintering agents. The pore forming additives are synthetic or organic powders or fibers which sublimate, melt, or otherwise disintegrate to produce in situ pores in the cement during the refractory treatment of a cast filter. The filters produced are permeable to high temperature gases commonly found in a coal furnace and can be used to collect particulate matter present in those gases.