Burners

A radiant having a high heat output and high thermal shock resistance comprising a body having an open high porosity structure of bonded refractory ceramic fiber, the continuous service temperature of fiber and bonding agent of said body being at least about 1000.degree.C, said body having gas passages therethrough through which a combustible gas mixture can be passed for combustion at the surface of the radiant and a surface configuration of raised square pyramids of side about one quarter inch and included angle between faces of adjacent pyramids about 60.degree., said gas passages being provided at corners of said pyramid where base lines of adjacent pyramids intersect, the porosity of said body, exclusive of said gas passages, being at least about 70 percent.