Low-porosity clay bricks are made from high-quality graphite, sintered mullite,“three-stone” materials, and low-impurity clays, which are formed under high pressure and sintered at high temperatures. These bricks have high compressive strength, resistance to erosion, a high refractoriness under load, and good thermal shock stability at medium to low temperatures. They are primarily used in the lower lattice and wall sections of the regenerator chambers in glass melting furnaces. When used below 950° C, they exhibit excellent resistance to alkali spalling.