Method of producing glazed ceramic building materials

In the known method of producing foamed ceramic bodies by:

• (a) introducing into an open refractory mold a SiO.sub.2 -containing composition that is known to have the ability of foaming and expanding in volume when heated to 800.degree.-1000.degree. C.,
• (b) heating said refractory mold and composition under strongly oxidizing conditions to a temperature within the range of 800.degree.-1000.degree. C. for a time sufficient to cause the SiO.sub.2 -containing composition to foam and expand in volume,
• (c) cooling the foamed ceramic body, and
• (d) removing the foamed ceramic body from the refractory mold, the improvement which comprises, prior to step (a), depositing on the bottom of the refractory mold a layer consisting of particles of crushed glass material, said crushed glass material having a melting point of 800.degree.-1200.degree. C. and said layer of crushed glass material being incapable of foaming on heating at a temperature of 800.degree.-1200.degree. C., said mold containing a member selected from the group consisting of carbon and carbon-containing materials, said latter materials being capable of forming carbon upon heating to said temperatures, whereby, in proceeding according to steps (a) and (b) the lower layer in the mold, consisting of crushed glass, will sinter together to form a dense lower surface layer and this dense lower surface layer will also be united by sintering to the overlying layer of the foamed SiO.sub.2 -containing composition, said oxidizing conditions being sufficient to oxidize said carbon and said organic compounds thereby to prevent formation of non-glossy spots on the glaze surface.