Method of manufacturing building elements from so-called foamed ceramics

In the method of manufacturing a block-like foamed ceramic building element in a mould of refractory material which comprises:

• (a) coating at least the bottom surface of the mould with a layer of a glass material or a glass-forming composition having a melting point of 800.degree.-1000.degree. C. and being non-expandable when heated,
• (b) charging an expandable ceramic composition into the mould, said expandable ceramic composition being capable of forming a foamed ceramic when heated to a temperature between 800.degree. and 1100.degree. C.,
• (c) heating the mould and its contents to temperatures between 800.degree. and 1000.degree. C. for a period of time sufficient for the foamed ceramic and the glass to fuse together at their interface,
• the improvement which comprises
• (1) said glass material or glass-forming composition being uncolored and free from substances which will cause coloring when the glass material or glass-forming composition is melted, said glass material or glass-forming composition being in the form of crushed particles, and
• (2) prior to charging the expandable mass to the mould placing on the layer of glass material or glass forming compositions a carrier sheet, said carrier sheet
• being composed of meltable or destructible material,
• carrying a layer of pigmented color glazing material,
• (3) said heating of the mould being carried out under oxidizing conditions to foam the ceramic and to fuse together the glass,
• whereby, after the expandable mass has expanded and the glass material or the glass-forming composition has been sintered and said carrier sheet has been melted or destroyed, the pigmented glaze layer appears as a colored background through the uncolored sintered glass layer.