Porous cleaning esp. building front slab prodn. - by firing porous ceramic coated with thin non-porous ceramic layer and top glaze layer

摘要

Porous ceramic prods. having bulk wt. 0.4-1.5kg/cu.dm. contain a glaze layer on at least one side of its surface. A non-porous layer is present between the glaze layer and the porous ceramic. Non-porous layer material melting temp. is above firing temp., its expansion coefft. is max. 1 times 10 power minus 6/deg.C smaller than that of the porous ceramic material and its contraction is min. 90% that of the porous ceramic material. The prods. are esp. large heat-insulating slabs for walls esp. visible, decorative building fronts. The bulk density is 0.4-1.5 kg/cubic dm. The ceramic surface requires no further treatment. The non-porous layer does not separate from the porous layer during firing and cooling, and crack-formation is prevented.