PURPOSE: To provide sanitary working environment and a natural tooth-like creamy color excellent in aesthetic properties without emitting unpleasant smell and any remaining carbon in a burned product by previously heat-treating a mixture composed of porcelain raw material powder and an organic substance, etc., in a vessel having a catalyst bed for catalytic combustion.

CONSTITUTION: Porcelain raw material powder [e.g. 50-70wt.% SiO2; 10-20wt.% Al2O3, 5-14wt.% K2O3, 4-7wt.% Na2O, 0-6wt.% BaO, 0-2wt.% CaO, 0-0.5wt.% MgO, 0-3wt.% B2O3 and 0-4wt.% TiO2] is mixed with an admixture liquid (≥50wt.% organic substance and water as the other component are contained and the organic substance may be alone or in a mixture of two or more thereof), irradiated with light for about 10 sec in a visible ray irradiator and cured. The cured product is then placed in a vessel having at least one surface constructed of a catalyst for catalytic combustion (e.g. platinum), heat-treated at 300-600°C for 3-20min, then heated to 800-1100°C at 40-50°C/min heating rate in a vacuum of 20-60mmHg and burned.