PROBLEM TO BE SOLVED: To enable effective vacuum defoaming of a high flow rate of the molten glass even when the degree of vacuum is lowered in order to reduce the difference of liquid surface levels between a melting furnace and a vacuum defoaming vessel by providing the production process with a melting stage for mixing fuel with gaseous oxygen to combust the fuel-oxygen mixture and to melt a glass raw material by the generated heat of combustion, a vacuum defoaming stage and a forming stage for forming the defoamed molten glass into glass articles. ;SOLUTION: In the above vacuum defoaming stage of this production process, the pressure is preferably 0.1 to 0.5 atm. Also, by mixing gaseous oxygen with a natural gas and combusting the resulting mixture, the gaseous combustion product contains water and carbon dioxide in amounts about 3.5 times as much as the amounts of those in the gaseous combustion product when an air-natural gas mixture is combusted and accordingly, comparatively large amounts of water and carbon dioxide are dissolved in molten glass G. Since the amount of dissolved water is sufficiently large, a sufficient defoaming effect is obtained under a ≥0.1 atm pressure, to lower the lifting height of the vacuum defoaming vessel 34 and to solve problems with respect to a similar larger defoaming device. Further, the molten glass G is transmitted to the vacuum defoaming device 30. The vacuum defoaming vessel 34 is placed in a vacuum housing 32 and a riser pipe 36 and a downcomer pipe 38 are placed on the sides of the both ends of the vacuum defoaming vessel 34 respectively and the molten glass G after the defoaming treatment is introduced into a float bath 52.;COPYRIGHT: (C)2000,JPO
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