PURPOSE: To enable such an intermittent work that does not exert a drastic fluctuation on the temp. of a furnace having a melting chamber and a working chamber for occasionally withdrawing glass by specifying the relations between the volume of the working chamber and the melting rate and use rate of the glass.

CONSTITUTION: This furnace is formed of a base structure section 6 defining the melting chamber 8 including the body of the molten glass, heating means 29, 41, a means for depositing a batch material on the body of the molten glass and the working chamber 12. The volume of the molten glass of the working chamber 12 decreases during the working time and is increased during the non-working time. The relations between the volume V of the working chamber 12, the rate P of production of the glass a day and the use rate R of the glass a day are expressed by V=2/3P+C, R=1/3P+V (where the volume of the glass in the working chamber 12 decreases down to the min. volume C at the end of the work and increases to the max. volume before the next start time.