| 摘要 |
PROBLEM TO BE SOLVED: To shorten a time for cooling the inside of a furnace from a sintering temperature to a temperature at which a preform can be taken out, after sintering a porous glass preform by using furnace gas containing corrosive gas.SOLUTION: In a production method of a glass preform, a porous glass preform 16 is stored into a furnace core tube 2 in a heating furnace, and at least corrosive gas is supplied into the furnace core tube 2, and the porous glass preform 16 is subjected to a dehydration treatment and a sintering treatment to obtain a transparent glass preform, and then after the temperature of furnace gas containing corrosive gas leaking out from inside the furnace core tube 2 falls to or below a prescribed temperature, the furnace gas is cooled by being circulated through a heat exchanger 7. |
