METHOD OF MANUFACTURING GLASS PREFORM

摘要

PROBLEM TO BE SOLVED: To provide a method of manufacturing a glass preform reduced in the number of bubble with sufficient dehydration by controlling dehydrator concentration or traverse speed complying with the bulk density of the porous glass preform to be treated. SOLUTION: A furnace has an inlet of the porous glass preform at its upper part, a heater assembled in it, a core tube to isolate the heater to the preform and an elevator to traverse the preform upward and downward. The preform is traversed upward and downward and heated sequentially to the longitudinal direction and dehydrated by the exposing of an adsorbed or involved gas in the preform to an atmospheric furnace gas containing chlorine or a chlorine compound as a dehydrator. The manufacturing method comprises the above primary heat treatment process and the secondary heat treatment process to transparentize the preform. The dehydrator concentration or the traverse speed in the primary process is changed complying with the bulk density of the preform.