This paper dealt with the viscosity measurement of transparent fused silica by S. English's method.
The elongation caused by weight hanged at the end of the specimen is measured by cathetometer as illustrated.
The viscosity is caluculated from following formula.
The softning temperature of the specimen is about 1150°C.
Duaring the investigation, minute crystals are observed on the surface of the specimen. This is crystobalite devitrified from fused silica.
By devitrification, elongation of specimen decressed with the lapse of time.
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