The ASTM C1351M test method is essential for measuring the viscosity of glass within the range where rotational viscometry and beam-bending viscometry are helpful. It can be used to calculate the temperature/viscosity curve near the softening point. ASTM C1351 (Standard Test Method for Measurement of Viscosity of Glass Between 104 Pa·s and 108 Pa·s by Viscous Compression of a Solid Right Cylinder) is useful for offering information about the behavior of glass.
ASTM C1351M Measurement of Viscosity of Glass by Viscous Compression
What is ASTM C1351M?
ASTM C1351M Sample Preparation Guide
For ASTM C1351M, the specimen’s (circular cylinder) diameter should be between 6 mm and 12 mm, and thickness should be between 3 mm and 6 mm.
What are the Testing Procedure and Requirements of ASTM C1351M?
In the ASTM C1351M test method, the background deflection curve is generated against temperature by measuring the upper loading plate in contact with the lower support plate. Then, the thickness change of the specimen is calculated by algebraic subtraction of this background curve from the measured angle. The extensometer, time, and temperature data are recorded when an operational deflection rate is reached. When an operational deflection rate is reached, the extensometer, time, and temperature data are recorded to reduce data. The viscosity is corrected by using the calibration curve. This is done by multiplying the viscosity by the fractional correction factor corresponding to that viscosity. The viscosity is corrected using the calibration curve by multiplying the viscosity by the fractional correction factor corresponding to that viscosity.
Analysis Result and Interpretation
ASTM C1351 measures the viscosity of glass from 104 Pa·s to 108 Pa·s by determining the rate of viscous compression of a small, solid cylinder.
The equation for calculating the viscosity in ASTM C1351M testing is:
ŋ=2Mgh530V dh/dt2h3+V1+aT
Here
Ŋ is viscosity, Pa·s
M is the applied load
dh/dt is the compression rate
g is the acceleration of gravity
h is the specimen thickness at time t
V is the specimen volume
α is the glass mean coefficient of thermal expansion
Updated on August 8, 2026
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