BS 7034-2:1988

National foreword
Committees responsible
Method
0 Introduction
1 Scope and field of application
2 Reference
3 Definitions
4 Apparatus
5 Test specimen
6 Procedure
7 Expression of results
8 Test report
Annexes
A Typical example of flow field in rotation viscometers
B Typical example of a rotation viscometer
C Bibliography
Figures
1 Relative decrease p in the flow field coefficient f
   as a function of the ratio of the radius of crucible
   ra to the radius of plunger ri
2 Schematic example of a Searle-type rotation
   viscometer for glass melts

Lays down a method of determining, by means of rotation viscometers, the dynamic viscosity of glass and, in particular, the viscosity-temperature relationship at any temperature or viscosity within the range of measurement. This covers the ranges of viscosity for melting, refining and working of glass. The method allows for continuous measurements and for measurements under various shearing stresses to check whether or not the glass behaves as a Newtonian liquid. Covers references, definitions, apparatus, test specimen, procedure, expression of results and test report.

This part of ISO 7884 specifies a method of determining, by means of rotation viscometers, the dynamic viscosity of glass and, in particular, the viscosity-temperature relationship at any temperature or viscosity within the range of measurement. This covers the ranges of viscosity for melting, refining and working of glass.

This method allows for continuous measurements and for measurements under various shearing stresses (i.e. for the determination of flow curves) in order to check whether or not the glass behaves as a Newtonian liquid.

Dependent on the particular viscosity-temperature relationship of the glass tested, the viscosity range covered by this method extends approximately from 10 to 10⁸ dPa s²⁾ in the temperature range from about 1 600 to 600 °C, the torque necessary ranging from 0,1 to 20 N mm according to the construction of the apparatus. The method is applicable if the rotational frequency does not exceed 8 s^-1; however, at rotational frequencies above 1 s^-1 it should be ascertained that inertia forces are negligible.