ASTM C965-23

Standard Practice for Measuring Viscosity of Glass Above the Softening Point

SIGNIFICANCE AND USE
3.1 This practice is useful in determining the viscosity-temperature relationships for glasses and corresponding useful working ranges. See Terminology C162.
SCOPE
1.1 This practice covers the determination of the viscosity of glass above the softening point through the use of a platinum alloy spindle immersed in a crucible of molten glass. Spindle torque, developed by differential angular velocity between crucible and spindle, is measured and used to calculate viscosity. Generally, data are taken as a function of temperature to describe the viscosity curve for the glass, usually in the range from 1 to 106 Pa·s.  
1.2 Two procedures with comparable precision and accuracy are described and differ in the manner for developing spindle torque. Procedure A employs a stationary crucible and a rotated spindle. Procedure B uses a rotating crucible in combination with a fixed spindle.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C965 − 23
Standard Practice for
1
Measuring Viscosity of Glass Above the Softening Point
This standard is issued under the fixed designation C965; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
3.1 This practice is useful in determining the viscosity-
1.1 This practice covers the determination of the viscosity
temperature relationships for glasses and corresponding useful
of glass above the softening point through the use of a platinum
working ranges. See Terminology C162.
alloy spindle immersed in a crucible of molten glass. Spindle
torque, developed by differential angular velocity between
4. Apparatus
crucible and spindle, is measured and used to calculate
viscosity. Generally, data are taken as a function of temperature 4.1 The apparatus shall consist of an electrically heated
to describe the viscosity curve for the glass, usually in the
furnace equipped with a temperature controller, temperature
6
range from 1 to 10 Pa·s. measuring equipment, a platinum alloy spindle, a crucible, a
device to rotate spindle or crucible, and equipment to measure
1.2 Two procedures with comparable precision and accu-
torque.
racy are described and differ in the manner for developing
NOTE 1—Spindles and crucibles manufactured from 90 % Pt–10 % Rh
spindle torque. Procedure A employs a stationary crucible and
or 80 % Pt–20 % Rh alloys have been found satisfactory for this purpose.
a rotated spindle. Procedure B uses a rotating crucible in
4.1.1 Procedure A employs an electrically heated tube-type
combination with a fixed spindle.
furnace with a fixed support for the crucible as shown in Fig.
1.3 This standard does not purport to address all of the
1. A platinum alloy resistance-heated crucible also may be
safety concerns, if any, associated with its use. It is the
used.
responsibility of the user of this standard to establish appro-
4.1.2 Procedure B employs a similar furnace but with a
priate safety, health, and environmental practices and deter-
removable, rotatable crucible support as shown in Fig. 2.
mine the applicability of regulatory limitations prior to use.
4.1.3 Furnaces other than resistance-wound muffle types
1.4 This international standard was developed in accor-
may be used provided they give uniform and stable tempera-
dance with internationally recognized principles on standard-
ture conditions. Temperature differences greater than 3 °C
ization established in the Decision on Principles for the
within the crucible (in glass) are excessive for high precision
Development of International Standards, Guides and Recom-
measurements.
mendations issued by the World Trade Organization Technical 4.1.4 A temperature controller shall be provided for main-
Barriers to Trade (TBT) Committee.
taining the glass temperature within 62 °C of a specified
temperature.
2. Referenced Documents 4.1.5 Temperatures shall be measured with a suitable ther-
mocouple calibrated in accordance with Test Method E220 in
2
2.1 ASTM Standards:
conjunction with a calibrated potentiometer or solid state
C162 Terminology of Glass and Glass Products
instrumentation capable of 0.5 °C accuracy. An immersion
E220 Test Method for Calibration of Thermocouples By
thermocouple is recommended but a thermocouple in air may
Comparison Techniques
be used provided measurements show equivalency.
4.1.6 A crucible to contain the glass similar to those shown
in Fig. 3 preferably shall be fabricated from a platinum alloy,
1
This practice is under the jurisdiction of ASTM Committee C14 on Glass and
but a refractory material may be used provided it does not
Glass Products and is the direct responsibility of Subcommittee C14.04 on Physical
contaminate the glass.
and Mechanical Properties.
4.1.7 A platinum alloy spindle with the geometry shown in
Current edition approved May 1, 2023. Published May 2023. Originally
Fig. 4 is recommended. An alternative design has a hollow
approved in 1981. Last previous edition approved in 2017 as C965 – 96 (2017).
DOI: 10.1520/C0965-23.
shaft to house the thermocouple (junction at the center of the
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
large diameter portion) which has the advantage of proximity,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
but the disadvantage of possible electrical disconnection during
Standards volume information, refer to the standard’s Document
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C965 − 96 (Reapproved 2017) C965 − 23
Standard Practice for
1
Measuring Viscosity of Glass Above the Softening Point
This standard is issued under the fixed designation C965; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers the determination of the viscosity of glass above the softening point through the use of a platinum alloy
spindle immersed in a crucible of molten glass. Spindle torque, developed by differential angular velocity between crucible and
spindle, is measured and used to calculate viscosity. Generally, data are taken as a function of temperature to describe the viscosity
6
curve for the glass, usually in the range from 1 to 10 Pa·s.
1.2 Two procedures with comparable precision and accuracy are described and differ in the manner for developing spindle torque.
Procedure A employs a stationary crucible and a rotated spindle. Procedure B uses a rotating crucible in combination with a fixed
spindle.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
C162 Terminology of Glass and Glass Products
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
3. Significance and Use
3.1 This practice is useful in determining the viscosity-temperature relationships for glasses and corresponding useful working
ranges. See Terminology C162.
4. Apparatus
4.1 The apparatus shall consist of an electrically heated furnace equipped with a temperature controller, temperature measuring
equipment, a platinum alloy spindle, a crucible, a device to rotate spindle or crucible, and equipment to measure torque.
1
This practice is under the jurisdiction of ASTM Committee C14 on Glass and Glass Products and is the direct responsibility of Subcommittee C14.04 on Physical and
Mechanical Properties.
Current edition approved Nov. 1, 2017May 1, 2023. Published November 2017May 2023. Originally approved in 1981. Last previous edition approved in 20122017 as
C965 – 96 (2012).(2017). DOI: 10.1520/C0965-96R17.10.1520/C0965-23.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C965 − 23
NOTE 1—Spindles and crucibles manufactured from 90 % Pt–10 % Rh or 80 % Pt–20 % Rh alloys have been found satisfactory for this purpose.
4.1.1 Procedure A employs an electrically heated tube-type furnace with a fixed support for the crucible as shown in Fig. 1. A
platinum alloy resistance-heated crucible also may be used.
4.1.2 Procedure B employs a similar furnace but with a removable, rotatable crucible support as shown in Fig. 2.
4.1.3 Furnaces other than resistance-wound muffle types may be used provided they give uniform and stable temperature
conditions. Temperature differences greater than 3°C3 °C within the crucible (in glass) are excessive for high precision
measurements.
4.1.4 A temperature controller shall be provided for maintaining the glass temperature within 62°C62 °C of a specified
temperature.
4.1.5 Temperatures shall be measured with Type R or S thermocouples a suitable thermocouple calibrated in accordance with Test
Method E220 in conjunction with a calibrated potentiometer or solid state instrumentation capable of 0.5°C0.5 °C accuracy. An
immersion thermocouple is recommended but a thermocouple in air may be used provided measurements show equivalency.
4.1.6 A crucible to contain the glass similar to those shown in Fig
...