ASTM C965-96(2002)

Standard Practice for Measuring Viscosity of Glass Above the Softening Point

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 10 6 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Oct-1996
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaces: ASTM C965-96 - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 10-Oct-1996
• Replaced By: ASTM C965-96(2007) - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 01-Apr-2007
• Referred By: ASTM C1351M-96(2022) - 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 [Metric]
• Effective Date: 10-Oct-1996
• Referred By: ASTM C1350M-96(2019) - Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range (Approximately 10⁸ Pa·s to Approximately 10¹³ Pa·s) by Beam Bending (Metric)
• Effective Date: 10-Oct-1996

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C965–96 (Reapproved 2002)
Standard Practice for
Measuring Viscosity of Glass Above the Softening Point
This standard is issued under the fixed designation C 965; 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 (e) indicates an editorial change since the last revision or reapproval.
4 4
1. Scope measuring equipment, a platinum alloy spindle, a crucible, a
device to rotate spindle or crucible, and equipment to measure
1.1 This practice covers the determination of the viscosity
torque.
ofglassabovethesofteningpointthroughtheuseofaplatinum
4.1.1 Procedure A employs an electrically heated tube-type
alloy spindle immersed in a crucible of molten glass. Spindle
furnace with a fixed support for the crucible as shown in Fig.
torque, developed by differential angular velocity between
1. A platinum alloy resistance-heated crucible also may be
crucible and spindle, is measured and used to calculate
used.
viscosity.Generally,dataaretakenasafunctionoftemperature
4.1.2 Procedure B employs a similar furnace but with a
to describe the viscosity curve for the glass, usually in the
removable, rotatable crucible support as shown in Fig. 2.
range from 1 to 10 Pa·s.
4.1.3 Furnaces other than resistance-wound muffle types
1.2 Two procedures with comparable precision and accu-
may be used provided they give uniform and stable tempera-
racy are described and differ in the manner for developing
ture conditions. Temperature differences greater than 3°C
spindle torque. Procedure A employs a stationary crucible and
within the crucible (in glass) are excessive for high precision
a rotated spindle. Procedure B uses a rotating crucible in
measurements.
combination with a fixed spindle.
4.1.4 A temperature controller shall be provided for main-
1.3 This standard does not purport to address all of the
taining the glass temperature within 62°C of a specified
safety concerns, if any, associated with its use. It is the
temperature.
responsibility of the user of this standard to establish appro-
4.1.5 Temperatures shall be measured with Type R or S
priate safety and health practices and determine the applica-
thermocouples calibrated in accordance with Method E 220 in
bility of regulatory limitations prior to use.
conjunction with a calibrated potentiometer or solid state
2. Referenced Documents
instrumentation capable of 0.5°C accuracy. An immersion
thermocouple is recommended but a thermocouple in air may
2.1 ASTM Standards:
be used provided measurements show equivalency.
C 162 Terminology of Glass and Glass Products
4.1.6 A crucible to contain the glass similar to those shown
E 220 Method for Calibration of Thermocouples by Com-
in Fig. 3 preferably shall be fabricated from a platinum alloy,
parison Techniques
but a refractory material may be used provided it does not
3. Significance and Use
contaminate the glass.
4.1.7 A platinum alloy spindle with the geometry shown in
3.1 This practice is useful in determining the viscosity-
Fig. 4 is recommended. An alternative design has a hollow
temperature relationships for glasses and corresponding useful
shaft to house the thermocouple (junction at the center of the
working ranges.
large diameter portion) which has the advantage of proximity,
4. Apparatus
butthedisadvantageofpossibleelectricaldisconnectionduring
torque measurement.
4.1 The apparatus shall consist of an electrically heated
furnace equipped with a temperature controller, temperature
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 Oct. 10, 1996. Published December 1996. Originally
e2
published as C 965 – 81. Last previous edition C 965 – 81 (1996) .
2 4
Annual Book of ASTM Standards, Vol 15.02. Spindles and crucibles manufactured from 90% Pt–10% Rh or 80% Pt–20% Rh
Annual Book of ASTM Standards, Vol 14.03. alloys have been found satisfactory for this purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C965–96 (2002)
1—Furnace Winding
2—Crucible
3—Spindle
4—Shaft
5—Viscometer (providing both rotation and torque measurement)
6—Thermocouple
FIG. 1 General Arrangement for Rotating Spindle, Fixed Crucible
Scheme (Procedure A)
NOTE 1—Details are the same as in Fig. 1 except that the viscometer is
4.1.8 Ameasurement system is necessary for measurement
replaced by a torque measuring device, and the crucible is mounted on a
of spindle torque to an accuracy of 1 %.
removable rotatable stand.
FIG. 2 General Apparatus Arrangement for Rotating Crucible
5. Preparation of Test Glass
Scheme (Procedure B)
5.1 Select a mass of glass that is free of foreign material.
Break or cut glass into pieces, each weighing about 10 to 50 g,
and place the correct quantity into the crucible that will make Avoid very small pieces of glass in the charge as they tend
the molten charge reach a level at some fixed distance (several
to make the molten glass seedy.
millimetres) above the point where the spindle narrows down. 5.2 Place the filled crucible in proper position in the furnace
Theweightofglassrequiredcanbeapproximatedsatisfactorily and heat to a temperature that lowers the viscosity of glass
with the following expression for a cylindrical crucible: sufficiently to allow trapped air bubbles to be released. This
temperature should be below the original melting temperature
W 5 [pd ~L 1 h!/4 2 V #r ~1 2 0.0007a! (1)
T s
to avoid reboil. If reboil occurs, allow additional time for the
glass to clear. Hold at this temperature at least 20 min before
where:
h = distance between crucible floor and spindle tip, mm starting measurements.
(generally greater than 10 mm to avoid end effects)
W = glass charge weight at room temperature, g, 6. Calibration and Viscosity Determination
T
d = inside diameter of crucible, mm,
6.1 The use of several standard reference glasses (see
L = immersed portion of spindle, mm,
Appendix X1), available from the National Institute of Stan-
V = volume of immersed portion of spindle, mm ,
s
dards and Technology, is recommended. These provide a wide
r = density of glass at room temperature, g/cm , and
range of temperatures and viscosities for calibration.
a = 0 to 300°C thermal expansion coefficient, cm/cm·°C
6.2 For constant angular velocity rotation:
(3 10 ).
h}V/v (2)
Equipment such as the Brookfield RVT or HBT manufactured by Brookfield
Engineering Laboratories, Inc., 240 Cushing St., Stoughton, MA 02072, or See NIST Special
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