ASTM C965-96(2007)

Standard Practice for Measuring Viscosity of Glass Above the Softening Point

SIGNIFICANCE AND USE
This practice is useful in determining the viscosity-temperature relationships for glasses and corresponding useful working ranges. See Terminology C 162.
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: 31-Mar-2007
• 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(2002) - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 01-Apr-2007
• Replaced By: ASTM C965-96(2012) - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 01-Mar-2012
• 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: 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: 01-Apr-2007

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 2007)
Standard Practice for
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 4. Apparatus
1.1 This practice covers the determination of the viscosity 4.1 The apparatus shall consist of an electrically heated
ofglassabovethesofteningpointthroughtheuseofaplatinum furnace equipped with a temperature controller, temperature
alloy spindle immersed in a crucible of molten glass. Spindle measuring equipment, a platinum alloy spindle, a crucible, a
torque, developed by differential angular velocity between device to rotate spindle or crucible, and equipment to measure
crucible and spindle, is measured and used to calculate torque.
viscosity.Generally,dataaretakenasafunctionoftemperature
NOTE 1—Spindles and crucibles manufactured from 90% Pt–10% Rh
to describe the viscosity curve for the glass, usually in the
or 80% Pt–20% Rh alloys have been found satisfactory for this purpose.
range from 1 to 10 Pa·s.
4.1.1 Procedure A employs an electrically heated tube-type
1.2 Two procedures with comparable precision and accu-
furnace with a fixed support for the crucible as shown in Fig.
racy are described and differ in the manner for developing
1. A platinum alloy resistance-heated crucible also may be
spindle torque. Procedure A employs a stationary crucible and
used.
a rotated spindle. Procedure B uses a rotating crucible in
4.1.2 Procedure B employs a similar furnace but with a
combination with a fixed spindle.
removable, rotatable crucible support as shown in Fig. 2.
1.3 This standard does not purport to address all of the
4.1.3 Furnaces other than resistance-wound muffle types
safety concerns, if any, associated with its use. It is the
may be used provided they give uniform and stable tempera-
responsibility of the user of this standard to establish appro-
ture conditions. Temperature differences greater than 3°C
priate safety and health practices and determine the applica-
within the crucible (in glass) are excessive for high precision
bility of regulatory limitations prior to use.
measurements.
4.1.4 A temperature controller shall be provided for main-
2. Referenced Documents
taining the glass temperature within 62°C of a specified
2.1 ASTM Standards:
temperature.
C162 Terminology of Glass and Glass Products
4.1.5 Temperatures shall be measured with Type R or S
E220 Test Method for Calibration of Thermocouples By
thermocouples calibrated in accordance with Test Method
Comparison Techniques
E220 in conjunction with a calibrated potentiometer or solid
3. Significance and Use state instrumentation capable of 0.5°C accuracy.An immersion
thermocouple is recommended but a thermocouple in air may
3.1 This practice is useful in determining the viscosity-
be used provided measurements show equivalency.
temperature relationships for glasses and corresponding useful
4.1.6 Acrucible to contain the glass similar to those shown
working ranges. See Terminology C162.
in Fig. 3 preferably shall be fabricated from a platinum alloy,
but a refractory material may be used provided it does not
This practice is under the jurisdiction of ASTM Committee C14 on Glass and
contaminate the glass.
Glass Products and is the direct responsibility of Subcommittee C14.04 on Physical
4.1.7 A platinum alloy spindle with the geometry shown in
and Mechanical Properties.
Fig. 4 is recommended. An alternative design has a hollow
Current edition approved April 1, 2007. Published May 2007. Originally
approved in 1981. Last previous edition approved in 2002 as C965 – 81 (2002). shaft to house the thermocouple (junction at the center of the
DOI: 10.1520/C0965-96R07.
large diameter portion) which has the advantage of proximity,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
butthedisadvantageofpossibleelectricaldisconnectionduring
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
torque measurement.
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.
C965–96 (2007)
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 A measurement 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 temperature should be below the original melting temperature
to avoid reboil. If reboil occurs, allow additional time for the
the molten charge reach a level at some fixed distance (several
millimetres) above the point where the spindle narrows down. glass to clear. Hold at this temperature at least 20 min before
starting measurements.
Theweightofglassrequiredcanbeapproximatedsatisfactorily
with the following expression for a cylindrical crucible:
6. Calibration and Viscosity Determination
W 5 [pd L 1 h!/4 2 V r 1 2 0.0007a! (1)
~ # ~
T s
6.1 The use of several standard reference glasses (see
where: Appendix X1), available from the National Institute of Stan-
h = distance between crucible floor and spindle tip, mm
dards and Technology, is recommended. These provide a wide
(generally greater than 10 mm to avoid end effects) range of temperatures and viscosities for calibration.
W = glass charge weight at room temperature, g,
6.2 For constant angular velocity rotation:
T
d = inside diameter of crucible, mm,
h}V/v (2)
L = immersed portion of spindle, mm,
V = volume of immersed portion of spindle, mm ,
s where:
r = density of glass at room temperature, g/cm , and
h = viscosity,
a = 0 to 300°C thermal expansion coefficient, cm/cm·°C
V = torque, and
(3 10 ).
v = angular velocity
Avoid very small pieces of glass in the charge as they tend
For aperiodic return:
to make the molten glass seedy.
5.2 Place the filled crucible in proper position in the furnace
and heat to a temperature that lowers the viscosity of glass
See NIST Special Publication 260, NIST Standard Reference Materials,
sufficientl
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