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)

SIGNIFICANCE AND USE
4.1 This test method is well suited for measuring the viscosity of glasses in ranges higher than those covered by parallel plate (see Test Method C1351M) and rotational viscometry (see Practice C965) methods. This test method is useful for providing information related to the behavior of glass after it has been formed into an object of commerce and in research and development.
SCOPE
1.1 This test method covers the determination of glass viscosity from approximately 108 Pa·s to approximately 1013 Pa·s by measuring the rate of viscous bending of a simply loaded glass beam.2 Due to the thermal history of the glass, the viscosity may not represent conditions of thermal equilibrium at the high end of the measured viscosity range. Measurements carried out over extended periods of time at any temperature or thermal preconditioning will minimize these effects by allowing the glass to approach equilibrium structural conditions. Conversely, the method also may be used in experimental programs that focus on nonequilibrium conditions.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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: 31-Jul-2019
• ICS: 81.040.01 - Glass in general
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaces: ASTM C1350M-96(2013) - 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-Aug-2019
• Refers: ASTM C336-71(2020) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Aug-2020
• Refers: ASTM C338-93(2019) - Standard Test Method for Softening Point of Glass
• Effective Date: 01-Aug-2019
• Refers: ASTM C598-93(2019) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Aug-2019
• Refers: ASTM C336-71(2015) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-May-2015
• Refers: ASTM C598-93(2013) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Oct-2013
• Refers: ASTM C338-93(2013) - Standard Test Method for Softening Point of Glass
• Effective Date: 01-Oct-2013
• Refers: ASTM C965-96(2012) - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 01-Mar-2012
• Refers: ASTM C1351M-96(2012) - 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-Mar-2012
• Refers: ASTM C336-71(2010) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Apr-2010
• Refers: ASTM C598-93(2008) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Apr-2008
• Refers: ASTM C338-93(2008) - Standard Test Method for Softening Point of Glass
• Effective Date: 01-Apr-2008
• Refers: ASTM C965-96(2007) - Standard Practice for Measuring Viscosity of Glass Above the Softening Point
• Effective Date: 01-Apr-2007
• Refers: ASTM C1351M-96(2007) - 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
• Refers: ASTM C336-71(2005) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Sep-2005

Overview

ASTM C1350M-96(2019): Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range by Beam Bending (Metric) establishes a reliable procedure for determining the viscosity of glass within the range of approximately 10⁸ Pa·s to 10¹³ Pa·s. This method is particularly relevant for glass manufacturers, researchers, and quality assurance professionals needing accurate viscosity data in the range not covered by parallel plate or rotational viscometry methods. The beam bending technique provides essential insights into the physical behavior of glass after formation, supporting process development and material performance analysis.

Key Topics

• Viscosity Measurement Range: This standard specifically applies to the viscosity range of glass from about 10⁸ to 10¹³ Pa·s, bridging the gap between the softening point and annealing range.
• Beam Bending Principle: The method involves measuring the rate at which a simply loaded glass beam bends under a controlled load and temperature, using highly sensitive extensometers and precise furnaces.
• Material Preparation: Glass specimens must be carefully prepared with strict dimensional tolerances to ensure reliable and reproducible results.
• Calibration: Instrument calibration using certified reference glasses (such as those from NIST) is essential to maintain the accuracy and traceability of viscosity measurements.
• Safety Considerations: The standard mandates the implementation of appropriate safety, health, and environmental practices when operating high-temperature furnaces and handling glass samples.

Applications

• Quality Control in Glass Manufacturing: This test method is a vital tool for manufacturers to analyze and confirm the viscosity properties of commercial glass products, ensuring they meet required thermal and mechanical specifications.
• Research and Development: R&D professionals use beam bending viscometry to study the thermal behavior of new glass formulations and to optimize compositions for specific applications.
• Process Optimization: Understanding glass viscosity profiles assists in fine-tuning annealing, forming, and cooling schedules, ultimately improving product durability and manufacturing efficiency.
• Material Certification: Laboratories can use this standardized method to certify glass batches, ensuring compliance with internal and external quality standards.

Related Standards

The following ASTM standards complement or provide alternative methods to ASTM C1350M-96(2019):

• ASTM C1351M: Test Method for Measurement of Viscosity of Glass Between 10⁴ Pa·s and 10⁸ Pa·s by Viscous Compression [Metric] - covers lower viscosity ranges using the compression technique.
• ASTM C965: Practice for Measuring Viscosity of Glass Above the Softening Point - uses rotational viscometry for higher temperature, lower viscosity measurements.
• ASTM C598: Test Method for Annealing Point and Strain Point of Glass by Beam Bending - related technique focused on annealing behavior.
• ASTM C336 / C338: Methods for evaluating the annealing, strain, and softening points of glass by other physical techniques.

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Keywords: ASTM C1350M, glass viscosity, beam bending viscometry, softening point, annealing range, glass manufacturing standards, viscosity test method, quality control, glass R&D, material calibration, thermal behavior of glass, high-temperature glass testing.

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: C1350M − 96 (Reapproved 2019)
Standard Test Method for
Measurement of Viscosity of Glass Between Softening Point
and Annealing Range (Approximately 10 Pa·s to
13 1
Approximately 10 Pa·s) by Beam Bending (Metric)
This standard is issued under the fixed designation C1350M; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the determination of glass
C336 Test Method for Annealing Point and Strain Point of
viscosity from approximately 10 Pa·s to approximately
13 Glass by Fiber Elongation
10 Pa·s by measuring the rate of viscous bending of a simply
2 C338 Test Method for Softening Point of Glass
loaded glass beam. Due to the thermal history of the glass, the
C598 Test Method for Annealing Point and Strain Point of
viscosity may not represent conditions of thermal equilibrium
Glass by Beam Bending
at the high end of the measured viscosity range. Measurements
C965 Practice for Measuring Viscosity of Glass Above the
carried out over extended periods of time at any temperature or
Softening Point
thermal preconditioning will minimize these effects by allow-
C1351M Test Method for Measurement of Viscosity of
ing the glass to approach equilibrium structural conditions. 4 8
Glass Between 10 Pa·s and 10 Pa·s by Viscous Com-
Conversely, the method also may be used in experimental
pression of a Solid Right Cylinder [Metric]
programs that focus on nonequilibrium conditions.
3. Terminology
1.2 The values stated in SI units are to be regarded as
3.1 Definitions:
standard. No other units of measurement are included in this
3.1.1 beam bending viscometer—a device used to determine
standard.
the viscosity of glass from approximately 10 Pa·s to approxi-
1.3 This standard does not purport to address all of the 13
mately 10 Pa·s by measuring the deflection rate of a simply
safety concerns, if any, associated with its use. It is the
supported beam. The equation for calculating viscosity by this
responsibility of the user of this standard to establish appro-
method is:
priate safety, health, and environmental practices and deter-
3 3
gL ρAL 11α T
~ !
s
mine the applicability of regulatory limitations prior to use.
η 5 M1 (1)
F G F G
1440 I ~dh/dt! 1.6 11α T
~ !
c g
1.4 This international standard was developed in accor-
where:
dance with internationally recognized principles on standard-
η = viscosity, Pa·s,
ization established in the Decision on Principles for the
M = load (applied load + loading train), gms,
Development of International Standards, Guides and Recom-
dh/dt = midpoint deflection rate of test beam, cm/s,
mendations issued by the World Trade Organization Technical
g = acceleration of gravity, 980 cm/s ,
Barriers to Trade (TBT) Committee.
I = cross-sectional moment of inertia, cm ,
c
ρ = density of glass, g/cm ,
A = cross-sectional area of the beam, cm ,
L = support span, cm, and
α and α = mean coefficient of linear thermal expansion of
s g
support stand and glass, respectively, 25 °C to
1 temperature of measurement, T, m/m/°C. See
This test method is under the jurisdiction of ASTM Committee C14 on Glass
and Glass Products and is the direct responsibility of Subcommittee C14.04 on Note 1.
Physical and Mechanical Properties.
Current edition approved Aug. 1, 2019. Published August 2019. Originally
approved in 1996. Last previous edition approved in 2013 as C1350M – 96 (2013).
DOI: 10.1520/C1350M-96R19. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Hagy, H. E., “Experimental Evaluation of Beam Bending Method of Deter- contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
8 15
mining Glass Viscosities in the Range 10 to 10 Poises”, Journal of the American Standards volume information, refer to the standard’s Document Summary page on
Ceramic Society, Vol 46, No. 2, 1963, pp. 95–97. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1350M − 96 (2019)
3 4
NOTE 1—The term (1 + α T) /(1 +α T) corrects for thermal expansion
members must be very similar so as to minimize motion of the
s g
changes of room temperature dimensions. It can be ignored when α and
s
loading rod due to expansion differences. A rectangular alu-
α are approximately equal. A fused silica support stand in combination
g
mina muffle or circular tube that can be notched to define
with a high expansion glass can make this term 3 % in magnitude. Only
specimen position is a suitable support stand (see Note 2). The
an estimate of α is required, singe the correction is small. Use 1.5 times
g
supporting surfaces of these notches shall be flat and lie in a
the room temperature coefficient if data are unavailable.
plane perpendicular to the axis of the furnace.The inside edges
4. Significance and Use
of these notches define the support span once the specimen
beam starts to deflect. A support span of about 5 cm (62 in.)
4.1 This test method is well suited for measuring the
is recommended. A suitable loading rod can be provided by a
viscosity of glasses in ranges higher than those covered by
single-crystal sapphire rod flame bent at one end in the form of
parallel plate (see Test Method C1351M) and rotational vis-
a shepherd’s crook. This crook will contribute to the load on
cometry (see Practice C965) methods. This test method is
the specimen, so its weight should be kept to a minimum.
useful for providing information related to the behavior of
glass after it has been formed into an object of commerce and
NOTE2—Vitreoussilicaisasuitablematerialforbothsupportstandand
in research and development.
loading rod. It is not recommended for temperatures above 900 °C.
5.6 Extensometer for Measuring Midpoint Deflection:
5. Apparatus
5.6.1 The means for observing the rate of deflection of the
5.1 The apparatus shall consist of a furnace, a means of
specimen shall allow reliable reading of total deflection of at
controlling its temperature and heating rate, specimen holders least 10 mm. The extensometer shall permit direct reading of
and loading rod, and a means of observing the rate of viscous
0.010 mm and estimates of 0.0010 mm. Its accuracy shall be
deflection of the glass specimen. such that the error of indication will not exceed 62 % for any
measured deflection. This will limit the minimum deflection
5.2 Furnace:
that may be used in calculation.Alinearly variable differential
5.2.1 The furnace shall be electrically heated by resistance
transformer (LVDT) is suitable for this purpose, as is any other
elements. The dimensions and the details of the furnace
device (for example, optical or capacitive), provided that
construction are not critical; its cross-section can be circular of
deflection is reliably measured as specified.
75 mm (;3 in.) diameter or square with sides of 75 mm. The
furnace should have a constant temperature zone that covers
5.7 Weights:
the specimen geometry, including the deflection range. Differ-
5.7.1 A set of weights spanning the range from 1 to 500 g
ences in temperature greater than 2 °C within that constant
and accurate to 0.1 % relative is required.
temperature zone are unacceptable.
5.8 Micrometre Calipers:
5.3 Temperature Measuring and Indicating Instruments:
5.8.1 Micrometre calipers which can be read to an accuracy
5.3.1 For the measurement of temperature, there shall be
of at least 0.01 mm are required for measuring specimen
provided a calibrated Type K, R, or S thermocouple. The
dimensions.
thermocouple shall be housed in a double-bore alumina tube
5.9 Analytical Balance:
with its junction placed within 5 mm of the specimen near the
5.9.1 An analytical balance capable of weighing the shep-
axis of the furnace. The thermocouple shall be referenced to
herd’s crook and loading train to an accuracy of 0.1 % relative.
0 °C by means of an ice bath, and its emf measured with a
calibrated potentiometer that can be read with a sensitivity of
6. Preparation of Test Specimen
0.1 °C and an accuracy of 60.5 °C. Precautions shall be taken
6.1 Specimens may either be flame drawn or centerless
to ensure that the ice bath is maintained at 0 °C throughout the
ground into cylindrical form or diamond-saw cut and mill
test. Alternately, the output of the thermocouple can be
ground into rectangular form. Nonuniformity of any dimension
measured on a calibrated, direct reading meter (electronic
along the length of the specimen shall not exceed 2 %. When
thermometer) that can be read with a sensitivity of 0.1 °C and
nonuniformity of any dimension exists, an average value shall
an accuracy of 60.5 °C. See Note 3 for temperature lag-lead
be used.
corrections.
6.2 The numerical ratio of beam span to moment of inertia
5.4 Furnace Control:
shall not be less than 60. The thickness or diameter to
...