ASTM C829-81(2000)
(Practice)Standard Practices for Measurement of Liquidus Temperature of Glass by the Gradient Furnace Method
Standard Practices for Measurement of Liquidus Temperature of Glass by the Gradient Furnace Method
SCOPE
1.1 These practices cover procedures for determining the liquidus temperature (Note 1) of a glass (Note 1) by establishing the boundary temperature for the first crystalline compound, when the glass specimen is held at a specified temperature gradient over its entire length for a period of time necessary to obtain thermal equilibrium between the crystalline and glassy phases.
Note 1--These terms are defined in Definitions C162.
1.2 Two methods are included, differing in the type of sample, apparatus, procedure for positioning the sample, and measurement of temperature gradient in the furnace. Both methods have comparable precision. Method B is preferred for very fluid glasses because it minimizes thermal and mechanical mixing effects.
1.2.1 Method A employs a trough-type platinum container (tray) in which finely screened glass particles are fused into a thin lath configuration defined by the trough.
1.2.2 Method B employs a perforated platinum tray on which larger screened particles are positioned one per hole on the plate and are therefore melted separately from each other.
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.
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Designation:C829–81 (Reapproved 2000)
Standard Practices for
Measurement of Liquidus Temperature of Glass by the
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Gradient Furnace Method
This standard is issued under the fixed designation C 829; 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.
1. Scope 2.2 Other Document:
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NIST Certificate for Liquidus Temperature, SRM 773
1.1 These practices cover procedures for determining the
liquidus temperature (Note 1) of a glass (Note 1) by establish-
3. Significance and Use
ing the boundary temperature for the first crystalline com-
3.1 Thesepracticesareusefulfordeterminingthemaximum
pound, when the glass specimen is held at a specified tempera-
temperature at which crystallization will form in a glass, and a
ture gradient over its entire length for a period of time
minimum temperature at which a glass can be held, for
necessarytoobtainthermalequilibriumbetweenthecrystalline
extended periods of time, without crystal formation and
and glassy phases.
growth.
NOTE 1—These terms are defined in Definitions C 162.
4. Apparatus
1.2 Two methods are included, differing in the type of
4.1 The apparatus for determining the liquidus temperature
sample, apparatus, procedure for positioning the sample, and
shall consist essentially of an electrically heated gradient
measurement of temperature gradient in the furnace. Both
furnace, a device for controlling the furnace temperature,
methods have comparable precision. Method B is preferred for
temperature measuring equipment, and other items listed.
veryfluidglassesbecauseitminimizesthermalandmechanical
4.1.1 Furnace:
mixing effects.
4.1.1.1 MethodA—Horizontaltemperaturegradient,electri-
1.2.1 Method A employs a trough-type platinum container
cally heated furnace, tube type, as illustrated in Fig. 1, Fig. 2,
(tray) in which finely screened glass particles are fused into a
and Fig. 3 and described in A1.1.
thin lath configuration defined by the trough.
4.1.1.2 Method B—An alternative furnace detail employing
1.2.2 Method B employs a perforated platinum tray on
pregrooved Al O cores and dual windings, as illustrated in
which larger screened particles are positioned one per hole on
2 3
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Fig. 4 and Fig. 5, and described in A1.2.
the plate and are therefore melted separately from each other.
4.1.1.3 Equivalenttemperaturegradientconditionsmayalso
1.3 This standard does not purport to address all of the
be obtained with furnaces having multiple windings equipped
safety concerns, if any, associated with its use. It is the
with separate power and control, or a tapped winding shunted
responsibility of the user of this standard to establish appro-
with suitable resistances. For high precision, temperature
priate safety and health practices and determine the applica-
gradients in excess of 10°C/cm should be avoided.
bility of regulatory limitations prior to use.
4.1.2 Furnace Temperature Control:
2. Referenced Documents
4.1.2.1 Method A—A suitable temperature controller shall
2.1 ASTM Standards: be provided to maintain a fixed axial temperature distribution
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over the length of the furnace.
C 162 Terminology of Glass and Glass Products
E 220 Method for Calibration of Thermocouples by Com- 4.1.2.2 MethodB—Arheostat shall be used to supply power
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to the outer winding.Aseparate rheostat and controller shall be
parison Techniques
used for the inner core winding. The basic furnace temperature
level is achieved by controlling power to both inner and outer
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These practices are under the jurisdiction of ASTM Committee C-14 on Glass
core windings. The slope of the gradient is achieved by
and Glass Productsand are the direct responsibility of Subcommittee C14.04 on
adjusting power input to the outer core winding only. The
Physical and Mechanical Properties.
established temperature gradient is then maintained by control-
Current edition approved Dec. 28, 1981. Published March 1982. Originally
published as C 829-76. Last previous edition C 829-76.
ling power to the inner core winding only.
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From NBS Research Paper RP2096, Vol 44, May 1950, by O. H. Grauer and
E. H. Hamilton, with modification and improvement by K. J. Gajewski, Ford Motor
Co., Glass Research and Development Office (work unpublished).
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Annual Book of ASTM Standards, Vol 15.02. National Institute of Standards and Technology, Office of Standard Reference
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Annual Book of ASTM Standards, Vol 14.03. Materials, Room B311, Chemical Building, Gaithersburg, MD 20899.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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