ASTM G179-04(2011)
(Specification)Standard Specification for Metal Black Panel and White Panel Temperature Devices for Natural Weathering Tests
Standard Specification for Metal Black Panel and White Panel Temperature Devices for Natural Weathering Tests
SCOPE
1.1 This specification provides specific information for the manufacturing and use of metal black and white panel temperature devices to measure temperatures that estimate highest maximum (black) and lowest maximum (white) temperatures of coated metal specimens during natural weathering tests.
1.1.1 The construction of a black or white panel has a significant effect on the indicated temperature. This standard describes a robust construction from the panels investigated, which has been shown to provide the highest, most consistent temperatures when compared side-by-side with other black panel constructions.
1.2 This specification includes details on design requirements and quantitative measurement techniques, which will lead to the proper selection of materials and use for black and white panel temperature sensors.
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 requirements prior to use.
Note 1—There is no equivalent ISO standard describing the selection and use of black panel sensors for natural weathering tests.
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Designation:G179 −04(Reapproved 2011)
Standard Specification for
Metal Black Panel and White Panel Temperature Devices for
Natural Weathering Tests
This standard is issued under the fixed designation G179; 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 E881 Practice for Exposure of Solar Collector Cover Mate-
rials to Natural Weathering Under Conditions Simulating
1.1 This specification provides specific information for the
Stagnation Mode
manufacturing and use of metal black and white panel tem-
E903 Test Method for Solar Absorptance, Reflectance, and
perature devices to measure temperatures that estimate highest
Transmittance of Materials Using Integrating Spheres
maximum (black) and lowest maximum (white) temperatures
(Withdrawn 2005)
of coated metal specimens during natural weathering tests.
G7 Practice for Atmospheric Environmental Exposure Test-
1.1.1 The construction of a black or white panel has a
ing of Nonmetallic Materials
significant effect on the indicated temperature. This standard
G113 Terminology Relating to Natural andArtificial Weath-
describes a robust construction from the panels investigated,
ering Tests of Nonmetallic Materials
which has been shown to provide the highest, most consistent
G147 Practice for Conditioning and Handling of Nonmetal-
temperatures when compared side-by-side with other black
lic Materials for Natural and Artificial Weathering Tests
panel constructions.
G151 Practice for Exposing Nonmetallic Materials inAccel-
1.2 This specification includes details on design require-
erated Test Devices that Use Laboratory Light Sources
ments and quantitative measurement techniques, which will
2.2 ISO Standard:
lead to the proper selection of materials and use for black and
ISO 4892-1 Plastics: Exposure to Laboratory Light
white panel temperature sensors.
Sources—General Guidance
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3. Terminology
responsibility of the user of this standard to establish appro-
3.1 The definitions given in Terminologies G113 and E772
priate safety and health practices and determine the applica-
are applicable to this practice.
bility of regulatory requirements prior to use.
4. Significance and Use
NOTE 1—There is no equivalent ISO standard describing the selection
and use of black panel sensors for natural weathering tests.
4.1 The measurement of the primary elements of weather;
solar radiation, temperature, and moisture is necessary to
2. Referenced Documents
quantify the weather conditions during exposure in natural
2.1 ASTM Standards:
weathering (outdoor) tests. This practice is applicable to
D523 Test Method for Specular Gloss
weathering tests described in Practices G7, G24, or D4141
E220 Test Method for Calibration of Thermocouples By
(Method A) and other standards in which these standards are
Comparison Techniques
referenced.
E430 TestMethodsforMeasurementofGlossofHigh-Gloss
4.2 The surface temperature of exposed materials depends
Surfaces by Abridged Goniophotometry
primarily on the amount of radiation absorbed, the emissivity
E772 Terminology of Solar Energy Conversion
of the specimen, the thermal conduction within the specimen,
and the heat transfer between the specimen and the air in
This specification is under the jurisdiction of ASTM Committee G03 on contact with the specimen surface and specimen holder. Since
Weathering and Durability and is the direct responsibility of Subcommittee G03.02
it is often not practical to measure the surface temperature of
on Natural and Environmental Exposure Tests.
individual test specimens, a specified black or white panel
Current edition approved July 1, 2011. Published August 2011. Originally
approved in 2004. Last previous edition approved in 2010 as G179 – 04(2010).
DOI: 10.1520/G0179-04R11.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G179−04(2011)
required.Alternate constructions may not compare to panel constructions
temperature sensor is used to measure a reference temperature.
described in this specification.
This reference temperature provides an indication of the
temperature of a black or white specimen of similar construc-
6.2 Primer—The panel shall be treated with an automotive
tion to the panel sensor. It is important to locate the black or
technology zinc phosphate and coated with an automotive
white panel sensor in proximity to the specimens, using the
after-market grade two-component epoxy primer to ensure
samesupport,sothatitreceivesthesameradiationandcooling
adequate corrosion resistance. Apply the two-component ep-
conditions as the test specimen. For sites where multiple
oxy primer, according to the manufacturer’s recommendations.
exposure racks are used, a single black or white panel
Allow to air-dry for 24 h or baked at 30 min at 60°C (140°F).
temperature measurement made at the site and at the same
Sand primer with 320-400 grit sandpaper. Remove sanding
exposure orientation as the exposure racks is acceptable.
residue with a final wash solvent and a clean cloth.
4.3 Black panels are used in weathering applications since
6.3 Sensor—The sensor shall consist of a Type T thermo-
they are an indicator of the maximum specimen temperature
couple (copper/constantan) meeting accuracy requirements of
achieved during exposure due to the high solar absorptance of
betterthanorequalto 61.0°Cthroughoutthemeasuringrange.
the black coating. White panels are used as an indicator of the
The sensor shall be small enough to attach to the panel and
lowest maximum specimen temperature.
have a known response throughout the expected temperature
range. The thermocouple shall be attached to the panel by
4.4 Consideration must be given to the panel construction
spot-welding it to the middle of the back side. The thermo-
(for example, type of metal, type of sensor, sensor mounting,
couple junction must be in contact with the bare metal panel.
type of backing, coating system), as different configurations
Care shall be taken to provide support to the spot weld joint to
may give different results.
NOTE 2—At low irradiance, the temperature difference between backed avoid loosening of the connection. This can be achieved by
andunbackedpanelswillbesmallcomparedtohigherlevelsofirradiance.
adding a mounting point on the thermocouple lead, which can
Backed panels also have a slower response time due to the insulating
act as a stress relief for the junction.
effects of the wood.
NOTE 3—In an effort to provide temperature comparisons between
6.4 Two coating colors are commonly used on temperature
laboratory and natural weathering, some users have used the black panels
reference panels in natural weathering tests: (a) Black coating,
described in Practice G151 or ISO 4892-1 in natural weathering tests.
or (b) White coating.
Direct comparisons between black panel temperatures in laboratory and
6.4.1 Black Coating—The top (exposed) surface of the
natural weathering should not be made unless correlation has been
established. For instance, the temperature of specimens in a laboratory panel shall be coated with a automotive technology high gloss
chamber with a black panel temperature of 60°C may be very different
black basecoat clearcoat system after the thermocouple sensor
from the temperature of outdoor specimens when the outdoor black panel
has been spot-welded to the panel. The coated panel shall
reads 60°C.
absorb90 %orgreateratallwavelengthsfrom300to2500nm
5. Reference Panel Types per Test Method E903.
6.4.2 White Coating—The top (exposed) surface of the
5.1 Two types of reference panel sensors are commonly
panel shall be coated with a automotive technology high gloss
used in natural weathering tests: (a) Unbacked metal panels, or
white basecoat clearcoat system after the thermocouple sensor
(b) Backed metal panels.
has been spot-welded to the panel.The reflectance of the white
5.1.1 Unbacked Panels—These panels are mounted directly
panelatallwavelengthsbetween300nmand1000nmshallbe
to the fixture by securing the top and bottom edges of the panel
90 % or greater and 60 % or greater between 1000 nm and
to the fixture. Ambient air can circulate on the front and back
2500 nm per Test Method E903.
side of the panel to provide maximum cooling conditions for
6.4.3 Basecoat—Wipe the prepared primer surface with a
the panel.
tack rag to remove dust and lint. Apply two to three coats of
5.1.2 Backed Panels—These panels are mounted onto a
either an acrylic or a polyester basecoat, according to the
plywood substrate, which insulates the back of the panel. The
manufactures recommendations. Allow 5 to 10 min flash off
panel and backing are then mounted on the exposure frame.
between coats and allow to dry for 30 min before applying
Ambient air is only cooling the front side of the panel since the
clearcoat.
back side is insulated, resulting in higher surface temperatures.
NOTE 4—The selection of the proper type of panel backing is very
6.4.4 Clearcoat—Wipe prepared basecoat surface with a
important since the measured temperatures will be different. Typically,
tack rag to remove dust and lint. Apply two coats of an
backed black panels are 5 to 10°C higher than unbacked black panels
automotive after-market two-component urethane clearcoat,
depending on the level of irradiance, wind speed, and other factors. If a
according to the manufacturers recommendations. Allow 5 to
more realistic exposure of the panel simulating test panel conditions is
desired, the panel shall be mounted in the same manner (backed or 10 min flash off between coats. Allow to air-dry for 24 h or
unbacked) as the test panels.
baked at 30 min at 60°C (140°F).
6. Reference Panel Requirements
NOTE 6—ASTM subcommittee G03.02 has conducted natural weath-
ering exposures on commercially available black coatings for a period of
6.1 Substrate—Unless otherwise specified, the substrate
6 years. For more information about this study and the coatings used see
shall be a flat cold rolled steel panel with nominal dimensions
Appendix X1.
of 300 mm long, 100 mm wide, and 1.0 mm thickness.
6.5 Backing (Backed Panels)—An exterior grade of 12 mm
NOTE 5—Less corrosive materials may need to be used if the black or
(nominal) thick plywood, with dimensions equal to the black
white panel is used in a corrosive environment. If a corrosion resistant
material is used as a substrate, an alternate construction method may be panel, shall be used as the insulating backing for backed black
G179−04(2011)
panels. The panel shall be attached to the backing using difference between any two sensors is 2°C. If the difference is
corrosion resistant screws to ensure uniform contact between greater than 2°C, the sensor with the farthest measurement
the panel and the wood substrate. The thermocouple lead shall farthest from the mean of all measurements must be replaced
be recessed in the wood the necessary distance to allow the and/or reattached to the panel and the verification procedure
paneltositflatonthewoodbacking.Theedgesoftheplywood repeated.
shall be sealed with a wood sealer or paint to prevent moisture 7.3.3 At least one of the minimum five panels shall be
penetration. Follow the guidelines in Practice G7 for replace- retained as a primary reference temperature device. This
ment of plywood backing. primary reference device shall be stored in a cool, dry location
per Practice G147 (room temperature of 20 to 30°C and the
6.6 Sensor Monitoring—The temperature should be moni-
relative humidity ideally should be less than 60 %) and
tored at frequent intervals to provide accurate and complete
shielded from any light source.
data. A maximum allowable time interval for monitoring/
7.3.4 Verification of the remaining in-use panels will be
recording panel temperatures is 6 min.
made annually against the primary reference temperature
7. Calibration/Verification And Maintenance device. The temperature difference between the in-use and
primary reference panels must be within a 62°C tolerance. If
7.1 The panels must be calibrated and verified for accuracy
the difference is greater than 2°C, the in-use panel’s sensor
prior to placing it in service and on an annual basis.
shall be replaced and/or reattached to the panel and the
7.2 Calibrate the panel, thermocouple, monitor system
verification procedure repeated.
against ice and boiling water baths per Test Method E220.
7.4 Hemispherical spectral reflectance measurements
Verify linearity against several mid range values.
should be performed in accordance with Test Method E903 to
7.3 Verificationmustbeperformedduringthesummerusing
verify solar absorptance prior to placing panels in service. If a
natural sunlight under unobstructed sunlight conditions when
lot of panels is placed in service, then measurement is only
wind speed is 8 km/h or less.
requiredonarepresentativepanelfromtheentirelot.Forblack
panels, if the solar absorptance falls below the requirements of
NOTE 7—ASTM subcommittee G03.02.01 is developing a procedure
for conducting intercomparisons of black and white panels between sites. 90 % at all wavelengths between 300 nm and 2500 nm, the
panels must be replaced or re-coated and the verification
7.3.1 The coated panels with their sensors attached shall be
procedurerepeated.Forwhitepanels,ifthereflectancerequire-
situated on either static test fixture normal to the sun (62°) or
ments fall below 90 % at all wavelengths between 300 nm and
a tracking rack and allowed to stabilize for a minimum of 30
1000 nm or 60 % for wavelengths between 1000 nm and 2500
min prior to initiating measurement. If a static test fixture is
nm, the panels must be replaced or re-coated and the verifica-
used, measurements shall be performed within 1 hour of solar
tion procedure repeated.
noon under unobstructed sunlight conditions to maximize solar
NOTE 9—Solar absorptance/reflection measurements can be made on a
radiant energy. If a tracking rack is used, measurements shall
regular ba
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