ASTM G156-17

Standard Practice for Selecting and Characterizing Weathering Reference Materials

SIGNIFICANCE AND USE
4.1 Weathering reference materials are used in laboratory accelerated exposure tests to verify consistency of tests run within the same instrument at different times (repeatability) or in different instruments or different laboratories (reproducibility), using the same exposure conditions, or both. Specifications defining consistency of exposure conditions are based on the property change of a reference material after a defined period of time. Some weathering reference materials are used to define periods of exposure. Specifications recommending the use of these materials require the material to be exposed until a defined change in the weathering reference material is achieved. Specifications are usually based on results for a single lot of the weathering reference material. When a new lot of the reference material is introduced, round-robin studies are necessary to compare the new and old lots and to establish appropriate limits for expected performance of the new lot.
Note 2: An example of the use of a clear polystyrene reference standard for this purpose is given in SAE J2412 and SAE J2527.
Note 3: Some weathering reference materials (for example blue wools) are also used to define periods of exposure. Although not specifically covered by this standard, the procedures described for characterizing a reference material used to monitor consistency of exposures are also generally applicable to characterizing reference materials used to define periods of exposure.  
4.2 It is important to test the consistency of exposure in the laboratory accelerated device with a weathering reference material that responds to the test conditions similar to the way the test materials respond. Therefore, the weathering reference material should be sensitive to the spectral region of the light source mainly responsible for producing degradation in the test materials to provide the most meaningful evaluation of exposure test consistency. The weathering reference material should also...
SCOPE
1.1 This standard describes the criteria to be used for selection of a weathering reference material (WRM) and procedures to be used for determining within lab and between lab tolerances of changes in measured properties of weathering reference materials. This standard also describes a procedure for comparing different lots of the same type of a weathering reference material.  
Note 1: Examples of laboratory accelerated tests in which a weathering reference material could be used to monitor consistency are exposure tests such as those described in Practices G152, G153, G154, and G155and other standards in which tests conducted according to these standards are referenced. Examples of outdoor exposures where a weathering reference material could be used to monitor consistency are those conducted according to Practices G7, G24, or G90. A reference material can also be used to monitor consistency of exposure or conditioning test that do not involve exposure to light.  
1.2 Weathering reference materials are most often used to (1) monitor consistency (that is, repeatability, reproducibility, or both) of exposure tests, (2) to determine the time or radiant exposure at which test materials are evaluated, (3) as a reference material for comparing to test materials exposed at the same time. Weathering reference materials cannot be used to classify or characterize the relative severity of any exposure test because of the large variability in material responses to the effects of light, heat, and water.  
1.3 This practice does not cover control materials which, by definition are selected to be of similar composition and construction to the test materials, and are exposed at the same time as test materials.  
1.4 This practice provides an outline of experiments required to determine how the measured properties of the reference material change as a function of exposure to specified test conditions. It includes establishment of re...

General Information

• Status: Published
• Publication Date: 31-Jan-2017
• ICS: 19.040 - Environmental testing
• Technical Committee: G03 - Weathering and Durability
• Drafting Committee: G03.01 - Joint Weathering Projects

Relations

• Replaces: ASTM G156-09 - Standard Practice for Selecting and Characterizing Weathering Reference Materials
• Effective Date: 01-Feb-2017
• Refers: ASTM E1169-18 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 01-Sep-2018
• Refers: ASTM E1169-17e1 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 01-Oct-2017
• Refers: ASTM E1169-17 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 01-Oct-2017
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E1169-14 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 01-May-2014
• Refers: ASTM G113-14 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 01-Mar-2014
• Refers: ASTM E1169-13a - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 15-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E1169-13 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 15-Apr-2013
• Refers: ASTM E1169-12a - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 15-Dec-2012
• Refers: ASTM G154-12 - Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials
• Effective Date: 01-Dec-2012
• Refers: ASTM E1169-12 - Standard Practice for Conducting Ruggedness Tests
• Effective Date: 01-Nov-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011

Overview

ASTM G156-17: Standard Practice for Selecting and Characterizing Weathering Reference Materials provides critical guidelines for the selection, evaluation, and use of weathering reference materials (WRMs) in laboratory and field exposure tests. These materials are essential to monitoring consistency and reliability in accelerated or natural weathering tests, supporting repeatability within instruments and reproducibility across laboratories. This standard, developed by ASTM International, applies to nonmetallic materials commonly tested for durability and weather resistance.

WRMs act as benchmarks, allowing laboratories to verify that weathering tests produce reliable, consistent results over time and across different test setups. ASTM G156-17 outlines rigorous procedures for characterizing these materials, ensuring effective performance monitoring and aiding in comparison of old and new lots of reference materials.

Keywords: weathering reference material, laboratory exposure, accelerated aging, repeatability, reproducibility, round-robin, ASTM G156-17.

Key Topics

• Selection of Reference Materials

  • Criteria for choosing a WRM that effectively reflects the environmental stresses relevant to the test material.
  • Emphasis on sensitivity to key exposure factors (e.g., light spectrum, temperature, humidity).

• Characterization Procedures

  • Guidance on measuring property changes in WRMs as a function of exposure.
  • Establishment of robust, reproducible measurement techniques to reduce operator error.
  • Importance of material homogeneity and precise evaluation methods.

• Consistency and Performance Evaluation

  • Use of WRMs to monitor within-lab repeatability and between-lab reproducibility.
  • Procedures for round-robin studies to assess and benchmark performance among different laboratories.
  • Statistical analysis for defining specification limits; use of standard deviation and significance testing.

• Lot Comparison and Validation

  • Protocols for comparing new lots of reference materials against established lots.
  • Requirements for comparative exposure tests and statistical validation before adopting new material batches.

Applications

Weathering reference materials, as addressed in ASTM G156-17, have broad applications in industries where material durability and aging are critical concerns:

• Quality Control in Accelerated Weathering Tests

  • Regular verification of test consistency for plastics, coatings, polymers, and other nonmetallic materials using equipment like xenon arc, UV, carbon arc, or fluorescent devices.
  • Application with standards such as ASTM G152, G153, G154, and G155 for laboratory exposures.

• Field and Outdoor Exposure Monitoring

  • Tracking environmental consistency in outdoor exposure tests by referencing WRMs, following standards like ASTM G7, G24, and G90.

• Round-Robin and Interlaboratory Studies

  • Establishment of benchmarks and validation of test reproducibility among multiple laboratories.
  • Ensuring global alignment in material testing protocols through standardized reference materials.

• Material Comparison and Specification Compliance

  • Use of WRMs as a reference point for comparing the weathering response of test materials exposed in parallel.
  • Assessment of material behavior under controlled test conditions for regulatory and customer requirements.

Related Standards

For organizations leveraging ASTM G156-17, the following complementary standards are often referenced:

• ASTM G152, G153, G154, G155: Practices for operating laboratory weathering instruments using various light sources.
• ASTM G7, G24, G90: Practices for outdoor weathering and environmental exposure.
• ASTM E177: Practice for use of terms precision and bias in ASTM test methods.
• ASTM E691: Practice for conducting interlaboratory (round-robin) studies.
• ASTM E1169: Practice for conducting ruggedness tests.
• ASTM G113, G178: Terminology and methodologies for weathering and spectral sensitivity evaluation.
• SAE J2412, SAE J2527: Procedures for automotive material exposure testing, often citing specific WRMs.

Maintaining compliance with ASTM G156-17 ensures consistent, high-quality weathering test results, strengthening material reliability and product performance in real-world applications.

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: G156 − 17
Standard Practice for
Selecting and Characterizing Weathering Reference
Materials
This standard is issued under the fixed designation G156; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope region in the light source causing the changes, and effects of
other critical exposure stresses such as temperature and mois-
1.1 This standard describes the criteria to be used for
ture.
selection of a weathering reference material (WRM) and
procedures to be used for determining within lab and between
2. Referenced Documents
labtolerancesofchangesinmeasuredpropertiesofweathering
2.1 ASTM Standards:
reference materials. This standard also describes a procedure
E177Practice for Use of the Terms Precision and Bias in
for comparing different lots of the same type of a weathering
ASTM Test Methods
reference material.
E691Practice for Conducting an Interlaboratory Study to
NOTE 1—Examples of laboratory accelerated tests in which a weather-
Determine the Precision of a Test Method
ing reference material could be used to monitor consistency are exposure
E1169Practice for Conducting Ruggedness Tests
tests such as those described in Practices G152, G153, G154, and
G7Practice for Atmospheric Environmental Exposure Test-
G155and other standards in which tests conducted according to these
standards are referenced. Examples of outdoor exposures where a weath- ing of Nonmetallic Materials
ering reference material could be used to monitor consistency are those
G24Practice for Conducting Exposures to Daylight Filtered
conducted according to Practices G7, G24,or G90. A reference material
Through Glass
can also be used to monitor consistency of exposure or conditioning test
G90Practice for Performing Accelerated Outdoor Weather-
that do not involve exposure to light.
ing of Nonmetallic Materials Using Concentrated Natural
1.2 Weathering reference materials are most often used to
Sunlight
(1) monitor consistency (that is, repeatability, reproducibility,
G113Terminology Relating to Natural andArtificialWeath-
or both) of exposure tests, (2) to determine the time or radiant
ering Tests of Nonmetallic Materials
exposure at which test materials are evaluated, (3) as a
G152Practice for Operating Open Flame CarbonArc Light
reference material for comparing to test materials exposed at
Apparatus for Exposure of Nonmetallic Materials
the same time. Weathering reference materials cannot be used
G153Practice for Operating Enclosed Carbon Arc Light
to classify or characterize the relative severity of any exposure
Apparatus for Exposure of Nonmetallic Materials
testbecauseofthelargevariabilityinmaterialresponsestothe
G154Practice for Operating Fluorescent Ultraviolet (UV)
effects of light, heat, and water.
Lamp Apparatus for Exposure of Nonmetallic Materials
G155Practice for Operating XenonArc LightApparatus for
1.3 Thispracticedoesnotcovercontrolmaterialswhich,by
definition are selected to be of similar composition and Exposure of Non-Metallic Materials
G178Practice for Determining theActivation Spectrum of a
construction to the test materials, and are exposed at the same
time as test materials. Material (Wavelength Sensitivity to an Exposure Source)
Using the Sharp Cut-On Filter or Spectrographic Tech-
1.4 This practice provides an outline of experiments re-
nique
quired to determine how the measured properties of the
2.2 SAE Standard:
referencematerialchangeasafunctionofexposuretospecified
SAE J2527,Accelerated Exposure of Automotive Exterior
test conditions. It includes establishment of reproducible mea-
Materials using a Controlled Irradiance Water-Cooled
surement procedures, determination of the critical spectral
Xenon Arc Apparatus
1 2
ThispracticeisunderthejurisdictionofASTMCommitteeG03onWeathering For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Durability and is the direct responsibility of Subcommittee G03.01 on Joint contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Weathering Projects. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2017. Published February 2017. Originally the ASTM website.
approved in 1997. Last previous edition approved in 2009 as G156–09. DOI: Available from Society of Automotive Engineers (SAE), 400 Commonwealth
10.1520/G0156-17. Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G156 − 17
SAE J2412,Accelerated Exposure of Automotive Interior specification limits defined by changes in the reference mate-
Materials Using a Controlled Irradiance Water-Cooled rial be based on a sound statistical analysis of results from a
Xenon Arc Apparatus properly designed round-robin experiment. This practice pro-
vides a procedure which can be followed to set up the
3. Terminology
round-robin, analyze results, and establish reasonable limits of
3.1 Definitions—ThedefinitionslistedinTerminologyG113
change in the characteristic property of the reference material
are applicable to this standard.
that can be used in specifications.
4.4.1 The results obtained according to this practice are
4. Significance and Use
valid only for the exposure cycle used for the round-robin and
4.1 Weathering reference materials are used in laboratory
cannot be applied to the same weathering reference material
accelerated exposure tests to verify consistency of tests run
used in different exposure cycles.
within the same instrument at different times (repeatability) or
4.5 The change in characteristic property of a reference
in different instruments or different laboratories
material may be affected by the placement of the reference
(reproducibility), using the same exposure conditions, or both.
material in the exposure device. This is often due to variations
Specifications defining consistency of exposure conditions are
in light intensity and temperature within the allowed exposure
based on the property change of a reference material after a
area. Random placement of replicate specimens of the weath-
defined period of time. Some weathering reference materials
ering reference material throughout the allowed exposure area
are used to define periods of exposure. Specifications recom-
provides an indication of the uniformity of conditions within
mending the use of these materials require the material to be
the exposure area.
exposed until a defined change in the weathering reference
materialisachieved.Specificationsareusuallybasedonresults
NOTE 5—In some cases, procedures require exposure of a weathering
reference material at a specific location within the exposure device or
for a single lot of the weathering reference material. When a
chamber.Resultsforareferencematerialusedinthiswaymaynotprovide
new lot of the reference material is introduced, round-robin
an accurate representation of the exposure conditions in other positions
studies are necessary to compare the new and old lots and to
within the device.
establish appropriate limits for expected performance of the
new lot.
5. Procedure
NOTE 2—An example of the use of a clear polystyrene reference
5.1 Select a weathering reference material that exhibits a
standard for this purpose is given in SAE J2412 and SAE J2527.
significant change in a characteristic property when exposed
NOTE 3—Some weathering reference materials (for example blue
for an acceptable period of time, to the exposure conditions
wools) are also used to define periods of exposure. Although not
specifically covered by this standard, the procedures described for described in the applicable test procedure.
characterizing a reference material used to monitor consistency of
5.2 Determine an evaluation procedure that can best mea-
exposures are also generally applicable to characterizing reference mate-
sure the change in characteristic property of the reference
rials used to define periods of exposure.
material.
4.2 It is important to test the consistency of exposure in the
5.2.1 Conduct a series of experiments to determine the
laboratory accelerated device with a weathering reference
effect of important factors in the measurement procedure. It is
material that responds to the test conditions similar to the way
recommended that this be done using a ruggedness test
the test materials respond.Therefore, the weathering reference
according to Guide E1169 to determine which factors signifi-
material should be sensitive to the spectral region of the light
cantly affect results. The results from this test can be used to
sourcemainlyresponsibleforproducingdegradationinthetest
tighten the test measurement procedures.
materials to provide the most meaningful evaluation of expo-
5.2.2 When the results from the ruggedness testing are
suretestconsistency.Theweatheringreferencematerialshould
complete, write a set of instructions for measuring the charac-
also provide information on consistency of temperature and
teristicpropertythatisunambiguousandclearlyunderstoodby
humidity conditions if the latter are important factors in
operators who will be making the measurement. Have two
degradation of the test materials.
operators in one laboratory conduct the measurement on at
NOTE 4—Material homogeneity can also be an important factor in
least three replicate specimens of the reference material.
selection of a weathering reference material, particularly if weathering is
Interview the operators to determine whether the procedure
initiated by the radiation absorbed by impurities as is the case in aliphatic
provides clear and easy to understand directions. Modify the
type polymers exposed to radiation longer than 300 nm.
procedure to remove any ambiguity in instructions.
4.3 The measurement of the characteristic property of a
weathering reference material can be subject to error depend- 5.3 Determine the homogeneity of the weathering reference
material by measuring the property change of randomly
ing on the instrument and the procedure used to measure the
property. It is important to use measurement procedures that selected replicate specimens that have been exposed to very
tight
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G156 − 09 G156 − 17
Standard Practice for
Selecting and Characterizing Weathering Reference
Materials
This standard is issued under the fixed designation G156; 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
1.1 This standard describes the criteria to be used for selection of a weathering reference material (WRM) and procedures to
be used for determining within lab and between lab tolerances of changes in measured properties of aweathering reference
materials. This standard also describes a procedure for comparing different lots of the same type of a weathering reference material.
NOTE 1—Examples of laboratory accelerated tests in which a weathering reference material could be used to monitor consistency are exposure tests
such as those described in Practices G152, G153, G154, and G155and other standards in which tests conducted according to these standards are
referenced. Examples of outdoor exposures where a weathering reference material could be used to monitor consistency are those conducted according
to Practices G7, G24, or G90. A reference material can also be used to monitor consistency of exposure or conditioning test that do not involve exposure
to light.
1.2 Weathering reference materials are most often used to (1) monitor consistency of conditions in (that is, repeatability,
reproducibility, or both) of exposure tests, (2) to determine the time or radiant exposure at which test materials are evaluated, (3)
as a reference material for comparing to test materials exposed at the same time. Weathering reference materials cannot be used
to classify or characterize the relative severity of any exposure test because of the large variability in material responses to the
effects of light, heat, and water.
1.3 This practice does not cover control materials which, by definition are selected to be of similar composition and construction
to the test materials, and are exposed at the same time as test materials.
1.4 This practice provides an outline of experiments required to determine how the measured properties of the reference material
change as a function of exposure to specified test conditions. It includes establishment of reproducible measurement procedures,
determination of the critical spectral region in the light source causing the changes, and effects of other critical exposure stresses
such as temperature and moisture.
2. Referenced Documents
2.1 ASTM Standards:
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1169 Practice for Conducting Ruggedness Tests
G7 Practice for Atmospheric Environmental Exposure Testing of Nonmetallic Materials
G24 Practice for Conducting Exposures to Daylight Filtered Through Glass
G90 Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using Concentrated Natural Sunlight
G113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
G152 Practice for Operating Open Flame Carbon Arc Light Apparatus for Exposure of Nonmetallic Materials
G153 Practice for Operating Enclosed Carbon Arc Light Apparatus for Exposure of Nonmetallic Materials
G154 Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials
G155 Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
G178 Practice for Determining the Activation Spectrum of a Material (Wavelength Sensitivity to an Exposure Source) Using the
Sharp Cut-On Filter or Spectrographic Technique
This practice is under the jurisdiction of ASTM Committee G03 on Weathering and Durability and is the direct responsibility of Subcommittee G03.01 on Joint
Weathering Projects.
Current edition approved June 1, 2009Feb. 1, 2017. Published July 2009February 2017. Originally approved in 1997. Last previous edition approved in 20022009 as
G156–02.–09. DOI: 10.1520/G0156-09.10.1520/G0156-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 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
G156 − 17
2.2 SAE Standard:
SAE J1960,J2527, Accelerated Exposure of Automotive Exterior Materials using a Controlled Irradiance Water-Cooled Xenon
Arc Apparatus
SAE J1885,J2412, Accelerated Exposure of Automotive Interior Materials Using a Controlled Irradiance Water-Cooled Xenon
Arc Apparatus
3. Terminology
3.1 Definitions—The definitions listed in Terminology G113 are applicable to this standard.
4. Significance and Use
4.1 Weathering reference materials are used in laboratory accelerated exposure tests to verify consistency amongof tests run
within the same instrument at different times and (repeatability) or in different laboratories, instruments or different laboratories
(reproducibility), using the same exposure conditions. conditions, or both. Specifications defining consistency of exposure
conditions are based on the property change of a reference material after a defined period of time. Some weathering reference
materials are used to define periods of exposure. Specifications calling forrecommending the use of these materials require the
material to be exposed until a defined change in the weathering reference material is achieved. Specifications are usually based
on results for a single lot of the weathering reference material. When a new lot of the reference material is introduced, round-robin
studies are necessary to compare the new and old lots and to establish appropriate limits for expected performance of the new lot.
NOTE 2—An example of the use of a clear polystyrene reference standard for this purpose is given in SAE J1885J2412 and SAE J1960.J2527.
NOTE 3—Some weathering reference materials (for example blue wools) are also used to define periods of exposure. Although not specifically covered
by this standard, the procedures described for characterizing a reference material used to monitor consistency of exposures are also generally applicable
to characterizing reference materials used to define periods of exposure.
4.2 It is important to test the consistency of exposure in the laboratory accelerated device with a weathering reference material
that responds to the test conditions similar to the way the test materials respond. Therefore, the weathering reference material
should be sensitive to the spectral region of the light source mainly responsible for producing degradation in the test materials to
provide the most meaningful evaluation of exposure test consistency. The weathering reference material should also provide
information on consistency of temperature and humidity conditions if the latter are important factors in degradation of the test
materials.
NOTE 4—Material homogeneity can also be an important factor in selection of a weathering reference material, particularly if weathering is initiated
by the radiation absorbed by impurities as is the case in aliphatic type polymers exposed to radiation longer than 300 nm.
4.3 The measurement of the characteristic property of a weathering reference material can be subject to error depending on the
instrument and the procedure used to measure the property. It is important to developuse measurement procedures that are clear
and which minimize chances for operator misinterpretation. It is also important to determine the level of variability caused by
measurement of the characteristic property.
4.4 When a reference material is used to monitor or specify the consistency of an exposure test, it is important that any
specification limits defined by changes in the reference material be based on a sound statistical analysis of results from a properly
designed round-robin experiment. This practice provides a procedure which can be followed to set up the round-robin, analyze
results, and establish reasonable limits of change in the characteristic property of the reference material that can be used in
specifications.
4.4.1 The results obtained according to this practice are valid only for the exposure cycle used for the round-robin and cannot
be applied to the same weathering reference material used in a different exposure cycle.cycles.
4.5 The change in characteristic property of a reference material may be affected by the placement of the reference material in
the exposure device. This is often due to variations in light intensity and temperature within the allowed exposure area. Random
placement of replicate specimens of the weathering reference material through-outthroughout the allowed exposure area provides
the best an indication of the overall consistency of uniformity of conditions within the exposure test.area.
NOTE 5—In some cases, procedures require exposure of a weathering reference material at a specific location within the exposure device or chamber.
Results for a reference material used in this way may not provide an accurate representation of the exposure conditions in other positions within the
device.
5. Procedure
5.1 Select a weathering reference material that exhibits a significant change in a characteristic property when exposed for an
acceptable period of time, to the exposure conditions described in the applicable test procedure.
5.2 Determine the an evaluation procedure used that can best measure the change in characteristic property of the reference
material.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
G156 − 17
5.2.1 Conduct a series of experiments to determine the effect of important factors in the measurement procedure. It is
recommended that this be done using a ruggedness test according to Guide E1169 to determine which factors significantly affect
results. The results from this test can be used to tighten the test measurement procedures.
5.2.2 When the results from the ruggedness testing are complete, write a set of instructions for measuring the characteristic
property that is unambiguous and clearly understood by operators who will be making the measurement. Have two operators in
one l
...