4.Summary of Practice
4.1Specimens are exposed to repetitive cycles of light and moisture under controlled environmental conditions.
4.1.1Moisture is usually produced by condensation of water vapor onto the test specimen or by spraying the speci-mens with demineralized/deionized water.
4.2The exposure condition may be varied by selection of: 4.2.1Thefluorescent lamp,
4.2.2The lamp’s irradiance level,
4.2.3The type of moisture exposure,
4.2.4The timing of the light and moisture exposure,
4.2.5The temperature of light exposure,and
4.2.6The temperature of moisture exposure,and
4.2.7The timing of a light/dark cycle.
4.3Comparison of results obtained from specimens exposed in same model of apparatus should not be made unless reproducibility has been established among devices for the material to be tested.
4.4Comparison of results obtained from specimens exposed in different models of apparatus should not be made unless correlation has been established among devices for the material to be tested.
5.Significance and Use
5.1The use of this apparatus is intended to induce property changes associated with the end use conditions,including the effects of the UV portion of sunlight,moisture,and heat.These exposures may include a means to introduce moisture to the test specimen.Exposures are not intended to simulate the deterioration caused by localized weather phenomena,such as atmospheric pollution,biological attack,and saltwater expo-sure.Alternatively,the exposure may simulate the effects of sunlight through window glass.Typically,these exposures would include moisture in the form of condensing humidity. N
OTE2—Caution:Refer to Practice G151for full cautionary guidance applicable to all laboratory weathering devices.
5.2Variation in results may be expected when operating conditions are varied within the accepted limits of this practice. Therefore,no reference shall be made to results from the use of this practice unless accompanied by a report detailing the specific operating conditions in conformance with the Section 10.
5.2.1It is recommended that a similar material of known performance(a control)be exposed simultaneously with the test specimen to provide a standard for comparative purposes. It is recommended that at least three replicates of each material evaluated be exposed in each test to allow for statistical evaluation of results.
6.Apparatus
6.1Laboratory Light Source—The light source shall be fluorescent UV lamps.A variety offluorescent UV lamps can be used for this procedure.Differences in lamp intensity or spectrum may cause significant differences in test results.A detailed description of the type(s)of lamp(s)used should be stated in detail in the test report.The particular testing application determines which lamp should be us
ed.See Ap-pendix X1for lamp application guidelines.
N OTE3—Do not mix different types of lamps.Mixing different types of lamps in afluorescent UV light apparatus may produce major inconsis-tencies in the light falling on the samples,unless the apparatus has been specifically designed to ensure a uniform spectral distribution.
N OTE4—Manyfluorescent lamps age significantly with extended use. Follow the apparatus manufacturer’s instructions on the procedure neces-sary to maintain desired irradiance(1,2).
6.1.1Actual irradiance levels at the test specimen surface may vary due to the type or manufacturer of the lamp used,or both,the age of the lamps,the distance to the lamp array,and the air temperature within the chamber and the ambient laboratory temperature.Consequently,the use of a radiometer to monitor and control the radiant energy is recommended.
6.1.2Several factors can affect the spectral power distribu-tion offluorescent UV lamps:
6.1.2.1Aging of the glass used in some types of lamps can result in changes in transmission.Aging of glass can result in a significant reduction in the short wavelength UV emission of some lamp types,
6.1.2.2Accumulation of dirt or other residue on lamps can affect irradiance,
6.1.2.3Thickness of glass used for lamp tube can have large effects on the amount of short wavelength UV radiation transmitted,and
6.1.2.4Uniformity and durability of phosphor coating. 6.1.3Spectral Irradiance:
N OTE5—Fluorescent UV A lamps are available with a choice of spectral power distributions that vary significantly.The more common may be identified as UV A-340and UV A-351.These numbers represent the characteristic nominal wavelength(in nm)of peak emission for each of these lamp types.The actual peak emissions are at343and350nm, respectively.
6.1.3.1Spectral Irradiance of UVA-340Lamps for Daylight UV—The spectral power distribution of UV A-340fluorescent lamps shall comply with the requirements specified in Table1. N OTE6—The main application for UV A-340lamps is for simulation of the short and middle UV wavelength region of daylight.
6.1.3.2Spectral Irradiance of UVA-351Lamps for Daylight UV Behind Window Glass—The spectral power distribution of UV A-351lamp for Daylight UV behind Window Glass shall comply with the requirements specified in Table2.
N OTE7—The main application for UV A-351lamps is for simulation of the short and middle UV wavelength region of daylight which has been filtered through window glass(3).
6.1.3.3Spectral Irradiance of UVB-313Lamps—The spec-tral power distribution of UVB-313fluorescent lamps shall comply with the requirements specified in Table2.
N OTE8—Fluorescent UVB lamps have the spectral distribution of radiation peaking near the313-nm mercury line.They emit significant amounts of radiation below300nm,the nominal cut on wavelength of global solar radiation,that may result in aging processes not occurring outdoors.Use of this lamp is not recommended for sunlight simulation. See Table3.
6.2Test Chamber—The design of the test chamber may vary,but it should be constructed from corrosion resistant material and,in addition to the radiant source,may provide for means of controlling temperature and relative humidity.When required,provision shall be made for the spraying of water
on
the test specimen for the formation of condensate on the exposed face of the specimen or for the immersion of the test specimen in water.
6.2.1The radiant source(s)shall be located with respect to
the specimens such that the uniformity of irradiance at the specimen face complies with the requirements in Practice G151.
6.2.2Lamp replacement,lamp rotation,and specimen repo-sitioning may be required to obtain uniform exposure of all specimens to UV radiation and temperature.Follow manufac-turer’s recommendation for lamp replacement and rotation.
6.3Instrument Calibration—To ensure standardization and accuracy,the instruments associated with the exposure appa-ratus(for example,timers,thermometers,wet bulb sensors,dry bulb sensors,humidity sensors,UV sensors,and radiometers) require periodic calibration to ensure repeatability of test results.Whenever possible,calibration should be traceable to national or international standards.Calibration schedule and procedure should be in accordance with manufacturer’s in-structions.
6.4Radiometer—The use of a radiometer to monitor and control the amount of radiant energy received at the sample is recommended.If a radiometer is used,it shall comply with the requirements in Practice G151.
6.5Thermometer—Either insulated or un-insulated black or white panel thermometers may be used.The un-insulated thermometers may be made of either steel or aluminum.Thermometers shall conform to the descriptions found in Practice G151.
6.5.1The thermometer shall be mounted on the specimen rack so that its surface is in the same relative position and subjected to the same influences as the test specimens.
6.5.2Some specifications may require chamber air tempera-ture control.Positioning and calibration of chamber air tem-perature sensors shall be in accordance with the descriptions found in Practice G151.
N OTE9—Typically,these devices control by black panel temperature only.
6.6Moisture—The test specimens may be exposed to mois-ture in the form of water spray,condensation,or high humidity.
6.6.1Water Spray—The test chamber may be equipped with
a means to introduce intermittent water spray onto the test specimens under specified conditions.The spray shall be uniformly distributed over the samples.The spray system shall be made from corrosion resistant materials that do not con-taminate the water used.
6.6.1.1Spray Water Quality—Spray water shall have a conductivity below5µS/cm,contain less than1-ppm solids, and leave no observable stains or deposits on the specimens.
TABLE1Relative Spectral Power Distribution Specification for
UVA-340Lamps for Daylight UV
Bandpass,nm Fluorescent UVA-340Lamp A Sunlight B Ultraviolet Wavelength Region
Irradiance as a percentage of total irradiance from260to400nm
260–2700.0%0
271–2800.0%0
281–2900.0%0
291–300<0.2%0
301–320  6.2–8.6%  5.6%
321–34027.1–30.7%18.5%
341–36034.2–35.4%21.7%
361–38019.5–23.7%26.6%
381–400  6.6–7.8%27.6% Ultraviolet and Visible Wavelength Region
Irradiance as a percentage of total irradiance from300to800nm C
300–40087.3%D11%E
401–70012.7%D72%E
A UVA-340data—The ranges given are based on spectral power distribution measurements made for lamps of different ages and operating at different levels of controlled irradiance.The ranges given are based on three sigma limits from the averages of this data.
B Sunlight data—The sunlight data is for global irradiance on a horizontal surface with a air mass of1.2,column ozone0.294atm cm,30%relative humidity,altitude 2100m(atmopsheric pressure of787.8mb),and an aerosol represented by an optical thickness of0.81at300nm and0.62at400nm.
C Data from701to800nm is not shown.
D UVA-340data—Because the primary emission offluorescent UV lamps is concentrated in the300-to400-nm bandpass,there are limited data available for visible light emissions offluorescent UV lamps.Therefore,the data in this table are based on very few measurements and are representative only.editorially
E Sunlight data—The sunlight data is from Table4of CIE Publication Number85, global solar irradiance on a horizontal surface with an air mass of1.0,column ozone of0.34atm cm,  1.42-cm precipitable water vapor,and an aerosol represented by an optical thickness of0.1at500nm.
TABLE2Relative Spectral Power Distribution Specification for UVA-351Lamps for Daylight UV Behind Window Glass
Bandpass,nm Fluorescent UVA-351Lamp A
Estimated Window Glass
Filtered Sunlight B
Ultraviolet Wavelength Region
Irradiance as a percentage of total irradiance from260to400nm
260–2700.0%0%
271–2800.0%0%
281–2900.0%0%
290–300<0.1%0%
301–3200.9–3.3%0.1–1.5%
321–34018.3–22.7%9.4–14.8%
341–36042.7–44.5%23.2–23.5%
361–38024.8–28.2%29.6–32.5%
381–400  5.8–7.6%30.9–34.5%
Ultraviolet and Visible Wavelength Region
Irradiance as a percentage of total irradiance from300to800nm C 300–40090.1%D9.0–11.1%E
401–7009.9%D71.3–73.1%E
A UVA-351data—The ranges given are based on spectral power distribution measurements made for lamps of different ages and operating at different levels of controlled irradiance.The ranges given are based on three sigma limits from the averages of this data.
B Sunlight data—The sunlight data is for global irradiance on a horizontal surface with an air mass of1.2,column ozone0.294atm cm,30%relative humidity, altitude2100m(atmospheric pressure of787.8mb),and an aerosol represented by an optical thickness of0.081at300nm and0.62at400nm.The range is determined by multiplying solar irradiance by the upper and lower limits for transmission of single strength window glass samples used for studies conducted by ASTM Subcommittee G03.02.
C Data from701to800nm is not shown.
D UVA-351data—Because the primary emission offluorescent UV lamps is concentrated in the300-to400-nm bandpass,there are limited data available for visible light emissions offluorescent UV lamps.Therefore,the data in this table are based on very few measurements and are representative only.
E Sunlight data—The sunlight data is from Table4of CIE Publication Number85, global solar irradiance on a horizontal surface with an air mass of1.0,column ozone of0.34atm cm,  1.42-cm precipitable water vapor,and an aerosol represented by an optical thickness of0.1at500nm.The range is determined by multiplying solar irradiance by the upper and lower limits for transmission of single strength window glass samples used for studies conducted by ASTM Subcommit-tee
G03.02.
Very low levels of silica in spray water can cause significant
deposits on the surface of test specimens.Care should be taken
to keep silica levels below 0.1ppm.In addition to distillation,
a combination of deionization and reverse osmosis can effec-
tively produce water of the required quality.The pH of the
water used should be reported.See Practice G 151for detailed
water quality instructions.
6.6.2Condensation —The test chamber may be equipped
with a means to cause condensation to form on the exposed
face of the test specimen.Typically,water vapor shall be
generated by heating water and filling the chamber with hot
vapor,which then is made to condense on the test specimens.
6.6.3Relative Humidity —The test chamber may be
equipped with a means to measure and control the relative
humidity.Such instruments shall be shielded from the lamp
radiation.
6.7Specimen Holders —Holders for test specimens shall be
made from corrosion resistant materials that will not affect the
test results.Corrosion resistant alloys of aluminium or stainless
steel have been found acceptable.Brass,steel,or copper shall
not be used in the vicinity of the test specimens.
6.8Apparatus to Assess Changes in Properties —The nec-
essary apparatus required by ASTM or ISO relating to the
determination of the properties chosen for monitoring shall be
used (see also ISO 4582).7.Test Specimen 7.1Refer to Practice G 151.8.Test Conditions 8.1Any exposure conditions may be used as long as the exact conditions are detailed in the report.Appendix X2shows some representative exposure conditions.These are not neces-sarily preferred and no recommendation is implied.These conditions are provided for reference only.9.Procedure 9.1Identify each test specimen by suitable indelible mark-ing,but not on areas used in testing.9.2Determine which property of the test specimens will be evaluated.Prior to exposing the specimens,quantify the appropriate properties in accordance with recognized ASTM or international standards.If required (for example,destructive testing),use unexposed file specimens to quantify the property.See ISO 4582for detailed guidance.9.3Mounting of Test Specimens —Attach the specimens to the specimen holders in the equipment in such a manner that the specimens are not subject to any applied stress.To assure uniform exposure conditions,fill all of the spaces,using blank panels of corrosion resistant material if necessary.N OTE 10—Evaluation of color and appearance changes of exposed materials shall be made based on comparisons to unexposed specimens of the same material which have been stored in the dark.Masking or shielding the face of test specimens with an opaque cover for the purpose of showing the effects of exposure on one panel is not recommended.Misleading results may be obtained by this method,since the masked portion of the specimen is still exposed to temperature and humidity that in many cases will affect results.9.4Exposure to Test Conditions —Program the selected test condi
tions to operate continuously throughout the required number of repetitive cycles.Maintain these conditions throughout the exposure.Interruptions to service the apparatus and to inspect specimens shall be minimized.9.5Specimen Repositioning —Periodic repositioning of the specimens during exposure is not necessary if the irradiance at the positions farthest from the center of the specimen area is at least 90%of that measured at the center of the exposure area.Irradiance uniformity shall be determined in accordance with Practice G 151.9.5.1If irradiance at positions farther from the center of the exposure area is between 70and 90%of that measured at the center,one of the following three techniques shall be used for specimen placement.9.5.1.1Periodically reposition specimens during the expo-sure period to ensure that each receives an equal amount of radiant exposure.The repositioning schedule shall be agreed upon by all interested parties.9.5.1.2Place specimens only in the exposure area where the irradiance is at least 90%of the maximum irradiance.9.5.1.3To compensate for test variability randomly position replicate specimens within the exposure area which meets the irradiance uniformity requirements as defined in 9.5.1.9.6Inspection —If it is necessary to remove a test specimen for periodic inspection,take care not to handle or disturb the test surface.After inspection,the test specimen shall be
TABLE 3Relative Spectral Power Distribution Specification for
UVB-313Lamps
Bandpass,nm Fluorescent UVB-313Lamp AB Sunlight C
Ultraviolet Wavelength Region A
Irradiance as a percentage of total irradiance from 260to 400nm
260–270<0.1%0
271–2800.1–0.7%0
281–290  3.2–4.4%0
291–30010.7–13.7%0
301–32038.0–44.6%  5.6%
321–34025.5–30.9%18.5%
341–3607.7–10.7%21.7%
361–380  2.5–5.5%26.6%
381–4000.0–1.5%27.6%
Ultraviolet and Visible Wavelength Region
Irradiance as a percentage of total irradiance from 300to 800nm D
300–40088.5%E 11%F
401–70011.5%E 72%F
A UVB-313data—Some UV
B lamps have measurable emittance at the 254-nm
mercury line.This may affect test results for some materials.
B UVB-313data—The ranges given are based on spectral power distribution
measurements made for lamps of a different ages and operating at different levels
of controlled irradiance.The ranges given are based on three sigma limits from the
averages of this data.Lamps that meet this specification are available from
different manufacturers.These lamps may have significantly different irradiance
levels (that is,total light output),but still have the same relative spectral power
distribution.
C Sunlight data—The sunlight data in for global irradiance on a horizontal surface
with a air mass of 1.2,column ozone 0.294atm cm,30%relative humidity,altitude
2100m (atmospheric pressure of 787.8mb),and an aerosol represented by an
optical thickness of 0.081to 300nm and 0.62at 400nm.
D Data from 701to 800nm is not shown.
E UVB-313data—Because the primary emission of fluorescent UV lamps is
concentrated in the 300-to 400-nm bandpass,there is limited data available for
visible light emissions of fluorescent UV lamps.Therefore,the data in this table are
based on very low measurements and are representative only.
F Sunlight data—The sunlight data is from Table 4of CIE Publication Number 85,
global solar irradiance on a horizontal surface with an air mass of 1.0,column
ozone of 0.34atm cm,  1.42-cm precipitable water vapor,and an aerosol
represented by an optical thickness of 0.1at 500
nm.
returned to the test chamber with its test surface in the same orientation as previously tested.
9.7Apparatus Maintenance—The test apparatus requires periodic maintenance to maintain uniform exposure conditions. Perform required maintenance and calibration in accordance with manufacturer’s instructions.
9.8Expose the test specimens for the specified period of exposure.See Practice G151for further guidance.
9.9At the end of the exposure,quantify the appropriate properties in accordance with recognized ASTM or interna-tional standards and report the results in conformance with Practice G151.
N OTE11—Periods of exposure and evaluation of test results are addressed in Practice G151.
10.Report
10.1The test report shall conform to Practice G151.
11.Precision and Bias
11.1Precision:
11.1.1The repeatability and reproducibility of results ob-tained in exposures conducted according to this practice will vary with the materials being tested,the material property being measured,and the specific test conditions and cycles that are used.In round-robin studies conducted by Subcommittee G03.03,the60°gloss values of replicate PVC tape specimens exposed in different laboratories using identical test devices and exposure cycles showed significant variability(3).The variability shown in these round-robin studies restricts the use of“absolute specifications”such as requiring a specific prop-erty level after a specific exposure period(4,5).
11.1.2If a standard or specification for general use requires
a definite property level after a specific time or radiant exposure in an exposure test conducted according to this practice,the specified property level shall be based on results obtained in a round-robin that takes into consideration the variability due to the exposure and the test method used to measure the property of interest.The round-robin shall be conducted according to Practice E691or Practice D3980and shall include a statistically representative sample of all labo-ratories or organizations that would normally conduct the exposure and property measurement.
11.1.3If a standard or specification for use between two or three parties requires a definite property lev
el after a specific time or radiant exposure in an exposure test conducted accord-ing to this practice,the specified property level shall be based on statistical analysis of results from at least two separate, independent exposures in each laboratory.The design of the experiment used to determine the specification shall take into consideration the variability due to the exposure and the test method used to measure the property of interest.
11.1.4The round-robin studies cited in11.1.1demonstrated that the gloss values for a series of materials could be ranked with a high level of reproducibility between laboratories.When reproducibility in results from an exposure test conducted according to this practice have not been established through round-robin testing,performance requirements for materials shall be specified in terms of comparison(ranked)to a control material.The control specimens shall be exposed simulta-neously with the test specimen(s)in the same device.The specific control material used shall be agreed upon by the concerned parties.Expose replicates of the test specimen and the control specimen so that statistically significant perfor-mance differences can be determined.
11.2Bias—Bias can not be determined because no accept-able standard weathering reference materials are available. 12.Keywords
12.1accelerated;accelerated weathering;durability;expo-sure;fluorescent UV lamps;laboratory weathering;light; lightfastness;non-metallic materials;temperature;ultraviolet; weathering
APPENDIXES
(Nonmandatory Information)
X1.APPLICATION GUIDELINES FOR TYPICAL FLUORESCENT UV LAMPS
X1.1General
X1.1.1A variety offluorescent UV lamps may be used in this practice.The lamps shown in this section are representa-tive of their type.Other lamps,or combinations of lamps,may be used.The particular application determines which lamp should be used.The lamps discussed in this Appendix differ in the total amount of UV energy emitted and their wavelength spectrum.Differences in lamp energy or spectrum may cause significant differences in test results.A detailed description of the type(s)of lamp(s)used shall be stated in detail in the test report.
X1.1.2All spectral power distributions(SPDs)shown in this section are representative only and are not meant to be used to calculate or estimate total radiant exposure for tests in fluorescent UV devices.Act
ual irradiance levels at the test specimen surface will vary due to the type and/or manufacturer of the lamp used,the age of the lamps,the distance to the lamp array,and the air temperature within the chamber.
N OTE X1.1—All SPDs in this appendix were measured using a spec-troradiometer with a double grating monochromator(1-nm band pass) with a quartz cosine receptor.Thefluorescent UV SPDs were measured at the sample plane in the center of the allowed sample area.SPDs for sunlight were measured in Phoenix,AZ at solar noon at the summer solstice with a clear sky,with the spectroradiometer on an equatorial follow-the-sum mount.
X1.2Simulations of Direct Solar UV Radiation Exposures X1.2.1UVA-340Lamps—For simulations of direct
solar

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