ASTM D523-89(2008)
(Test Method)Standard Test Method for Specular Gloss
Standard Test Method for Specular Gloss
SIGNIFICANCE AND USE
Gloss is associated with the capacity of a surface to reflect more light in some directions than in others. The directions associated with mirror (or specular) reflection normally have the highest reflectances. Measurements by this test method correlate with visual observations of surface shininess made at roughly the corresponding angles.
Measured gloss ratings by this test method are obtained by comparing the specular reflectance from the specimen to that from a black glass standard. Since specular reflectance depends also on the surface refractive index of the specimen, the measured gloss ratings change as the surface refractive index changes. In obtaining the visual gloss ratings, however, it is customary to compare the specular reflectances of two specimens having similar surface refractive indices. Since the instrumental ratings are affected more than the visual ratings by changes in surface refractive index, non-agreement between visual and instrumental gloss ratings can occur when high gloss specimen surfaces differing in refractive index are compared.
Other visual aspects of surface appearance, such as distinctness of reflected images, reflection haze, and texture, are frequently involved in the assessment of gloss (1), (6), (7). Test Method E 430 includes techniques for the measurement of both distinctness-of-image gloss and reflection haze. Test Method D 4039 provides an alternative procedure for measuring reflection haze.
Little information about the relation of numerical-to-perceptual intervals of specular gloss has been published. However, in many applications the gloss scales of this test method have provided discriminations between coated specimens that have agreed well with visual discriminations of gloss (10).
When specimens differing widely in perceived gloss or color, or both, are compared, nonlinearity may be encountered in the relationship between visual gloss difference ratings and instrumental gloss reading differences.
SCOPE
1.1 This test method covers the measurement of the specular gloss of nonmetallic specimens for glossmeter geometries of 60, 20, and 85° (1-7).
1.2 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
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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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D523–89(Reapproved2008)
Standard Test Method for
Specular Gloss
This standard is issued under the fixed designation D 523; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3. Terminology
1.1 Thistestmethodcoversthemeasurementofthespecular 3.1 Definitions:
gloss of nonmetallic specimens for glossmeter geometries of 3.1.1 relative luminous reflectance factor—the ratio of the
60, 20, and 85° (1-7). luminous flux reflected from a specimen to the luminous flux
1.2 The values stated in inch-pound units are to be regarded reflected from a standard surface under the same geometric
as the standard. The values given in parentheses are for conditions. For the purpose of measuring specular gloss, the
information only. standard surface is polished glass.
1.3 This standard does not purport to address all of the 3.1.2 specular gloss—the relative luminous reflectance fac-
safety concerns, if any, associated with its use. It is the tor of a specimen in the mirror direction.
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 4.1 Measurements are made with 60, 20, or 85° geometry
(8, 9). The geometry of angles and apertures is chosen so that
2. Referenced Documents
these procedures may be used as follows:
2.1 ASTM Standards: 4.1.1 The 60° geometry is used for intercomparing most
D 823 Practices for Producing Films of Uniform Thickness specimens and for determining when the 20° geometry may be
of Paint, Varnish, and Related Products on Test Panels more applicable.
D 3964 Practice for Selection of Coating Specimens for 4.1.2 The 20° geometry is advantageous for comparing
Appearance Measurements specimens having 60° gloss values higher than 70.
D 3980 Practice for Interlaboratory Testing of Paint and 4.1.3 The 85° geometry is used for comparing specimens
Related Materials for sheen or near-grazing shininess. It is most frequently
D 4039 Test Method for Reflection Haze of High-Gloss applied when specimens have 60° gloss values lower than 10.
Surfaces
5. Significance and Use
E97 Test Method for Directional Reflectance Factor, 45-
5.1 Gloss is associated with the capacity of a surface to
Deg 0-Deg, of Opaque Specimens by Broad-Band Filter
Reflectometry reflect more light in some directions than in others. The
directions associated with mirror (or specular) reflection nor-
E 430 Test Methods for Measurement of Gloss of High-
Gloss Surfaces by Abridged Goniophotometry mally have the highest reflectances. Measurements by this test
method correlate with visual observations of surface shininess
made at roughly the corresponding angles.
5.1.1 Measured gloss ratings by this test method are ob-
This test method is under the jurisdiction of ASTM Committee E12 on Color
tained by comparing the specular reflectance from the speci-
and Appearance and is the direct responsibility of Subcommittee E12.03 on
Geometry. men to that from a black glass standard. Since specular
Current edition approved Feb. 1, 2008. Published April 2008. Originally
reflectance depends also on the surface refractive index of the
approved in 1939. Last previous edition approved in 1999 as D 523 – 89 (1999).
specimen, the measured gloss ratings change as the surface
The boldface numbers in parentheses refer to the list of references at the end of
refractive index changes. In obtaining the visual gloss ratings,
this test method.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
however, it is customary to compare the specular reflectances
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
of two specimens having similar surface refractive indices.
Standards volume information, refer to the standard’s Document Summary page on
Since the instrumental ratings are affected more than the visual
the ASTM website.
Withdrawn. ratings by changes in surface refractive index, non-agreement
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D523–89 (2008)
between visual and instrumental gloss ratings can occur when receptor lens in a collimated-beam-type instrument, as illus-
high gloss specimen surfaces differing in refractive index are trated in Fig. 1, and from the test surface in a converging-
compared. beam-type instrument, as illustrated in Fig. 2. See Fig. 1 and
5.2 Other visual aspects of surface appearance, such as Fig. 2 for a generalized illustration of the dimensions. The
distinctness of reflected images, reflection haze, and texture, tolerances are chosen so that errors in the source and receptor
are frequently involved in the assessment of gloss (1), (6), (7). apertures do not produce an error of more than one gloss unit
TestMethodE 430includestechniquesforthemeasurementof at any point on the scale (5).
both distinctness-of-image gloss and reflection haze. Test 6.2.1 The important geometric dimensions of any specular-
Method D 4039 provides an alternative procedure for measur- gloss measurement are:
ing reflection haze. 6.2.1.1 Beam axis angle(s), usually 60, 20, or 85°.
5.3 Little information about the relation of numerical-to- 6.2.1.2 Accepted angular divergences from principal rays
perceptual intervals of specular gloss has been published. (degree of spreading or diffusion of the reflected beam).
However, in many applications the gloss scales of this test
NOTE 1—The parallel-beam glossmeters possess the better uniformity
method have provided discriminations between coated speci-
of principle-ray angle of reflection, but the converging-beam glossmeters
mensthathaveagreedwellwithvisualdiscriminationsofgloss
possess the better uniformity in extent of angular divergence accepted for
(10).
measurement.
5.4 When specimens differing widely in perceived gloss or
NOTE 2—Polarization—An evaluation of the impact of polarization on
color, or both, are compared, nonlinearity may be encountered gloss measurement has been reported (11). The magnitude of the polar-
ization error depends on the difference between the refractive indices of
in the relationship between visual gloss difference ratings and
specimen and standard, the angle of incidence, and the degree of
instrumental gloss reading differences.
polarization. Because the specimen and standard are generally quite
similar optically, measured gloss values are little affected by polarization.
6. Apparatus
6.3 Vignetting—There shall be no vignetting of rays that lie
6.1 Instrumental Components—The apparatus shall consist
within the field angles specified in Table 1.
of an incandescent light source furnishing an incident beam,
6.4 Spectral Conditions—Results should not differ signifi-
means for locating the surface of the specimen, and a receptor
cantly from those obtained with a source-filter photocell
located to receive the required pyramid of rays reflected by the
combination that is spectrally corrected to yield CIE luminous
specimen. The receptor shall be a photosensitive device re-
efficiency with CIE source C. Since specular reflection is, in
sponding to visible radiation.
general, spectrally nonselective, spectral corrections need to be
6.2 Geometric Conditions—The axis of the incident beam
applied only to highly chromatic, low-gloss specimens upon
shallbeatoneofthespecifiedanglesfromtheperpendicularto
agreement of users of this test method.
the specimen surface. The axis of the receptor shall be at the
6.5 Measurement Mechanism—The receptor-measurement
mirror reflection of the axis of the incident beam. The axis of
mechanism shall give a numerical indication that is propor-
the incident beam and the axis of the receptor shall be within
tional to the light flux passing the receptor field stop with
0.1°ofthenominalvalueindicatedbythegeometry.Withaflat
61 % of full-scale reading.
piece of polished black glass or other front-surface mirror in
the specimen position, an image of the source shall be formed
7. Reference Standards
at the center of the receptor field stop (receptor window). The
lengthoftheilluminatedareaofthespecimenshallbenotmore
7.1 Primary Standards—Highlypolished,plane,blackglass
than one third of the distance from the center of this area to the
with a refractive index of 1.567 for the sodium D line shall be
receptor field stop. The dimensions and tolerance of the source
assigned a specular gloss value of 100 for each geometry. The
and receptor shall be as indicated in Table 1. The angular
gloss value for glass of any other refractive index can be
dimensions of the receptor field stop are measured from the
computed from the Fresnel equation (5). For small differences
inrefractiveindex,however,theglossvalueisalinearfunction
of index, but the rate of change of gloss with index is different
TABLE 1 Angles and Relative Dimensions of Source Image and
for each geometry. Each 0.001 increment in refractive index
Receptors
produces a change of 0.27, 0.16, and 0.016 in the gloss value
In Plane of Perpendicular to
assigned to a polished standard for the 20, 60, and 85°
Measurement Plane of Measurement
geometries, respectively. For example, glass of index 1.527
Relative Relative
u,° 2 tan u/2 u,° 2tan u/2
would be assigned values of 89.2, 93.6, and 99.4, in order of
Dimension Dimension
increasing geometry.
Source image 0.75 0.0131 0.171 2.5 0.0436 0.568
Tolerance 6 0.25 0.0044 0.057 0.5 0.0087 0.114
NOTE 3—Polished black glass has been reported to change in refractive
index with time largely due to chemical contamination (10). The original
60° receptor 4.4 0.0768 1.000 11.7 0.2049 2.668
values can be restored by optical polishing with cerium oxide.Awedge of
Tolerance6 0.1 0.0018 0.023 0.2 0.0035 0.046
high-purity quartz provides a more stable reference standard than glass.
20° receptor 1.8 0.0314 0.409 3.6 0.0629 0.819
Tolerance 6 0.05 0.0009 0.012 0.1 0.0018 0.023 7.2 Working Standards—Ceramic tile, depolished ground
opaque glass, emery paper, and other semigloss materials
85° receptor 4.0 0.0698 0.909 6.0 0.1048 1.365
having hard and uniform surfaces are suitable when calibrated
Tolerance6 0.3 0.0052 0.068 0.3 0.0052 0.068
against a primary standard on a glossmeter known to meet the
D523–89 (2008)
FIG. 1 Diagram of Parallel-Beam Glossmeter Showing Apertures and Source Mirror-Image Position
FIG. 2 Diagram of Converging-Beam Glossmeter Showing Apertures and Source Mirror-Image Position
requirements of this test method. Such standards should be 9. Instrument Calibration
checked periodically for constancy by comparing with primary
9.1 Operate the glossmeter in accordance with the manufac-
standards.
turer’s instructions.
7.3 Store standards in a closed container when not in use.
9.2 Verify the instrument zero by placing a black cavity in
Keep them clean and away from any dirt that might scratch or
the specified position. If the reading is not within 60.1 of zero,
mar their surfaces. Never place standards face down on a
subtract it algebraically from subsequent readings or adjust the
surface that may be dirty or abrasive.Always hold standards at
instrument to read zero.
thesideedgestoavoidgettingoilfromtheskinonthestandard
9.3 Calibrate the instrument at the start and completion of
surface. Clean the standards in warm water and a mild
every period of glossmeter operation, and during the operation
detergent solution brushing gently with a soft nylon brush. (Do
at sufficiently frequent intervals to assure that the instrument
not use soap solutions to clean standards, because they can
response is practically constant. To calibrate, adjust the instru-
leave a film.) Rinse standards in hot running water (tempera-
ment to read correctly the gloss of a highly polished standard,
turenear150°F(65°C))toremovedetergentsolution,followed
properly positioned and oriented, and then read the gloss of a
by a final rinse in distilled water. Do not wipe standards. The
working standard in the mid-gloss range. If the instrument
polished black glass high-gloss standard may be dabbed gently
reading for the second standard does not agree within one unit
with a lint-free paper towel or other lint-free absorbent
of its assigned values, check cleanliness and repeat. If the
material. Place the rinsed standards in a warm oven to dry.
instrument reading for the second standard still does not agree
within one unit of its assigned value, repeat with another
8. Preparation and Selection of Test Specimens
mid-range standard. If the disparity is still more than one unit,
8.1 This test method does not cover preparation techniques.
do not use the instrument without readjustment, preferably by
Whenever a test for gloss requires the preparation of test
the manufacturer.
specimens, use the procedures given in Practice D 823.
10. Procedure
NOTE 4—To determine the maximum gloss obtainable from a test
material,suchasapaintorvarnish,useMethodsBorCofPracticeD 823.
10.1 Position each specimen in turn beneath (or on) the
8.2 Select specimens in accordance with Practice D 3964. glossmeter. For specimens with brush marks or similar texture
D523–89 (2008)
effects, place them in such a way that the directions of the 12.1.4 Manufacturer’s name and model designation of the
marks are parallel to the plane of the axes of the incident and glossmeter.
reflected beams. 12.1.5 Working standard or standards of gloss used.
10.2 Take at least three readings ona3by 6-in. (75 by
13. Precision
150-mm) area of the test specimen. If the range is greater than
13.1 On the basis of studies of this test method by several
twoglossunits,takeadditionalreadingsandcalculatethemean
laboratories in which single determinations were made on
after discarding divergent results as in the section on Test for
different days on several ceramic tiles and painted panels
Outliers of Practice D 3980. For larger specimens, take a
differing in visually perceived gloss, the pooled within-
proportionately greater number of readings.
laboratory and between-laboratories standard deviations were
11. Diffuse Correction
found to be those shown in Table 3. Based on these standard
deviations,thefollowingcriteriashouldbeusedforjudgingthe
11.1 Apply diffuse corrections only upon agreement be-
acceptability of results at the 95 % confidence level:
tween the producer and the user. To apply the correction,
13.1.1 Repe
...
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