ASTM D523-89(1999)
(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.
5.1.1 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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Designation:D523–89(Reapproved1999)
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 reflected from a standard surface under the same geometric
conditions. For the purpose of measuring specular gloss, the
1.1 Thistestmethodcoversthemeasurementofthespecular
standard surface is polished glass.
gloss of nonmetallic specimens for glossmeter geometries of
2 3.1.2 specular gloss—the relative luminous reflectance fac-
60, 20, and 85° (1-7).
tor of a specimen in the mirror direction.
1.2 The values stated in inch-pound units are to be regarded
as the standard. The values given in parentheses are for
4. Summary of Test Method
information only.
4.1 Measurements are made with 60, 20, or 85° geometry
1.3 This standard does not purport to address all of the
(8, 9). The geometry of angles and apertures is chosen so that
safety concerns, if any, associated with its use. It is the
these procedures may be used as follows:
responsibility of the user of this standard to establish appro-
4.1.1 The 60° geometry is used for intercomparing most
priate safety and health practices and determine the applica-
specimens and for determining when the 20° geometry may be
bility of regulatory limitations prior to use.
more applicable.
2. Referenced Documents 4.1.2 The 20° geometry is advantageous for comparing
specimens having 60° gloss values higher than 70.
2.1 ASTM Standards:
4.1.3 The 85° geometry is used for comparing specimens
D 823 Practices for Producing Films of Uniform Thickness
for sheen or near-grazing shininess. It is most frequently
of Paint, Varnish, and Related Products on Test Panels
applied when specimens have 60° gloss values lower than 10.
D 3964 Practice for Selection of Coating Specimens for
Appearance Measurements
5. Significance and Use
D 3980 Practice for Interlaboratory Testing of Paint and
4 5.1 Gloss is associated with the capacity of a surface to
Related Materials
reflect more light in some directions than in others. The
D 4039 Test Method for Reflection Haze of High-Gloss
3 directions associated with mirror (or specular) reflection nor-
Surfaces
mally have the highest reflectances. Measurements by this test
E97 Test Method for Directional Reflectance Factor, 45-
method correlate with visual observations of surface shininess
deg 0-deg, of Opaque Specimens by Broad-Band Filter
5 made at roughly the corresponding angles.
Reflectometry
5.1.1 Measured gloss ratings by this test method are ob-
E 430 Test Method for Measurement of Gloss of High-
3 tained by comparing the specular reflectance from the speci-
Gloss Surfaces by Goniophotometry
men to that from a black glass standard. Since specular
3. Terminology reflectance depends also on the surface refractive index of the
specimen, the measured gloss ratings change as the surface
3.1 Definitions:
refractive index changes. In obtaining the visual gloss ratings,
3.1.1 relative luminous reflectance factor—the ratio of the
however, it is customary to compare the specular reflectances
luminous flux reflected from a specimen to the luminous flux
of two specimens having similar surface refractive indices.
Since the instrumental ratings are affected more than the visual
This test method is under the jurisdiction of ASTM Committee E12 on Color
ratings by changes in surface refractive index, non-agreement
and Appearance and is the direct responsibility of Subcommittee E12.03 on
between visual and instrumental gloss ratings can occur when
Geometry.
high gloss specimen surfaces differing in refractive index are
Current edition approved March 31, 1989. Published May 1989. Originally
e1
compared.
published as D 523 – 39 T. Last previous edition D 523 – 85 .
The boldface numbers in parentheses refer to the list of references at the end of
5.2 Other visual aspects of surface appearance, such as
this test method.
distinctness of reflected images, reflection haze, and texture,
Annual Book of ASTM Standards, Vol 06.01.
4 are frequently involved in the assessment of gloss (1), (6), (7).
Discontinued; see 1997 Annual Book of ASTM Standards, Vol 06.01.
Discontinued; see 1992 Annual Book of ASTM Standards, Vol 14.02. Test Method E 430 includes techniques for the measurement of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D523–89 (1999)
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.
NOTE 2—Polarization—An evaluation of the impact of polarization on
5.4 When specimens differing widely in perceived gloss or
gloss measurement has been reported (11). The magnitude of the polar-
color, or both, are compared, nonlinearity may be encountered
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
7.1 Primary Standards—Highlypolished,plane,blackglass
lengthoftheilluminatedareaofthespecimenshallbenotmore
with a refractive index of 1.567 for the sodium D line shall be
than one third of the distance from the center of this area to the
assigned a specular gloss value of 100 for each geometry. The
receptor field stop. The dimensions and tolerance of the source
gloss value for glass of any other refractive index can be
and receptor shall be as indicated in Table 1. The angular
computed from the Fresnel equation (5). For small differences
dimensions of the receptor field stop are measured from the
inrefractiveindex,however,theglossvalueisalinearfunction
receptor lens in a collimated-beam-type instrument, as illus-
of index, but the rate of change of gloss with index is different
trated in Fig. 1, and from the test surface in a converging-
for each geometry. Each 0.001 increment in refractive index
beam-type instrument, as illustrated in Fig. 2. See Fig. 1 and
produces a change of 0.27, 0.16, and 0.016 in the gloss value
Fig. 2 for a generalized illustration of the dimensions. The
assigned to a polished standard for the 20, 60, and 85°
tolerances are chosen so that errors in the source and receptor
geometries, respectively. For example, glass of index 1.527
apertures do not produce an error of more than one gloss unit
would be assigned values of 89.2, 93.6, and 99.4, in order of
at any point on the scale (5).
increasing geometry.
NOTE 3—Polished black glass has been reported to change in refractive
index with time largely due to chemical contamination (10). The original
TABLE 1 Angles and Relative Dimensions of Source Image and
values can be restored by optical polishing with cerium oxide.Awedge of
Receptors
high-purity quartz provides a more stable reference standard than glass.
In Plane of Perpendicular to
Measurement Plane of Measurement
7.2 Working Standards—Ceramic tile, depolished ground
Relative Relative
opaque glass, emery paper, and other semigloss materials
u,° 2 tan u/2 u,° 2tan u/2
Dimension Dimension
having hard and uniform surfaces are suitable when calibrated
Source image 0.75 0.0131 0.171 2.5 0.0436 0.568
against a primary standard on a glossmeter known to meet the
Tolerance 6 0.25 0.0044 0.057 0.5 0.0087 0.114
requirements of this test method. Such standards should be
60° receptor 4.4 0.0768 1.000 11.7 0.2049 2.668 checked periodically for constancy by comparing with primary
Tolerance6 0.1 0.0018 0.023 0.2 0.0035 0.046
standards.
7.3 Store standards in a closed container when not in use.
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 Keep them clean and away from any dirt that might scratch or
mar their surfaces. Never place standards face down on a
85° receptor 4.0 0.0698 0.909 6.0 0.1048 1.365
surface that may be dirty or abrasive.Always hold standards at
Tolerance6 0.3 0.0052 0.068 0.3 0.0052 0.068
thesideedgestoavoidgettingoilfromtheskinonthestandard
D523–89 (1999)
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
surface. Clean the standards in warm water and a mild 9.3 Calibrate the instrument at the start and completion of
detergent solution brushing gently with a soft nylon brush. (Do every period of glossmeter operation, and during the operation
not use soap solutions to clean standards, because they can
at sufficiently frequent intervals to assure that the instrument
leave a film.) Rinse standards in hot running water (tempera- response is practically constant. To calibrate, adjust the instru-
turenear150°F(65°C))toremovedetergentsolution,followed
ment to read correctly the gloss of a highly polished standard,
by a final rinse in distilled water. Do not wipe standards. The
properly positioned and oriented, and then read the gloss of a
polished black glass high-gloss standard may be dabbed gently
working standard in the mid-gloss range. If the instrument
with a lint-free paper towel or other lint-free absorbent
reading for the second standard does not agree within one unit
material. Place the rinsed standards in a warm oven to dry.
of its assigned values, check cleanliness and repeat. If the
instrument reading for the second standard still does not agree
8. Preparation and Selection of Test Specimens
within one unit of its assigned value, repeat with another
8.1 This test method does not cover preparation techniques. mid-range standard. If the disparity is still more than one unit,
Whenever a test for gloss requires the preparation of test do not use the instrument without readjustment, preferably by
specimens, use the procedures given in Practice D 823. the manufacturer.
NOTE 4—To determine the maximum gloss obtainable from a test
10. Procedure
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
9. Instrument Calibration
effects, place them in such a way that the directions of the
marks are parallel to the plane of the axes of the incident and
9.1 Operate the glossmeter in accordance with the manufac-
reflected beams.
turer’s instructions.
10.2 Take at least three readings ona3by 6-in. (75 by
9.2 Verify the instrument zero by placing a black cavity in
the specified position. If the reading is not within 60.1 of zero, 150-mm) area of the test specimen. If the range is greater than
twoglossunits,takeadditionalreadingsandcalculatethemean
subtract it algebraically from subsequent readings or adjust the
instrument to read zero. after discarding divergent results as in the section on Test for
D523–89 (1999)
Outliers of Practice D 3980. For larger specimens, take a 13. Precision
proportionately greater number of readings.
13.1 On the basis of studies of this test method by several
laboratories in which single determinations were made on
11. Diffuse Correction
different days on several ceramic tiles and painted panels
11.1 Apply diffuse corrections only upon agreement be-
differing in visually perceived gloss, the pooled within-
tween the producer and the user. To apply the correction,
laboratory and between-laboratories standard deviations were
subtract it from the glossmeter reading. To measure the
found to be those shown in Table 3. Based on these standard
correction, illuminate the specimen perpendicularly and view
deviations,thefollowingcriteriashouldbeusedforjudgingthe
at the incident angle with the receiver aperture specified in 6.2
acceptability of results at the 95 % confidence level:
for the corresponding geometry. To compute
...
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