ASTM D2457-21

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Designation: D2457 − 13 D2457 − 21
Standard Test Method for
Specular Gloss of Plastic Films and Solid Plastics
This standard is issued under the fixed designation D2457; 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 test method describes procedures for the measurement of gloss of plastic films and solid plastics, both opaque and
transparent. It contains four separate gloss angles (Note 1):
1.1.1 60-deg, recommended for intermediate-gloss films,
1.1.2 20-deg, recommended for high-gloss films,
1.1.3 45-deg, recommended for intermediate and low-gloss films,
1.1.4 85-deg, recommended for intermediate and low gloss films, and
1.1.5 75-deg, recommended for plastic siding and soffit.
NOTE 1—The 85-deg, 75-deg, 60-deg, and 20-deg apparatus and method of measurement duplicate those in Test Method D523 and D3679; those for the
45° procedure are similarly taken from Test Method C346.
1.2 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 2—There is no known ISO equivalent to this standard.
1.3 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.
2. Referenced Documents
2.1 ASTM Standards:
C346 Test Method for 45-deg Specular Gloss of Ceramic Materials
D523 Test Method for Specular Gloss
D3679 Specification for Rigid Poly(Vinyl Chloride) (PVC) Siding
E284 Terminology of Appearance
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.40 on Optical Properties.
Current edition approved April 1, 2013May 1, 2021. Published April 2013June 2021. Originally approved in 1965. Last previous edition approved in 20082013 as
ε1
D2457 – 08D2457 – 13. . DOI: 10.1520/D2457-13.10.1520/D2457-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
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D2457 − 21
TABLE 1 Angular Dimensions and Tolerances of Geometry of Source and Receptor Field Stops
Source Field Stop Receptor Field Stop
In Plane of Measurement, Perpendicular to Plane of Perpendicular to Plane of
Geometry, deg Incidence Angle, deg In Plane of Measurement, deg
deg Measurement, deg Measurement, deg
75 75 ± 0.1 3.0 max
60 60 ± 0.1 0.75 ± 0.25 3.0 max 4.4 ± 0.1 11.7 ± 0.2
20 20 ± 0.1 0.75 ± 0.25 3.0 max 1.80 ± 0.05 3.6 ± 0.1
45 45 ± 0.1 1.4 ± 0.4 3.0 ± 1.0 8.0 ± 0.1 10.0 ± 0.2
E1347 Test Method for Color and Color-Difference Measurement by Tristimulus Colorimetry
E1349 Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional (45°:0° or 0°:45°) Geometry
E2935 Practice for Conducting Equivalence Tests for Comparing Testing Processes
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, see Terminology E284.
4. Significance and Use
4.1 Specular gloss is used primarily as a measure of the shiny appearance of films and surfaces. Precise comparisons of gloss
values are meaningful only when they refer to the same measurement procedure and same general type of material. In particular,
gloss values for transparent films should not be compared with those for opaque films, and vice versa. Gloss is a complex attribute
of a surface which cannot be completely measured by any single number.
4.2 Specular gloss usually varies with surface smoothness and flatness. It is sometimes used for comparative measurements of
these surface properties.
5. Apparatus
5.1 Instrumental Components—Each apparatus (Note 3) shall consist of an incandescent light source furnishing an incident beam,
means for locating the surface of the specimen, and a receptor located to receive the required pyramid of rays reflected by the
specimen. The receptor shall be a photosensitive device responding to visible radiation.
NOTE 3—The 75-, 60-, and 20-deg procedures require apparatus identical to that specified in Test Method D523. The 45° procedure requires apparatus
like that specified in Test Method C346.
5.2 Geometric Conditions—The axis of the incident beam shall be at one of the specified angles from the perpendicular to the
specimen surface. The axis of the receptor shall be at the mirror reflection of the axis of the incident beam. With a flat piece of
polished black glass or other front-surface mirror in specimen position, an image of the source shall be formed at the center of the
receptor field stop (receptor window). The length of the illuminated area of the specimen shall be equal to not more than one third
of the distance from the center of this area to the receptor field stop. The angular dimensions and tolerances of the geometry of
the source and receptor shall be as indicated in Table 1. The angular dimensions of the receptor field stop are measured from the
center of the test surface. The angular dimensions of the source field stop are mostly easily measured by the specimen-to-window
angular size of the mirror image of the source formed in the receptor field stop. (See Fig. 1 for a generalized illustration of the
dimensions.) The tolerances are chosen so that errors of no more than one gloss unit at any point on the scale will result from errors
in the source and receptor aperture.
5.3 Vignetting—There shall be no vignetting of rays that lie within the field angles specified in 5.2.
5.4 Spectral Conditions—Results should not differ significantly from those obtained with a source-filter-photocell combination
that is spectrally corrected to yield CIE luminous efficiency with CIE Source C. Since specular reflection is, in general, spectrally
nonselective, spectral corrections need be applied only to highly chromatic, low-gloss specimens upon agreement of users of this
test method.
5.5 Measurement Mechanism—The receptor-measurement mechanism shall give a numerical indication that is proportional to the
light flux passing the receptor field stop within 61 percent of full-scale reading.
D2457 − 21
FIG. 1 Diagram of Glossmeter Showing Essential Components and Dimensions
6. Reference Standards
6.1 Primary Working Standards may be highly polished, plane, black glass surfaces. The specular reflectance, in percent, (R ) of
s
such surfaces shall be computed by the following equation:
R ~percent!5 (1)
s
2 2
2 2 2 2 2
cos i 2=n 2 sin i n cosi 2=n 2 sin i
50 1
FF G F G G
2 2 2 2 2
= =
cos i1 n 2 sin i n cosi1 n 2 sin i
where:
i = the specular (incidence) angle, and
n = the index of refraction of the surface.
i = the specular (incidence) angle, and
n = the index of refraction of the surface.
Multiply the computed R at each angle by the scale factors shown in Table 2.
s
NOTE 4—On the 45 and 60° scales, a perfect mirror measures 1000.
6.2 Secondary Working Standards of ceramic tile, glass, porcelain enamel, or other materials having hard, flat, and uniform
surfaces may be calibrated from the primary standard on a glossmeter determined to be in strict conformance with the requirements
prescribed in 5.2.
7. Preparation and Selection of Test Specimens
7.1 This test method does not cover preparation techniques. Whenever a test for gloss requires the preparation of a test specimen,
report the technique of specimen preparation.
7.2 Test results have been found to be seriously affected by surface warpage, waviness, or curvature. Ensure that specimen surfaces
have good planarity. Perform tests with the directions of machine marks, or similar texture effects, both parallel and perpendicular
to the plane of the axes of the incident and reflected beams, unless otherwise specified. (Note that this does not avoid the
second-surface reflection.)
7.3 Surface test areas shall be kept free of soil and abrasion. Gloss is due chiefly to reflection at the surface; therefore, anything
that changes the surface physically or chemically is likely to affect gloss.
D2457 − 21
A
TABLE 2 Scale Factors for Gloss Standards, Perfect Mirror and Perfect Matt White
Scale Factors (multiply
Value for Black Glass when
Geometry R of black glass Value for Perfect Mirror Value for Perfect Matt White
s
n = 1.540
standard by)
60° 10.0 95.8 1000 2.1
20° 20.3 92.3 2030 1.4
45° 10.0 55.9 1000 5.4
A
The latter are useful for estimating corrections to gloss readings for reflection from sample backing (see Note 6).
8. Mounting Films for Measurement
8.1 Any nonrigid film must be mounted in a device that will hold it flat, but will not stretch the film while it is measured. Three
different filmholding devices have each proved satisfactory for at least some types of films:
8.1.1 Vacuum Plate (see Fig. 2) is required for stiff films. Connect the vacuum plate by rubber tube to a vacuum pump or vacuum
line. With thin, soft films it is sometimes necessary to use a valve and pressure gage and to limit the vacuum so as to keep from
collapsing the soft film into the pores of the ground plate.
8.1.2 Flat Plate with two-side pressure-sensitive tape (see Fig. 3). Make sure each specimen is pulled smooth, but not stretched
before holding it by the two strips of adhesive tape. Replace the tape whenever it loses its adhesiveness.
8.1.3 Telescoping Ring or Hoop (see Fig. 4)—To mount the specimen in the telescoping ring, lay the flexible film over the base
(male) section and drop the top over the base. Push down carefully, taking care to pull the test film taut without stretching it.
Measure the taut area.
8.2 Backing for Films That Transmit Light—A matt black backing or (even better) a black cavity must be placed behind any film
that transmits light. Erroneous measurements will occur without a suitable trap or backing.
9. Procedure
9.1 Operate the glossmeter in accordance with the manufacturer’s instructions.
9.2 Calibrate the instrument at the start and completion of every period of glossmeter operation and during the operation at
sufficiently frequent intervals to assure that the instrument response is practically constant. If at any time an instrument fails to
repeat readings of the standard to within 2 percent of the prior setting, the intervening results should be rejected. To calibrate, adjust
the instrument to read correctly the gloss of a highly polished standard, and then read the gloss of a standard having poorer
image-forming characteristics. If the instrument reading for the second standard does not agree within 1 percent of its assigned
value, do not use the instrument without readjustment, preferably by the manufacturer.
NOTE 5—Correct readings on black-glass and intermediate standards do not guarantee instrument conformity to specification requirements. In ad
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