ASTM D2457 - 21

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Designation: 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 measure-

ment 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 appro-

priate safety, health, and environmental practices and deter-

mine 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 accor-

dance with internationally recognized principles on standard-

ization established in the Decision on Principles for the

Development of International Standards, Guides and Recom-

mendations 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

E1347 Test Method for Color and Color-Difference Mea-

surement 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 Com-

paring 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 measure-

ments 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 photosensi-

tive 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

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 May 1, 2021. Published June 2021. Originally

approved in 1965. Last previous edition approved in 2013 as D2457 – 13. DOI:

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

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.

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 signiﬁ-

cantly from those obtained with a source-ﬁlter-photocell com-

bination 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 propor-

tional to the light ﬂux passing the receptor ﬁeld stop within 61

percent of full-scale reading.

6. Reference Standards

6.1 Primary Working Standards may be highly polished,

plane, black glass surfaces. The specular reﬂectance, in

percent, (R

) of such surfaces shall be computed by the

following equation:

percent

5(1)

cos i2

2sin

cos i1

2sin

cosi2

2sin

cosi1

2sin

where:

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.

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.

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 satisfac-

tory 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.

TABLE 1 Angular Dimensions and Tolerances of Geometry of Source and Receptor Field Stops

Source Field Stop Receptor Field Stop

Geometry, deg Incidence Angle, deg In Plane of Measurement,

deg

Perpendicular to Plane of

Measurement, deg In Plane of Measurement, deg Perpendicular to Plane of

Measurement, deg

75 75 ± 0.1 3.0 max

60 60±0.1 0.75±0.25 3.0max 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

D2457 − 21

9. Procedure

9.1 Operate the glossmeter in accordance with the manufac-

turer’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

FIG. 1 Diagram of Glossmeter Showing Essential Components and Dimensions

TABLE 2 Scale Factors for Gloss Standards, Perfect Mirror and Perfect Matt White

Geometry

Scale Factors (multiply

of black glass

standard by)

Value for Black Glass when

n= 1.540 Value for Perfect Mirror Value for Perfect Matt White

60° 10.0 95.8 1000 2.1

20° 20.3 92.3 2030 1.4

45° 10.0 55.9 1000 5.4

The latter are useful for estimating corrections to gloss readings for reﬂection from sample backing (see Note 6).

FIG. 2 Vacuum Plate Used to Hold Films Flat

D2457 − 21

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摘要：

ASTM D2457 - 21 是当前最新版本的 ASTM 标准规范，专门用于测定塑料薄膜与固体塑料表面的镜面光泽度。该标准通过采用 20°、45° 或 60° 等不同几何角度的入射光，量化材料表面的反射特性，适用于透明、半透明及不透明塑料制品的光泽度评估。规范详细规定了仪器校准、样品制备、测试步骤及数据处理方法，确保实验室间结果的重复性与可比性。对于塑料薄膜、板材、注塑件及涂层表面，ASTM D2457 - 21 为质量控制和产品开发提供了关键的光学性能指标，广泛应用于包装、汽车内饰、电子外壳

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