ASTM E2194-14(2021)
(Test Method)Standard Test Method for Multiangle Color Measurement of Metal Flake Pigmented Materials
Standard Test Method for Multiangle Color Measurement of Metal Flake Pigmented Materials
SIGNIFICANCE AND USE
5.1 Instrumental Measurement Angles—This test method is designed to provide color data at specific measurement angles that can be utilized for quality control, color matching, and formulating in the characterization of metal flake pigmented materials.
5.2 Materials—This test method provides meaningful color information for metal flake pigmented materials. This test method has been tested and verified on paint and coatings, and the same principles should apply to plastics containing metallic flake. For materials containing pearlescent materials refer to Test Method E2539.
5.3 Utilization—This test method is appropriate for measurement and characterization of metal flake pigmented materials. These data may be used for quality control, incoming inspection, or color correction purposes.
5.4 Specimen Requirements—Even though a pair of specimens have the same color values at three angles, if there are differences in gloss, orange peel, texture, or flake orientation, they may not be a visual match.
Note 2: Information presented in this test method is based upon data taken on metallic materials coatings. Applicability of this test method to other materials should be confirmed by the user.
SCOPE
1.1 This test method covers the instrumental requirements, standardization procedures, material standards, and parameters needed to make precise instrumental measurements of the colors of gonioapparent materials. This test method is designed to encompass gonioapparent materials; such as, automotive coatings, paints, plastics, and inks.
1.2 This test method addresses measurement of materials containing metal flake and pigments. The measurement of materials containing metal flakes requires three angles of measurement to characterize the colors of the specimen. The optical characteristics of materials containing pearlescent and interference materials are not covered by this test method.
Note 1: Data taken by utilizing this test method are for gonio-appearance quality control purposes. This procedure may not necessarily supply appropriate data for spatial-appearance or pigment identification.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
General Information
Relations
Standards Content (Sample)
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.
Designation: E2194 − 14 (Reapproved 2021)
Standard Test Method for
Multiangle Color Measurement of Metal Flake Pigmented
Materials
This standard is issued under the fixed designation E2194; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Surfaces that exhibit different colors depending on the angles of illumination or sensing are said to
be “gonioapparent.” Colorimetric values of reflecting gonioapparent materials are derived from
spectrometric (narrow band) or colorimetric (broad band) measurements of reflectance factor, at
various aspecular angles. When using spectral values, tristimulus values are computed using the CIE
StandardObserverandthespectrumoftheilluminant,asdescribedinPracticeE308.Thistestmethod,
E2194, specifies the measurement of color observed at various aspecular angles.
1. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method covers the instrumental requirements,
mendations issued by the World Trade Organization Technical
standardization procedures, material standards, and parameters
Barriers to Trade (TBT) Committee.
needed to make precise instrumental measurements of the
colorsofgonioapparentmaterials.Thistestmethodisdesigned
2. Referenced Documents
to encompass gonioapparent materials; such as, automotive
2.1 ASTM Standards:
coatings, paints, plastics, and inks.
E284Terminology of Appearance
1.2 This test method addresses measurement of materials
E308PracticeforComputingtheColorsofObjectsbyUsing
containing metal flake and pigments. The measurement of
the CIE System
materials containing metal flakes requires three angles of
E805Practice for Identification of Instrumental Methods of
measurement to characterize the colors of the specimen. The
Color or Color-Difference Measurement of Materials
optical characteristics of materials containing pearlescent and
E1345Practice for Reducing the Effect of Variability of
interference materials are not covered by this test method.
Color Measurement by Use of Multiple Measurements
NOTE 1—Data taken by utilizing this test method are for gonio- E1708Practice for Electronic Interchange of Color and
appearance quality control purposes. This procedure may not necessarily
Appearance Data
supply appropriate data for spatial-appearance or pigment identification.
E2539Test Method for Multiangle Color Measurement of
1.3 The values stated in SI units are to be regarded as
Interference Pigments
standard. The values given in parentheses are for information
2.2 CIE Document:
only.
Publication No. 15Colorimetry
1.4 This standard does not purport to address all of the
2.3 NIST (NBS) Publication:
safety concerns, if any, associated with its use. It is the
LC-1017StandardsforCheckingtheCalibrationofSpectro-
responsibility of the user of this standard to establish appro-
photometers
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
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
This test method is under the jurisdiction of ASTM Committee E12 on Color Standards volume information, refer to the standard’s Document Summary page on
and Appearance and is the direct responsibility of Subcommittee E12.12 on the ASTM website.
Gonioapparent Color. Available from CIE (International Commission on Illumination) at
Current edition approved June 1, 2021. Published June 2021. Originally www.cie.co.at or www.techstreet.com.
approved in 2003. Last previous edition approved in 2017 as E2194–14 (2017). Available from National Institute of Standards and Technology (NIST), 100
DOI: 10.1520/E2194-14R21. Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2194 − 14 (2021)
other materials should be confirmed by the user.
2.4 ISO Publication:
ISO InternationalVocabulary of Basic and GeneralTerms in
6. Apparatus
Metrology (VIM)
6.1 Instrument—This test method requires measurement at
3. Terminology
multiple aspecular angles, usually accomplished by the use of
a multiangle spectrometer as specified in this test method to
3.1 Terms and definitions in Terminology E284 are appli-
characterize metal flake pigmented materials. Measurement
cable to this test method. See Section “Specialized Terminol-
with a single geometry cannot characterize the gonioappear-
ogy on Gonioapparent Phenomena.”
ance of these materials.
3.2 Definitions:
6.2 Standardization—A standardization plaque with as-
3.2.1 Usually the term metallic refers to a metal material.
signedspectralreflectancefactorortristimulusvaluestraceable
However,thisstandardemploysthealternativedefinitiongiven
to a national standardizing laboratory for each specified as-
in Terminology E284 as:
pecular angle is required to standardize the instrument. The
3.2.2 metallic, adj—pertainingtotheappearanceofagonio-
instrument manufacturer typically assigns the values to this
apparent material containing metal flakes.
plaque.
3.3 Definitions of metrology terms in ISO International
Vocabulary of Basic and General Terms in Metrology (VIM)
7. Geometric Conditions
are applicable to this test method.
7.1 Conventional Color Measurement—In general purpose
colorimetry, the common geometry involves illuminating at
4. Summary of Test Method
45°andsensingat0°.Thisgeometryisdesignated45:0(45/0).
4.1 This test method describes the procedures for the
Reverse geometry has the illumination at 0° and the sensing at
spectrometric and colorimetric measurement of metal flake
45°. That is, the illuminator and sensing geometries are
pigmented materials. The results are reported in terms of CIE
interchanged. This reciprocal geometry is designated 0:45
tristimulus values and other color coordinate systems. Stan-
(0/45). Either geometry is used.
dardizationoftheinstrumentusedtomeasurethesematerialsis
7.1.1 A single bi-directional geometry is specified by illu-
defined. Guidelines are given for the selection of specimens
mination and sensing angles with respect to the normal of the
and a measurement protocol given. Characterization of these
plane of the specimen. Angles are measured relative to the
materials requires measurement at a near-specular angle, a
normal. Angles on the same side of the normal as the
mid-specular angle and a far-specular angle. These preferred
illumination beam are written as positive angles; those on the
aspecular angles are 15°, 45°, and 110°.
other side are shown as negative, as shown in Fig. 1.
7.2 Multiangle Uniplanar Measurement—The color of me-
5. Significance and Use
tallic materials specimens varies with the angle of view. Thus
5.1 Instrumental Measurement Angles—This test method is
measurements must be taken at more than one aspecular angle
designed to provide color data at specific measurement angles
to characterize the change of color with angle. The measure-
that can be utilized for quality control, color matching, and
ment geometry for multiangle measurements is specified by
formulating in the characterization of metal flake pigmented
aspecular angles. The aspecular angle is the viewing angle
materials.
measured from the specular direction, in the illuminator plane
5.2 Materials—This test method provides meaningful color
unless otherwise specified. The angle is considered positive
information for metal flake pigmented materials. This test
when measured from the specular direction towards the illu-
method has been tested and verified on paint and coatings, and
minator axis.Thus, if the specimen is illuminated at 45° to the
thesameprinciplesshouldapplytoplasticscontainingmetallic
normal the specular reflection will be at -45° (see Fig. 1).
flake. For materials containing pearlescent materials refer to
Test Method E2539.
5.3 Utilization—This test method is appropriate for mea-
surement and characterization of metal flake pigmented mate-
rials. These data may be used for quality control, incoming
inspection, or color correction purposes.
5.4 Specimen Requirements—Even though a pair of speci-
mens have the same color values at three angles, if there are
differences in gloss, orange peel, texture, or flake orientation,
they may not be a visual match.
NOTE 2—Information presented in this test method is based upon data
taken on metallic materials coatings. Applicability of this test method to
NOTE 1—Anormal illumination angle=45° and anormal sensing
ISO/IDE/OIML/BIPM,InternationalVocabularyofBasicandGeneralTermsin
angle=65°; therefore, aspecular angle=45+65=110°.
Metrology, International Organization for Standardization, Geneva Switzerland,
1984. FIG. 1 Example of Illuminating and Sensing Geometry
E2194 − 14 (2021)
Sensingat65°fromthenormal,andonthesamesideofnormal
as the illumination, is sensing 110° away from the specular
direction; that is an aspecular angle of 110°. Thus, the
aspecular angle is the sum of the anormal illumination and
sensing angles. It has been established that for metallic
materials or colors, a specific aspecular angle gives the same
measurement regardless of angle of illumination.
7.3 Annular and Circumferential Geometry—Annular illu-
mination provides incident light to a specimen at all azimuthal
angles. This type of illumination minimizes the contribution
from directional effects such as the venetian blind effect and
NOTE 1—Solid lines indicate preferred angles.
surface irregularities. Circumferential illumination is an ap-
FIG. 2 Diagram of Aspecular Angles
proximation to annular illumination, incident light being pro-
vided from a discrete number of representative azimuthal
angles. A large number or an odd number of illumination
detecting specular light. Surface imperfections can cause light
sources more closely approximates annular illumination. An-
to be reflected in a direction slightly away from the nominal
nular or circumferential illumination minimizes directional
specular direction. Measurement at 15° from the specular
effects. Therefore, measurements with annular or circumferen-
minimizes the effects of surface imperfections encountered in
tial illumination may or may not correlate with how that
most practical industrial specimens. Differences in surface
specimen appears under directional illumination. For example,
texture may result from spray application differences which
this system averaging may cause the measured color values of
can cause flake orientation differences. Measurement at 20° or
two specimens to be the same or similar, even though these
25° from specular may be chosen when less sensitivity to
same two specimens would not match visually due to the fact
application differences between standard and batch is desired.
that one specimen exhibits the venetian blind effect.
In critical color matching applications, batches should be
7.4 Recommended Geometry—The instrument shall con-
resampled and resprayed to eliminate surface differences and
formtothefollowinggeometricrequirementsformeasurement
measurements shall be performed at 15°.
of reflectance factor unless otherwise agreed upon between the
7.4.2 Mid-specular Angle—The mid-specular color mea-
buyer and the seller. The preferred aspecular angles for
surement shall be at an aspecular angle of 45° conforming to
measurement are 15°, 45°, and 110°.
the geometrical specifications of CIE 15:2004.
7.4.3 Far-specular Angle—Visual observation of color dif-
NOTE 3—Given a geometric configuration, the reverse geometry is
ferences in a few cases detects sidetone scattering better at
consideredequivalent,ifallothercomponentsoftheinstrumentdesignare
equivalent; for example, in the example shown in Fig. 1, the same result anglesfurtherawayfromspecular;hence,110°isthepreferred
wouldbeobtainedwiththeilluminationangleat65°andthesensingangle
aspecular angle for far-specular measurement. In most but not
at 45°. The aspecular angle would still be 110°.
all cases, angles down to 70° give acceptable results.
NOTE 4—Measurement angles below are stated in terms of aspecular
(Warning—Visual assessments of gonioapparent matches
angles.Ithasbeenestablishedthatformetallicmaterialscolors,aspecific
typically cover a wide range of aspecular angles, from very
aspecular angle gives the same measurement regardless of angle of
illumination. For pearlescent materials, it is known that color is also a
nearspecular,allthewaytofar-specularanglesof110°oreven
function of angle of illumination. The importance of this phenomenon in
higher. Therefore, instrumental measurement at far-specular
measurementofpearlescentandinterferencematerialsforcolordifference
angles below 110° may occasionally result in measurements
for quality control or color correction purposes has not been established.
not agreeing with typical visual assessments. This will occur
NOTE 5—Uniplanar instruments can measure the venetian blind effect.
when specimens are an acceptable visual and instrumental
Circumferential and annular illumination will not quantify this gonioap-
parent effect.
match at angles such as 75° but unacceptable at 110°.)
NOTE 6—There are instruments commercially available with uniplanar,
7.4.4 Illuminating and Sensing Beam Aperture Angles—The
multiangle geometries that give results that characterize gonioapparent
illuminating beam aperture angle and the sensing beam aper-
materials.Theseinstrumentswilldetectthevenetianblindeffectandother
ture angle must be less than 8°.
anomalies. Table 1 delineates the preferred angles. Note that circumfer-
ential geometry is limited to <90° aspecular angle. With the variety of
8. Test Specimen
instrumentation in common usage, it is incumbent upon the user to
determine if an instrument with angles other than the preferred angles is
8.1 Measured values depend on the quality of the test
appropriate in their application.
specimens. The specimens must be statistically representative
7.4.1 Near Specular Angle—The near specular angle used
of the lot being tested and should meet the requirements listed
shouldbeasclosetothespeculardirectionaspossible,without
below. If the specimens do not meet these require
...
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