1、Designation: E2194 14Standard Test Method forMultiangle Color Measurement of Metal Flake PigmentedMaterials1This standard is issued under the fixed designation E2194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONSurfaces that exhibit different colors depending on the angles of illumination or sensing are said tobe “gonioapparent.” C
3、olorimetric values of reflecting gonioapparent materials are derived fromspectrometric (narrow band) or colorimetric (broad band) measurements of reflectance factor, atvarious aspecular angles. When using spectral values, tristimulus values are computed using the CIEStandard Observer and the spectru
4、m of the illuminant, as described in Practice E308. This test method,E2194, specifies the measurement of color observed at various aspecular angles.1. Scope1.1 This test method covers the instrumental requirements,standardization procedures, material standards, and parametersneeded to make precise i
5、nstrumental measurements of thecolors of gonioapparent materials. This test method is designedto encompass gonioapparent materials; such as, automotivecoatings, paints, plastics, and inks.1.2 This test method addresses measurement of materialscontaining metal flake and pigments. The measurement ofma
6、terials containing metal flakes requires three angles ofmeasurement to characterize the colors of the specimen. Theoptical characteristics of materials containing pearlescent andinterference materials are not covered by this test method.NOTE 1Data taken by utilizing this test method are for gonio-ap
7、pearance quality control purposes. This procedure may not necessarilysupply appropriate data for spatial-appearance or pigment identification.1.3 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to
8、 address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E284 Term
9、inology of AppearanceE308 Practice for Computing the Colors of Objects by Usingthe CIE SystemE805 Practice for Identification of Instrumental Methods ofColor or Color-Difference Measurement of MaterialsE1345 Practice for Reducing the Effect of Variability ofColor Measurement by Use of Multiple Measu
10、rementsE1708 Practice for Electronic Interchange of Color andAppearance DataE2539 Test Method for Multiangle Color Measurement ofInterference Pigments2.2 CIE Document:3Publication No. 15:2004 Colorimetry2.3 NIST (NBS) Publication:4LC-1017 Standards for Checking the Calibration of Spectro-photometers
11、2.4 ISO Publication:5ISO International Vocabulary of Basic and General Terms inMetrology (VIM)1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee E12.12 onGonioapparent Color.Current edition approved Nov. 1, 2014.
12、Published November 2014. Originallyapproved in 2003. Last previous edition approved in 2012 as E2194 12. DOI:10.1520/E2194-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,
13、 refer to the standards Document Summary page onthe ASTM website.3Available from U.S. National Committee of the CIE (International Commissionon Illumination), http:/www.cie-usnc.org or http:/ from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899
14、-1070, http:/www.nist.gov.5ISO/IDE/OIML/BIPM, International Vocabulary of Basic and General Terms inMetrology, International Organization for Standardization, Geneva Switzerland,1984.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.
15、Terminology3.1 Terms and definitions in Terminology E284 are appli-cable to this test method. See Section “Specialized Terminol-ogy on Gonioapparent Phenomena.”3.2 Definitions:3.2.1 Usually the term metallic refers to a metal material.However, this standard employs the alternative definition givenin
16、 Terminology E284 as:3.2.2 metallic, adjpertaining to the appearance of a gonio-apparent material containing metal flakes.3.3 Definitions of metrology terms in ISO InternationalVocabulary of Basic and General Terms in Metrology (VIM)are applicable to this test method.4. Summary of Test Method4.1 Thi
17、s test method describes the procedures for thespectrometric and colorimetric measurement of metal flakepigmented materials. The results are reported in terms of CIEtristimulus values and other color coordinate systems. Stan-dardization of the instrument used to measure these materials isdefined. Gui
18、delines are given for the selection of specimensand a measurement protocol given. Characterization of thesematerials requires measurement at a near-specular angle, amid-specular angle and a far-specular angle. These preferredaspecular angles are 15, 45, and 110.5. Significance and Use5.1 Instrumenta
19、l Measurement AnglesThis test method isdesigned to provide color data at specific measurement anglesthat can be utilized for quality control, color matching, andformulating in the characterization of metal flake pigmentedmaterials.5.2 MaterialsThis test method provides meaningful colorinformation fo
20、r metal flake pigmented materials. This testmethod has been tested and verified on paint and coatings, andthe same principles should apply to plastics containing metallicflake. For materials containing pearlescent materials refer toTest Method E2539.5.3 UtilizationThis test method is appropriate for
21、 mea-surement and characterization of metal flake pigmented mate-rials. These data may be used for quality control, incominginspection, or color correction purposes.5.4 Specimen RequirementsEven though a pair of speci-mens have the same color values at three angles, if there aredifferences in gloss,
22、 orange peel, texture, or flake orientation,they may not be a visual match.NOTE 2Information presented in this test method is based upon datataken on metallic materials coatings. Applicability of this test method toother materials should be confirmed by the user.6. Apparatus6.1 InstrumentThis test m
23、ethod requires measurement atmultiple aspecular angles, usually accomplished by the use ofa multiangle spectrometer as specified in this test method tocharacterize metal flake pigmented materials. Measurementwith a single geometry cannot characterize the gonioappear-ance of these materials.6.2 Stand
24、ardizationA standardization plaque with as-signed spectral reflectance factor or tristimulus values traceableto a national standardizing laboratory for each specified as-pecular angle is required to standardize the instrument. Theinstrument manufacturer typically assigns the values to thisplaque.7.
25、Geometric Conditions7.1 Conventional Color MeasurementIn general purposecolorimetry, the common geometry involves illuminating at45 and sensing at 0. This geometry is designated 45:0 (45/0).Reverse geometry has the illumination at 0 and the sensing at45. That is, the illuminator and sensing geometri
26、es areinterchanged. This reciprocal geometry is designated 0:45(0/45). Either geometry is used.7.1.1 A single bi-directional geometry is specified by illu-mination and sensing angles with respect to the normal of theplane of the specimen. Angles are measured relative to thenormal. Angles on the same
27、 side of the normal as theillumination beam are written as positive angles; those on theother side are shown as negative, as shown in Fig. 1.7.2 Multiangle Uniplanar MeasurementThe color of me-tallic materials specimens varies with the angle of view. Thusmeasurements must be taken at more than one a
28、specular angleto characterize the change of color with angle. The measure-ment geometry for multiangle measurements is specified byaspecular angles. The aspecular angle is the viewing anglemeasured from the specular direction, in the illuminator planeunless otherwise specified. The angle is consider
29、ed positivewhen measured from the specular direction towards the illu-minator axis. Thus, if the specimen is illuminated at 45 to thenormal the specular reflection will be at -45 (See Fig. 1).Sensing at 65 from the normal, and on the same side of normalas the illumination, is sensing 110 away from t
30、he speculardirection; that is an aspecular angle of 110. Thus, theaspecular angle is the sum of the anormal illumination andsensing angles. It has been established that for metallicmaterials or colors, a specific aspecular angle gives the samemeasurement regardless of angle of illumination.7.3 Annul
31、ar and Circumferential GeometryAnnular illu-mination provides incident light to a specimen at all azimuthalNOTE 1Anormal illumination angle = 45 and anormal sensingangle = 65; therefore, aspecular angle = 45 + 65 = 110.FIG. 1 Example of Illuminating and Sensing GeometryE2194 142angles. This type of
32、illumination minimizes the contributionfrom directional effects such as the venetian blind effect andsurface irregularities. Circumferential illumination is an ap-proximation to annular illumination, incident light being pro-vided from a discrete number of representative azimuthalangles. A large num
33、ber or an odd number of illuminationsources more closely approximates annular illumination. An-nular or circumferential illumination minimizes directionaleffects. Therefore, measurements with annular or circumferen-tial illumination may or may not correlate with how thatspecimen appears under direct
34、ional illumination. For example,this system averaging may cause the measured color values oftwo specimens to be the same or similar, even though thesesame two specimens would not match visually due to the factthat one specimen exhibits the venetian blind effect.7.4 Recommended GeometryThe instrument
35、 shall con-form to the following geometric requirements for measurementof reflectance factor unless otherwise agreed upon between thebuyer and the seller. The preferred aspecular angles formeasurement are 15, 45, and 110.NOTE 3Given a geometric configuration, the reverse geometry isconsidered equiva
36、lent, if all other components of the instrument design areequivalent; for example, in the example shown in Fig. 1, the same resultwould be obtained with the illumination angle at 65 and the sensing angleat 45. The aspecular angle would still be 110.NOTE 4Measurement angles below are stated in terms
37、of aspecularangles. It has been established that for metallic materials colors, a specificaspecular angle gives the same measurement regardless of angle ofillumination. For pearlescent materials, it is known that color is also afunction of angle of illumination. The importance of this phenomenon inm
38、easurement of pearlescent and interference materials for color differencefor quality control or color correction purposes has not been established.NOTE 5Uniplanar instruments can measure the venetian blind effect.Circumferential and annular illumination will not quantify this gonioap-parent effect.N
39、OTE 6There are instruments commercially available with uniplanar,multiangle geometries that give results that characterize gonioapparentmaterials. These instruments will detect the venetian blind effect and otheranomalies. Table 1 delineates the preferred angles. Note that circumfer-ential geometry
40、is limited to 10 when being observed.This observation usually occurs at approximately 45 cm (17.7 in.) fromthe eye. This specimen size is well suited for instrumental measurementand visual assessment.8.5.2 The surface of the specimen to be measured should beessentially planar.8.6 Specimen Optical Re
41、quirements:8.6.1 UniformityReference specimens and test specimensshould be uniform in color and appearance when viewed in alighting booth. They must be similar in appearance to makemeaningful observations. There should be no appearance ofmottling or banding in the specimens.8.6.2 GlossSpecimens shou
42、ld be uniform and similar ingloss when viewed in a lighting booth.8.6.3 Surface TextureThe standard and batch being com-pared should have substantially similar surface textures. Or-ange peel is a common example of surface texture.8.6.4 Specimen Flake DistributionExamine the specimensto ensure that t
43、hey have similar flake size and distribution.Dissimilar flake distributions will cause results to vary signifi-cantly.8.6.5 OrientationConsistent orientation of the specimenfor presentation to the measuring instrument must be controlledfor repeatable measurements. This is necessary to minimizeerrors
44、 due to indiscriminate matching of the directionality ofthe specimen to that of the instrument.9. Instrument Standardization9.1 Standardization is essential to ensure that spectrometricor tristimulus measurements with minimum bias are reported.For the measurement of reflectance factor, two standardi
45、zationsare required, namely,9.1.1 Optical Zero (0) Level StandardizationTo verify theoptical zero, the instrument manufacturer normally supplies ahighly polished black glass or a black trap that has an assignedreflectance factor value.9.1.2 Full Scale StandardizationTo standardize the instru-ment re
46、lative to the perfect reflecting diffuser, the instrumentmanufacturer should provide a standardization plaque withmultiangle calibration traceable to a standardizing laboratory.9.1.3 Photometric Scale ValidationTo ascertain properstandardization, measure a reference plaque immediately afterthe stand
47、ardization sequence and validate that the measuredvalues agree with the assigned values within 0.05 reflectanceunit.9.1.4 DiscussionTypically a neutral gray of 50 % reflec-tance is used for this purpose.10. Instrumental Performance Verification10.1 The use of validation standards to verify spectrome
48、tricperformance of an instrument is recommended. These stan-dards are readily available from multiple sources. The instru-ment user must assume responsibility for obtaining thesestandards and their appropriate use. See NIST LC-1017 forfurther discussion.10.2 It is recommended that a user measure a d
49、urablegonioapparent specimen over time, recording and comparingvalues to ascertain proper instrument performance.11. Measurement Procedure11.1 Select Measurement VariablesSelect and validate theinstrumental configuration before measurement.11.1.1 Select the desired illuminating and sensing geom-etries. See Section 6 for definition of angles when measuringgonioapparent materials.11.1.2 Select the desired observer.11.1.3 Select the desired illuminant.11.1.4 Select the desired colorimetric space, for
