ASTM E2194-14(2017) Standard Test Method for Multiangle Color Measurement of Metal Flake Pigmented Materials.pdf

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1、Designation: E2194 14 (Reapproved 2017)Standard 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

2、, the year of last 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

3、“gonioapparent.” Colorimetric 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 Observ

4、er and the spectrum 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

5、 to make precise instrumental 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. Th

6、e measurement ofmaterials 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 metho

7、d are for gonio-appearance 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 d

8、oes not purport to 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.1.5 This international standard wa

9、s developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenc

10、ed Documents2.1 ASTM Standards:2E284 Terminology 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 ofC

11、olor Measurement by Use of Multiple MeasurementsE1708 Practice for Electronic Interchange of Color andAppearance DataE2539 Test Method for Multiangle Color Measurement ofInterference Pigments2.2 CIE Document:3Publication No. 15 Colorimetry2.3 NIST (NBS) Publication:4LC-1017 Standards for Checking th

12、e Calibration of Spectro-photometers1This 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 June 1, 2017. Published July 2017. Originally approvedin 2003. Last prev

13、ious edition approved in 2014 as E2194 14. DOI: 10.1520/E2194-14R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM w

14、ebsite.3Available from CIE (International Commission on Illumination) atwww.cie.co.at or .4Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,

15、 West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the Worl

16、d Trade Organization Technical Barriers to Trade (TBT) Committee.12.4 ISO Publication:5ISO International Vocabulary of Basic and General Terms inMetrology (VIM)3. Terminology3.1 Terms and definitions in Terminology E284 are appli-cable to this test method. See Section “Specialized Terminol-ogy on Go

17、nioapparent Phenomena.”3.2 Definitions:3.2.1 Usually the term metallic refers to a metal material.However, this standard employs the alternative definition givenin Terminology E284 as:3.2.2 metallic, adjpertaining to the appearance of a gonio-apparent material containing metal flakes.3.3 Definitions

18、 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 This test method describes the procedures for thespectrometric and colorimetric measurement of metal flakepigmented materials. The results a

19、re reported in terms of CIEtristimulus values and other color coordinate systems. Stan-dardization of the instrument used to measure these materials isdefined. Guidelines are given for the selection of specimensand a measurement protocol given. Characterization of thesematerials requires measurement

20、 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 Instrumental Measurement AnglesThis test method isdesigned to provide color data at specific measurement anglesthat can be utilized for quality cont

21、rol, color matching, andformulating in the characterization of metal flake pigmentedmaterials.5.2 MaterialsThis test method provides meaningful colorinformation for metal flake pigmented materials. This testmethod has been tested and verified on paint and coatings, andthe same principles should appl

22、y to plastics containing metallicflake. For materials containing pearlescent materials refer toTest Method E2539.5.3 UtilizationThis test method is appropriate for mea-surement and characterization of metal flake pigmented mate-rials. These data may be used for quality control, incominginspection, o

23、r 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, orange peel, texture, or flake orientation,they may not be a visual match.NOTE 2Information presented in this test method is based upon

24、datataken on metallic materials coatings. Applicability of this test method toother materials should be confirmed by the user.6. Apparatus6.1 InstrumentThis test method requires measurement atmultiple aspecular angles, usually accomplished by the use ofa multiangle spectrometer as specified in this

25、test method tocharacterize metal flake pigmented materials. Measurementwith a single geometry cannot characterize the gonioappear-ance of these materials.6.2 StandardizationA standardization plaque with as-signed spectral reflectance factor or tristimulus values traceableto a national standardizing

26、laboratory for each specified as-pecular angle is required to standardize the instrument. Theinstrument manufacturer typically assigns the values to thisplaque.7. Geometric Conditions7.1 Conventional Color MeasurementIn general purposecolorimetry, the common geometry involves illuminating at45 and s

27、ensing 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 geometries areinterchanged. This reciprocal geometry is designated 0:45(0/45). Either geometry is used.7.1.1 A single bi-directional geometry is

28、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 side of the normal as theillumination beam are written as positive angles; those on theother side are shown as negative, as shown in Fig

29、. 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 aspecular angleto characterize the change of color with angle. The measure-ment geometry for multiangle measurements is specified byaspecu

30、lar angles. The aspecular angle is the viewing anglemeasured from the specular direction, in the illuminator planeunless otherwise specified. The angle is considered positivewhen measured from the specular direction towards the illu-minator axis. Thus, if the specimen is illuminated at 45 to thenorm

31、al 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 the specular5ISO/IDE/OIML/BIPM, International Vocabulary of Basic and General Terms inMetrology, International Organization for Standardiz

32、ation, Geneva Switzerland,1984.NOTE 1Anormal illumination angle = 45 and anormal sensingangle = 65; therefore, aspecular angle = 45 + 65 = 110.FIG. 1 Example of Illuminating and Sensing GeometryE2194 14 (2017)2direction; that is an aspecular angle of 110. Thus, theaspecular angle is the sum of the a

33、normal 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 Annular and Circumferential GeometryAnnular illu-mination provides incident light to a specimen at all azi

34、muthalangles. This type of 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 a

35、zimuthalangles. A large number 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 thatsp

36、ecimen appears under directional 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 Recomme

37、nded GeometryThe instrument 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 g

38、eometry isconsidered equivalent, 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

39、 below are stated in terms 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 import

40、ance of this phenomenon inmeasurement 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 t

41、his gonioap-parent effect.NOTE 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

42、 circumfer-ential geometry 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 pla

43、nar.8.6 Specimen Optical Requirements: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 specimen

44、s.8.6.2 GlossSpecimens should 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 th

45、e specimensto ensure that they 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

46、necessary to minimizeerrors 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 reflec

47、tance factor, two standardizationsare 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 sta

48、ndardize the instru-ment relative 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

49、 immediately afterthe standardization 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 spectrometricperformance of an instrument is recommended. These stan-dards are readily available from multiple sources. The instru-ment user must assume responsibility for obtaining thesestand