ASTM_C_609_-_07_2014.pdf

Designation:C60907(Reapproved 2014)Standard Test Method forMeasurement of Light Reflectance Value and Small ColorDifferences Between Pieces of Ceramic Tile1This standard is issued under the fixed designation C609;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,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.1.Scope1.1 This test method covers the measurement of LightReflectance Value(LRV)and visually small color differencebetween pieces of glazed or unglazed ceramic tile,using anyspectrophotometer that meets the requirements specified in thetest method.LRV and the magnitude and direction of the colordifference are expressed numerically,with sufficient accuracyfor use in product specification.1.2LRV may be measured for either solid-colored tile ortile having a multicolored,speckled,or textured surface.Fortile that are not solid-colored,an average reading should beobtained from multiple measurements taken in a patternrepresentative of the overall sample as described in 9.2 of thistest method.Small color difference between tiles should onlybe measured for solid-color tiles.Small color differencebetween tile that have a multicolored,speckled,or texturedsurface,are not valid.1.3 For solid colored tile,a comparison of the test specimenand reference specimen should be made under incandescent,fluorescent and daylight illuminant conditions.The use ofmultiple illuminants allows the color difference measurementto be made without the risk of wrongly accepting a match whenthe tiles being compared are metamers.(See 3.1.4.)1.4 The values stated in inch-pound units are to be regardedas the standard.The values given in parentheses are forinformation only.1.5 This standard does 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.2.Referenced Documents2.1 ASTM Standards:2C242 Terminology of Ceramic Whitewares and RelatedProductsD2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesE259 Practice for Preparation of Pressed Powder WhiteReflectance Factor Transfer Standards for Hemisphericaland Bi-Directional GeometriesE284 Terminology of Appearance3.Terminology3.1 Definitions:3.1.1 color difference,E*and EHthe vector sum of thethree component differences L*,a*,and b*for E*andLH,aH,bHfor EH.The superscript*indicates colordifference based on the use of CIELAB color space equations,while the subscript H indicates color difference based on theuse of the Hunter equations.EHis expressed in units of judds,while E*is a unit-less value.Either form of the E can besolved for using the equation shown in 10.3.For both theCIELAB and Hunter equations,the values L,a,and b areobtained by calculating the component differences as follows:L 5 Lt2 Lra 5 at2 arb 5 bt2 brwhere:t=test specimen,andr=reference specimen.The quantity E has a positive value and it describes themagnitude but not the direction of color difference between thetest specimen and the reference specimen.The direction of1This test method is under the jurisdiction ofASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.06 on Ceramic Tile.Current edition approved Jan.1,2014.Published February 2014.Originallyapproved in 1967.Last previous edition approved in 2007 as C609 07.DOI:10.1520/C0609-07R14.2For 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 website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 color difference depends upon the algebraic signs of thecomponents L,a,and b.A positive L value means thatthe test specimen is lighter than the reference against which itis being compared,and a negative L value means that the testspecimen is darker.However,the algebraic signs of chroma-ticity components,a and b,do not convey an easilyvisualized difference in color attributes and can best bevisualized by plotting the corresponding points in the chroma-ticity plane.33.1.2 color spacethe colors of opaque specimens such asceramic tile are described in terms of three color scales L,a,and b.Scale L is a measure of lightness,a is a measure ofredness or greenness,and b is a measure of yellowness orblueness.The units for each of the three scales are so chosenthat they represent equally perceptible color differences.Theinterrelation of these color scales is more readily visualized ifthe scales are represented geometrically as the three mutuallyperpen