ASTM_D_2805_-_11.pdf

Designation:D280511Standard Test Method forHiding Power of Paints by Reflectometry1This standard is issued under the fixed designation D2805;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.This standard has been approved for use by agencies of the U.S.Department of Defense.INTRODUCTIONUsing equations derived from Kubelka-Munk turbid media theory(1-4)2(see Annex A1),thereflectance of a coating can be predicted for any film thickness from measurements made at only one.On this basis several rapid and accurate test methods(5,6)have been developed for determininghiding power.In the past such test methods have been considered difficult due to complexities,apparent and actual,in the treatment of data.The present test method has been simplified in thisrespect,primarily by adapting it fully for computer calculations.Although the use of broad-band reflectometry makes this test method theoretically valid only fornonchromatic(white or gray)colors,good agreement has been obtained with chromatic paints as well.This is undoubtedly because the experimental measurements are made fairly close to the hiding powerend point so that the Kubelka-Munk extrapolation and thus any associated error is relatively small.This test method is therefore recommended without restriction as to color.1.Scope1.1 This test method covers the determination,withoutreference to a material paint standard,of the hiding power ofair dry coatings with Y tristimulus values greater than 15%.With appropriate modification,it can also be used to testbaking finishes.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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:3D344 Test Method for Relative Hiding Power of Paints bythe Visual Evaluation of BrushoutsD1475 Test Method For Density of Liquid Coatings,Inks,and Related ProductsD3924 Specification for Environment for Conditioning andTesting Paint,Varnish,Lacquer,and Related MaterialsE284 Terminology of AppearanceE1247 Practice for Detecting Fluorescence in Object-ColorSpecimens by SpectrophotometryE1331 Test Method for Reflectance Factor and Color bySpectrophotometry Using Hemispherical GeometryE1347 Test Method for Color and Color-Difference Mea-surement by Tristimulus ColorimetryE1349 Test Method for Reflectance Factor and Color bySpectrophotometry Using Bidirectional(45:0 or 0:45)Geometry3.Terminology3.1 DefinitionsFor definitions used in this test method,seeTerminology E284.3.2 Definitions of Terms Specific to This Standard:3.2.1 contrast ratio,nthe ratio of the reflectance of a filmon a black substrate to that of an identical film on a whitesubstrate.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.26 on Optical Properties.Current edition approved June 1,2011.Published June 2011.Originallyapproved in 1969.Last previous edition approved in 2003 as D2805 96a(2003).DOI:10.1520/D2805-11.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For 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 3.2.1.1 CW,nthe contrast ratio with a white substrate ofreflectance W.Thus:CW5 R0/RW3.2.1.2 C,nthe contrast ratio with a white substrate forwhich W=0.80.Thus:C 5 R0/R0.803.2.2 reflectance,nthe daylight luminous diffuse reflec-tance factor(specular reflection excluded).Also referred to inthis test method as the Y-tristimulus value.This value may beexpressed as a percent or a decimal fraction,the latter beingpreferred and usually required for mathematical calculations.3.2.2.1 reflectivity,R,nthe reflectance of film thickenough to have the same reflectance over both a black and awhite substrate.3.2.2.2 R0,nthe reflectance of a film on a black surfacewith a reflectance of 1%or less,which is effectively zero forthe purpose of this test.3.2.2.3 W,nthe reflectance of a white substrate.3.2.2.4 RW,nthe reflectance of a film applied on a whitesubstrate of reflectance W.3.2.2.5 R0.80,nthe reflectance of a film applied on asubstrate having a reflectance of 80%,which is the standardwhite-substrate reflectance