ASTM_D_3964_-_10_2020.pdf

Designation:D396410(Reapproved 2020)Standard Practice forSelection of Coating Specimens for AppearanceMeasurements1This standard is issued under the fixed designation D3964;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 practice provides a guide to selection of specimensfor appearance measurement by reflected light as well as adiscussion of factors to be considered in their preparation formeasurement.Standardized selection and presentation proce-dures will assist in achieving agreement between evaluationscarried out in different laboratories as well as helping toachieve better correlations between visual evaluations andinstrumental measurements.NOTE1This standard is not a practice for preparation of test panels ofcoatings;see Practices D823.1.2 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.3 This international standard was 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.Referenced Documents2.1 ASTM Standards:2D823 Practices for Producing Films of Uniform Thicknessof Paint,Coatings and Related Products on Test PanelsE284 Terminology of Appearance3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice,refer toTerminology E284.4.Significance and Use4.1 Many of the specimens that are regularly submitted tomeasurement depart in some degree from the ideal require-ments.For this reason instrumental readings are affectedimportantly by the manner in which specimens are selected andpresented for measurement.Reproducible measurements arefacilitated by standardization and control of test conditions.5.General Requirements5.1 SelectionIn making appearance measurements it isimportant that the specimens selected be representative of thematerial of interest.Once selected,the specimens must becarefully examined to determine if they are suitable formeasurement,and if not,they must be cleaned or otherwiseprepared.Careful attention to these factors is necessary if themeasurements are to be valid.5.2 Specimen SizeThe minimum size is dictated by thesize of the specimen port of the instrument to be used formeasurement.When an instrument provides a choice of speci-men port sizes,use the largest port that can be completelycovered by the specimen.A large measured area helps tominimize the effect of any small area nonuniformity and istherefore more likely to provide results that agree with theinvoluntary averaging that takes place when specimens areobserved visually.In addition,a large specimen also permitsthe operator to make measurements on several areas of thespecimen when desired,thereby providing further specimenaveraging.5.3 OpacityFor determination of gloss or color,an opaquespecimen shall be selected whenever possible.When thespecimen is translucent or transparent,the following practicesshall be implemented:5.3.1 For Gloss EvaluationThe specimen shall preferablybe sufficiently thick that a secondary reflection from the backor second surface of the specimen cannot enter the receptoroptics of the glossmeter.When thin transparent specimensmust be measured,adopt one of the following procedures:1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.26 on Optical Properties.Current edition approved June 1,2020.Published July 2020.Originally approvedin 1980.Last previous edition approved in 2015 as D3964 10(2015).DOI:10.1520/D3964-10R20.2For 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 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 World Trade Organization Technical Barriers to Trade(TBT)Committee.15.3.1.1 Back the specimen with a light-absorbing materialof the same refractive index as the specimen,and in opticalcontact with it.5.3.1.2 Use an agreed-upon specimen thickness,inclu