Designation:D661−93(Reapproved2011)StandardTestMethodforEvaluatingDegreeofCrackingofExteriorPaints1ThisstandardisissuedunderthefixeddesignationD661;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope1.1Thistestmethodcoverstheevaluationofthedegreeofcrackingofexteriorpaintsbycomparisonwithphotographicstandards.2.ReferencedDocuments2.1ASTMStandards:2D660TestMethodforEvaluatingDegreeofCheckingofExteriorPaints2.2OtherStandards:PictorialStandardsofCoatingDefectsHandbook33.Terminology3.1DefinitionsofTermsSpecifictoThisStandard:3.1.1cracking,n—thatphenomenonmanifestedinpaintfilmsbyabreakextendingthroughtothesurfacepainted.3.1.1.1Discussion—Wherethisisdifficulttodetermine,thebreakshouldbecalledacrackonlyiftheunderlyingsurfaceisvisible.Theuseofamagnificationof10diametersisrecom-mendedincaseswhereitisdifficulttodifferentiatebetweencrackingandchecking(seeTestMethodD660).4.SignificanceandUse4.1Crackingfailureofpaintfilmscanoccurinuse.Thistestmethodprovidesameansofevaluatingthedegreeofthefailurebycomparingthepictorialstandards.5.TypesofCracking5.1Threetypesofcrackingarerecognized:5.1.1IrregularPatternType—Crackinginwhichthebreaksinthefilmareinnodefinitepattern.5.1.2LineType—Crackinginwhichthebreaksinthefilmaregenerallyarrangedinparallellines,usuallyeitherhorizon-tallyorvertically,overthesurfaceofthefilm.Thesebreaksoftenfollowthelineofbrushmarks.5.1.3SigmoidType—Crackinginwhichthebreaksinthefilmformapatternconsistingofcurvesmeetingandintersect-ing,usuallyonarelativelylargescale.6.UseofPhotographicReferenceStandards6.1ThephotographicreferencestandardsthatarepartofthistestmethodandareprovidedinthePictorialStandardsofCoatingDefectsHandbookarerepresentativeofthedegreeofcrackingofexteriorpaintfilms.Fi...
