Designation:C336−71(Reapproved2015)StandardTestMethodforAnnealingPointandStrainPointofGlassbyFiberElongation1ThisstandardisissuedunderthefixeddesignationC336;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thistestmethodcoversthedeterminationoftheanneal-ingpointandthestrainpointofaglassbymeasuringtheviscouselongationrateofafiberoftheglassunderprescribedcondition.1.2Theannealingandstrainpointsshallbeobtainedbyfollowingthespecifiedprocedureaftercalibrationoftheapparatususingfibersofstandardglasseshavingknownannealingandstrainpoints,suchasthosespecifiedandcertifiedbytheNationalInstituteofStandardsandTechnology(NIST)2(seeAppendixX1).1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:3C338TestMethodforSofteningPointofGlassC598TestMethodforAnnealingPointandStrainPointofGlassbyBeamBending3.Definitions3.1annealingpoint—thattemperatureatwhichinternalstressesinaglassaresubstantiallyrelievedinamatterofminutes.4,5,6Duringatestinaccordancewiththerequirementsofthismethod,theviscouselongationrateismeasuredbyasuitableextensometerwhilethespecimenfiberiscoolingatarateof461°C/min.Theelongationrateattheannealingpointisapproximately0.14mm/minforafiberof0.65mmdiam-eter.63.2annealingrange—therangeofglasstemperatureinwhichstressesinglassarticlescanberelievedatacommer-ciallydesirablerate.Forpurposesofcomparingglasses,theannealingrangeisassumedtocorrespondwiththetempera-turesbetweentheannealingpoint(AP)andthestrainpoint(StP).3.3strainpoint—thattemperatureatwhichtheinternals...
