Designation:C148−17StandardTestMethodsforPolariscopicExaminationofGlassContainers1ThisstandardisissuedunderthefixeddesignationC148;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thesetestmethodsdescribethedeterminationofrela-tiveopticalretardationassociatedwiththestateofannealofglasscontainers.Twoalternativetestmethodsarecoveredasfollows:SectionsTestMethodA—ComparisonwithReferenceStandardsUsingaPolariscope6–9TestMethodB—DeterminationwithPolarimeter10–121.2TestMethodAisusefulindeterminingretardationslessthan150nm,whileTestMethodBisusefulindeterminingretardationslessthan565nm.NOTE1—Theapparenttempernumberasdeterminedbythesetestmethodsdependsprimarilyon(1)themagnitudeanddistributionoftheresidualstressintheglass,(2)thethicknessoftheglass(opticalpathlengthatthepointofgrading),and(3)thecompositionoftheglass.Forallusualsoda-limesilicabottleglasscompositions,theeffectofthecompositionisnegligible.Inanexaminationofthebottomofacontainer,thethicknessofglassmaybetakenintoaccountbyuseofthefollowingformula,whichdefinesarealtempernumber,TR,intermsoftheapparenttempernumber,TA,andthebottomthickness,t:TR5TA~0.160⁄t!,wheretisininches,orTR5TA~4.06⁄t!,wheretisinmillimetres.Thisthicknessshouldbemeasuredatthelocationofthemaximumap-parentretardation.Interpretationofeitherrealorapparenttempernum-berrequirespracticalexperiencewiththeparticularwarebeingevalu-ated.1.3ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesareforinformationonly.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspri...
