ASTM_C_148_-_17.pdf

Designation:C14817Standard Test Methods forPolariscopic Examination of Glass Containers1This standard is issued under the fixed designation C148;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.1.Scope1.1 These test methods describe the determination of rela-tive optical retardation associated with the state of anneal ofglass containers.Two alternative test methods are covered asfollows:SectionsTest Method AComparison with Reference StandardsUsing a Polariscope6 9Test Method BDetermination with Polarimeter10 121.2 Test Method A is useful in determining retardations lessthan 150 nm,while Test Method B is useful in determiningretardations less than 565 nm.NOTE1The apparent temper number as determined by these testmethods depends primarily on(1)the magnitude and distribution of theresidual stress in the glass,(2)the thickness of the glass(optical pathlength at the point of grading),and(3)the composition of the glass.Forall usual soda-lime silica bottle glass compositions,the effect of thecomposition is negligible.In an examination of the bottom of a container,the thickness of glass may be taken into account by use of the followingformula,which defines a real temper number,TR,in terms of the apparenttemper number,TA,and the bottom thickness,t:TR5 TA0.160 t!,where t is in inches,orTR5 TA4.06 t!,where t is in millimetres.This thickness should be measured at the location of the maximum ap-parent retardation.Interpretation of either real or apparent temper num-ber requires practical experience with the particular ware being evalu-ated.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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.1.5 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:2C162 Terminology of Glass and Glass ProductsC224 Practice for Sampling Glass ContainersC1426 Practices for Verification and Calibration of Polarim-eters3.Terminology3.1 Definitions For definitions of terms used in these testmethods see Terminology C162.4.Significance and Use4.1 These two test methods are provided for evaluating thequality of annealing.These test methods can be used in thequality control of glass containers or other products made ofsimilar glass compositions,where the degree of annealing mustbe verified to ensure quality products.These test methodsapply to glass containers manufactured from commercialsoda-lime-silica glass compositions.5.Sampling5.1 Methods of sampling a minimum lot from a group ofcontainers of a given type are given in Practice C224 for thevarious situations to which that method may apply.TEST METHOD ACOMPARISON WITHREFERENCE STANDARDS USING A POLARISCOPE6.Apparatus6.1 Polariscope,conforming to the following requirements:1These test methods are under the jurisdiction of ASTM Committee C14 onGlass and Glass Products and are the direct responsibility of Subcommittee C14.07on Glass Containers.Current edition approved May 1,2017.Published May 2017.Originallyapproved in 1939.Last previous edition approved in 2014 as C148 14.DOI:10.1520/C0148-17.2For 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.1 6.1.1 The degree of polarization of the field at all pointsshall not be less than 99%.6.1.2 The field shall be a minimum of 51 mm(2 in.)indiameter greater than the diameter of the container to bemeasured.The distance between the polarizing and analyzingelements shall be sufficient to allow the inside bottle bottomsurface to be viewed through the open container finish.6.1.3 A sensitive tint plate