Designation: C148 − 17Standard Test Methods forPolariscopic Examination of Glass Containers 1This standard is issued under the f i xed 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 A—Comparison with Reference StandardsUsing a Polariscope6 – 9Test Method B—Determination with Polarimeter 10 – 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.N OTE 1—The 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 def i nes a real temper number, T R , in terms of the apparenttemper number, T A , and the bottom thickness, t:T R 5 T A ~ 0.160 ⁄ t ! , where t is in inches, orT R 5 T A ~ 4.06 ⁄ 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 Verif i cation and Calibration of Polarim-eters3. Terminology3.1 Def i nitions— For def i nitions of terms used in these testmethods see Terminology C162.4. Signif i cance 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 verif i ed 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 A—COMPARISON WIThrefERENCE STANDARDS USING A POLARISCOPE6. Apparatus6.1 Polariscope, conforming to the following requirements:1 These 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/C0148-17.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s 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 Copyright by ASTM Int'l (all rights reserved); Sat Sep 30 13:02:22 EDT 2017Downloaded/printed byUniversity of Edinburgh (University of Edinburgh) pursuant to License Agreement. No further reproductions authorized.
