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    ASTM C148 - 17

    Standard Test Methods for Polariscopic Examination of Glass Containers

    Active Standard ASTM C148 | Developed by Subcommittee: C14.07

    Book of Standards Volume: 15.02

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    Significance and Use

    4.1 These two test methods are provided for evaluating the quality of annealing. These test methods can be used in the quality control of glass containers or other products made of similar glass compositions, where the degree of annealing must be verified to ensure quality products. These test methods apply to glass containers manufactured from commercial soda-lime-silica glass compositions.

    1. Scope

    1.1 These test methods describe the determination of relative optical retardation associated with the state of anneal of glass containers. Two alternative test methods are covered as follows:






    Test Method A—Comparison with Reference Standards
         Using a Polariscope

    6 – 9



    Test Method B—Determination with Polarimeter

    10 – 12


    1.2 Test Method A is useful in determining retardations less than 150 nm, while Test Method B is useful in determining retardations less than 565 nm.

    Note 1: The apparent temper number as determined by these test methods depends primarily on (1) the magnitude and distribution of the residual stress in the glass, (2) the thickness of the glass (optical path length at the point of grading), and (3) the composition of the glass. For all usual soda-lime silica bottle glass compositions, the effect of the composition is negligible. In an examination of the bottom of a container, the thickness of glass may be taken into account by use of the following formula, which defines a real temper number, TR, in terms of the apparent temper number, TA, and the bottom thickness, t:

    Equation C0148-17_1

    Equation C0148-17_2

    This thickness should be measured at the location of the maximum apparent retardation. Interpretation of either real or apparent temper number requires practical experience with the particular ware being evaluated.

    1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

    1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

    1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    C162 Terminology of Glass and Glass Products

    C224 Practice for Sampling Glass Containers

    C1426 Practices for Verification and Calibration of Polarimeters

    ICS Code

    ICS Number Code 81.040.30 (Glass products)

    Referencing This Standard
    Link Here
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    DOI: 10.1520/C0148-17

    Citation Format

    ASTM C148-17, Standard Test Methods for Polariscopic Examination of Glass Containers, ASTM International, West Conshohocken, PA, 2017, www.astm.org

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