4.1 This test method is useful for accurate measurement of from a wide variety of glass samples, whose ranges from 1.48–1.55.

4.2 It should be recognized that measurement of surface fragments, especially from float glass samples, can result in refractive index values which are different than the refractive index values of fragments from the interior of (for example, bulk) the same broken glass source (5).

4.3 The precision of this test method shall be established in each laboratory that employs it as part of the validation protocol (see Section 9).

4.4 It should be recognized that this technique measures the refractive index of the glass at the match point temperature, which will be higher than ambient temperature, and thus, may give different values from those obtained by other methods, which measure the refractive index at room temperature.

1.1 This test method covers a procedure for measuring and comparing the refractive index (η) at a fixed wavelength (λ) and temperature (T) ( ) of glass from known sources to recovered fragments from a questioned source.

1.2 This test method does not include the measurement of optical dispersion or the measurement of refractive index ( ) at any other wavelength other than the Sodium D line ( ). This method employs a narrow band pass filter at 589 nm, but other filters could be employed using the described method, allowing the to be determined at other wavelengths, and therefore, also allowing for the dispersion value to be calculated.

1.3 Alternative methods for the determination of are listed in Refs (1-5).2

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard cannot replace knowledge, skills, or abilities acquired through education, training, and experience and is to be used in conjunction with professional judgment by individuals with such discipline-specific knowledge, skills, and abilities.

1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 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.