4.1 Specular gloss is used primarily as a measure of the shiny appearance of films and surfaces. Precise comparisons of gloss values are meaningful only when they refer to the same measurement procedure and same general type of material. In particular, gloss values for transparent films should not be compared with those for opaque films, and vice versa. Gloss is a complex attribute of a surface which cannot be completely measured by any single number.

4.2 Specular gloss usually varies with surface smoothness and flatness. It is sometimes used for comparative measurements of these surface properties.

1.1 This test method describes procedures for the measurement of gloss of plastic films and solid plastics, both opaque and transparent. It contains four separate gloss angles (Note 1):

1.1.1 60-deg, recommended for intermediate-gloss films,

1.1.2 20-deg, recommended for high-gloss films,

1.1.3 45-deg, recommended for intermediate and low-gloss films,

1.1.4 85-deg, recommended for intermediate and low gloss films, and

1.1.5 75-deg, recommended for plastic siding and soffit.

Note 1: The 85-deg, 75-deg, 60-deg, and 20-deg apparatus and method of measurement duplicate those in Test Method D523 and D3679; those for the 45° procedure are similarly taken from Test Method C346.

1.2 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.

Note 2: There is no known ISO equivalent to this standard.

1.3 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.