ASTM D 2457-21 is a standard test method for the measurement of specular gloss of Plastic films and solid plastics. The method describes gloss measurement procedures for opaque and transparent materials, covering measurements of multiple Glossiness angles, including 60, 20, 45, and 75 degrees, among others. Accurate comparisons of Glossiness require the same measurement procedures and material types. In addition, Glossiness is affected by surface smoothness and Smoothness, so it can be used to compare surface properties. The standard emphasizes the need for users to establish appropriate safety, health, and environment practices before use, and to identify applicable regulatory restrictions. The ASTM D 2457-21 is developed in accordance with international standards and provides a consistent technical basis for global trade.