Meaning and Purpose
5.1 Gloss is related to the ability of a surface to reflect more light in the direction close to the mirror. The measurement made by this test method is correlated with the visual observation of the surface gloss made at a roughly corresponding Angle.

5.1.1 By comparing the specular reflectance of the sample with that of the black glass standard, the gloss grade measured by the test method is compared. Since the specular reflectance also depends on the surface refractive index of the specimen, the measured gloss class will vary with the surface refractive index. However, when obtaining visual gloss grades, it is customary to compare the specular reflectance of two specimens with similar surface refractive indices.

5.2 Other visual aspects of surface appearance, such as the sharpness of reflected images, reflected haze, and texture, are often involved in the evaluation of gloss (1), (6), (7). The test method E430 includes techniques for measuring image gloss and reflected haze. Test method D4039 provides an alternative procedure for measuring reflected haze.

ASTM D523-2018 Standard Test Method for Mirror Gloss

5.3 There is little information on the relationship between the numerical value of specular gloss and the perceived interval. However, in many applications, the glossiness scale of this test method provides an instrumental scaling for coated specimens that is in good agreement with visual scaling (10).

5.4 Nonlinearities may be encountered in the relationship between visual gloss difference grades and instrumental gloss reading differences when comparing specimens that differ substantially in perceived gloss or color or both.

ASTM D523-2018 Standard Test Method for Mirror Gloss

Scope of
1.1 The test method covers the specular gloss measurement of non-metallic specimens with 60°, 20 and 85° (1-7) glossometer geometries. Arabic numerals

1.2 Values expressed in inch-pounds should be considered standard values. The values given in parentheses are mathematical transformations of SI units and are for reference only and are not considered standard.

1.3 This standard is not intended to address all safety issues, 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 to determine the applicability of regulatory restrictions prior to use.

1.4 This international Standard has been developed in accordance with the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the Committee on Technical Barriers to Trade of the World Trade Organization.