ASTM D4449 Standard test method for visually evaluating gloss differences between surfaces of similar appearance includes the use of special types of lighting to visually evaluate gloss differences on coated surfaces. It identifies six aspects or types of gloss that you might look for when using a lamp to assess gloss differences between surfaces.
Meaning and use

5.1 Glossiness 3 correlates with a surface’s ability to reflect more light in certain directions. The directions associated with specular (or specular) reflection usually have high reflectivity. The gloss can be better seen and analyzed when the surface under study is illuminated by a light source that provides a strong contrasting pattern of light and dark. This light source is described in the test method.

5.2 The simple gloss concept is that it corresponds to the specular reflection of the surface. However, the distribution and intensity of this surface reflected light (for real materials) is highly variable and influenced by a variety of factors: surface smoothness and profile, refractive index, absorptivity, incidence Angle, and (usually to a small extent) wavelength. From the wide variety of surface reflection patterns encountered in commercial materials, it has been possible to identify seven surface reflection criteria or “gloss types” that are frequently used by technicians to compare and evaluate the gloss of their products with each other. Six of the seven criteria, or “gloss types,” are identified in the definition section. Seventh, gloss or contrast gloss, rarely involved in the coatings industry.

ASTM D4449-2015 Standard Test Method for Visual Evaluation of Gloss Differences between Surfaces of Similar Appearance

Step 1: Scope

1.1 The test method includes the use of a special type of lighting to visually assess the difference in gloss of the coated surface. It identifies six aspects or types of gloss that you might look for when using a lamp to assess gloss differences between surfaces. It describes the conditions for using lamps to better identify small differences in each of the six glosses. Four levels of visual gloss difference are distinguished.

1.2 While this technique is useful for both weathered and unweathered samples, it has not yet been applied to metallic materials.

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

1.4 This standard is not intended to address all safety concerns, if any, associated with its use. It is the responsibility of persons using this standard to consult and establish appropriate safety and health practices and to determine the applicability of the rules restrictions prior to use.