ASTM D4449-15 (R2021) pdf free download.Standard Test Method for Visual Evaluation of Gloss Differences Between Surfaces of Similar Appearance.
1.1 This test method covers the visual evaluation of gloss differences of coating surfaces, using special types of lamps for illumination. It identitIes six aspects or types of gloss that one may look fcr when using the lamp to assess gloss differences between surfaces. It describes the conditions for using the lamps to best identify small differences in each of the six types of gloss. Four levels of visual gloss differences are distinguished.
1.2 While this technique is useful for both weathered and unweathered specimens, it has not been applied to metallics.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
3. Terminology
3.1 Definitions—For definitions of terms used in this method. see Terminology E284.
3.2 Definitions of Terms Specific to This Standard.
3.2.1 directionality of surface, n—perceived change of glossy appearance of a surface with rotation of the surface in its own plane (see Fig. 1).
3.2.2 gloss, distinctness-of-image, n—perceived sharpness of images reflected by an object surface (see Fig. 2).
3.2.3 gloss, of a surface, n—perceived directionally selective reflecting properties responsible for the degree to which reflected highlights or images of objects may he seen as superimposed on the surface.
3.2.4 reflection hace, n—cloudy or milky appearance of a surface adjacent to directions of specular reflection (see Fig. 3).
3.2.5 .sheen, n—perceived shininess at a near-grazing angle of incidence for an otherwise matte specimen (difficult to photograph).
3.2.6 specular gloss, n—the relative luminous reflectance factor of a specimen in the specular direction. The luminous reflectance factor is the ratio of the luminous flux reflected from, to that incident on. a specimen for specified solid angles (see Fig. 4).
3.2.7 texture, n—perceived structure, pattern, or topography or combination thereof, of a surface (see Fig. 5).
4. Summary of Test Iethod
4.1 Test specimens are illuminated by special light sources that provide reflected images suitable for rating the gloss of coating surfaces. Two types of lamps may be used to produce reflected images. Lamp A consists of a modified fluorescent desk lamp covered with screen mesh. Lamp B consists of an incandescent bare filament bulb installed in an adjustable angle fixture.
4.2 Light from the selected lamp illuminates the test specimens. The reflected images reveal specular gloss reflection; the sharpness of the images of the screen or lamp filament reveals the detail and quality of the surface reflection. ASTM D4449 pdf download.