Gloss is an optical phenomenon caused when evaluating the appearance of a surface. The evaluation of gloss describes the ability of a surface to reflect directed light. A gloss meter measures specular reflection. The intensity of reflected light depends on the material and angle of lighting. In order to obtain clear distinctions across the entire measurement range from high gloss to matte, 3 geometries (ranges) are defined.
Gloss angle
Using the 60º gloss angle as the reference angle, the working range for the 60º gloss is 10-70 GU (gloss units). This is considered the semi-gloss range. Below 10 GU or above 70 GU, 60º gloss measurements do not correlate with visual gloss. Therefore, for measurements above 70 GU, a 20º gloss meter can be used for high gloss surfaces. For under 10 GU, use an 85º gloss meter. This is called low gloss or matte.
There are two additional angles: 45º and 75º. These angles are industry specific angles for measuring paper and plastic films.
