Glossiness is a physical quantity that evaluates the ability of material surface to reflect light under a set of geometric conditions. Therefore, it expresses the reflective property with direction selection. According to the characteristics of gloss, gloss can be divided into several categories. We usually say that gloss refers to "mirror gloss", so gloss meter
, sometimes also called mirror gloss meter. Glossiness is completely different from the concept of "smoothness" or "roughness" in mechanical processing industry, which is the evaluation of micro-roughness of material surface. When we use gloss meter, we often don't know how to choose the glossiness measurement angle. All light sources reflect from the surface, and the magnitude of the reflected light is called the surface gloss value. Glossiness value is measured in glossiness unit (GU), which corresponds to the standard value approximating 100GU. Glossiness can be divided into three general ranges: low gloss, half gloss and high gloss. All angles are calculated from the vertical angle. Each range is measured at its own angle. To know which angle is the most suitable for measurement, it is better to start at 60 degrees. If the result is between 10 and 70 GU, the coating can be called semi-gloss and measured at this angle. If the result is less than 10GU, the product is called low gloss and should be measured at 85 degrees. If the result is higher than 70GU, the product is high gloss and measured at 20 degrees.