We know that when an object is illuminated by light, a reflection phenomenon occurs, and the reflected light in this phenomenon is expressed by an index that is gloss, and the size of the reflection intensity is gloss. Because different objects have different degrees of surface unevenness, that is, roughness, the intensity of reflected light is different. The smoother the surface, the greater the intensity of the reflected light and the greater the gloss; the more uneven the surface, the smaller the intensity of the reflected light and the smaller the gloss. Gloss is usually used to measure gloss. Some glossmeters have three positions of 20 °, 60 ° and 85 ° according to the angle of incidence. According to the size of the gloss, the paint can be divided into several types such as light, matte, and matte.

Coatings are classified according to gloss as follows (take 60 ° reflective gloss as an example): gloss of matte paint <10%, gloss of matte paint 15% to 60%, gloss paint Gloss is> 60%.