Why is a part attractive or repulsive? The first contact between a human and a thing is the first sight that is impressed by the shape, colour and gloss.
Impression inferred by gloss or mat aspect is partly objective and partly subjective depending on the reflected light, the individual, the purpose of the item, its shape and colour, the targeted application. For example, in a same car it is preferred to have a glossy body part and a mat interior trim.
Gloss can be physically and objectively measured by an optical method but from a marketing point of view it is necessary to test the part with a representative panel of consumers.
* An incident beam of light is reflected by a perfectly plane surface with nearly the same intensity and in a homogeneous direction. The angle of reflection is equal to the angle of incidence. The eye receives the optimal intensity of light and the surface is glossy.
* If there is an unevenness of the surface, the part of the beam that irradiates the unevenness is reflected in other directions and the eye receives only a part of the beam and, even more, of heterogeneous directions.