Gloss is measured by shining a known amount of light at a surface and quantifying
the reflectance. The angle of the light and the method by which the reflectance is
measured are determined by the surface.
Gloss is measured using a Gloss Meter also known as a Glossmeter) which directs a
light at a specific angle to the test surface and simultaneously measures the amount
of reflection. The type of surface to be measured determines the gloss meter angle to
be used and thus the gloss meter model.
The intensity is dependent on the material
and the angle of illumination. In case of nonmetals (coatings, plastics) the amount
of reflected light increases with the increase of the illumination angle. The remaining
illuminated light penetrates the material and is absorbed or diffusely scattered
dependent on the color.
Metals have a much higher reflection and are less angle dependent than non metals.
The measurement results of a glossmeter are related to the amount of reflected light
from a black glass standard with a defined refractive index, and not to the amount
of incident light. The measurement value for this defined standard is equal to
100 gloss units. Materials with a higher refractive index can have a measurement
value above 100 gloss units (GU), e.g. films.