% Reflectance

Whilst the Gloss Unit (GU) scale is linear, each angle of incidence has a different measurement range; 0 – 2000GU (20°), 0 – 1000GU (60°), 0 – 160GU (85°).

% Reflectance compares the amount of light energy transmitted and received by a glossmeter and expresses the value as a percentage of the angle of incident's full measurement range and the value is displayed as a percentage relative to the selected angle of incidence.

For example:

As the measurement range for a 20° glossmeter is 0 -2000GU; a value of 1000GU at 20° would be expressed as 50%20, and a value of 500GU would be expressed as 25%20

A value of 500GU at 60°, but would be expressed as 50%60 as the measurement range for the 60° is 0 – 1000GU

The shinier a surface is, the closer the value will be to 100%.

Materials with a high refractive index, such as clear plastics or varnishes, can have measurement values above 100GU. Highly reflective metals can have gloss values up to 2000GU. Furthermore, the measurement value can be increased for transparent materials due to multiple reflections in the bulk of the material. In all these cases, it is common to express the measurement results in % Reflectance.

% Reflectance