Gloss measurement

How does a gloss meter work?

A gloss meter determines the gloss level of a flat surface, such as paint, plastic, paper or polished stone. To do this, it directs light onto the surface at a specified angle and measures how much light is reflected back in the direction of the specular reflection. A matt surface scatters the light more, whilst a glossy surface reflects it more strongly in a specific direction.

The measurement result is expressed in GU (Gloss Units). 0 GU represents an ideally matt surface. A defined standard made of polished black glass serves as the reference for 100 GU. GU are not expressed as a percentage; values above 100 GU are also possible.

An angle of 60° is often used initially for the measurement. If the value lies between 10 and 70 GU, this angle is suitable for assessing surfaces with medium gloss. For very matt surfaces below 10 GU, a measurement angle of 85° provides better distinction. For high-gloss surfaces above 70 GU, measurements are often taken at 20°. Measurement values should therefore always be stated together with the measurement angle used.

Gloss meters help to compare surfaces objectively. This is useful, for example, in quality control when several components are required to have the same gloss appearance or when a coating must be applied uniformly.