Gloss is the shiny appearance on a surface. Gloss adds to the visual perception of an object and is influenced by many different factors. The automotive industry is where gloss is measured quite often, as the paint finish of a vehicle is important for its overall appearance.
It is important to keep the level of gloss consistent across all products, as it’s important for the end user to get the correct product they are paying for.
Gloss is measured using a specific piece of equipment called a glossmeter. Specific angles of measurement are used based on the level of gloss of the surface.
The correct angle for gloss measurement is based on what gloss range is expected. Three angles are used which cover most coating applications. These angles are 20°, 60°, and 85° and are used as shown below.
At 60° if the measurement exceeds 70 GU then the glossmeter needs to be changed to 20° and then retested. If a measurement is taken which is less than 10 GU, then the machine needs to be set at 85°. A surface which is medium gloss is measured using the 60° setting on the glossmeter.
There are two other angles which are used to measure other materials. These are 45° and 75°, the 45° angle is used for ceramics, films, textiles and anodised aluminium. The larger 75° angle is used for paper.
Glossmeters must be calibrated to ensure they provide the correct readings every time they are used. A tile is used for calibration at every angle and is kept in optimum conditions to ensure it doesn’t become contaminated. The calibration tiles themselves need to be checked at regular intervals and corrected if necessary as they can change gloss units over time.
Haze and orange peel can both affect the gloss levels of a surface. Glossmeters are unable to detect these issues with a surface, so other machines need to be used.