The principle of gloss measurement on even surfaces is simple: the reflection of an incident light in a defined angle will be measured.

However, gloss measurements often have to be carried out on curved surfaces. If the surface to be measured is not even, the following aspects should be considered: 

 Only measurements which were carried out on exactly identically shaped surfaces can be compared. Therefore an appropriate holder for the sample and for the measuring equipment should be provided in order to always locate the same measuring position on the samples.

The resulting values are not absolute gloss values, they cannot be compared directly with measurements carried out on even surfaces with the same structure. For every element or even for every measuring position on the element, appropriate minimum and maximum gloss values have to be defined separately. An intelligent data analysis software, as e.g. the Zehntner`s GlossTools allows to store upper and lower threshold values for a multitude of samples in order to ease and to accelerate the quality control.

It is advisable to use a glossmeter with small measuring and supporting surfaces for optimal positioning. Zehntner`s ZGM 1120 is the top-selling glossmeter for measurements on curved surfaces or for hard to reach areas.


Zehntner GmbH Testing Instruments offers a range of solutions for measuring gloss on difficult surfaces and offers consultancy on choosing the right measuring method.