Many mineral oil-based objects and liquids such as plastics and oils have a more or less pronounced character. Industrial applications also use marker substances that exhibit considerable fluorescence in the visible wavelength range under the influence of UVA.

The colour and intensity of the fluorescence is determined by the respective marker and its concentration in the carrier object. An understanding of this behaviour enables for example, improved recognition of transparent objects such as films and transparent traces of glue.

The fluorescence effect of mineral oils, lubricating greases or even punching and drawing oils can be used to determine layer thickness down to the sub-µm range. As glass is not transparent in the UVC range, different glass surfaces can be distinguished easily. For example, the so-called fire side can be distinguished from the tin side; it is also relatively easy to determine the side to which a hydrophobic nanolayer has been applied.