Gloss

Gloss is an opti­cal pro­per­ty of a sur­face, cha­racter­ized by its ability to re­flect light. If a light beam strikes a sur­face - e.g. a lacquer - with a cer­tain angle of inci­dence (ε), most of it will pene­trate the layer of paint, the rest will be re­flec­ted.

Usually, the measuring results for paints and varnishes are indicated between 0 and 100 gloss units. It is important to remember that this number is not a value in percentage. The reflectometer value is not related to the amount of light but to a black polished glass standard of a defined refractive index (1,567). For this standard, the measured value is set to 100 gloss units (GU).

Polished metals, mirrors and certain foils have a much higher refractive index than varnishes and as the black glass standard used for calibration. For this reason, you may find much higher gloss values than 100 for these products, in fact up to 2‘000 GU.