The control of visual parameters of a surface, such as brightness and colour, play a fundamental role in final and aesthetic evaluation of a product (called appearance).
The visual perception of the operator can be influenced by brightness, as each surface can be altered by various factors, such as the angle of incidence of light, the position of the observer, the physical characteristics of the surface and observation conditions.
The measurement of gloss occurs through the reflection of light on a surface and is carried out with gloss meters. There are tri-angle gloss meters (20° – 60° – 85°), single angle gloss meters (60°) or gloss meters for small or curved surfaces. The latter have a very small opening that allows measuring on curved surfaces or where the precise measurement of a detail is necessary.
Other visual inspection of a surface is that of colour. Color meters or spectrophotometers are the most suitable for this inspection.
Color meters are measuring instruments capable of evaluating many chromatic values and guaranteeing the operator the variation (delta E) of colour, of a value or of the sum of all chromatic values, which may be present between one sample and another.
Spectrophotometers, on the other hand, in addition to making all the measurements of a color meter, are able to guarantee the operator a complete spectrographic analysis of the color covering the entire wavelength of the visible, checking the spectral curves and the metamerism of the sample analyzed.
To measure the white value of a sample, the whiteness meter is employed, while reflectance meters measure the value of light refraction on a surface.