ZOL 1150

A specular reflection or gloss is what you get from a polished surface or mirror. It is clear, and you can see "through" the mirror. A diffuse reflection is what you get from a white wall. The light is bounced off it, but...

A specular reflection or gloss is what you get from a polished surface or mirror. It is clear, and you can see "through" the mirror. A diffuse reflection is what you get from a white wall. The light is bounced off it, but in random directions, so you cannot see the light source in the reflection. Many surfaces will be a mix of specular and diffuse - e.g. a smooth desktop will give both kinds of reflection. A polished surface gives more specular reflection and less diffuse reflection.

Measurement angle refers to the angle between the incident light on a surface and the line perpendicular to the surface at the point of incidence. In specular reflection the incident and reflected angle are...

Measurement angle refers to the angle between the incident light on a surface and the line perpendicular to the surface at the point of incidence. In specular reflection the incident and reflected angle are identical.

Typically, three measurement angles (20°, 60°, and 85°) are used to cover the majority of industrial coatings applications (Figure 1). The angle is selected based on the anticipated gloss range. Some measurement instruments offer the option to measure multiple angles at the same time.

There are no distinct differences in gloss units for the human eye to point out between the two samples.

The detectable differences depend on the gloss level of the sample e.g. 3.0 GU difference measured on a very matte...

There are no distinct differences in gloss units for the human eye to point out between the two samples.

The detectable differences depend on the gloss level of the sample e.g. 3.0 GU difference measured on a very matte surface (perhaps 5GU), would be seen by the human eye but on a higher gloss coating (perhaps 60 GU) the difference would be very difficult to notice.

For a dedicated product the tolerances have to be evaluated experimentally (by end users tests of your coatings or internal "experts").

Another good option is the use of a 20/60/85 degrees instrument, which show more equality to the gloss differences due to the three measurement angles. Experience shows that a gloss difference of 5 GU, when measured with the correct geometry is just visible to a trained observer.

Gloss is the opti­cal proper­ty of a sur­face to reflect light into the specu­lar direction, an important appear­ance factor. The visual impres­sion of gloss is depen­dent on the individual per­ception, there­fore...

Gloss is the opti­cal proper­ty of a sur­face to reflect light into the specu­lar direction, an important appear­ance factor. The visual impres­sion of gloss is depen­dent on the individual per­ception, there­fore the gloss values are deter­mined using gloss­meter. A Glossmeter directs a light at a specific angle to the test surface and simultaneously measures the amount of (specular) reflection.