BS EN ISO 2813-2014 pdf download.Paints and varnishes – Determination of gloss value at 20 degrees, 60 degrees and 85 degrees.
Note 4 to entry: A glass surface with a reflective indes of 1,S67 at a wavelength of S46.l nm (which is the central wavelength olthe spectral luminous efficiency function) may be used.
Note S to entry: The gloss value is influenced by the surface characteristics. e.g. roughness, texture, structure, of the sample.
4 Principle
With a reflectometric apparatus, gloss values are determined on coated surfaces, correlating with the visual gloss perception. In this context (glossineter), the ratio of the gloss of the coating and the gloss of a polished plane glass plate with specified reference refractive index is obtained.
The method of gloss measurement is specified by the following parameters:
— measuring angles.
— field slop apertures;
— spectral adaptation;
— reference refractive index.
5 BasIc principles of the gloss measurement
Gloss isa visual perception caused by looking at surfaces. The specular reflection of oblects is even nioce distinct when light is reflected more directionally from the surface. The incident light is reflected on high-gloss surfaces only in the main specular direction. On matt surfaces the light is not only reflected in the main specular direction but also diffusely scattered in all soled angles. The more uniformly the light Is scattered into the space the smaller is the intensity of the directed component and the matter the surface appears.
The principle of gloss measurement is based on the measurement of the directionally reflected light, In this context its intensity is measured in a defined angular field around the reflection angle. The intensity of the reflected light depends on the surface material and the incident angle. Accordingly, on coated surfaces with increasing incident angle more light is reflected, The remaining light is refracted at the interface air/coating, and within the coating diffusion and/or absorption of the light occurs.
The gloss values are not related to the intensity of the incident light but to the reflection properties of a black, polished glass standard with specified refractive index.
For different viewing angles the gloss perception can vary widely. For example matt surfaces can appear glossy under grazing incidence of light and low viewing angle, because under these reflection conditions a lot of light is reflected directionally and also the intensity of diffusion is low,
hgurc_1 illustrates the relation between the gloss perception of visually equally classified coating specimens (from matt to glossy) and the assigned gloss values for the measuring angles of 20’, 60” and
85”.
EXAMPLE Visual classllication 9 corresponds to 35 GU under 20’. 70 GU under 60” and 95 GU undee 8$’.BS EN ISO 2813 pdf download.