BS EN ISO 2813:2014 pdf free.Paints and varnishes – Determination of gloss value at 20 degrees, 60 degrees and 85 degrees.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in Iso 4618 and the following apply.
3.1 gloss optical property of a surface, characterized by its ability to reflect light specularly
Note ito entry: Examples of degrees of gloss are high gloss, gloss, silk gloss, semigloss, satin, matt, and dead matt.
[SOURCE: ISO 4618:20 14, 2.132]
3.2 geometry identification of a method of gloss measurement using a specified angle with assigned apertures
3.3 gloss value atio multiplied by 100 of the luminous flux reflected from a specimen to that reflected by a glass surface with a refractive index of 1,567 at a wavelength of 587,6 nm in specular direction for a specified reflection angle and specified aperture angles of light source and receptor.
4 Principle
With a reflectometric apparatus, gloss values are determined on coated surfaces, correlating with the visual gloss perception. In this context (glossmeter), 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 stop apertures;
— spectral adaptation;
— reference refractive index.
5 Basic principles of the gloss measurement
Gloss is a visual perception caused by looking at surfaces. The specular reflection of objects is even more 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 solid 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.
Figure 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 200, 600 and 85°.
EXAMPLE Visual classification 9 corresponds to 35 GtJ under 20°, 70 Gti under 60° and 95 GU under 85°.BS EN ISO 2813 pdf free download.