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2024-12-16
Glossiness is a physical quantity used to indicate the ability of an object's surface to reflect light. It can generally be measured using a gloss meter and a specific value can be given. However, in the application of glossiness, two symbols, GS and GU, are often involved, and most users do not understand their meaninGS. This article introduces the units of glossiness and the relationship between GS and GU.
Gloss is produced by the interaction of light and the physical properties of an object. What we usually call gloss refers to specular gloss, so gloss is also called specular gloss, which is used as a standard parameter to measure the glossiness of an object's surface. When external light hits the surface of an object in a specific direction, due to the fact that the actual surface has certain ups and downs in topography, after the light hits the surface, it will be affected by the difference in the topography of the incident position and reflected in different directions. Part of the reflected light will be reflected in the specular direction relative to its normal to the incident direction (the reflection angle is equal to the incident angle). These specular reflected light rays are reflected into the observer's eyes and thus form the glossiness of the object's surface.
Gloss (GS) is a physical quantity that evaluates the ability of a material surface to reflect light under specific geometric measurement conditions. It measures the degree of surface brightness and is defined as the ratio of the specular reflectivity of the measured surface to the specular reflectivity of a standard black glass plate. The calculation formula is: GS=R/R0x100%.
Where: R is the specular reflectivity of the measured surface, that is, the ratio of the luminous flux of the reflected light in the receiving angle in the specular reflection direction to the luminous flux of the incident light. R0 is the specular reflectivity of the standard plate (the refractive index of the ideal polished black glass is n=1.567. When the standard plate reaches the ideal plane standard, the natural light beam is specularly reflected by the plane, and the gloss value at this time is defined as 100.0GU).
Glossiness is often used as an appearance evaluation index and is applied to the surfaces of many products with high aesthetic requirements. Glossiness and surface evaluation index roughness are two completely different concepts. The former is a characterization of the degree of specular reflection of light, while the latter is a characterization of surface unevenness.
Gloss is the reflective property of an object's surface to light. In layman's terms, the stronger the ability of an object's surface to reflect light, the higher the gloss. The ability of an object's surface to reflect light depends on the smoothness of the surface, that is, the ability of the light to reflect in a certain direction varies with the smoothness of the surface. The smoother the surface, the greater the reflective ability and the higher the gloss; conversely, the rougher the surface, the worse the reflective ability and the lower the gloss.
The measurement of glossiness is called glossiness. Glossiness is obtained by measuring the ability of the surface of an object to reflect light. The instrument for measuring glossiness is a gloss meter. The measuring principle of the gloss meter is that the measuring head of the instrument consists of a transmitter and a receiver. The transmitter consists of an incandescent light source and a group of lenses, which produces an incident light beam with certain requirements. The receiver consists of a lens and a photosensitive element, which is used to receive the light beam reflected from the sample surface. It is usually expressed by multiplying the reflectivity of the sample relative to the standard surface in the mirror reflection direction by 100, that is, glossiness GS=100R/R0, where R is the reflectivity of the sample surface, and R0 is the reflectivity of the standard sample. The standard sample is referenced by perfectly polished black glass, and its refractive index is 1.568.
According to the international standard ISO-2813, gloss measurement is carried out under three standard geometric conditions, namely, the incident angles of 20°, 60° and 85°. For most surfaces with a certain glossiness, the glossiness can be measured under the condition of 60° incident angle, and the typical glossiness measurement value is within the range of 10-70 units. For highly reflective shiny surfaces, if the measurement is carried out under the condition of 60° incident angle, the measured value will be far more than 70 units, which is too close to each other. In this case, the 20° incident angle can be used for measurement. In another extreme case, that is, the surface of the material with very low gloss, if the measurement is carried out under the condition of 60° incident angle, the measured value will be far less than 10 units, which is also too close to each other. In this case, the 85° incident angle can be used for measurement. However, it should be noted that when comparing the glossiness of a group of samples, it is necessary to measure at the same angle, otherwise the measured values are not comparable. Most measuring instruments measure gloss mainly on flat areas, and measure curved surfaces with curvature. If the curvature is too small, it will affect the accuracy of the measurement.
Gloss can be said to be a physical quantity that evaluates the ability of a material surface to reflect light under a set of geometrically specified conditions, and can be expressed as % or numbers. People usually say GU, but that is not the unit of gloss. GU is actually the abbreviation of the English word "glossunit", which is translated into "gloss unit" in Chinese. In fact, the surface gloss that people often talk about is actually a ratio, so there is no clear unit, and it is usually expressed in GU. According to the JIs standard, the gloss unit can be written as a percentage or a number. GU is a dimensionless unit, which is used to indicate the ability of an object surface to reflect light. The higher the gloss value, the stronger the light reflection ability of the object surface, and vice versa. Its relationship with GS is as follows:
1. Gloss unit symbol: GS or GU.
2. The unit of the gloss meter is called gloss unit. The international convention symbol is GS or GU, which is the abbreviation of Gloss unit. According to the JIS standard, the gloss unit can be written as a percentage or a number.
3. Relationship between gloss symbols GS and GU: gloss is abbreviated as GS in English, and gloss unit is abbreviated as GU in English. So when we say gloss, it is GS, and the gloss unit is GU.
