The principle of glossmeter

The Glossmeter is an instrument used to measure the surface glossiness of materials such as ceramics, paint, ink, plastic, marble, aluminum, and hardware. The Glossmeters with single angle or with three angles.

Firstly, glossiness is a physical quantity that evaluates the ability of a material’s surface to reflect light under a set of geometric specified conditions, with directional reflective properties. The gloss we usually refer to is’ mirror gloss’, so glossometers are sometimes also called ‘mirror glossometers’. Gloss is completely different from the concept of “smoothness” or “roughness” in the mechanical processing industry, which is a continuation of small surface irregularities of materials.

The measurement principle of the glossmeter is shown in the figure “Measurement Principle”. The measuring head of the instrument is composed of a transmitter and a receiver, and the transmitter is composed of an incandescent light source and a set of lenses, which generate a certain required incident beam. The receiver which is used to receive a conical beam of light reflected back from the surface of the sample.

Mirror glossiness is a relative measurement of specular gloss. The reference standard is black glass with a refractive index of np=1.567. Assuming that its plane is in an ideal polished state, it reflects natural light beams in a mirror direction, and the glossiness value at this point is defined as 100.0 gloss units.

The glossiness board is divided into three types based on the glossiness value: high, medium, and low. The high gloss plate is made of black optical glass or other materials. Medium gloss plate and low gloss plate are made of glazed ceramic or black optical glass frosting.

The glossmeter uses the principle of light reflection to measure the glossiness of the sample. That is, irradiate the sample under the conditions of a specified incidence angle and a specified beam of light, and obtain the reflected light in the direction of the mirror reflection angle.

Many optical properties of materials can be qualitatively explained using wave theory. According to wave theory, the ratio of the energy W of incident light passing through unit area per unit time to the energy flow W of reflected light can be derived.

W1 sin2（i-r） tg2(i-r)

——=[——————— + ——————]

W02 sin2（I+r） tg2(i-r)

In the formula, i is the angle between the incident light and the normal (incident angle),

R is the refractive angle.
Gloss is the property of directional selective reflection on the surface of an object, which presents different bright spots or forms images of objects overlapping on the surface. Glossiness is the ability of an object’s surface to reflect light when illuminated, usually expressed by multiplying the reflectance of the sample in the mirror (positive reflection) direction relative to the standard surface by 100, i.e. G=100R/R.

R in the formula – the reflectivity of the sample surface,/R—— The reflectivity of the standard plate. With polished black glass as the reference standard plate, the refractive index of sodium D-rays is 1.568, and the specular gloss calibration for each geometrical optics condition is 105 gloss units.

Gloss meters AGM-580 are mainly used in the surface gloss measurement for paint, plastic, metal, ceramics, building materials. It conforms to the DIN67530, ISO2813, ASTM D523, JIS Z8741, BS 3900 Part D5, JJG696 standards and so on.

AGM-580_Gloss Meter with 3 Angles (20, 60 and 85º)

AGM-500PRO Gloss Meter with Single Angle.

AGM-500PRO_Gloss Meter with Single Angle

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