Glossmeter
Encyclopedia
A glossmeter measures specular reflection
. The light intensity
is registered over a small range of the reflection angle. The intensity is dependent on the material and the angle of illumination. In case of non-metals (coatings, plastics) the amount of reflected light increases with the increase of the illumination angle. The remaining illuminated light penetrates the material and is absorbed or diffusely scattered dependent on the color
. Metals have a much higher reflection and are less angle dependent than non-metals.
A glossmeter gives the amount of reflected light from a sample, compared to that reflected from a black glass calibration standard with a defined refractive index
. The result is independent of the amount of incident light. The gloss value of the reference standard is defined to be 100 gloss units. Materials with a higher refractive index can have a measurement value above 100 gloss units. For transparent materials, the gloss can be increased by multiple reflections in the bulk of the material. Due to the high reflectivity of metals, values as high as 3500 gloss units can be obtained. For these applications it is common to use percent reflection of incident light rather than gloss units.
Glossmeters usage procedures, as well as their defined angles of measurement, are internationally standardized to allow comparison of measurement values. Angle of illumination is the most important criterion. To clearly differentiate between high gloss and low gloss, several different measurement angles are used, with incident angles of 20, 60, and 85 degrees the most common. The 20-degree angle is normally used for high-gloss surfaces, the 60-degree angle for medium-gloss surfaces, and the 85-degree angle for low-gloss surfaces. Other angles of measurement are used for specific applications, such as 75 degrees for plastic film, and 45 degrees for vinyl siding.
used in the ASTM D2457 standard that defines standard test methods for measuring gloss. A glossmeter
is used to measure gloss value, which can be quoted in gloss units.
Glossmeters measure the specular reflection
of light from a surface. In the ASTM D2457 system used for plastics, low gloss is less than 10 units, semi-gloss is between 10 and 70 units, and high gloss is above 70 units. A perfect mirror is defined as 1000 gloss units. Gloss is evaluated by measuring reflected and incident light at various angles to the surface; the standard test methods define different angles for different ranges of gloss. Artifact standards held by national laboratories can be used to calibrate gloss meters. Some standards define the reflection from a polished black glass surface as 100 gloss units. Standard measurement methods will describe the incident and observed angles and the types of light source to be used.
Different technical standards are used for different materials, and international standards also differ from each other.
Different definitions of gloss are used for different materials and different industries. Gloss may be described in terms of the specular reflection (where the angle of reflection is the same as the angle of incidence), or reflection at low grazing angles, or the amount of light scattered back to the source perpendicular to the surface. Gloss may be evaluated by the distinctness of a reflected image, or by an overall relative evaluation of surface texture.
Specular reflection
Specular reflection is the mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected into a single outgoing direction...
. The light intensity
Irradiance
Irradiance is the power of electromagnetic radiation per unit area incident on a surface. Radiant emittance or radiant exitance is the power per unit area radiated by a surface. The SI units for all of these quantities are watts per square meter , while the cgs units are ergs per square centimeter...
is registered over a small range of the reflection angle. The intensity is dependent on the material and the angle of illumination. In case of non-metals (coatings, plastics) the amount of reflected light increases with the increase of the illumination angle. The remaining illuminated light penetrates the material and is absorbed or diffusely scattered dependent on the color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
. Metals have a much higher reflection and are less angle dependent than non-metals.
A glossmeter gives the amount of reflected light from a sample, compared to that reflected from a black glass calibration standard with a defined refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
. The result is independent of the amount of incident light. The gloss value of the reference standard is defined to be 100 gloss units. Materials with a higher refractive index can have a measurement value above 100 gloss units. For transparent materials, the gloss can be increased by multiple reflections in the bulk of the material. Due to the high reflectivity of metals, values as high as 3500 gloss units can be obtained. For these applications it is common to use percent reflection of incident light rather than gloss units.
Glossmeters usage procedures, as well as their defined angles of measurement, are internationally standardized to allow comparison of measurement values. Angle of illumination is the most important criterion. To clearly differentiate between high gloss and low gloss, several different measurement angles are used, with incident angles of 20, 60, and 85 degrees the most common. The 20-degree angle is normally used for high-gloss surfaces, the 60-degree angle for medium-gloss surfaces, and the 85-degree angle for low-gloss surfaces. Other angles of measurement are used for specific applications, such as 75 degrees for plastic film, and 45 degrees for vinyl siding.
Gloss units
A Gloss unit is a unit of measure of surface glossGloss (material appearance)
Gloss is an optical property, which is based on the interaction of light with physical characteristics of a surface. It is actually the ability of a surface to reflect light into the specular direction. The factors that affect gloss are the refractive index of the material, the angle of incident...
used in the ASTM D2457 standard that defines standard test methods for measuring gloss. A glossmeter
Glossmeter
A glossmeter measures specular reflection. The light intensity is registered over a small range of the reflection angle. The intensity is dependent on the material and the angle of illumination. In case of non-metals the amount of reflected light increases with the increase of the illumination angle...
is used to measure gloss value, which can be quoted in gloss units.
Glossmeters measure the specular reflection
Reflection
Reflection or reflection may refer to:-Science:* Mirror image, a reflection in a mirror or in water* Reflection nebula, a nebula that is extended and has no boundaries* Reflection , a common wave phenomenon...
of light from a surface. In the ASTM D2457 system used for plastics, low gloss is less than 10 units, semi-gloss is between 10 and 70 units, and high gloss is above 70 units. A perfect mirror is defined as 1000 gloss units. Gloss is evaluated by measuring reflected and incident light at various angles to the surface; the standard test methods define different angles for different ranges of gloss. Artifact standards held by national laboratories can be used to calibrate gloss meters. Some standards define the reflection from a polished black glass surface as 100 gloss units. Standard measurement methods will describe the incident and observed angles and the types of light source to be used.
Different technical standards are used for different materials, and international standards also differ from each other.
Different definitions of gloss are used for different materials and different industries. Gloss may be described in terms of the specular reflection (where the angle of reflection is the same as the angle of incidence), or reflection at low grazing angles, or the amount of light scattered back to the source perpendicular to the surface. Gloss may be evaluated by the distinctness of a reflected image, or by an overall relative evaluation of surface texture.