Gloss is an essential component of how our eyes interpret the shape and form of things. The finish of a product, its texture, as well as the way a sample is lighted and seen, may all have an effect on the impression of gloss. Surfaces that have a high reflectivity are viewed as being glossy, shiny, or lustrous, while surfaces that have a lower reflectance are regarded as having a semi-gloss or matte finish.
There are a few different methods that may be used to evaluate gloss. Using a piece of optical equipment known as a gloss meter is one of the methods. A gloss meter gives quantified gloss measurements, given in gloss units (GU).
How to Measure Gloss
Gloss is assessed by shining a light beam of consistent intensity onto a test surface at a predetermined angle, and then observing the quantity of light that is reflected off of the surface when seen from the same angle as the light beam. A glossmeter is used to determine the level of this material’s specular reflectivity. Various surfaces need varying reflective angles.
High Gloss: Clear reflections of pictures are produced by surfaces that have a dazzling or highly polished quality. This particular reflection is brought about when the light that strikes the surface reflects off of it in a specular direction.
Semi & Matt Gloss: Surfaces with a semi-glossy or matte finish reflect pictures with less crisp detail and less intense brightness. Light not only reflects in a specular direction on semi-glossy or matte surfaces, but it also scatters, causing the reflected image to look more diffused than specular.
Figure: Gloss meter
Choosing the Correct Angle for Gloss Measurement
Gloss is quantified in terms of the quantity of light that is reflected off of a surface in comparison to a polished glass reference standard. Gloss units are the standard for measuring gloss (GU). The angle of incidence, as well as the characteristics of the surface, play important roles in determining the quantity of light that is reflected off of it.
Matte, semi-gloss, and high-gloss are the three different levels of gloss. Beginning with a gloss meter that has been adjusted to an angle of incidence of sixty degrees is the best way to select the measuring angle that will provide the most accurate results.
If the result is between 10 and 70 GU, the coating is considered to have a “semi-gloss” finish, and the glossmeter should be set at the 60° angle when measuring it. If the result is less than 10GU, the product is considered to have a “low gloss,” and the glossmeter should be adjusted so that it reads at an angle of 85°. If the result is greater than 70GU, however, the product is considered to have a “high gloss,” and the glossmeter should be adjusted so that it reads at an angle of 20°.
85% Reflectance
While the Gloss Unit (GU) scale is linear, the measurement ranges for each angle of incidence are distinct: 0–2000GU for 20°, 0–1000GU for 60°, and 0–160GU for 85°.
The percentage of reflectance is calculated by comparing the amount of light energy that is transmitted and received by a gloss meter. This value is then expressed as a percentage of the full measurement range of the angle of incidence, and the value is displayed as a percentage relative to the angle of incidence that was selected.
A gloss meter calibrated for 20 degrees has a measuring range of 0 to 2000 GU; hence, a value of 1000 GU at 20 degrees would be stated as 50, while a value of 500 GU would be expressed as 25. A value of 500GU at 60°, yet it would be represented as 50 since the measurement range for the 60° is 0–1000GU. The glossier the surface is, the closer the value will be to being exactly 100%.
There are several substances that may have measurement values that are more than 100GU. Some examples of these substances are clear plastics and varnishes. Metals with a high degree of reflectivity may have gloss levels as high as 2000GU. In addition, the value of the measurement may be raised for transparent materials owing to many reflections in the bulk of the material, which might cause this. In each of these circumstances, it is usual practice to describe the findings of the measurements in terms of the percentage of reflectance.
Haze (HU)
Haze produces a decrease in the contrast that is reflected and causes ‘halos’ to emerge around the light sources that are reflected, which substantially reduces the visual quality.
In line with ASTM D4039, the term “haze” is defined inside the LISUN Gloss Meter as the numerical difference that exists between the specular reflectance measured at 60 degrees and 20 degrees.
This is measured in Haze Units (HU).
Glossmeters (also Gloss Meters)
LISUN provides a complete selection of single, dual, and triple angle glossmeters as well as DOI meters. These instruments evaluate the gloss, percent reflectance, and haze of a variety of different surfaces.
The LISUN AGM-500Pro Glossmeter may be purchased as either a basic entry-level gloss meter at 60 degrees or as a cutting-edge Single, Dual, or Triple Angle Glossmeter with the ability to detect haze and percentage reflectance respectively.
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