Understanding Standards And Process Of Gloss Measurement

Reviewed by Anurag Mishra (Sr. Technical Consultant)

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The gloss of material can be measured by an instrument known as gloss meter which calculates the gloss in the unit (GU) i.e. gloss unit to a specified surface. The GU scale of a gloss meter is based on an extremely polished surface that has black glass standard with a positive refractive index having a specular reflectance of 100 GU at the specific angle. The scaling of material needs to be done for most non-metallic coatings such as plastics and paints. For the highly refractive surfaces such as plated products, mirrors, and raw metals, a higher value of 2000 GU can be reached easily when the gloss is measured from an angle of 20 degrees. Many manufacturers from different industries choose to adopt the 20/60/85 Degree geometries as it is clearly specified in ASTM D523 standard. The three primary standards of gloss measurement are D 523 specular gloss measurement, D 4039 for haze measurement of highly glossy surfaces and the D4449 measurement of the difference between surfaces that have a similar appearance.

If you are trying to learn more about the gloss measurement, there are many differences that a human eye can detect. While measuring the gloss from 60 degrees, the detectable gloss differences are totally dependent on the gloss level of the sample. For an instance, a 3.0 GU gloss difference can be easily detected on one surface but not another. While measuring a gloss difference of 3.0 GU on a matte surface measuring around 5 GU would be visible to the naked eye. However, measuring the same difference on a high gloss coating measuring around 60 GU would be tough to notice.

The true way to determine gloss tolerances of different products would be experimentally done by preparing printed samples at various gloss levels that you can easily show directly to the customers or internal experts. Another way to measure the gloss of material is using 20/60/85 degrees Tri- dimensional gloss measurement instrument. By making use of 85 degrees viewing angle of gloss you would have more sensitivity to differences in gloss below 10 GU @60 Degree and by using a 20-degree viewing angle of gloss would have a high resolution on high gloss coating (above 70 GU @ 60-degree angle). The advantages of using 20-degree, 60-degree and 85-degree instrument, there is no more equality to evaluate the gloss differences.

How Do You Measure Gloss?

Several methods help to measure a surface’s glossy appearance that needs to be achieved throughout the production processes. The major thing is to measure the specular gloss. It is the ratio of light which is reflected at a particular angle on both sides of a surface. There are also certain products which require that the ratio of specularly reflected lights diffusely reflect the surface which is also worked by the angle of light shined. Observing the gloss at grazing angles of incidence and viewing, then qualifying the results is known as measuring contrast gloss. Furthermore, the absence of bloom, or the absence of haze adjacent to the specularly reflected light, is measured in order to adjust the desired surface appearance effect. To read more on Gloss Meter, visit: www.testronixinstruments.com

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