From High gloss, to semi-gloss, to matte surfaces, the gloss level of any given material or object has a direct impact on the human visual perception of that material or object. Companies strive to achieve specific levels of gloss of their products for both functional reasons, and to improve the appearance of their products and help them stand out from the competition. It is, therefore, important that companies know how to measure gloss as proper guidelines will help companies consistently produce high-quality products.

Below, learn more about what gloss is, why it is important, and how it is measured. You may also want to know more about the kinds of industries that rely on gloss and how companies can meet gloss standards, which we will expand on.

What Is Gloss?

Gloss is the reflection of incident light from the surface of an object. The Reflection Law states that the incoming angle (the angle of incidence) is equal to the outgoing angle (the angle of reflection) denoted as Ɵi = Ɵr. For a wave that is incident on the boundary between two media, a reflection occurs.  

When surface imperfections at the boundary are small (compared to the wavelength of the incident light), the reflection is specular, and an image of the source is observed. An example would be the coatings used on automobiles, which are typically high-gloss and reflect a mirror image of their surroundings.

Diffuse Reflection is overwhelmingly more common and happens when the surface of the object is not smooth but rough or textured. Here, the light scatters in random directions. Diffuse reflection does not preserve an image of the source. A typical example is a low gloss or matte finish paint used on interior walls of houses and other buildings. 

Of course, it is also possible to have a mixed reflection (specular + diffuse), over which light is scattered in distribution about the specular.  Mixed reflections include semi-gloss samples, where an image of the source is observed but not well defined.

From a functional standpoint, controlling the gloss of manufactured products is critical for manufacturers to ensure batch-to-batch consistency, and to achieve the desired result for their products. Consumers do not want high-gloss mirror-like finishes on their interior walls, and they typically do not desire low-gloss low-sheen coatings on their automobiles (though this is a trend in some markets). 

And, since gloss levels directly impact consumer psychology and can make people give an object a second look, companies like to outfit their products with packaging and surfaces featuring specific gloss finishes to improve their visual appearance, potentially increasing sales.

Why Measure Gloss?

The first step in controlling gloss levels is being able to measure them. The gloss appearance of an object can be affected by several factors, such as the texture of the substrate, the smoothness of the material itself, and even film thickness of coatings applied to an object or surface. With all the factors that can affect gloss’s appearance, companies regularly measure gloss to ensure all their products have a consistent look. 

Not measuring gloss on a product can lead to several problems. For example, coatings manufacturers typically use gloss additives to achieve specific levels of gloss. Too much or too little can affect not only the coatings appearance when dried but also the coatings flow and leveling, curing times, adhesion, and long-term durability. Gloss levels also change the visual perception of the color of the surface or object. Coating a smooth surface and a textured surface with the same coating will result in the smooth-coated surface appearing much darker than the textured coated surface.

How to Measure Gloss?

Gloss is measured using a gloss meter, which functions by assigning a gloss unit (GU) to a measured surface. The gloss meter projects an incident light onto the surface. At an equal but opposite angle, the gloss meter measures the amount of reflected light. Typically, in industry, three angles are used to measure gloss, depending on the gloss level desired. High-gloss surfaces with a GU of 70 or above should be measured using a 20° gloss meter. Semi-gloss surfaces with a GU range of 10-70GU should be measured using a 60° gloss meter. Low-gloss surfaces having a GU below 10 should be measured using an 85°angle on a gloss meter.

What Is a Gloss Unit?

A GU is a measurement used for gloss. A standard GU measurement scale of gloss meters is determined by a reference black glass standard. This black glass is highly polished and features a defined refractive index that, when placed at a specific angle, has a 100GU specular reflectance. GUs are determined through this standard, as 100GU establishes an upper point calibration on a matte surface that can then be used to find how many GUs a product’s surface has. 

These 100GU gloss meters are appropriate for most non-metallic coatings and materials, such as plastics and paints. For more reflective materials, like mirrors or plated metal parts, companies use gloss meters with a higher upper calibration, regularly going up to 2,000GU. 

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What Industries Need to Measure Gloss?

Several industries rely on products featuring gloss finishes to capture the attention of fast-moving consumers. Even if a product is the very best, people won’t likely purchase it if they don’t find it attractive. For instance, those in the pharmaceutical, furniture and consumer electronics industries all need to measure gloss to ensure their products have a consistent visual appeal.

Find out more about some of the primary industries that rely on gloss and what they use it for:

  • Consumer electronics: Consumer electronics manufacturers design their products so they feature a glossy surface, making their products more attractive and shiny as a result. Since gloss provides a metallic appearance, it can give electronics a more cutting-edge look.
  • Pharmaceuticals: Pharmaceutical manufacturers manufacture their tablets and packaging with gloss finishes to enhance their products’ appearance. Sometimes, pharmaceutical companies use gloss as a film-coating for dietary supplements.
  • Food: Food manufacturers rely on glossy finishes to improve the appearance of food packaging. As gloss can be very eye-catching to consumers, packaging that employs it can stand out from the competition while sitting on a store’s shelves.
  • Furniture: Furniture manufacturers sometimes utilize gloss paints and materials with glossy finishes to give their products a more shiny and lustrous appearance. For example, manufacturers apply high gloss paint on furniture, such as chairs, to give them an attractive appearance.
  • Printing: Printing manufacturers often use coated papers with glossy finishes for the covers of magazines and books, giving them an aesthetic that’s attractive to certain consumer bases. These companies also utilize glossy brochures, flyers and printed photographs to make the coloring more bright and vivid.
  • Vehicles: Vehicle manufacturers craft some vehicles with gloss body panels to give them a more metallic, attention-getting appearance. Gloss paint is also sold individually to customers who want to style their ride.

How to Stay Within Gloss Standards

Gloss standard compliance is one of the most critical components of applying gloss to a product. While you can occasionally detect differences in low GU products with the eye, the more GUs a product has, the harder it is to tell differences between gloss samples. As such, it’s crucial for companies to know how to stay within gloss level standards and measure their gloss appropriately.

There are several international standards available that define the requirements and use of various kinds of gloss meters. These standards give users information about using gloss meters with particular kinds of materials like plastics, metals, papers, ceramics and paint. For example, ISO 2813 is an international standard that helps you understand how to check paint gloss. Companies will regularly utilize these standards and gloss meter specifications during the quality control stage to ensure consistency in producing their gloss products.

A major part of knowing how to check gloss properly and meet gloss standards is selecting the right angle for gloss measurement. There are three primary measurement angles used for most industrial coating applications, with the measurement angle referring to the angle between the incident and reflected light. The three primary measurement angles are 20, 60 and 85 degrees.

Using the right gloss measurement is crucial to meeting gloss standards, as the right angle helps you determine the gloss quality more accurately. You’ll begin with a 60-degree measurement to determine whether you’re working with low, medium or high gloss. Lower gloss surfaces will have a measurement lower than 10GUs and will need to have the angle changed to 85 degrees. If you have 10-70GUs, you can maintain the same 60-degree angle. For times when your measurement exceeds 70GUs, you’ll need to adjust the setup to a 20-degree angle.

Besides the three main kinds of measurements, you’ll need 45-degree angles for films, anodized aluminum, textiles and ceramics. If you measure paper, the angle should be adjusted to 75 degrees. By following these angle standards, you can ensure products have the most accurate measurements across the board.

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Measure Gloss With HunterLab Instruments

At HunterLab, we carry several types of instruments that can measure gloss and colors. Our various measurement solutions and technologies can provide you with plenty of information about the appearance and color of your products. For example, our Agera Spectrophotometer features impressive quality control software and a 60-degree gloss meter for accurate measurements.

If you’re ready to measure gloss more accurately, turn to HunterLab for high-quality measurement instruments and technologies. To find the perfect solution for your needs, contact us today.