The Gloss Meter – The Coating Instruments Guide

The Gloss Meter guide: from matte to gloss

The gloss of a surface tells us much more than just how smooth it is. Surface characteristics reveal problems such as a curing failure, issues with surface preparation, or inconsistencies with film build. Furthermore, the gloss level of a surface is almost as important as color when it comes to consumer choices – inconsistency across products will be attributed to poor quality or defects, neither of which will lead them to a purchase. In fact, a glossy product adds to the impression of value, and quality control measures like the gloss meter are vital for monitoring and maintaining the high performance of a coating or surface. There are quantitative gloss requirements in many industries and applications, ensuring a standard is set.

In this article we look at the gloss meter, how it is used, and where to buy these measurement instruments in the United States.

Detecting reflection – what the Gloss Meter measures

The term “gloss” refers to the impression of the shininess of a surface – the more light a surface reflects, the higher gloss it is. Highly polished, smooth surfaces directly reflect incident light, so the reflected image appears very clear; think of a mirror or the reflection on a spoon. Both are high gloss surfaces but the angles of the spoon change the angle of reflection, which distorts the image without it losing definition. Matte or semi-gloss surfaces diffuse light, scattering it in all directions from the uneven surface. The surface therefore seems dull and flat, with reflections blurred and unclear.

A gloss meter measures the intensity of reflected light bounced back from a surface. In order for this measurement to make sense across industries and machines, there are several standards used. The light source is standardized, and the reflective surface which it is calibrated against is a highly polished, plane black glass  This standard is given the value of 100 gloss units (GU) across angles. The intensity is dependent on both the material and the angle of illumination. Non-metals reflect more light with higher illumination angles, while metals are reflective at any angle and can produce measurements of up to 2000GU.

How the Gloss Meter works – what the measurements mean

Taking a meaningful measurement means understanding the processes involved in producing the final number. Taking a measurement from the wrong angle could lead to erroneous and unhelpful results. Firstly you need to identify whether the surface you are testing is gloss, semi gloss, or matte, and what type of material it is. The angle of incident light is chosen based on the expected gloss level of the surface – high gloss uses the 20°, semi gloss uses 60°, and matte uses 85°.

• The 20° range: The measurement range for the 20° geometry is from 0 to 2000GU. It is the widest range because it is used to measure high gloss surfaces. This angle is sensitive to effects like haze.
• The 60° range: All gloss levels can be measured with the 60° geometry, and it is used as a reference angle. Its values go from 0 to 1000GU, and the reason to opt for the higher or lower angles is because they provide more accurate results for the high gloss and matte surfaces – a reading of 70GU at 60° means a more accurate reading might be taken from the 20°, while a result of 10GU or below would lead to using the 85° measurements. 60° is particularly good for semi gloss.
• The 85° range: This is the range for the most accurate readings of matte and low gloss surfaces. It gives a larger measurement area which evens out the differences provided by surface texture.

There are also units for 45° and 75° which are used in the ceramics/films and paper/vinyl industries, respectively. The gloss unit value returned by the measurement is commonly translated into a percentage. For example, a 1000GU rating from 20° is 50% of its 0-2000GU range, but would be 100% of the 60° range. The higher the percentage, the shinier the surface.

Gloss meter calibration standards – for the instrument and industry

Each gloss meter is calibrated by the manufacturer against a set of master calibration tiles. In order to maintain the accuracy and performance of the gloss meter there are standard tiles with assigned gloss units for each angle of measurement. These tile are known as the calibration standard or calibration tile, and they keep the instrument performing to standard.

In the US, ASTM D523 is the main specular gloss standard. For paint and varnishes the international standard is ISO 2813, for determination of specular gloss of non-metallic paint films at 20°, 60° and 85°. The color of a coating can also affect its gloss reading.

Below is a table of the standards and the gloss measurements to which they relate. The 20°, 60°, and 85° measurements relate to coatings, plastics, and related materials.

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Where to find Gloss Meter suppliers and companies in the US

There are many gloss meter suppliers and companies operating in the US. These companies provide the range of gloss meter instrumentation for all applications. Gloss meters are available as single angle units (for 20°, 45°, 60°, 75°, or 85°), dual angle instruments (combined 20° and 60° geometry units for medium to high gloss surfaces), and triple angle instruments with three geometries (20°, 60°, and 85° for matte surfaces or 20°, 60°, 75° for paper). Below is a list of the instruments available on the American market from a range of gloss meter suppliers including Elcometer, PCE Instruments, and Rhopoint Instruments.

Some companies have full ranges of gloss meters while others focus on all in one units. The gloss meter is just one in a whole suite of coating appearance measurement instruments, including those for measuring haze and the Reflected Image Quality (a surface structure measure).

If you need a gloss meter for your project or business, we are here to help. Get in touch through the “Request a Quote” form by clicking the button beneath this article and tell us about the requirements you have for the instrument. We will collaborate with our coating partners to determine the right gloss meter for the job.