Detect surface property problems with a gloss meter
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 colour 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 will look at the gloss meter as a surface property measurement tool, how it is used, and where to buy these instruments in the UK.
Gloss meter detects reflection and measures smoothness
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. Matt 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, several standards are 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.
The meaning of the measurements by gloss meter
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 matt, 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 matt uses 85°.
- The 85° range – This is the range for the most accurate readings of matt and low gloss surfaces. It gives a larger measurement area which evens out the differences provided by surface texture.
- 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
- 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.
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.
The calibration standards for the gloss meter instrument and the industry
Each gloss meter is calibrated by the manufacturer according to 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 tiles are known as the calibration standard or calibration tiles, and they keep the instrument performing to standard. The colour 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 other materials alike.
|Relevant Standard||20° – High Gloss||60° – Semi Gloss||85° – Low Gloss||45° – Semi Gloss Ceramics||75° – Low Gloss Paper|
|DIN EN ISO 2813||✔||✔||✔|
|EN ISO 7668||✔||✔||✔||✔|
|JI Z 8741||✔||✔||✔||✔||✔|
For paint and varnishes the international specular gloss standard is ISO 2813, for determination of specular gloss of non-metallic paint films at 20°, 60° and 85°. Also ASTM D523 is globally acknowledged as a specular gloss standard.
Buying gloss meters in the United Kingdom
There are many gloss meter suppliers and companies operating in the UK. 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 matt surfaces or 20°, 60°, 75° for paper). Below is a list of the instruments available on the British market from a range of gloss meter suppliers including BYK, Elcometer, PCE Instruments, and Rhopoint Instruments.
|Gloss meter company||Product name||Geometries included||Description|
|BYK-Gardner||Micro-TRI-gloss||Standard geometries of 20°, 60° and 85° measure at the same location simultaneously||The micro-TRI-gloss can be used to determine the gloss level of paint coatings, plastics, ceramics and metal surfaces. It has statistics, Pass/Fail and memory. Micro-gloss conforms to the standards ISO 2813, 7668, ASTM D 523 and D 2457, DIN 67530, and JIS Z8741|
|Elcometer||Elcometer 480||Geometry of 60°||This unit has a range of 10-100GU, with a standard, auto-repeat and scan mode, storage of up to 40,000 readings, and up to 40 limits for the master standards storage.|
|Erichsen GmbH & Co. KG||Gloss Meter Spektromaster 565-D||Geometry of 60°||Long life time (8000 measurements), a gloss unit measurement range of 0-100 GU (gloss unit), and the ability to measure color and gloss simultaneously.|
|PCE Instruments||Gloss Meter PCE-GM 60Plus||A handheld 60° gloss meter||The PCE-GM 60Plus has a measuring range of 0-200GU. The rechargeable gloss meter or gloss tester uses reflected light for gloss measurement per ISO 2813, GB/T 9754, ASTM D523 and ASTM D2457 standards.|
|Rhopoint insturments||Novo Gloss Trigloss Gloss Meter 20/60/85˚||Geometries of 20°, 60°, 85°||Small, lightweight and durable the gloss meter can be used in production and laboratory environments. Conforms to standards ISO 2813, ISO 7668, ASTM D523, ASTM D2457, DIN 67530, JIS 8741, and JIS K 5600-4-7|
|Zehntner GmbH||Gloss Meter ZGM 1023||Gloss measurement geometries of 20°, 60°, 75°||A portable, battery-powered instrument for measurements of all gloss ranges from matt to high gloss surfaces. The test equipment calibration is traceable to BAM (Federal Institute for Materials Research and Testing, Germany). According to ASTM, DIN, ISO, TAPPI, BE standards|
Some companies have full ranges of gloss meters (like BYK’s micro-gloss range where there is a micro-gloss unit for each geometry) 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.