How to Measure Gloss using a Gloss Meter
Gloss can be measured by several different techniques. One of them is by using an optical instrument called a gloss meter. A glossmeter provides quantifiable gloss measurements, expressed as gloss units (GU).
How to Measure Gloss
Gloss is measured by directing a constant intensity light beam, at a fixed angle, onto the test surface and then monitoring the amount of reflected light from the same angle. This specular reflectance is measured using a glossmeter. Different surfaces require different reflective angles.
High Gloss: Surfaces with a brilliant or highly polished finish reflect images clearly. This distinct reflection is caused by the incident light reflecting on the surface in a specular direction.
Semi & Matt Gloss: Semi and matt surfaces reflect images less distinctly and with reduced intensity. On semi or matt surfaces light not only reflects in a specular direction but also is scattered causing the reflected image to appear diffused.
Choosing the Correct Angle for Gloss Measurement
Gloss measurement is based on the amount of light reflected on the surface relative to a polished glass reference standard, measured in Gloss Units (GU). The amount of light that is reflected on the surface is dependent on the angle of incidence and the properties of the surface.
Gloss is categorised as either matt, semi or high gloss. In order to determine the most appropriate measurement angle start with a glossmeter set at a 60° angle of incidence.
If the result is between 10 - 70GU, the coating is termed 'semi-gloss' and should be measured using the 60° angle on the glossmeter. If the result is less than 10GU, the product is 'low gloss' and should be measured using the 85° angle on the glossmeter and if it is greater than 70GU, the product is known as 'high gloss' and should be measured using the 20° angle on the glossmeter.
All three angles should be recorded (20, 60 & 85°) when measuring gloss on anodised metals to ensure a complete understanding of the specular reflectance between the coating and the metal substrate.
2025-04-24 10:25