What is a Glossmeter?
Is an optical measuring instrument that measures the specular reflection of a surface (gloss level) of a surface. Gloss is measured by projecting a light beam at a fixed angle and intensity onto the surface being measured and the amount of reflected light at and opposite but equal angle.
Geometries for Gloss measurements
There are a number of key geometries for glossmeters (gloss meters) and gloss measurement, each being best suited for a particular type of coating, material or gloss range. For non-metal materials such as inks, paints and plastics the amount of light reflected increases with the angle of illumination and is either diffusely scattered depending on its colour or some of the light is absorbed into the surface. Metals tend to be more reflective therefore less sensitive to different angles of measurement.
Selecting the right angle for the Glossmeter test
The angle reference is the angle between the incident and reflected light. The three common angles are 20°, 60°, and 85° these cover most of industries coatings applications.
|Gloss Range||60° Value||Notes|
|High Gloss||>70 GU||If measurement exceeds 70 GU, change test setup to 20°|
|Medium Gloss||10 – 70 GU|
|Low Gloss||<10 GU||If measurement is less than 10 GU, change test setup to 85°|
In addition to the angle above 45° is used for the gloss measurement of plastic films, ceramics, anodised aluminium and textiles. 75° is for measurement of paper and paper products.
The unit of measurement for gloss is the Gloss Unit (GU). The GU is a scaling based on a polished black highly reflective gloss standard with a defined refractive index having a specular reference of 100 GU at the angle specified. This gloss standard is used to establish the upper range of the glossmeter and the 0 being established on a perfectly matt surface. This scaling works well for most non-metallic surfaces and coatings as they normally fall within this range. For other more reflective materials such as polished metals and mirrors a scale of up to 2000 GU can be achieved using a mirror gloss standard.
Gloss Measurement Standards
Comparison of standards for gloss measurement
Standard 20° 60° 85° 45° 75°
High Gloss Medium Gloss Low Gloss Medium Gloss Low Gloss
Coatings, plastics and related materials Ceramics Paper
ASTM C346 X
ASTM D523 X X X
ASTM C584 X
ASTM D2457 X X X
BS3900 D5 X X X
DIN 67530 X X X
DIN EN ISO 2813 X X X
EN ISO 7668 X X X X
JI Z 8741 X X X X X
TAPPI T480 X
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For Service and Calibration of Gloss Meter by AML Instruments