Gloss
Everyone see gloss and color differently and visual perception is subjective and it differs from people to people. Gloss and color are interaction of light on a surface and is the reflection of light off a surface. The measurement unit for gloss is gloss units (GU). To measure gloss, the correct geometry must be used.
- Matte Finish – 85°
- Semi Gloss – 60°
- High Gloss – 20°
Practically, if the gloss units at 60° geometry is greater than 70 GU, it is recommended that a 20° geometry meter be used to optimize measurement accuracy. And for readings less than 10 GU, gloss measurement should be taken at 85° geometry.
Rhopoint Instrument has a close tolerance gloss meter, Rhopoint IQ-S. The IQ-S model has improved accuracy in measuring low gloss. This model is designed for automotive interior parts where a very low gloss is desired, for example the surface of a car dashboard to prevent light reflecting off a dashboard or interior parts into the drivers’ eyes.
Reflectance Haze
Haze is an undesirable effect in coatings and polished surfaces. Milky finishes, loss of reflected contrast, halos and patterns around the reflections of strong reflected light sources especially on high gloss surfaces such as mirrors and metallic coatings are some common defects.
Causes of reflectance haze include:
- Coating and raw materials
- Dispersion
- Pigment properties
- Particle size
- Binder compatibility
- Influence and migration of additives
- Curing
- Drying conditions
- Curing temperature
- Post coating
- Polishing marks
- Cleanliness
- Ageing and oxidation
The wheel covers shown on the right have the same gloss value at 60° geometry but they have visually different reflected image clarity. To quantify the differences, Rhopoint IQ-S is useful in providing a numerical value to the reflected image quality. This is useful in quantifying quality in highly polished surfaces.
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