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Haze FAQs

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What is reflection haze?

A surface with a highly reflective finish can be seen to have a deep reflection and a high reflective contrast. However, one that exhibits a slight “milky” finish, observed as a milky halo or bloom from a reflection on the surface, is said to be suffering from Haze; the word Haze, therefore, is used to describe this effect.

Image showing deep reflection and high reflective contrast
Image showing shallow reflection and low reflective contrast

Haze is caused by microscopic surface textures that diffuse light adjacent to the main specular component of reflected light. When viewing the reflection of a strong light source in a surface with high haze the image “blooms” and has a bright halo around it.

Image showing reflection of strong light source in a surface with low haze
Image showing reflection of strong light source in a surface with high haze

Surface haze can be problematic in many coatings applications including automotive manufacture, powder coatings and other high gloss coatings. It can be attributed to a number of causes including incompatible materials in a formulation, poor dispersion and problems encountered during drying/curing/stoving. Haze is an important measure for highly polished metals and is often associated with polishing marks and machining direction.

How can I measure reflection haze?

Reflection haze meters are traditionally used to measure reflection haze and use a standard glossmeter design with additional detectors 2º on either side of the specular angle to measure the haze component.

As the Rhopoint IQ incorporates an LDA, a 512 element, linear, photo-diode array (LDA) at the 20° angle instead of a single detector enabling measurement of the distribution of reflected light. haze measurement is easily accomplished using the reflected light data 2º on either side of the specular angle. The instrument can display the natural haze value (HU) or LogHaze value (HULOG).

Haze compensation is also required to correct variations when measuring different surface colours.

As reflection haze is caused by micro-textures on a surface, a small amount of light is reflected adjacent to the gloss angle. White surfaces, bright colours and metallics also produce a certain amount of diffuse light, reflected from within the material, to be present in this region. This diffuse light exaggerates the haze signal causing a higher than expected reading.

Diagram showing how micro-textures on a surface produces reflection haze

An advantage of the IQ is that, unlike a conventional instrument, compensation is calculated using a region adjacent to the haze angle. This technique gives compatible readings on solid colours but also compensates for directional reflection from metallic coatings and speciality pigments.

Diagram showing how the Rhopoint IQ can compensate for reflection haze utilising a diode array

Rhopoint glossmeter comparison table

Rhopoint Products 20º Gloss 45º Gloss 60º Gloss 85º Gloss Haze (Reflectance) DOI / RIQ RSpec Flat surface Curved surface Surfaces with curvature
Novo-Gloss 45 Glossmeter              
Novo-Gloss 60 Glossmeter                
Novo-Gloss Trio 20/60/85 Glossmeter            
Novo-Gloss 20/60/85 Glossmeter with Haze to ASTM E430          
Rhopoint IQ 20/60 Gloss Haze DOI Meter      
Rhopoint IQ 20/60/85 Gloss Haze DOI Meter    
Concrete Clarity Meter (CCM)        
Novo-Curve Glossmeter            
Novo-Gloss Flex 60 Glossmeter            

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