Haze FAQs

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.

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.

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 (HU_LOG).

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.

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.