ALTANA Micro-Haze Plus - Manual (Page 36)

35
The visual impression of gloss is a
multidimensional parameter. For
many years, reflectometers have
been used to measure gloss. For a
full characterisation of surface
reflection, however, additional
measurands are required.
Microscopically small defects in a
high gloss surface will result in
scattered light of low intensity
adjacent to the main reflection (fig.
18). The surface will appear shiny
covered by a milky and dull haze.
This haze is mostly caused by
specific parameters during the
production process, such as
• Pigment type and degree of
dispersion
• Binding agents, additives
• Application and processing
methods
In addition, weathering and
mechanical wear (cleaning, polish-
ing, abrasive wear) can also result
in a hazy appearance.
Measuring Principles 10
Reflectometer for Measuring
Gloss
The principle of a reflectometer is
based on the measurement of the
specular component of the
reflected light (fig. 17). To this end
the intensity of the reflected light is
measured in an angle range limited
by the aperture.
The measurement of the
reflectometer value is a relative
measurement. The measurement
results are related to a polished,
black glass standard with a defined
refractive index (calibration).
In order to obtain a good
differentiation between the
measurement results over the
whole range from high gloss to low
gloss surfaces three different
angles of illumination, i.e. three
measurement ranges, have been
defined:
20° high gloss surfaces
60° semi gloss surfaces
85° low gloss surfaces