ALTANA Haze-Gard Dual - Manual (Page 42)

41
English
11.1 Appearance of Transparent
Materials
When a transparent specimen is
illuminated by focused light, a
number of effects may result,
depending on the nature of the
material:
• Homogenous material with a
smooth surface
Some of the light will be reflected
from the border surfaces and some
will pass through the specimen un-
altered. The specimen will appear
glossy and crystal clear.
The intensity of the transmitted light
will be diminished by the inherent
absobance of the materials, dyes, or
pigments.
• Haze
Diffuse scattering will decrease the
imaging quality of an object. Parti-
cles or irregularities in the material
may act as “scatterers”. The light in
these areas is diffused uniformly in
all directions and the light intensity
per angle is small. This reduces
contrast and results in a milky or
cloudy appearance. This effect is
called haze.
11.2 Criteria for the Evaluation
of Transparency
The appearance of a transparent
product is a function of gloss, color,
and transparency. The key parame-
ters with respect to transparency
are total transmittance and haze.
The total transmittance is the ratio of
the total transmitted light to incident
light. It is reduced by reflectance
and absorbance.
According to ASTM 1003, haze is
the percentage of light that deviates
from the incident beam by more
than 2.5° on average.
11 Parameters