Gloss is a
measurement of the relative luster or
shininess of a film surface. ExxonMobil uses
45-degree gloss, where the incident light beam
strikes the film surface at a 45 degree angle
from the perpendicular. A sensor measures the
amount of light reflected by the film at a
mirror image angle. The gloss value is the
ratio of this reflected light to incident
light and is reported in gloss units.
Theoretically, the range of the gloss scale is
0 to 100.
Shininess,
brilliance, and sparkle are properties related
to a film's gloss value. They can be valuable
appearance attributes for packages, labels, or
graphic arts items.
Precise comparisons
of gloss values can only be made when the
measurements are performed on samples of the
same general type of material, using the same
procedure and test angle. In particular, it is
not valid to compare the gloss values of
transparent films and opaque films.
Gloss is primarily
determined by material selection and surface
smoothness, which are defined during product
and process development. Day-to-day process
variations will have an insignificant effect
on gloss. Transparent films have two
reflecting surfaces. Although rare, this can
lead to gloss values that exceed 100.
ExxonMobil
uses commercially available glossmeters to
measure 45-deg gloss consistent with ASTM
procedure D 2457. The simplified diagram in
Figure 2 graphically summarizes the test.
