Gloss is the shiny characteristic of a coating.
The smoother the surface is, the better the gloss. That is why the presence of irregularities
on the surface may prevent you from having good gloss property.
Figure 1: Comparison between
obtained (1) and expected (2) gloss
Surface modifying additives, surfactants
in particular, can maximize surface smoothness by preventing pigment flocculation
or increasing flow at the coating surface.
Surfactants are a possible solution to obtain
the gloss effect you are looking for.