What is the ingredient in semi-gloss paint that makes it glossy that flat paint doesn have?
A. The ingredients of glossy and flat paints are essentially the same. The difference is that in glossy (high gloss) paints the ratio of pigments to resin (pigment volume concentration or PVC) is lower than in flat paints where you have considerably more pigments for the same amount of resin. When the paint dries some of the pigments at the surface break through the upper layer and diffuse the incident light. In some low gloss paints a very small concentration of light weight flatting agent is added so that it quickly rises to the top to break up the incident light.
