The primary ingredient in housepaint is rutile titanium dioxide particles, which have a very high refractive index. The particles are suspended in a carrier whi

The primary ingredient in housepaint is rutile titanium dioxide particles, which have a very high refractive index. The particles are suspended in a carrier which, when drying, creates air voids. The air/TiO2 refractive index change, as light bounces around inside, is what gives white paint it's hiding/wall covering power. In other words, artist paint and house paint use the same base pigment. Almost all commercially available "white" housepaints are based on titanium dioxide pigment. The special thing about artist paint is the extraordinarily high concentration of pigment.