Is house paint a homogeneous mixture?
There are water-based and oil-based paints. Generally (and I am happy to be corrected by a professional), oil-based paints are used on the EXTERIOR, whereas water-based paints are used on the interior of the house. With oil-based paints, in order to clean the brush, you need a non-aqueous solvent: mineral and gum turpentine, methylene chloride, petroleum solvents. It contains particles of white stuff (titanic dioxide, stuff that is whiter than white!) that coat the surface when it is applied.
Water-based paints allow water clean-up of your brushes and rollers. Interior paints are called EMULSIONS in this country; here the paint material is dispersed in water as a suspension. For both sorts of paint the water or solvent dispersing agent dries off, and leaves the paint material behind as a nice surface.