I see the term “Volume Solids” in most specifications. What does it mean, and why is it so important?

Paint is made up of four basic elements: solvent, binder, pigment and additives. The material left on a substrate after the solvent evaporates and the coating cures is its solids content. When calculated as a percentage of the total gallon of paint, the solids are referred to as “Volume Solids.” A higher percentage of Volume Solids is usually an indication of a better quality paint, because more binder and pigment are left to protect the surface compared to a coating with a lower Volume Solids rating.