Solvents may be further classified as true or active solvents, diluents, reducers and thinners. A true solvent can dissolve and rapidly reduce the viscosity of a binder. Within limits, a diluent solvent is able to reduce viscosity, but it
simultaneously weakens solvent power of the true solvent. Various solvents can
function as true solvents or diluents, depending on the particular type of binder.
The terms “thinner” and “reducer” are inexact and refer to any volatile liquid
used in mixing paints.