A thinner is a volatile solvent that is used to dilute or extend oil-based paints or cleanup after use. Common solvents used as paint thinner chemicals include mineral spirits, mineral and true turpentine, acetone, naphtha, toluene, methyl ethyl ketone (MEK), dimethylformamide (DMF), glycol ethers and xylene.
They are commonly used in painting and coating applications to thin down the viscosity of paint or varnish, making it easier to apply and achieve a smooth, even finish.