Paint thinner and lacquer thinner both contain petroleum by-products, but they have different characteristics, and you use them for different purposes. Paint thinner is a general term that includes turpentine and its more modern counterpart, petroleum distillates. Mineral spirits is a refined form of petroleum distillates. Lacquer thinner is another general term that can refer to any one of a number of mixtures of powerful solvents, some of which are petroleum distillates and some of which aren't. Lacquer thinner evaporates quickly, but you don't always need its strength and volatility.
Paint Thinner and Mineral Spirits
Before the days of petroleum distillation, painters used turpentine, which is distilled pine sap. Not only could it thin the oil-based paints that were prevalent, it can dissolve wax and cut grease. When petroleum is distilled, the gases that make gasoline evaporate first, and the ones that are left are useful for cleaning and thinning paint.
Naphtha is one result of distillation, and mineral spirits, which evaporates more slowly, is another. The latter is what painters usually refer to a paint thinner. In its unrefined state, it contains toluene and xylene, two relatively smelly and toxic chemicals. White mineral spirits is processed to remove these toxins, leaving behind a stable mixture of relatively odorless hydrocarbons.
There are many formulations of lacquer thinner -- manufacturers offer a variety with a range of evaporation rates for applying lacquer at various temperatures. The solvents in lacquer thinner might include
- methyl ethyl ketone
- butyl acetate
... and a host of others. Unlike mineral spirits, lacquer thinner has a strong odor, and the fumes are harmful. Moreover, lacquer thinner usually contains highly flammable chemicals.
Which to Choose
You can use lacquer thinner to thin oil-based paint, but painters seldom do, because its volatility would make the paint dry too quickly and crack. It's better to use paint thinner to thin paint, and it's the better solvent for cleaning wax and thinning varnish.
You need the volatility and strength of lacquer thinner whenever you want to spray nitrocellulose, CAB or catalyzed lacquer. It is a better cleaner than mineral spirits, but its strong odor, toxicity and flammability contraindicate using it for household purposes.