Turpentine vs Mineral Spirits: Which Solvent for Which Job, and How to Store Both

Where they come from and how they behave. Turpentine is distilled from pine resin: it smells strongly of pine, evaporates fast, dissolves natural resins that mineral spirits will not touch, costs more, and is harder on skin and lungs. Mineral spirits is a petroleum cut: milder smell, slower and more even evaporation, cheaper, less irritating, and it does nearly every job in a shop. For thinning oil paint and cleaning brushes they are interchangeable. For an oil painter's medium or a beeswax finish, turpentine.

Effectively indefinitely in a sealed metal can kept cool and dark; it is a stable petroleum fraction with nothing to spoil. An opened can loses the lighter fractions to evaporation over years and gets slower and oilier, which still works for degreasing. Dirty spirits from brush cleaning settle out: let the pigment sink, pour the clear solvent off the top into a new can, and use it again.

Slowly, once air reaches it. The pinenes oxidize, the liquid yellows and thickens toward a resin, and it stops thinning cleanly. Sealed in the original metal can, cool and dark, it keeps for years; a half-empty can with the cap off in a hot shed is gummy inside a year or two. Buy small cans, keep them full, cap them tight.

Turpentine, on every count: it irritates skin faster, its vapor stings eyes and lungs at lower concentrations, some people become sensitized to it, and swallowed it is more dangerous. Mineral spirits is not harmless; its vapor causes headaches and dizziness in a closed room and it dries skin badly. Both are aspiration hazards if swallowed: a person who drinks either is never made to vomit, because solvent drawn into the lungs causes chemical pneumonia, and Poison Control gets a call.

Yes. It dissolves most adhesives, tar, sap, wax and grease on metal, glass, finished wood and most hard plastics. Dampen a rag, let it sit a minute, wipe. Test a corner on plastic, painted surfaces and anything with a soft finish, because it softens some of them. Then wash with soap and water, because it leaves an oily film.

In the original metal can with the cap tight, or a metal safety can, in a cool, dark, ventilated spot away from any flame, pilot light, water heater or spark: a metal cabinet in a detached shop is ideal, a closet in the house is not. Keep it full or move it to a smaller can; air in the can is what ruins it. Never in a food container, never in the sun, never in a hot vehicle. Rags soaked in turpentine or oil finishes go in a metal can with a lid or are laid flat outdoors to dry, because a pile of them can heat and ignite on its own.

No. Both have flash points far below kerosene's; in a wick lamp the vapor above the reservoir can ignite, the flame runs up the wick, and the lamp becomes a fire. Lamps and lanterns get kerosene or lamp oil only. As a fire starter outdoors a splash of either on dry kindling works, poured on before the match, never toward a burning fire, and the can stays well back.

For thinning oil-based paint, varnish and stain, cleaning brushes, wiping down wood before finishing and degreasing, yes, and it is the better choice: cheaper, milder, slower to flash off. It cannot replace turpentine for dissolving natural resins like rosin, damar and pine pitch, in traditional oil painting mediums, or in a beeswax and turpentine furniture polish, where the turpentine's solvency and evaporation are part of the recipe.