Last Updated on October 6, 2026
Paint thinner does one thing: it dissolves the binder that holds an oil-based coating together, which drops the viscosity so the paint flows and lets you wipe the coating off a brush or a spill. The product sold under that name is 80 to 100% Stoddard solvent, a petroleum distillate, with 3 to 7% trimethylbenzene.
It does not thin latex, and it does not mix with water. At a specific gravity of 0.78 it floats, and it is rated very slightly soluble in cold water. That single fact decides most of what follows — which paints it works on, how you clean up, and why you cannot pour it down a drain.
It is also not one chemical. The can beside it on the shelf marked lacquer thinner is toluene, acetone and methanol, and it catches fire 70°F lower.
What is in the can
| Component | CAS | Share | Why it matters |
|---|---|---|---|
| Stoddard solvent | 8052-41-3 | 80–100% | The petroleum distillate doing the dissolving |
| Trimethylbenzene | 25551-13-7 | 3–7% | The tightest exposure limit in the can, at 25 ppm |
| Property | Figure |
|---|---|
| Flash point | Over 100°F — NFPA Class II |
| Boiling range | 318 to 385°F |
| Vapor pressure | 0.3 mm Hg at 68°F |
| Vapor density | 5, against air at 1 |
| Specific gravity | 0.78 — it floats on water |
| Water solubility | Very slightly soluble in cold water |
| VOC | 778 g/L |
| Exposure limit | OSHA 500 ppm; recommended limit 100 ppm |
778 grams of volatile organic compound per liter is about as high as a consumer product goes. And the legal exposure ceiling is 5 times the limit the occupational hygienists actually recommend — 500 ppm against 100.
The five solvents people call paint thinner, and what separates them
| Solvent | Flash point | Vapor pressure | Mixes with water? | Use it for |
|---|---|---|---|---|
| Acetone | -4°F | 184 mm Hg | Yes | Lacquer, fiberglass resin, nail-polish-grade cleanup |
| Lacquer thinner | 30°F | 87 mm Hg | Yes | Lacquer, shellac, 2K automotive, stripping |
| Denatured alcohol | 53°F | — | Yes, completely | Shellac, de-waxing, glass |
| Turpentine | 91°F | 3.48 mm Hg | No | Artists’ oils, traditional varnish |
| Paint thinner | Over 100°F | 0.3 mm Hg | Barely | Oil-based house paint, enamel, brush cleaning |
| Mineral spirits | 100–151°F | 2 mm Hg | No | The same jobs, with less odor and less residue |
Read the vapor pressure column before the flash point one. Acetone pushes 184 mm Hg of vapor at room temperature against paint thinner’s 0.3 — 613 times as fast into the air you are standing in. That is why a splash of acetone is dry before you reach for a rag and a splash of paint thinner is still wet twenty minutes later, and it is also why the same size garage is a very different room with each one open in it.
Flash point sorts them into fire classes. Anything under 100°F is NFPA Class I, which is the category that wants no pilot light, no grinder and no space heater in the room. Acetone at -4°F gives off ignitable vapor in a freezer. Paint thinner, at over 100°F, needs the room warmer than most rooms get.
The number nobody prints: the vapor sinks
Vapor density 5 means the vapor coming off paint thinner is 5 times heavier than air. It does not rise and drift out of an open window. It runs downhill, pools on the floor, and collects in basements, pits, and the gap under a water heater where the pilot light is.
A window open at head height does nothing for a vapor sitting at ankle level. Cross-draft at floor level, a fan pointed out of a doorway, or working outside is what actually clears it. Acetone at vapor density 2.0 behaves differently again — still heavier than air, but half as determined to stay on the floor.
What paint thinner will not do
It will not thin latex or acrylic
Water-based paint uses water as its carrier. Adding a petroleum distillate to it does not thin it; it breaks the paint apart and leaves you with a curdled, unusable mess. 1 ounce is enough to ruin a quart. Latex gets water, in measured amounts — the ratios in fluid ounces are a separate job with separate arithmetic.
It will not dilute with water
Shake the two together and they separate again within minutes, the lighter solvent sitting on top. Denatured alcohol is the opposite. It is 60 to 100% ethanol with 3 to 7% isopropyl alcohol, 100% water soluble, and that is exactly why shellac cleans up with it and oil paint does not.
It will not sit safely in most plastics
A petroleum distillate attacks polystyrene and many polyethylene containers, softening or perforating them — a thin yogurt pot can fail in under 10 minutes. Glass or the original metal can is the only sensible storage. The same caution applies to putting a solvent lacquer over a water-based coat.
Using it on the three jobs it is actually for
1. Thinning oil-based paint
Start at 10% by volume and work up in 5% steps, measuring rather than pouring. 10% of a 32 fl oz cup is 3.2 oz. Solvent thins further than water does, so an oil-based paint needs less of it than a latex needs of water, and the same holds for an oil-based primer. The step-by-step ratios for oil-based paint and the viscosity targets each gun is rated for cover the measurement side.
2. Cleaning brushes and tools
Work the brush in a jar of thinner against the bottom, press the bristles out from the ferrule, then repeat in a second clean jar. Two dirty jars beat one, because the first jar does the heavy lifting and the second actually gets the brush clean. Finish with soap and warm water and reshape the bristles, and do the same for roller covers if they are worth saving. The full brush-cleaning sequence and the sprayer version go further.
3. Wet spills and mistakes
Only while wet. A fresh oil-based splash lifts with a thinner-damped cloth in the first few minutes. Once the film has cured the thinner softens it unevenly and usually smears it, and you are into stripper territory instead.
What it does to skin and lungs
Skin contact: irritation, drying, dermatitis, and — the one people do not expect — numbness in the fingers and arms. Inhalation: dizziness, headache, watering eyes, weakness, nausea, muscle twitches and depression of the central nervous system.
Nitrile gloves, not latex. Latex gloves swell and fail against petroleum distillates within minutes. Eye protection matters because the vapor irritates eyes at concentrations well below the ones that make you dizzy, and by the time you notice the headache you have been over the recommended limit for a while.
Lacquer thinner deserves a harder line: its 7 to 11% methanol fraction is absorbed through skin, and its toluene fraction carries the tightest limit of the group at 50 ppm. A respirator rated for organic vapor is the right call in an enclosed space.
Storage and disposal
- Keep it in the original metal can or glass, sealed, away from any pilot light or spark source. The vapor is 5 times heavier than air and pools low, so a shelf at waist height is safer than the floor.
- Never pour it down a drain or onto soil. It floats on water, which is exactly what makes it a problem downstream.
- Let used thinner stand in a sealed jar for 3 to 5 days. The pigment settles out, and the 80% or so of clear solvent on top is reusable for first-stage brush cleaning.
- Take the sludge and anything you will not reuse to a household hazardous waste drop-off. Most counties run them free.
- Oily rags go flat on a non-combustible surface to dry, or in a sealed metal can with water. Balled up in a bin they generate their own heat and can reach ignition without a spark — the one fire risk in this list that needs no flame at all.
Frequently asked questions
Is it necessary to use paint thinner?
Not for most jobs. Modern oil-based paint is formulated to brush straight from the can, and a full-size airless sprayer atomizes it unthinned. You need it when a coating has thickened in storage, when you are feeding a small sprayer that cannot handle full-bodied material, or when you are cleaning oil-based paint off tools. For water-based paint the answer is never — that is a water job.
Is rubbing alcohol a paint thinner?
No, and the difference is measurable. Rubbing alcohol is isopropyl alcohol diluted with water, typically to 70%, so you are adding two liquids in a ratio you did not pick. It is also 100% water soluble where paint thinner is barely soluble at all, which means it behaves like water in the film rather than like a solvent. It will soften fresh acrylic and shellac. It will not thin oil-based paint. If you want to avoid solvent altogether there are ways to clean oil-based brushes without it.
When should you thin paint?
When the coating will not level, will not atomize, or has thickened past the tool you are using. Thin to a target rather than a feeling: a cup reading inside the range your sprayer is rated for, or a brush load that flows off without dragging. Thinning costs film thickness in direct proportion to what you add, so 10% thinner is roughly 10% less paint left on the surface per coat.
Is paint thinner bad for your health?
It depends almost entirely on the air you use it in. The legal ceiling is 500 ppm over an 8-hour shift; the figure hygienists actually recommend is 100 ppm, and the trimethylbenzene fraction is held to 25 ppm. You will smell it long before you reach any of those, so a smell strong enough to notice from the next room is your signal to open the space up, not to work faster.
Is paint thinner just acetone?
No — there is no acetone in it. Paint thinner is 80 to 100% Stoddard solvent. Acetone is a different chemical that appears as 9 to 14% of lacquer thinner. Their flash points are over 100°F and -4°F, and their vapor pressures 0.3 and 184 mm Hg. Swapping one for the other changes both what dissolves and how dangerous the room is.
Can I touch paint thinner with bare hands?
Avoid it. A single splash washed off quickly is not an emergency, but repeat exposure over a day strips the skin’s own oils and leaves the cracked hands most painters recognise. Wear nitrile. A latex glove fails against a petroleum distillate in minutes, which is worse than no glove because you keep working in it.
The short version
Paint thinner is 80 to 100% Stoddard solvent. It dissolves oil-based binders, it floats on water at 0.78 specific gravity, and it does nothing useful to latex. Start at 10% by volume if you are thinning, and measure it.
Check the flash point before you check anything else: over 100°F for paint thinner, 30°F for lacquer thinner, -4°F for acetone. And remember the vapor sinks at 5 times the density of air, so ventilation means a draft across the floor, not a window above your head.
Can paint thinner be used to oil remove canned spray paint?
You can try, but you may have better luck with acetone or nail polish remover. Apply the paint thinner with a rag, using a clean part for each wipe.
Can you use paint thinner to clean up residual from wood that has been stripped of paint?
Also can it be used to remove stains or old varnish from stripped woodwork?
Have a headboard that someone painted very lighty…I want to remove the paint and bring it back to its original color. What can I use? Not even sure the headboard is real wood.