Quick answer: A solvent in art is a liquid that dissolves or thins paint, mediums or varnish so they can be applied, mixed or cleaned away. In oil painting, the common solvents are odorless mineral spirits and turpentine; they thin oil paint for early layers, dissolve some resins and clean brushes. For water-based paints like acrylic and watercolor, water acts as the solvent or diluent. Solvents evaporate as the paint dries, leaving the binder and pigment behind.
Ask a chemist what is a solvent in art and you will get a short answer: a substance that dissolves another substance. Ask a painter and the answer gets more practical. A solvent is the jar on the side table that thins paint, rescues a stiff brush, removes a mistake and, if used carelessly, fills the room with fumes. Understanding what solvents actually do helps you use less of them, use them safely and avoid the structural problems they can cause.
This explainer covers the definition, how solvents work in different paint types, the main solvents artists use and their trade-offs, and where solvents fit into cleaning and conservation. If you are choosing one for brush cleaning, our comparison of oil painting solvents for cleaning covers the product types in more detail.
The Definition, Made Practical
A solvent is a liquid that dissolves a solid or another liquid into a uniform mixture. In the studio, that means three main jobs:
- Thinning: lowering the thickness of paint so it flows, spreads further and dries faster to the touch.
- Dissolving: turning solid resins, waxes or dried films back into liquid form, for making mediums and varnishes or removing them.
- Cleaning: breaking down paint left on brushes, palettes and tools.
Solvents are meant to leave. Unlike the binder, which stays in the paint film permanently, a solvent evaporates. Once it is gone, what remains is pigment held in oil, polymer, gum or resin.
What Does Solvent Do in Paint?
Inside a paint mixture, a solvent separates the binder molecules and pigment particles, making the paint more fluid. As it evaporates, the paint becomes thicker again and eventually sets.
In oil paint specifically, solvent has several effects:
- It thins the paint so you can lay in quick washes, tone a canvas or sketch an underdrawing.
- It speeds surface drying, because part of the volume disappears quickly. The remaining oil still cures by reacting with oxygen, which takes longer.
- It makes paint leaner. Removing oil content relative to pigment keeps early layers less flexible than later ones, which supports the fat over lean rule.
- It reduces gloss. Heavily thinned paint usually dries matte.
- It can weaken the film if overused. Too much solvent dilutes the binder so much that pigment may not be properly bound, producing a chalky, fragile surface.
Solvent vs Diluent vs Thinner
These words get used interchangeably, but there is a useful distinction.
| Term | Meaning | Example |
|---|---|---|
| Solvent | Dissolves a substance into solution | Turpentine dissolving damar resin |
| Diluent | Thins a mixture without necessarily dissolving everything | Water thinning acrylic emulsion |
| Thinner | Everyday term for anything that makes paint more fluid | Mineral spirits added to oil paint |
Water in acrylic is technically more of a diluent. Acrylic paint is an emulsion of polymer particles in water; once those particles fuse during drying, water no longer redissolves them. That is why dry acrylic is water-resistant even though wet acrylic washes out with water.
Common Solvents Artists Use
Odorless mineral spirits
A petroleum distillate refined to remove most aromatic compounds, which reduces smell. It is the most common solvent in contemporary oil studios for thinning paint and cleaning brushes. “Odorless” does not mean harmless: it still evaporates into the air and should be used with ventilation.
Gum turpentine
Distilled from pine resin, turpentine is the traditional oil painting solvent. It is a stronger solvent than odorless mineral spirits, which makes it better at dissolving natural resins like damar. It also has a strong smell and is more irritating to skin and lungs for many people.
Citrus and other plant-based solvents
Solvents derived from citrus peel oils are marketed as natural alternatives. They can be effective, but natural is not the same as non-toxic, and some people find the vapors irritating. They may also evaporate more slowly and leave residues, so check the manufacturer’s guidance for painting use.
Water
For watercolor, gouache, acrylic and casein, water is the thinning and cleaning agent. It is also used with water-mixable oil paints, which have been modified to accept water.
Alcohol
Isopropyl and denatured alcohol dissolve dried acrylic and shellac. Artists sometimes use alcohol to clean dried acrylic from brushes or palettes. It is also used in some conservation contexts.
Acetone and stronger solvents
These dissolve many dried films quickly. They are rarely needed in general painting and are best avoided at the easel because of strong fumes and the risk of damaging surfaces.
Solvent Comparison
| Solvent | Strength | Odor | Typical studio use | Cautions |
|---|---|---|---|---|
| Odorless mineral spirits | Moderate | Low | Thinning oil paint, brush cleaning | Still volatile; ventilate; flammable |
| Gum turpentine | Strong | High | Dissolving resins, traditional mediums | Irritant; strong vapors; flammable |
| Citrus-based solvent | Moderate | Citrus scent | Brush cleaning, some thinning | Can irritate; slower evaporation |
| Water | Mild | None | Water-based paints, water-mixable oils | Does not dissolve dried acrylic |
| Isopropyl alcohol | Moderate to strong for acrylic | Noticeable | Removing dried acrylic | Flammable; can damage some finishes |
Is Oil a Solvent?
Not in the usual sense. Linseed, safflower and other drying oils are binders: they stay in the paint and harden into a film. They do not evaporate. However, oil can dissolve or loosen fresh oil paint, which is why some painters clean brushes with vegetable or safflower oil instead of solvent. The oil works the paint out of the bristles; soap and water then remove the oil.
That distinction matters for structure. Thinning paint with oil makes it fatter and slower drying, while thinning with solvent makes it leaner and faster drying. Mixing up the two can break the fat over lean rule and contribute to cracking or wrinkling. For more on why water and oil paint do not mix in the first place, see our explanation of whether you can use water with oil paint.
What Is a Solvent-Based Paint?
A solvent-based paint uses an organic solvent, rather than water, as its main vehicle. Traditional oil paint is often called solvent-based because it is thinned and cleaned with solvents, though tube oil paint itself typically contains little or no solvent; the oil is the binder. Alkyd paints, enamel and many industrial coatings are more clearly solvent-based, since they rely on solvent to stay liquid in the can.
Water-based paints, by contrast, include acrylic, watercolor, gouache, casein and water-mixable oils. They use water as the vehicle and are cleaned up with water while wet.
How Much Solvent Is Too Much?
There is no single safe percentage, because paints vary in oil content, but some practical guidelines help painters stay on the right side of the line.
| Situation | Solvent use | Reason |
|---|---|---|
| Toning a canvas | Generous; paint becomes a thin wash | Fast drying, very lean first layer |
| Underdrawing or block-in | Moderate; paint flows but still has color strength | Keeps early layers lean |
| Middle layers | Little or none; switch to an oil-containing medium | Begins building flexibility |
| Final layers and glazes | Avoid adding solvent directly | Upper layers should be the fattest |
A useful visual test: if thinned paint runs like ink and the color looks weak and streaky when brushed out, the binder is probably too diluted for anything but a first wash. If it dries noticeably chalky or rubs off on a finger, too much solvent was used.
Solvents in Mediums and Varnishes
Many oil painting mediums contain solvent. A classic homemade glazing medium might combine stand oil, a natural resin and turpentine. Commercial alkyd mediums usually contain mineral spirits. The solvent keeps the mixture fluid in the bottle and evaporates after application.
Picture varnishes depend on solvents too. A resin is dissolved in a solvent, brushed or sprayed on, and the solvent evaporates to leave a clear protective layer. Because the right solvent can dissolve that layer again later, varnish is removable. That reversibility is why conservators can clean and revarnish old paintings without touching the paint underneath, as long as they choose a solvent that affects the varnish but not the paint.
Solvents in Cleaning and Conservation
Conservators select solvents carefully, testing different strengths to find one that lifts dirt or old varnish while leaving the original paint unharmed. At home, owners should be far more cautious. Solvents strong enough to remove grime can also soften paint, especially on newer or unvarnished works. Our guide on how to safely clean an oil painting explains the gentle methods to try first and when to stop.
How to Use Solvents Safely
- Ventilate. Work with a window open or fresh air flowing, and avoid painting in a closed bedroom.
- Use the smallest amount possible. A small lidded jar holds enough for most sessions.
- Keep lids on. An open jar keeps releasing vapor even when you are not using it.
- Protect skin. Wear nitrile gloves if you clean brushes in solvent often, and never clean paint off your hands with solvent.
- Store oily rags safely. Rags soaked with oil and solvent can self-heat. Keep them in a closed metal container or let them dry flat outdoors, and dispose of them according to local guidance.
- Do not pour solvents down the drain. Let used solvent settle, decant the clear liquid for reuse, and take sludge to a hazardous waste collection point.
- Keep away from kids and heat. Most solvents are flammable.
Reusing solvent
Brush-cleaning solvent does not need to be thrown out after one session. Leave the jar undisturbed and pigment will settle to the bottom over a day or two. Carefully pour the clear solvent into a clean jar and reuse it. Many painters use a two-jar system: one for the first, dirty rinse and one for a final cleaner rinse.
Solvent-Free Painting
It is entirely possible to paint in oils without solvents. Painters who want to avoid fumes often:
- Use paint straight from the tube or thinned with a little oil or a solvent-free medium.
- Tone canvases with acrylic instead of thinned oil.
- Wipe brushes with a rag, rinse in safflower or another vegetable oil, then wash with soap.
- Choose water-mixable oils, which thin and clean with water.
The trade-off is slower drying in early layers and needing to plan fat over lean using oil content alone. Many painters find the reduced odor worth it.
Common Mistakes With Solvents
- Thinning every layer heavily, which weakens the paint film
- Using solvent-heavy layers on top of oily layers
- Leaving brushes standing in solvent, which bends bristles and loosens the ferrule
- Mixing solvent into acrylic, which can disrupt the emulsion
- Assuming “odorless” or “natural” means safe to use in a closed room
FAQs
What does solvent do in paint?
It thins paint so it flows, dissolves resins in mediums and varnishes, and speeds surface drying by evaporating. It does not stay in the finished paint film.
Is oil a solvent?
No. Drying oils are binders that stay in the paint. Oil can loosen fresh paint from brushes, but it makes paint fatter, not leaner, and does not evaporate.
What is a solvent-based paint?
A paint that uses an organic solvent rather than water as its vehicle, such as many alkyd and enamel paints. Oil paint is often grouped with them because it is thinned and cleaned with solvents.
What is the safest solvent for oil painting?
Odorless mineral spirits are generally considered a lower-odor option than turpentine, but all solvents need ventilation. Solvent-free cleaning with oil and soap avoids vapors entirely.
Do you need solvent for oil painting?
No. You can paint with tube paint or oil-based mediums and clean brushes with oil and soap. Solvent is a convenience for thinning and cleaning, not a requirement.
Is water a solvent in art?
Yes, for water-based paints. Water thins and cleans watercolor, gouache and wet acrylic, though it will not redissolve dry acrylic.
Final Thoughts
A solvent is a temporary helper: it thins, dissolves and cleans, then leaves. Used sparingly and safely, it makes oil painting easier; overused, it weakens paint films and fills the room with vapor. When you are ready to pick a cleaning solvent for your studio, our roundup of the best solvents for cleaning oil brushes and palettes compares low-odor and traditional options.
