Turpentine is a solvent used in oil painting to thin paint, create translucent washes, clean brushes, and make varnishes and painting mediums. It has been a core studio material for centuries, and despite the rise of modern alternatives, many oil painters still rely on it for its unique handling properties. Here’s how it works and when to use it.
Thinning Paint for Early Layers
The most common use of turpentine in painting is thinning oil paint in the early stages of a work. When you add turpentine to oil paint, it breaks down the pigment-and-oil mixture into a thinner, more fluid consistency. This makes the paint behave almost like watercolor, allowing you to lay down transparent or semi-transparent layers quickly. These lean, solvent-heavy layers dry fast because the turpentine evaporates, leaving behind only a thin film of pigment and a small amount of oil.
This matters because of a fundamental rule in oil painting: fat over lean. Each successive layer of paint should contain more oil (fat) than the layer beneath it. If you put a lean layer on top of a fat one, the upper layer dries and becomes rigid before the oily layer underneath has finished curing, which causes cracking. Turpentine gives you a reliably lean starting point. Many painters use just a small amount of solvent for the initial underpainting, then gradually shift to oil-rich mediums in later layers. A good rule of thumb is to keep any added medium to roughly 20% or less of the total paint mixture.
Underpainting, Sketching, and Imprimatura
Turpentine is especially useful in three specific early-stage techniques. The first is imprimatura, where you tint a white-primed canvas to a warm or neutral tone before painting on it. A small amount of paint dissolved in turpentine creates a thin, even wash that dries within minutes, giving you a toned ground to work on rather than glaring white.
The second is brush sketching. Instead of drawing your composition in pencil or charcoal, you can sketch directly onto the canvas with a brush dipped in turpentine-thinned paint. The lines are thin, dry quickly, and can be easily wiped away or painted over. The third is blocking in, where you establish the major shapes, values, and color relationships of a painting with broad, diluted strokes. At this stage, the goal isn’t detail but structure, and turpentine-thinned paint lets you cover large areas efficiently. Some painters, like the illustrator Frank Frazetta, painted entire backgrounds with heavily thinned paint, dried them rapidly, then built up thicker layers on top.
Making Painting Mediums and Varnishes
Beyond thinning paint directly, turpentine is the base solvent for many traditional painting mediums and varnishes. Damar varnish, one of the most widely used varnishes in fine art, is made by dissolving damar resin crystals in turpentine. The standard recipe from pigment suppliers like Kremer Pigmente calls for a 1:3 ratio by weight: 100 grams of damar resin dissolved in 300 milliliters of turpentine. This produces a clear, glossy varnish used as a final protective coat over finished paintings, as an intermediate varnish between painting sessions, or mixed into paint as a medium to add gloss and transparency.
A thicker 1:2 ratio (100 grams of resin to 200 milliliters of turpentine) produces a more concentrated solution used in emulsion recipes or as an additive when grinding certain pigments. These mediums give painters precise control over the surface quality, drying speed, and optical depth of their work in ways that premixed commercial mediums can’t always replicate.
Cleaning Brushes and Equipment
Turpentine dissolves oil paint effectively, making it a standard brush cleaner. Swirling a loaded brush in a jar of turpentine breaks down the paint so you can wipe the brush clean between color changes or at the end of a session. It also removes dried or semi-dried paint from palettes, palette knives, and other tools. Many painters keep a dedicated jar of “dirty” turpentine for initial brush rinsing and a cleaner supply for mixing into paint, since contaminated solvent can muddy colors.
Gum Spirits vs. Hardware Store Alternatives
Not all turpentine is the same, and the distinction matters for painting. True gum spirits of turpentine is distilled from the resin of live pine trees, primarily longleaf pine. Its chemical makeup is about 60 to 65 percent alpha-pinene along with other naturally occurring compounds, giving it broad solvent power and a characteristic pine-forest smell.
What you’ll find labeled as “turpentine” at a hardware store is often petroleum-based, distilled from crude oil rather than tree resin. It contains mostly different hydrocarbons, smells like gasoline rather than pine, and can leave residues that affect paint film quality. For fine art, look for products specifically labeled as gum spirits of turpentine. Artist-grade versions from art supply manufacturers are refined to a higher purity. If you’re unsure what you have, the smell is a reliable indicator: real gum spirits smells like a Christmas tree farm, while petroleum-based substitutes smell like a garage.
One Caution: Use It With Ventilation
Turpentine-thinned paint does have a downside in later layers. When paint is heavily diluted with turpentine and applied in thin, watercolor-like washes over an existing painting, the colors can appear wilted and dull as the solvent evaporates and leaves behind an under-bound pigment film. This is why turpentine works best in the early stages, where thinness is the goal, and why painters switch to oil-based mediums for building color richness in upper layers.
Turpentine also carries real health risks. It enters the body through inhalation, skin absorption, and ingestion. Short-term exposure can irritate your eyes, skin, nose, and throat, cause headaches and dizziness, and trigger nausea. Prolonged or heavy exposure targets the central nervous system and kidneys. Your skin can also become sensitized to it over time, meaning reactions get worse with repeated contact. Always work in a well-ventilated space, ideally with a window open or an exhaust fan pulling fumes away from your breathing zone. Use nitrile gloves when handling it, keep containers sealed when not in use, and avoid eating or drinking in your painting area. Many painters now use odorless mineral spirits as a less toxic alternative for brush cleaning, reserving turpentine for the specific tasks where its solvent properties are genuinely superior, like dissolving damar resin or creating certain traditional mediums.