A painting medium is any substance added to paint to change its properties. From stand oil and dammar to modern alkyd gels, learn how mediums shape oil painting.
On a shelf at the back of Bradbury Art in the UK, three bottles sit next to each other: stand oil, dammar varnish, and distilled turpentine. Most customers walk past them. But those three bottles are the recipe for the painting medium that every Old Master from Rubens to Sargent used. Pre-mixed mediums like Liquin, Galkyd, and Miracle Medium are convenient, but the three-bottle approach is what came before, what those branded mediums were designed to replace, and what serious oil painters still mix from scratch when they want full control over how their paint behaves.
In painting, a medium is any substance added to paint to modify its properties. Mediums can change the paint's viscosity, drying time, transparency, gloss, texture, flow, or flexibility. The term is used in two related but distinct ways. It can refer to the binder itself, the substance that holds pigment together and adheres it to the surface, as in "oil paint uses linseed oil as its medium." Or it can refer to additives mixed into the paint on the palette to alter its handling characteristics. This entry focuses on the second meaning: the substances painters add to their paint to control how it flows, how it dries, and how it looks when it is finished.
This entry covers the history of painting mediums, the main types used in oil painting, how they work, and what modern alternatives offer.
A painting medium is a mixture of one or more of three categories of material: oil, resin, and solvent. The oil provides body, gloss, and flexibility. The resin provides transparency, faster drying, and structural hardness. The solvent thins the mixture to a brushable consistency and adjusts the drying rate by controlling how quickly the volatile component evaporates.
The classical medium, used in various proportions from the 17th century onward, consists of stand oil (heat-polymerized linseed oil), dammar varnish (dammar resin dissolved in turpentine), and distilled turpentine. Mixed in equal parts, this produces a medium that increases the paint's transparency and flow, speeds drying slightly, and produces a smooth, enamel-like surface. The stand oil self-levels, meaning brush marks smooth out as the paint sits. The dammar lifts gloss and transparency. The turpentine adjusts viscosity and evaporates, leaving the oil and resin behind in the paint film.
Different ratios produce different effects. More stand oil (2:1:1) gives slower drying, a glossier surface, more flow, and a more flexible film, suitable for final layers and glazing. More dammar (1:2:1) increases gloss and transparency but adds brittleness, so the oil must be increased to match. More turpentine (1:1:2) produces a lean, fast-drying mixture suitable for underpainting and early layers.
The fat over lean principle governs how mediums are used across layers. Early layers use more solvent and less oil (lean), drying quickly and providing a stable base. Later layers use more oil and less solvent (fat), drying more slowly but forming more flexible films that can accommodate the movement of the underlying layers without cracking.
The use of mediums in oil painting is as old as oil painting itself. Early Netherlandish painters like Jan van Eyck mixed their oil with natural resins to modify its handling properties. A 2023 study published in the Journal of Cultural Heritage found that crushed glass particles were frequently mixed with red lake pigments in 15th- and 16th-century oil paint glazes to increase transparency and accelerate drying. The glass particles acted as a transparent filler, increasing the translucency of the paint film without significantly altering its rheological properties. This practice was common in Italian, German, and Netherlandish painting. Read the study at ScienceDirect.
Through the Renaissance, artists worked with combinations of tree resins, thickened vegetable oils, waxes, and balsams. The exact organization of these raw materials varied from one artist to another, and even within the practice of an individual artist. Mastic resin, from the Greek island of Chios, was the most common resin, used for over 800 years before dammar began to replace it in the late 18th century.
The latter half of the 18th century saw the first widespread use of resin-oil mediums throughout paintings, not just in specific passages. A preparation of linseed oil cooked with lead and mastic spirit varnish became common, known as megilp. As early as 1768, William Donaldson wrote about this medium in The Life and Adventures of Sir Bartholomew Sapskull: "The magilp was a nostrum known only to the ancients; but our modern artists have labour'd to find out this valuable mystery." Many painters at this time believed that certain "secrets" of the Old Masters had been lost, and if rediscovered, would make it easier to achieve the same effects. The search for these secrets became so pervasive that it attracted ridicule. The president of the Royal Society of Arts, Benjamin West, trusted a fraudulent claim of the discovery of the "Venetian Secret" that put his reputation at serious risk. James Barry, writing in the 1760s, poked fun at "such people of ours who are floating about after Magilphs and mysteries."
Megilp is a thixotropic gel consisting of mastic varnish and lead-treated oil (also called "black oil"). Its properties vary significantly as the proportion of oil and resin changes. The film-forming capability, tendency to segregate, tackiness, and dust absorption all depend on the exact proportions. Joshua Reynolds used a variety of megilp formulations, which has led to variations of yellowing and solubility in his paintings and made them very sensitive to cleaning. Turner used walnut oil, sometimes heat-bodied, as his principal medium, but analysis shows a range of resins mixed with the oil in different areas of his paintings: pine resin and mastic in shadows, pine resin and dammar in lighter passages. Read more about resin mediums at Natural Pigments.
Rubens used a medium based on linseed oil, possibly heat-bodied, mixed with pine resin. His paintings, including The Elevation of the Cross (1610-1611, Cathedral of Saint Bavo, Antwerp), show the luminous, fluid surface that a well-formulated medium produces. Rubens's medium allowed him to paint wet-into-wet with a fluidity that would be impossible with paint straight from the tube (or, in his case, straight from the bladder).
Reynolds was the most experimental painter of the 18th century when it came to mediums. He used various formulations of megilp, sometimes with copal varnish, sometimes with wax, sometimes with unconventional binders like beeswax and drying oils. His experimental approach produced paintings that are notoriously unstable. Many of his works at the Royal Academy have suffered from cracking, flaking, and discoloration because the mediums he used did not age well. Reynolds's failures are as instructive as his successes: they demonstrate that a medium that produces beautiful short-term effects can be disastrous over centuries.
Turner was a prolific experimenter with mediums. Analysis of his paintings shows walnut oil as the principal medium, with pine resin, mastic, and dammar added in different areas. Turner purchased various proprietary mediums and varnishes and mixed them into his paint on the palette. His The Fighting Temeraire (1839, National Gallery, London) shows the luminous, translucent surface that resin-oil mediums produce.
Sargent used a traditional medium of stand oil, dammar, and turpentine for his portraits. His Madame X (1884, Metropolitan Museum of Art) shows the smooth, enamel-like surface that this medium produces. Sargent's medium gave his paint enough flow to self-level brush marks while retaining enough body to hold the shape of each stroke.
Bacon used turpentine and linseed oil as his primary mediums, often applying them directly to the canvas to create the streaked, blurred effects in paintings like Three Studies for Figures at the Base of a Crucifixion (1944, Tate). Bacon's use of medium was unconventional: he used it to break paint down rather than to build it up, creating surfaces that drip, smear, and dissolve.
The 20th century brought synthetic alternatives to the traditional oil-resin-solvent medium. Alkyd mediums, such as Liquin (Winsor and Newton) and Galkyd (Gamblin), are based on synthetic alkyd resins that dry faster than natural oil-resin mediums and produce a harder, more flexible film. They are popular because they speed up the drying process, allowing painters to layer paint in days rather than weeks. The trade-off is that alkyd mediums have a different feel than traditional mediums: they are stickier, less buttery, and produce a more uniform surface.
A 2026 article from Bradbury Art noted that Michael Harding's Miracle Medium is a plant-based ester oil formulation with no resin and no solvent. It extends the flow of oil paint and lifts transparency for glazing without changing the fundamental character of the paint. This represents a new direction in medium formulation: moving away from both traditional resins and synthetic alkyds toward plant-based formulations that avoid the health and aging concerns of earlier materials. Read the comparison at Bradbury Art.
Natural Pigments offers a range of solvent-free mediums based on gelled drying oils. Oleogel, made from linseed oil and fumed silica, adds body and transparency without solvents. Velazquez Medium, made from finely ground calcite in heat-bodied linseed oil, extends paint and creates ropey impastos. These products represent a return to the material logic of Old Master painting, using the same ingredients (linseed oil, calcite, silica) but processed with modern technology. Read the guide at Natural Pigments.
Mediums are made from oils, resins, and solvents. They are used in glazing to create transparent layers and in impasto to create thick texture. The fat over lean principle governs how mediums are used across layers. For more on how mediums fit into painting practice, read our post on oil painting, glazing, and impasto, or explore our guide to reading a painting.
You see the effects of medium in every oil painting, though you may not realize it. The luminous transparency of a Titian glaze, the smooth enamel surface of a Sargent portrait, the streaked drips of a Bacon canvas, the thick ridges of a Van Gogh impasto: all of these are products of the medium the painter chose. The paint itself, straight from the tube, is just pigment and oil. The medium is what transforms it into something with specific optical and physical properties.
To see what different mediums do, compare a Rubens at the National Gallery in London with a Bacon at the Tate. Rubens's medium gives his paint a luminous, flowing quality. Bacon's medium gives his paint a raw, broken, dissolving quality. Both are oil paintings. The difference is in what the painter added to the paint.
For more on painting materials, read our entries on linseed oil and turpentine, or explore our post on chiaroscuro and the materials of light.
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