Oil paint takes months to dry. In some cases, it takes years. Thick impasto passages can remain tacky for a decade or more. This seems like a terrible flaw — until you realize that it is actually oil paint's greatest advantage. That slow drying time gives artists something no other painting medium provides: time. Time to blend, time to adjust, time to build up translucent layers, time to scrape down and start over, time to push and pull a composition until it is exactly right. For five centuries, oil paint has been the dominant medium of Western art, and that dominance is a direct consequence of its extraordinary versatility, richness, and forgiveness.
From Jan van Eyck's jewel-like Flemish panels to Rembrandt's luminous portraits, from Monet's shimmering landscapes to Gerhard Richter's blurred photorealism, oil paint has accommodated virtually every style and ambition artists have brought to it. Understanding how oil paint works — its chemistry, its techniques, its possibilities — enriches your experience of the vast majority of paintings you will encounter in any museum. It also helps explain why certain paintings look the way they do, from the glowing depth of a Vermeer interior to the sculptural energy of a Van Gogh landscape.
This article explains the essential techniques of oil painting, the science behind the medium, and why it remains one of the most powerful tools in an artist's arsenal.
What Is Oil Paint?
Oil paint is simply pigment (finely ground colored powder) mixed with a drying oil, usually linseed oil. When applied to a surface, the oil does not evaporate like water — it undergoes a chemical reaction called oxidative polymerization, absorbing oxygen from the air and forming a tough, flexible film. This process is slow (days to months depending on thickness and conditions), which is why oil paintings remain workable for so long.
The medium was not invented in a single moment. Medieval artists had experimented with oil-based paints for centuries, but Jan van Eyck (c. 1390–1441) is traditionally credited with perfecting the technique in 15th-century Flanders. Van Eyck's innovation was not the oil binder itself but the systematic use of transparent oil glazes over an opaque underpainting — a technique that produced a luminous depth of color impossible to achieve with the older tempera medium.
Jan van Eyck, "Arnolfini Portrait" (1434), oil on oak panel, 82.2 × 60 cm. National Gallery, London. Van Eyck's mastery of oil glazing produces extraordinary depth and luminosity in fabrics, metals, and skin. Image: Public domain, via Wikimedia Commons
Why Oil Paint Dominated Western Art
Before oil paint, European artists primarily used tempera (pigment mixed with egg yolk) and fresco (pigment applied to wet plaster). Both had significant limitations:
Tempera dries within seconds, making blending difficult. It produces a flat, matte finish and is applied in thin, overlapping strokes (hatching) rather than smooth gradations.
Fresco must be painted onto wet plaster, requiring fast work in small sections. Colors are limited to those that survive the alkaline plaster chemistry, and corrections are nearly impossible.
Oil paint solved all these problems. It dries slowly, allowing smooth blending. It can be applied thickly or thinly. It can be opaque or transparent. It accommodates a vast range of pigments. It can be reworked, scraped off, and repainted. And it produces a rich, saturated, slightly glossy finish that gives colors extraordinary depth and vibrancy. By the 16th century, oil on canvas had become the standard painting medium throughout Europe — a position it held for four hundred years.
Essential Oil Painting Techniques
Glazing
Glazing is the technique of applying thin, transparent layers of oil paint over dried opaque layers. Each glaze modifies the color beneath it, creating optical depth — light penetrates the transparent layers, bounces off the opaque underlayer, and passes back through the glazes on its way to your eye. This produces colors of a richness and luminosity that cannot be achieved by mixing paint on a palette.
Van Eyck, Titian, and Vermeer were supreme glazers. When you look at the red fabric in a Titian painting and it seems to glow from within, you are seeing the effect of multiple red glazes over a lighter underlayer. The depth of color is literally built into the painting's physical structure.
Glazing requires patience. Each layer must be completely dry before the next is applied — and with oil paint, "completely dry" can mean days or weeks. A fully glazed painting might take months to complete, with each layer adding another dimension of color and light.
Impasto
Impasto is the opposite approach — applying paint so thickly that it stands up from the surface in three-dimensional ridges. Where glazing creates depth through transparency, impasto creates depth through physical texture. The raised paint catches actual light and casts actual shadows, adding a sculptural dimension to the painting surface.
Rembrandt used impasto selectively, building up highlights on noses, jewelry, and armor while keeping shadows smooth and transparent. This contrast between thick lights and thin darks creates a powerful sense of three-dimensionality. Van Gogh took impasto further, covering entire canvases with thick, energetic strokes that make his paintings vibrate with physical force. Frank Auerbach in the 20th century pushed impasto to its extreme, layering paint so heavily that his portraits become near-reliefs.
Alla Prima (Wet-on-Wet)
Alla prima (Italian for "at once") means completing a painting in a single session, working wet paint into wet paint without waiting for layers to dry. This technique produces fresh, energetic surfaces where colors blend directly on the canvas. The Impressionists used alla prima extensively when painting outdoors, where changing light demanded rapid execution.
Alla prima requires confident decision-making — there is no going back to adjust dried layers. The freshness and spontaneity of the result are the reward for this risk. John Singer Sargent's portraits demonstrate alla prima at its most dazzling — faces and fabrics rendered in a few bold, perfectly placed strokes.
Scumbling
Scumbling is the technique of applying a thin, opaque or semi-opaque layer of lighter paint over a darker dried layer, allowing some of the underlayer to show through irregularly. The result is a broken, hazy, atmospheric effect. Turner used scumbling to create his characteristic veils of mist and light. The technique works because the thin upper layer only partially covers the lower layer, creating an optical interplay between the two colors.
Fat Over Lean
The most important technical rule in oil painting is fat over lean: each successive layer should contain more oil (fat) than the layer beneath it. This ensures that upper layers dry more slowly than lower layers, preventing cracking. If a fast-drying lean layer is applied over a slow-drying fat layer, the upper layer hardens and becomes rigid while the lower layer is still moving, causing the surface to crack.
When you see a cracked old painting in a museum, it is often because the artist (or a later restorer) violated this principle. Properly layered oil paintings can remain stable for centuries — the oldest surviving oil paintings are over 600 years old and still in excellent condition.
Rembrandt van Rijn, "Self-Portrait with Beret and Turned-Up Collar" (1659), oil on canvas. National Gallery of Art, Washington, D.C. Rembrandt's late self-portraits combine transparent glazes in the shadows with thick impasto in the highlights. Image: Public domain, via Wikimedia Commons
Oil Painting Materials
Paints
Artist-grade oil paints (Winsor & Newton Artists', Gamblin, Old Holland, Michael Harding) contain higher pigment concentrations and fewer fillers than student-grade paints. The difference in color intensity, texture, and handling is substantial. A basic palette of eight to twelve colors — including titanium white, cadmium yellow, yellow ochre, cadmium red, alizarin crimson, ultramarine blue, cerulean blue, viridian, burnt sienna, and ivory black — can mix virtually any color you need.
Mediums
Oil painting mediums modify the paint's consistency, drying time, and finish. Common mediums include:
Linseed oil — Increases transparency and flow, slows drying. Yellows slightly over time.
Turpentine or mineral spirits — Thins paint for lean underlayers. Evaporates, leaving less oil.
Liquin (alkyd medium) — Speeds drying time, increases transparency. Popular with modern painters.
Stand oil — A thicker, honey-like linseed oil that produces smooth, enamel-like surfaces with minimal yellowing.
Surfaces
Oil paint can be applied to any properly prepared surface. Pre-stretched, pre-primed canvas is the most common support. Canvas panels and primed wooden panels are also popular. The surface must be sealed with a ground (usually gesso) to prevent oil from seeping into the support and degrading it over time.
How to Appreciate Oil Paintings in Museums
Understanding oil painting techniques transforms your museum experience. Next time you are in front of an oil painting:
Get close and look at the surface — Can you see individual brushstrokes? Are some areas thick and others thin? The physical texture tells you about the artist's process.
Look for glazed areas — Deep, luminous shadows and rich, glowing fabrics are usually achieved through glazing. Compare these areas to the lighter, more opaque passages.
Notice the brushwork — Is it smooth and invisible (academic technique) or visible and expressive (alla prima)? The brushwork tells you about the artist's priorities — precision versus spontaneity.
Check the edges — Are the boundaries between forms sharp or soft? Hard edges advance, soft edges recede. Masters like Rembrandt and Velázquez used edge control with extraordinary sophistication.
Final Thoughts
Oil paint's slow drying time, luminous transparency, and extraordinary versatility have made it the medium of choice for Western artists for over five hundred years. From the microscopic precision of Van Eyck to the explosive energy of de Kooning, oil paint has accommodated every artistic ambition. Understanding its techniques — glazing, impasto, alla prima, scumbling — is not just useful for aspiring painters. It is essential for anyone who wants to truly see and appreciate the vast majority of paintings in museums and galleries worldwide.
The next time you stand in front of a Rembrandt or a Monet, look not just at the image but at the paint itself. The way it catches light, the way it builds depth, the way it records the artist's hand — that physical reality is what separates an original oil painting from any reproduction, and it is what makes these works as alive today as the day they were painted.
Want to learn more about painting and art techniques? Explore watercolor basics, or discover how the essential visual elements work across all mediums.
