Oil paint is a slow-drying medium in which pigment is bound in linseed or other drying oils. Its extended open time — hours to days — allows for extended wet-into-wet blending, subtle tonal transitions, and extensive revision, making it the dominant medium of Western painting for five centuries. The fundamental rule of oil painting is 'fat over lean': earlier layers should contain less oil (thinner, faster-drying) while later layers contain more oil, preventing cracking as layers dry at different rates. Solvents like odorless mineral spirits are used to thin early layers; mediums increase oil content for later glazes.
Begin with a limited palette (titanium white, yellow ochre, burnt sienna, ultramarine blue, ivory black) and paint monochromatic or near-monochromatic studies before adding full color. Practice blending two colors wet-into-wet directly on canvas to understand the medium's unique handling characteristics.
If you've worked with acrylics, you know the experience of paint drying quickly — sometimes frustratingly so — leaving you scrambling to blend before edges set. Oil painting is a fundamentally different experience. Because oil paint cures through oxidation (a slow chemical reaction with air) rather than evaporation, it stays workable on your palette and canvas for hours or even days. This extended open time is the medium's defining characteristic and the reason it dominated Western painting from the Renaissance onward: it gives you time to think, to blend, to revise, and to build up complex color relationships gradually.
The most important technical rule in oil painting is fat over lean. "Lean" paint has less oil (thinned with solvent like odorless mineral spirits); "fat" paint has more oil (used straight from the tube or mixed with an oil-based medium). Earlier layers should be leaner, later layers fatter. The reason is structural: lean layers dry faster than fat ones. If you put a fast-drying lean layer over a slow-drying fat layer, the top dries and becomes rigid while the bottom is still moving — and the result is cracking. By building lean-to-fat, each layer dries before the one above it, creating a stable paint film. In practice, this means your first block-in should use paint thinned with a little solvent, while later refinements and glazes can use paint at full consistency or enriched with medium.
Your knowledge of color mixing transfers directly to oils, but the medium adds some new behaviors. Oil paint is more transparent than acrylics in many pigments, which enables glazing — applying a thin, transparent layer of color over a dry opaque layer. A glaze of transparent red over dry yellow produces a luminous orange that looks different from the same two colors mixed on the palette, because light passes through the glaze, bounces off the opaque layer beneath, and passes through the glaze again. This optical mixing produces richer, more complex color than direct mixing alone. If you've studied color temperature, you'll find that glazing is one of the most powerful ways to shift the temperature of a passage without muddying it.
A practical starting point is a limited palette: titanium white, yellow ochre, burnt sienna, ultramarine blue, and ivory black. These five colors can mix a surprisingly wide range of values and muted colors, and the constraint forces you to focus on value relationships and color temperature rather than chasing exact hues. Begin with monochromatic studies — a single color plus white — to learn how the paint handles: how much pressure to apply with the brush, how wet-into-wet blending feels compared to acrylics, how to load the brush for thick impasto strokes versus thin coverage. Once the medium's physical behavior feels natural, introduce the full limited palette and start exploring the color possibilities that make oil painting so rewarding.
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