Painting in oil colours, a medium consisting of pigments suspended in drying oils. Oil paint enables both fusion of tones and crisp effects and is unsurpassed for textural variation. The standard consistency of oil paint is a smooth, buttery paste. It is applied with brushes or a thin palette knife, usually onto a stretched linen canvas. Finished oil paintings are often coated with varnish. Oil as a painting medium is recorded as early as the 11th century, though the practice of easel painting with oil colours stems directly from 15th-century techniques of painting with tempera (see tempera painting). In the 16th century oil colour emerged as the basic painting material in Venice; it has been the most widespread medium for easel paintings ever since.

Pigments ground in slow-drying oils like linseed oil could be used in a variety of ways. To begin with, layers of oil and varnish-thinned glazes could enrich the rather dry surfaces of tempera paintings on panel without suppressing their clear-cut, sculptural contours. This was the general practice of the fifteenth century Flemish painters, and was continued in Italy, particularly by painters in Florence and Rome.

Because of its thick, greasy consistency, and because it dried slowly, oil paint could be worked, corrected, and blended right on the picture surface. This simplified the shading and modeling which painters had developed during the fifteenth century. Blending and blurring also made it possible to immense figures in atmosphere, and this had enormous consequences for subsequent painting. Oil paint could also be applied in thick, opaque layers. These heavy impastos literally raised the surface into a kind of brushed, low relief. This characteristic was enhanced in the nineteenth century, when the addition of thicker oils (such as poppy seed oil) to the vehicle gave the paint a buttery consistency which held its shape as it dried. Thereafter, oil paint could be literally toweled onto the surface.

Before the development of oil paint, artistic personality was defined primarily by the drawing of shapes and contours. After its introduction-and especially after the introduction of stretched canvas-expressive paint-handling and brushwork were added to this.