Impasto

In painting, impasto (from the Italian for dough) describes areas of the surface of a painting which are heavily built up with paint layers. Impastoed paint is highly textured; brush or palette knife marks are usually clearly evident. The intention is to make the light falling across the painting reflect in a particularly noticeable way. Highlights, or perhaps jewels on a costume, may be heavily impastoed for this reason, as in some of the works of Rembrandt. Later, artists such as Van Gogh employed the technique extensively for decorative and expressive purposes.

Chiaroscuro

This is an Italian term that literally means 'light-dark'. In painting the description refers to clear tonal contrasts which are often used to suggest the volume and modeling of the subject depicted.

Glaze

Certain pigments when combined with an oil or oil and resin medium form transparent or translucent paint or glazes. When applied over another colour, generally lighter in tone, they modify that colour but being transparent does not obscure it.

Scumble

A Scumble is a thinly applied paint layer, which is lighter in tone than the underlying colour (as opposed to a glaze, that is darker). A scumble is translucent because of its thinness. A paint mixture scumbled over a dark underlayer will appear cooler and bluer in hue than the same colour over a lighter ground.

Underdrawing, underpainting

The preliminary technique of blocking in the drawing, composition and establishing tonal values in a painting. Colours rather than tone are sometimes used in the underpainting. Generally this stage is kept basic, leaving finesse and complexity until later stages.

Fat over Lean

A painting technique which allows the bottom layer of paint to dry before further applications. Fat paint is mixed with oil to create a thick paste while lean paint is thinned with a diluents such as white spirit which helps it dry more quickly.