An impasto is when a thicker layer of paint is laid onto the canvas with brush or knife which gives the painting physical dimensionality. You will definitely see the strokes of the brush or palette knife used. Two good examples of an artists that used this technique was Vincent Van Gogh and Frank Auerbach

Painting in oil paints is most suitable for this technique, due to the medium’s thickness and slow drying time. You can do in acrylic paint, but it can be hard due to the paints faster drying time.

There are two purposes impasto-ed paint serves. First, it makes the light reflect in a particular way, giving the artist some control over the light in their painting. Second, it adds some expression to the painting where the viewer is able to notice the strength and the speed applied by the artist. While both purposes are commonly accepted today, the first objective was originally sought by masters such as Rembrandt and Tizian, to represent folds in clothes or jewels: it was then juxtaposed with more delicate painting. The second objective is more prominent in later works, Vincent van Gogh using it frequently for aesthetics and expression. Still more recently, Frank Auerbach has used such heavy impasto that some of his paintings almost become three-dimensional.