Painting oil is most suitable to this technique,
due to its thickness and slow drying time. The latter can even
be extended with additional
linseed oil. Acrylic paint can also be impastoed, though the technique
is rarely used because of the faster drying time of this material.
Impasto is not possible in watercolor or tempera, owing to the
inherent thinness of these media.
Purposes of Impasto Painting Technique
Impastoed paint serves two purposes. Firstly, it makes the light
reflect in a particular way, giving the artist some control over
light. Secondly, it adds some expression to the painting, the
viewer being able to notice the strength and speed applied by
the artist. While both purposes are commonly accepted today,
the first objective was originally chosen by masters such as
Rembrandt and Titian, 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.
Because impasto gives texture to the painting, it can be opposed
to flat, smooth, or blending techniques.