What is a painting done on wet plaster called?

A painting done on wet plaster is called a fresco. The word comes from the Italian fresco, meaning “fresh,” because the pigments are applied while a new layer of lime plaster is still damp.

In the traditional buon fresco method, artists mix powdered, alkali-resistant pigments with water and brush them onto wet plaster called intonaco. As the plaster dries and reacts with carbon dioxide in the air, the pigment becomes integrated into its surface. Artists usually worked in daily sections known as giornate, because each patch had to be completed before the plaster set.

Fresco became especially associated with Italian Renaissance art. Michelangelo’s ceiling of the Sistine Chapel and Raphael’s Vatican frescoes are among its most famous examples. The technique is durable, but it demands speed and careful planning; corrections are difficult once the plaster hardens.

A common mix-up is fresco secco, in which paint is applied to dry plaster. “Fresco” is also often used loosely for any wall painting, even when it was not made on wet plaster.