Fresco is a technique of mural painting executed upon freshly laid ("wet") lime plaster. The word fresco (Italian: affresco) is derived from the Italian adjective fresco meaning "fresh". The technique has been employed since antiquity and is closely associated with Italian Renaissance painting. The colors are made by grinding dry-powder pigments in pure water, and they dry and set with the plaster to become a permanent part of the wall. There are three types of fresco painting: buon affresco (true fresco), mezzo fresco (medium fresco), and fresco secco (dry fresco).

• Buon Fresco: This is the most durable technique and consists of three successive coats of specially prepared plaster, sand, and sometimes marble dust that are troweled onto a wall. Each of the first two rough coats is applied and then allowed to set (dry and harden). In the meantime, the artist, who has made a full-scale cartoon (preparatory drawing) of the image to be painted, transfers the outlines of the design onto the wall from a tracing made of the cartoon. The paint is applied directly onto freshly mixed plaster, and due to the natural tack of the wet intonaco, the pigment used to paint a buon fresco does not need to contain a binding medium; instead, it can simply be mixed with water.

• Fresco Secco: This process dispenses with the complex preparation of the wall with wet plaster. Instead, dry, finished walls are soaked with limewater and painted while wet. The colors do not penetrate into the plaster but form a surface film, like any other paint. Secco is useful for detailed painting and for retouching true fresco.

• Mezzo Fresco: This is painted onto nearly dry intonaco. During the Renaissance, this type of fresco became widely used, eventually surpassing buon fresco in popularity.

Fresco painting is ideal for making murals because it lends itself to a monumental style, is durable, and has a matte surface. The surface unity of the fresco is important because the pigment used bonds with the drying plaster, becoming part of the wall rather than a surface coating.